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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 102, NO. B8, PAGES 18,179-18,201, AUGUST 10, 1997
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The German Continental Deep Drilling Program KTB:
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Overview and major results
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Rolf EmmermannandJ6mLauterjung
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GeoForschungsZentPruomtsdamP,otsdamG, ermany
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Abstract.The GermanContinentaDl eepDrilling Program(KTB) wasdesignedto studythe propertiesandprocesseosf thedeepercontinentaclrustby meansof a superdeepboreholeM. ajor researchthemeswere(1) thenatureof geophysicasl tructuresandphenomena(,2) thecrustal stressfield andthe brittle-ductiletransition,(3) the thermalstructureof the crust,(4) crustal fluidsandtransportprocessesa,nd(5) structureandevolutionof thecentralEuropeanVariscan basementT. he projectwasconductedin distinctphasesa: preparatoryphase(1982-1984),a phaseof siteselection(1985-1986), anda pilot phase(1987-1990), whichincluded sinkingof a pilotboreholeto 4000 m anda 1-yearexperimentatiopnrogramT. he mainphase(1990-1994) compriseddrillingof a superdeepboreholewhichreacheda final depthof 9101 m anda temperatureof ~265øC,andthreesubsequenltarge-scaleexperimentsin theuncased-bottomhole sectionA. mongtheoutstandingresultsarethefollowing(1) A continuousprofileof the completestresstensorwasobtained.(2) Severallinesof evidenceindicatethatKTB reachedthe present-daybrittle-ductiletransition(.3) The drilledcrustalsegmenits distinguishedby large amountsof freefluidsdownto midcrustalevels.(4) The roleof postorogenibcrittledeformation hadbeengrosslyunderestimated(5.) Steep-angleseismicreflectionsurveysdepictthe deformationpatternof theuppercrust.(6) High-resolutionseismicimagesof thecrustcanbe obtainedwith a newlydevelopedtechniqueof true-amplitudep,restackdepthmigration.(7) The electricalbehaviorof thecrustis determinedby secondarygraphite(+sulfides)in shearzones.
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Introduction
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requireclosecooperationbetweengeoscientistasndengineers,a
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prerequisitewhichdevelopedintoa fruitful symbiosisL. ike any
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In October1994, after 1468daysof drilling, the superdeep expedition to uncharted regions, the KTB project was
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boreholeof the GermanContinentaDl eep Drilling Program meticulouslyplannedto foreseeand minimizepotentialrisks.
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KTB (KontinentalesTiefbohrprogrammder Bundesrepublik Thusthe projectproceededin distinctphasesa, fter eachof
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Deutschlandr)eacheditsfinaldepthof 9101 m at a temperature whicha fundamenttaelevaluatiownasmadeandstrategiewsere
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of ~265øC. The main phaseof the KTB was then concluded redefinedA.ftera preparatorpyhase(1982-1984a) nda phaseof
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with threemajorexperimentsin the uncasedbottomsectionof presiteinvestigationasndsiteselection(1985-1986),the KTB
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the hole: a dipole-dipoleexperiment,a draw-downtestand a pilotphasebeganin 1987.Thisinvolvedsinkinga pilotholeto
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combinedhydrofracturinagndfluid injectionexperimentW. ith 4000m (the"VorbohrungK"T, B-VB)anda subseque1n-tyear this climax to the scientificprogram,the main phaseof the logging,testingand experimentatiopnrogram(until April
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KTB was terminated as scheduledon December 31, 1994.
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1990).The resultsof thepilot phasehada majorimpacton
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The KTB was the largest and most expensiveresearch scientificand technicalplanningof the superdeephole
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programin the geoscienceesver undertakenin Germany.The CHauptbohrung"K, TB-HB), and providedthe basisfor the Federal Ministry for Researchand Technologycommitteda officialgo-aheafdorthemainphaseA. pprovawl asgiventothe
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total of 528 million DM (~$350,000,000U.S.) to the project, designand constructioonf a specializeddrill rig with a
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fromtheplanningphasein 1982throughto completionin 1994. maximumcapacityof 12 km, the targetdepthwassetat the
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A KTB projectgroupe, stablisheadt theGeologicaSlurveyof temperatulreevelof 300øC(expecteadtabout10km),a budget
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LowerSaxony,Hannoverw, asresponsiblfeor thetechnicaal nd wasdetermineda,nd a time framefor the main phasewas
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operational realization of the program. The Deutsche limitedto December31, 1994.The year 1995 wascommitted
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Forschungsgemeinscha(fDt FG) oversaw and coordinatedall for siteshut-dowanndfinaldataevaluationa,ndonJanuary1,
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KTB-relatedscientificactivities.At onetime or anotherduring 1996, the GeoForschungsZentrPumotsdam(GFZ) took over
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this period, more than 700 scientistsand technicianswere responsibilitfyor the final phase.In thisphase,the two drill
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employedin KTB-relatedwork.
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holes,whicharesome200 m apart,will beusedovera 5-year
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KTB fully deservesthe term "superdeepadventure"because periodas a deepcrustallaboratoryfor in situ scientificand
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it advancedthe frontiersof many geoscientificand technical technicalexperiments.
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fields.It wasclearfrom the very beginningthatsuccesswould
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Copyfight1997by theAmericanGeophysicaUl nion
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Papernumber96JB03945. 0148-0227/97/96JB-03945509.00
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Realization of an Idea
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In 1977 the Senate Commission on Geoscientific Research of
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theDeutscheForschungsgemeinschafifrtst discussedtheideaof investigatingthe continentalcrust by meansof a superdeep
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18,179
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21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
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•oo
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EMMERMANN AND LAUTEPOUNG: KTB DEEP DRILL HOLE
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18,180
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21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
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EMMERMANN AND LAUTERJUNG: KTB DEEP DRILL HOLE
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18,181
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borehole.At that time, conceptualmodelsof the makeupand Collapse of the Variscan orogen started in the late
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evolution of the continentalcrust were primarily based on Carboniferous(~300 Ma) andwasenhancedby mantle-induced
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interpretationof the geological record, interpretationof crustalextensionand magmaticactivity which heraldedthe
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geophysicalimages obtained from various deep-soundingbreak-upof thenewlyassemblePdangeaT.hisepisodecreateda
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methodsa, ndapplicationof laboratorydatafromexperimental multitudeof Permian(300-250 Ma) bimodal volcanic suites,
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petrologyandgeochemistrtoy realrocks.The commissiofnelt intramontanebasinsandgrabenstructuresm, anyof whichare
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thatfurtherprogressrequired"groundtruth"thatcouldonlybe wrench-relatedD. uringthe Alpine orogeny(~100-30 Ma) the
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obtainedby direct observationthroughdrilling. From the region was affected by compressionaalnd transpressional
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beginningt,hereforet,wo fundamentagl oalsof globalrelevance tectonicswhich were followedby yet anotherstageof rifting
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weresingledout:(1) calibrationof crustalgeophysicsa,nd(2) andgrabenformationin theTertiary(since~25 Ma). Manyof
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studyof thecrustalstressfield andtherheologicablehaviorof theseeventswere accompaniedby magmatismand enhanced
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the crust.In the ensuingyears,discussionws ithin the whole hydrothermaalctivity,causingthe formationof widespread
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geosciencceommunityled to a muchbroadedr efinitionof the mineralization.
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conceptof continentasl uperdeedprilling. In 1984the official This multiply reworkedcentralEuropeancrustis relatively
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proposatlo establishtheKTB wassubmitteadndfive priority thin (~30 km) andextremelyheterogeneousb,oth laterallyand
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areasweredefined:(1) thenatureof geophysicasltructuresand vertically. It is distinguishedby regionally variable but
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phenomenas:eismicreflectorsand electrical,magneticand generally high heat flow values, complex gravimetric and
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gravimetricanomalies;(2) the crustalstressfield and the magnetic patterns, pronounced seismic reflectivity, the
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brittle-ductiletransition:orientationand magnitudeof stresses occurrenceof high-andlow-velocitylayers,andzonesof high
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as a function of depth; (3) the thermal structureof the electricalconductivityat differentdepths.
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continentalcrust: temperaturedistribution,heat flow, heat
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productiona,ndheattransport(;4) crustalfluidsandtransport processesfl:uid systemsf,luid sourcesa,ndfluid movements;Site Selection: A Difficult Decision
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and(5) structureandevolutionof thecentralEuropeanVailscan basement: properties, deformation mechanisms, and geodynamicosf a multiply reactivatedcontinentacl rustal
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environment.
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Altogether,more than 40 potentialdrill siteswere initially suggestedb,utonlyfoursurvivedthefinal definitionof project objectives,and the first main selectionconferencein 1983
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narrowed the choice to two final candidates, the Schwarzwald
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From technicacl onsiderationsa,ndbasedon theexpectation and Oberpfalzregions.As existingknowledgewas inadequate
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of importantchangesin rheologyandreactionkineticsabove to decide betweenthe two, a 2-year programof geological,
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about250øC,the targetwassetat the 250ø-300øCtemperature petrologicala, ndgeophysicasltudieswasstartedin eachregion.
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window. This temperaturetarget was combined with the The results were discussed at a final selection conference in
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objectiveof penetratingat least8000 m into the continental September1986, attendedby over 200 geoscientistosf all
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crust.
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disciplines.
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Fromits inceptionc, losetieswereestablishedbetweenKTB and the German Continental Seismic Reflection Program (DEKORP), whichstartedin 1983 and wasalsofundedby the FederalMinistry for ResearchandTechnology.Together,these projectswereintendedto providea major Germancontribution to understandintghearchitecturec, ompositiona, ndevolutionof
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At thatmeetingit wasacknowledgedthateachregionoffered highly attractive targets for solving a range of pressing geoscientificproblemsand preferencefor one site over the other becamea partisanissueamongthe variousdisciplines. The deadlock was broken by focusing on the expected geothermalgradient.Extrapolationof geothermaldataobtained
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the central Europeancrust. Perhapsbecauseof its relatively young age (typically < 500 Ma), this crustal type differs fundamentallyfrom that sampledby the Russiansuperdeep
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from shallow-drillingstudiescarried out in both regions especiallyfor thispurposeindicatedthatthetargettemperature of 250ø-300øCmight be encounteredat 7 km depth in the
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boreholeKola SG3. Neverthelessc, entralEuropeancrusthasa Schwarzwald,whereasit could lie about 5 km deeperin the
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complexhistory and has been repeatedlyaffectedby major Oberpfalz.Therefore,taking the original depthcriterioninto
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compressionaalndtensionalprocessesIt. waslargelyformedor reshapedduring the Variscan orogeny(~400-300 Ma), which wasan importantsteptowardthe assemblyof Pangea(at ~300
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account,the DeutscheForschungsgemeinschasfetlectedthe Oberpfalz site for the superdeepborehole [Emmermannand Behr, 1987]. The specificscientificattractionsof this site were
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Ma).
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seento be (1) its locationin the suturezone betweentwo first-
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The Variscan belt represents a collage of arcs and microcontinentsresulting from collision of the Old Red Continent(Laurentia+ Baltica + East Avalonia) with Armorica
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order units of the Variscanorogen;(2) the existenceof an appealingand testablegeologicmodelwhich had far-reaching
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implicationsfor crustalarchitectureand geodynamics(;3) the
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and Gondwana.An important rifting phasein Cambrian and Ordoviciantimes(~500 Ma) first separatedthe microplatesof
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East Avalonia and Armorica from mainland Gondwana and
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occurrenceof marked gravity, magnetic,and electrical selfpotential anomalies; (4) the expected presenceof seismic
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reflectors at drillable depths and of an electrical high-
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createdlargeareasof thinnedcontinentalor evenoceaniccrust. conductivitzyoneat 10 __1 km; and(5) thechanceto testfor
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The crustalblocksinvolved beganto convergein Ordovician thermal and geochemicalinfluencesfrom the nearbyTertiary
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time (by ~450 Ma) and were finally weldedtogetherduring a Eger rift.
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prolongedstageof collisionin the Devonianand Carboniferous
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(400-300 Ma) to form thepresent-dayVariscides.Incorporation
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of magmaticarcs and back arc basins,long-distancenappe Two-Step Drilling Concept
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transport, a final stage of low-pressure,high-temperature
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metamorphism, and voluminous intrusion of late to Sincethegeologicabl oundaryconditionsandtheirimpacton
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postorogenigcraniteshavedonemuchto obscurethe recordof the technicalrequirementfsor reachingthe envisageddepth
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oceansopeningandclosing.
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targetwerenotknownsufficientlyt,heKTB conceptwasbased
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21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
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18,182
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EMMERMANN AND LAUTERJUNG: KTB DEEP DRILL HOLE
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on drilling two holes,first a pilot hole as a sortof "fact-finding about1.5wt % DEHYDRIL-HT,a synthetich,ectoritc-typLei,-
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mission"andthenthesuperdeepholeitself.
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bearingNa-Mg silicatewhichyieldeda thixotropics, olid-free,
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Main objectives of the pilot phase were to acquire a highly lubricantmud system.Later, due to its electrolyte
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comprehensive set of geoscientific data from core sensitivityc,orrosivebehaviori,nstabilityat hightemperatures,
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investigations,cuttingsanalyses,and boreholemeasurements and other factors,it was continuouslmy odifiedby adding
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with which to develop the methodologyrequiredfor optimal HOSTADRILLa, norganicpolymera,ndNaOHplusNa•CO•to
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evaluation of the superdeephole and to test the geological fix a pH valueof 10 to 11. With increasingtemperaturien the
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prognosesM. oreover, the pilot hole would reducethe needfor deeperpartsof the KTB-HB (below7100 m) and owingto
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samplingand loggingin the upper,largecalibersectionof the continuingsmallinfluxesof salineformationwaters,a steady
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superdeephole and would provide the information on rock deteriorationin rheologicalpropertiesand water-binding
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propertiesanddrillability, boreholestability,potentialgain and capacityrequireda partialreplacemenbty addinga mixtureof
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loss zones,temperatureprofile, etc., critically neededfor the different commercial polymers (KEMSEAL, MILTEMP,
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technicalplanning.
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PYROTROL). Furthermore, in order to reduce borehole
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The KTB pilot hole was spuddedon September27, 1987. instabilitietshemudweightwasraisedfrom 1.06kg/L to 1.40
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The conceptdevelopedby the KTB engineers,which was to kg/L by addingbarite(seeTable 1 for a summaryof fluid
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modify a conventionadl rill rig from industryand to combine systemsusedat variousstages).
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rotarydrilling andwire line coringtechniquest,urnedout to be After completionof the pilothole,a 1-yearmeasuringand
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very successfulW. ith a high-speedtopdriverotatingsystemand experimentationprogram was conducted,which included a
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using an internal and externalflush-jointed5 V2inch mining comprehensiveloggingprogram,14 hydrofracmeasurements
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drill stringwith 6 inch thin-kerfeddiamondcorebits,560 days and a large-scalethree-dimensiona(l3D) seismic reflection
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of drilling and logging were needed to achieve a basement survey,coveringan areaof 19 x 19 km aroundthe drill site. In
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penetrationof 4000 m, and a total of 3564 m of excellent April 1990 the hole was caseddownto 3850 m, leavingan
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quality cores was recovered.By applying straight vertical openholesectionof 150m. Thepilotphasewasthencompleted drillingcapabilitiesthistechniquehasa depthpotentialof 5 to 6 with a first short-termpumptest,whichyielded71 m3 of
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km andthusmaybe of specialimportancefor futurecontinental basemenbtrineswith highamountosf N2 andCH4 fromthe
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researchdrilling to intermediatedepths.
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uncased bottom zone.
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A prerequisitefor the successof the drilling techniquewas The main resultsof the pilot phase[Emrnermann1, 989],
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the developmentof a new water-baseddrilling fluid system, whichdeterminedthetechnicacloncepftor thesuperdeehpole,
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which was undertakenin close cooperationbetween KTB were (1) the considerablyhigher than expectedgeothermal
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engineersand geochemists.This system met all technical gradientw, hichled to a definitionof thedepthtargetat 10 km
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requirementsw, asenvironmentallysafeand,for the first time, (correspondintogabout300øC);(2) thelithologicheterogeneity
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alloweda quantitativegeoscientificmonitoringof the drilled andthecontinuoussteepinclinationof rockunits,whichcaused basementT. he startingcompositionwasa mixtureof waterwith severe deviation of the hole out of the vertical and resulted in
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developmentof a vertical drilling strategy;and (3) the
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frequencyof cataclasticshear zones and fluid inflow zones
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Table 1. Drilling Fluid SystemsUsedin theKTB Main Hole
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which, in combinationwith the high horizontaldifferential stressesl,ed to the expectationthat boreholeinstabilitieswould
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Borehole section
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DrillingFluid System
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|
|
Properties
|
||
|
|
|
||
|
|
becomea major problemat depth.This resultedin a slimclearancecasing strategyand developmentof water-based, high-temperaturderillingmudsystemdsescribedabove.
|
||
|
|
|
||
|
|
0 - 6760m
|
||
|
|
|
||
|
|
0.7%Dehydril plasticviscosity9-22mPas
|
||
|
|
|
||
|
|
(1,sidetrack) 1%Hostadrill densit1y.06g/cm3
|
||
|
|
|
||
|
|
Plate 1 showsthe drill rig of the superdeepboreholeKTBHB, UTB 1, which,at a totalheightof 83 m, is thelargestland-
|
||
|
|
|
||
|
|
NaOH, NarCO, pH 10-11
|
||
|
|
|
||
|
|
baseddrill rig in theworld.The rig is fully electricallydriven,
|
||
|
|
|
||
|
|
6460- 7220 m (2, correction)
|
||
|
|
|
||
|
|
1.5% Dehydril 1.5% Hostadrill
|
||
|
|
NaOH, Barite
|
||
|
|
|
||
|
|
plasticviscosity29-53 mPas
|
||
|
|
density1.06g/cm3
|
||
|
|
pH 11
|
||
|
|
|
||
|
|
and incorporatesa number of technical innovations and improvementisncluding,for example,an automaticpipehandling system and remotely controlled gear-driven
|
||
|
|
drawworks.
|
||
|
|
|
||
|
|
7140 - 8330 m (2, sidetrack)
|
||
|
|
|
||
|
|
Bentonitc
|
||
|
|
|
||
|
|
plasticviscosity35-91 mPas
|
||
|
|
|
||
|
|
KemseaMl,iltemp, density1.25g/cm•
|
||
|
|
|
||
|
|
Pyrotrol,NaOH pH 10
|
||
|
|
|
||
|
|
Barite
|
||
|
|
|
||
|
|
To ensuresufficientreservest,he drill stringlayout was madefor a maximumdepthof 12,000m (diameterof 5 •Ainch, enhancedsteelquality).By using40 m standsof drill pipe
|
||
|
|
insteadof the standard27 m stands,and in combinationwith the
|
||
|
|
|
||
|
|
7460 - 8730 m
|
||
|
|
(3, sidetrack)
|
||
|
|
|
||
|
|
Bentonite
|
||
|
|
|
||
|
|
plasticviscosity25-90 mPas
|
||
|
|
|
||
|
|
KemseaMl,iltemp, densit1y.40g/cm•
|
||
|
|
|
||
|
|
Pyrotrol,NaOH pH 9-10
|
||
|
|
|
||
|
|
Barite
|
||
|
|
|
||
|
|
pipe-handlingsystem,roundtriptime was reducedby about 30%. In orderto achievethe targeteddeptha verticaldrilling system(VDS) was developedand deployed.The VDS is an actively self-steeringsystem mounteddirectly above the
|
||
|
|
|
||
|
|
8630 - 9100 m Bentonitc
|
||
|
|
|
||
|
|
plasticviscosity27-59mPas
|
||
|
|
|
||
|
|
KemseaMl,iltemp, densit1y.40g/cm•
|
||
|
|
|
||
|
|
downholemotor.It effectivelyminimizedthe frictionbetween drill stringand boreholewall and allowed a 50% reductionof
|
||
|
|
|
||
|
|
Pyrotrol,NaOH pH 9-10 Barite,Polyglycol
|
||
|
|
|
||
|
|
the drilled rock volume by realizationof the slim-clearance casingconcept.
|
||
|
|
|
||
|
|
The VDS systemwas usedto a depth of 7500 m at the
|
||
|
|
|
||
|
|
All drillingfluid systemsare water-basedD.ehydrilis a synthetic clay mineral (Hectoritc-type)H. ostadrill,Kemseal,Milltemp and
|
||
|
|
|
||
|
|
maximumallowabletemperatureof
|
||
|
|
|
||
|
|
175øCfor
|
||
|
|
|
||
|
|
the electronics,
|
||
|
|
|
||
|
|
Pyrotrolare syntheticviscosifiersand organicadditives.NaOH and whosedata were pulsedthroughthe mud to the surface.The
|
||
|
|
|
||
|
|
Na:CO3 havebeenaddedto controlthepH value.Baritecontrolsthe horizontaldisplacemenatt this depthwas only 12 m, which
|
||
|
|
|
||
|
|
density.
|
||
|
|
|
||
|
|
meantthatthe boreholewaspracticallyvertical.The hole then
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
EMMERMANN AND LAUTERJUNG' KTB DEEP DRILL HOLE
|
||
|
|
|
||
|
|
18,183
|
||
|
|
|
||
|
|
1. Correction for Deviation 1000 rn 1300 rn
|
||
|
|
2. Correction for Deviation 1800 rn 2000 m
|
||
|
|
3. Correction for Deviation 2600 m 2700 m
|
||
|
|
|
||
|
|
track I 1710rnI
|
||
|
|
199m8 I
|
||
|
|
2.Side
|
||
|
|
track 3767m
|
||
|
|
,.,389m3
|
||
|
|
|
||
|
|
- 0 1000 2000 3000
|
||
|
|
-4000
|
||
|
|
|
||
|
|
VB
|
||
|
|
|
||
|
|
HB
|
||
|
|
|
||
|
|
Paragne•sses Metabasites VariegaSteedquences
|
||
|
|
Major Faults
|
||
|
|
|
||
|
|
1. Correction for Deviation 5530 m 5600 rn
|
||
|
|
13518I"
|
||
|
|
2. Correction for Deviation 7140 m 7220 m
|
||
|
|
|
||
|
|
1.Side
|
||
|
|
track I •o m I
|
||
|
|
track 7460m I
|
||
|
|
m,I
|
||
|
|
track I 8630m
|
||
|
|
,, 8730m
|
||
|
|
|
||
|
|
10000
|
||
|
|
Figure1. Anoutlineof thefinalboreholceonfiguratiosnh,owintghesidetracksandcorrectionfosrdeviation, casingschemaendlithologicaplrofileof(left)thepilotholaend(right)thesuperdeehpole.
|
||
|
|
|
||
|
|
deviatedtowardtheNE, almostperpendiculatro thegeneraldip boreholeenlargementsp, referentiallyrelatedto shearzones. of the foliation, andat 9069 m, wherethe final deviationsurvey Below that depth,boreholeconvergence(i.e., reductionof the
|
||
|
|
was conducted,it showeda horizontaldisplacemenot f about boreholediameter)first occurredand resultedin undergauge 300 m. Down to a depthof 8120 m the superdeephole was hole sectionsU. ndergaugesectionsw, ith uniaxialnarrowingin drilledalmostexclusivelywith downholemotors,whichcould the direction of the maximum horizontal stress, developed be usedto maximumoperatingtemperatureosf about190øC. within hoursandbecamethe major sourceof drilling problems Thelaststeptothefinaldepthwasdonewithrotarydrilling. [Bormet aL, this issue].The drill stringfrequentlygot stuck,
|
||
|
|
As coringis oneof the mostexpensivedrillingoperations,and side-trackingoperationsconsumedover 1 year of total maximizingcore recoveryand core qualitywas of special operationtime.Thistypeof instabilityw, hichcauseda creepimportanceT.he experiencewith thethin-kerfeddiamondcore like structuraldisintegrationin the rock, resultedfrom the bits in the pilot hole justified the decisionto adapt this extremely unfavourablecombinationof high differential technologyto the superdeephole. A large diametercoring stressesa,preferreddip of planesof weaknesisn thedirection system(LDCS) wasdevelopedwhich,in the 12 •Ainchphase, of the minimumhorizontalstresscomponent,he presenceof cutcoresof 234 mm diameterandprovidedrockcolumnswith formationwatersandtheelevatedtemperaturesT.he instability a lengthof up to 5 m. In comparisotno rollerco.necorebits, eventuallyformed a technicalbarrier which could not be which were also used,the averagecore recoverywith this overcomewithinthestrictlimitationsof budgetandtime.It was systemwasincreasedfrom41% to about80%. Altogether3, 5 thereforedecidedto stopthedrillingoperationisn October1994 corerunswereperformedin thesuperdeehpolewithanoverall at a depthof 9101m anda temperaturoef ~265øCin orderto recoveryof 84 m. A large additionacl ollectionof partly usethedrillrigandtheothertechnicaflacilitiesforthreelargeorientedrockfragmentsu,pto 10cmin lengthw, asprovidedby scalescientificexperimentsin the uncasedopen-holebottom a junk basket,a simple,but very effectivetool attachedabove section. thedrill bit whichwasalwaysusedin noncoredsections.
|
||
|
|
Figure1 showsthe KTB-HB in its final conditionwith the Realizationof the ScientificProgram differentsidetracksandthecasingschemeR. easonsfor theside tracks were corrections for deviation, unsuccessfulfishing The scientific program of KTB was carried out by an operationsa,ndboreholeinstabilitiesD. own to about7500 m integratedevaluationandjoint interpretationof dataandresults theseinstabilitiesmainlyoccurredin theformof breakoutsand obtainedfrom threesources'(1) the field laboratoryestablished drilling-inducedtensile fractures that producedlocalized at the drill site, (2) boreholemeasurementsand experiments,
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
18,184
|
||
|
|
|
||
|
|
EMMERMANANNDLAUTERJUNKGT:BDEEPDRILLHOLE
|
||
|
|
|
||
|
|
and (3) individual specializedresearchprojectscarriedout at
|
||
|
|
universities and other research institutions. All KTB-related scientific activities were coordinated and
|
||
|
|
|
||
|
|
Field Laboratory
|
||
|
|
|
||
|
|
reviewed by the DeutscheForschungsgemeinscha(DfiFG), whichestablisheda PriorityProgram"KTB" thatwasfundedat an annuallevel of ~7 million DM. During the lifetime of the KTB, from 1982 to 1995, the DFG administereda total of 75
|
||
|
|
million DM (~$ 50 million US) to over 300 different research projectsinvolvingabout500 scientistsI.n addition,some 100 foreignscientistsfrom 11 countriesparticipatedin KTB with a total of 70 researchprojectsfinancedby their nationalfunding agencies.Scientific communicationwithin the DFG Priority Program,periodicdiscussionof the resultsand definition of major experimentswere ensuredby workshops,task group
|
||
|
|
|
||
|
|
Fluids
|
||
|
|
|
||
|
|
Solids
|
||
|
|
|
||
|
|
Gases
|
||
|
|
|
||
|
|
Drillingfluid Fluidsampler
|
||
|
|
,,
|
||
|
|
|
||
|
|
Cores Cuttings
|
||
|
|
Rock flour
|
||
|
|
i • ,
|
||
|
|
|
||
|
|
Gas trap Sampler
|
||
|
|
,
|
||
|
|
I I
|
||
|
|
|
||
|
|
Petrology and Structure
|
||
|
|
|
||
|
|
Petrography
|
||
|
|
|
||
|
|
Macrostructures
|
||
|
|
|
||
|
|
Ore microscopy Microstructures
|
||
|
|
|
||
|
|
Texture
|
||
|
|
|
||
|
|
C ore ode ntation
|
||
|
|
|
||
|
|
Borehole
|
||
|
|
measurements
|
||
|
|
|
||
|
|
meetings,thematicsessionsa, nd the annualKTB colloquium. As of 1995 a total of over2000 publicationshavecomeout of the variousresearchprojects.
|
||
|
|
Establishmenot f a field laboratoryat thedrill sitewasa top priority from the time of the first discussionsabout a continental deep drilling program in Germany. The field laboratory became an indispensible component for the realization of the ambitious scientific program. Figure 2 summarizes the tasks of the field laboratory and its organizationalstructure.This lab, which was a modernand completelyequippedresearchinstitute,was supportedby nine university "mother institutes" (under the guidance of the Instituteof GeosciencesU, niversityof Giessen),andstaffedby up to 20 scientistsand 18 techniciansI.ts primarypurposewas
|
||
|
|
|
||
|
|
Petrophysics Density,Porosityand Permeability, Electricand magneticproperties, Soundvelocities,Heat conductivity, y-spectroscopyS, tressrelaxation
|
||
|
|
,
|
||
|
|
Geochemistry Chemical& mineralogicaclomposition
|
||
|
|
of rocks;Fluid-and Gasanalysis
|
||
|
|
|
||
|
|
KTB-Database
|
||
|
|
|
||
|
|
Storage
|
||
|
|
|
||
|
|
Documentation
|
||
|
|
|
||
|
|
Correlations Modelling
|
||
|
|
|
||
|
|
to collect extensivegeoscientificdata on cores,cuttings,rock
|
||
|
|
|
||
|
|
flour, drilling fluidsandgases.Propertiesandcharacteristic(s1) weremeasuredwhichwerenecessaryfor operationadl ecisions
|
||
|
|
|
||
|
|
ISpaamrt•pi_eUl•is[nngiv-ersKitTieBs- concerningdrilling, sampling, and testing, (2) had to be
|
||
|
|
determinedon a quasi-continuoubsasisas a functionof depth,
|
||
|
|
|
||
|
|
Reports
|
||
|
|
|
||
|
|
(3) aretime-dependenatndthereforehadto be recordedassoon
|
||
|
|
|
||
|
|
as possibleafter sampling,and (4) were neededfor calibration of boreholemeasurementsand were requiredto guide sample
|
||
|
|
|
||
|
|
Figure2. A flow chartshowingthe samplingandanalysis
|
||
|
|
schemeof the KTB field laboratory.
|
||
|
|
|
||
|
|
selection and as basic information for all individual research
|
||
|
|
|
||
|
|
projects.
|
||
|
|
|
||
|
|
Apart from establishedmethodsa, numberof new techniques influxes could be identified and localized,facilitating quick
|
||
|
|
|
||
|
|
were developedand continuouslyimproved.Among them were operationadlecisionsconcerningpositioningof drill stemtests
|
||
|
|
|
||
|
|
a computerizedreorientationtechniquefor cores,a new tool for anddownholefluid sampling.
|
||
|
|
|
||
|
|
high-qualitydensityimagingof coresby gammaray absorption Togetherwith the work in the field laboratoryd, ownhole
|
||
|
|
|
||
|
|
and a four-componendt ilatometerfor the measuremenot f the measurementpslayeda centralrole in thereconstructioonf the
|
||
|
|
|
||
|
|
stressrelaxion of cores. Becauseof the new drilling fluid drilledbasementandprovidedimportantinformationon the in
|
||
|
|
|
||
|
|
systemand a speciallydesignedautomaticsamplingsystem,a situ propertiesof the rocks.Prior to KTB therewas little
|
||
|
|
|
||
|
|
real break-throughwas achievedin the evaluationof cuttings, experiencein the integratedinterpretationof loggingdata
|
||
|
|
|
||
|
|
rock flour, drilling fluid, and gasesdissolvedin the drilling obtainedfrom crystalline rocks [Pechnig et al., this issue].
|
||
|
|
|
||
|
|
fluid. The quantitativechemicaland mineralogicacl omposition Thereforean extensiveloggingtestprogramwasconductedin
|
||
|
|
|
||
|
|
of cuttings and rock flour was determined using a newly thepilotholeusingall availabletypesof tools,andtheborehole
|
||
|
|
|
||
|
|
developed combination of X ray fluorescenceand X ray log responseswere calibratedagainstcore, cuttingsand other
|
||
|
|
|
||
|
|
diffraction, which allowed a reliable reconstruction of the dataprovidedby thefield laboratory.
|
||
|
|
|
||
|
|
drilled basementwithin 1 hourafter sampling[Emrnermannand During the drilling phaseof the pilot hole, sevenlogging
|
||
|
|
|
||
|
|
Lauterjung, 1990]. Because the pilot hole was almost campaignswereperformedat variousintervals,mainlyfor data
|
||
|
|
|
||
|
|
completelycored,it was possibleto comparethe lithological acquisitionand technical purposes.After completionof the
|
||
|
|
|
||
|
|
profile obtained from direct study of cores with that hole,24 differentexperimentswereconducteda,nda totalof 55
|
||
|
|
|
||
|
|
reconstructedfrom cuttings and rock flour analyses.It was toolsweredeployed.On thebasisof theresultsandexperiences
|
||
|
|
|
||
|
|
demonstratedthat the agreeementwas excellent and that every from thesemeasurementst,he combinationof loggingtoolsfor
|
||
|
|
|
||
|
|
rock type, even minor lithologicalchanges,fault zones, and the KTB superdeephole was defined and, altogether,266
|
||
|
|
|
||
|
|
alteredintervals,hadbeenunequivocallyidentified.
|
||
|
|
|
||
|
|
logging runs were performed. Although there were some
|
||
|
|
|
||
|
|
In addition,quasi-onlineanalysesof the drilling fluid, and standard high-temperaturelogging tools available from
|
||
|
|
|
||
|
|
the gasesreleasedfrom drilling fluid, were performed.These industry, several tools were upgradedespeciallyfor KTB.
|
||
|
|
|
||
|
|
fluid logs turned out to be very sensitive indicators of Among thesewas a high-temperatureformationmicroscanner
|
||
|
|
|
||
|
|
cataclastic shear zones and fluid inflow zones. Even minor fluid (FMS) whichcouldbe usedup to 260øC.Figure3 presentsan
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
EMMERMANNANDLAUTERJUNGK:TBDEEPDRILLHOLE
|
||
|
|
|
||
|
|
18,185
|
||
|
|
|
||
|
|
[
|
||
|
|
|
||
|
|
KTB-Oberpfalz HB
|
||
|
|
|
||
|
|
VMG..LS•.TV.•-_R_.••oBH•TV
|
||
|
|
|
||
|
|
14.02.9515:17 / KTB-GP-BM Kiick
|
||
|
|
Figur3e. Summoarftyhemajolorggintogolasndtheirrespecmtiveeasurinintegrvinatlhesuperdheoelpe.
|
||
|
|
AbbreviatiaorneNsGSn, aturgalammsapectroscDoLpLy;,electricraelsistivistyo;nics,eismvicelocitBy;GT,
|
||
|
|
borehgoeleomeTtrEyM' Pte, mperaltougrM'e AGm, agnetomGeLtTeg,r;eochemloicgaglintogolS; Ps, elf potentIiPal,'inductilong;FMS/FMfoI,rmatimonicroscanner/fmorimcraotiimonaBgHeTr;Vb,orehole
|
||
|
|
televieweBr;HGM,borehogleravimeteVrS; P,verticasleismipcrofiling.
|
||
|
|
|
||
|
|
overviewof themajortoolsdeployedandthemeasureddepth Apartfromarchivingth, emaintaskof dataprocessinwgas
|
||
|
|
|
||
|
|
sections.
|
||
|
|
|
||
|
|
tointegrataelldataintoa singlea, ccessibilneformatiosnystem,
|
||
|
|
|
||
|
|
A newandveryprecisemethodof lithologiecvaluatioonf which was achievedusingthe metadataconcept.Metadata
|
||
|
|
|
||
|
|
loggingdatawithmultivariatsetatisticwsasdevelopebdy the characterize data sets and include information on data sources
|
||
|
|
|
||
|
|
use of a broadspectrumof Schlumbergetor ols and the andstructuree,xperimentabloundarcyonditionse,xperimental
|
||
|
|
|
||
|
|
comparisoandcalibratiownithcorec, uttingsa,ndmudsample methodsl,iteraturea, nd,mostimportantt,heactuallocationof
|
||
|
|
|
||
|
|
data. This method, which relies on discriminationof thedatasets.The metadataconcepits a basicrequiremenfot r
|
||
|
|
|
||
|
|
"electrofaciesis"d, iscussebdyPechnigetal. [thisissue]a, ndit therealizationof an integratedd,istributedatabasewhichcan
|
||
|
|
|
||
|
|
contributegdreatlytotherefinemenotf thelithologipcrofileof beaccessebdy anycomputenr etwork.
|
||
|
|
|
||
|
|
thesuperdeepborehole.
|
||
|
|
|
||
|
|
The KTB database "KTBase" is a relational database: that is,
|
||
|
|
|
||
|
|
it contains material such as tables of measured data and
|
||
|
|
|
||
|
|
The Information SystemKTBase'.
|
||
|
|
|
||
|
|
observationadlescription(se.g.,thin sectionpetrographyf)rom
|
||
|
|
|
||
|
|
Access to KTB Data
|
||
|
|
|
||
|
|
thefield laboratoryt,hedownholelogginggroup,andthemud
|
||
|
|
|
||
|
|
KTBhasproduceadnenormouasmounotf dataof variouslogginggroupw, hicharestoredseparatealyndcanberetrieved
|
||
|
|
|
||
|
|
kinds(descriptivveersusquantitativneumericadlata)from andconnecteidn anywayby theuser.KTBaseis embeddeidn
|
||
|
|
|
||
|
|
differentsourcesi,ncludingthe field laboratoryb, orehole anapplicatiolnayercomprisinignterfacefsor thepresentation
|
||
|
|
|
||
|
|
measuremenmtsu,dloggingt,echnicaml onitoringe, ophysicaal ndapplicatioonf KTBdataindifferenwt aysT. heapplications
|
||
|
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|
|
experimentfsie,ld investigationans,d externasl cientificcover administration tasks, telecommunication facilities,
|
||
|
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|
||
|
|
investigations.
|
||
|
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|
||
|
|
databasemanagementa, nd software modulesdeveloped
|
||
|
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|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
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|
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|
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18,186
|
||
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|
||
|
|
EMMERMANN AND LAUTERJUNG: KTB DEEP DRILL HOLE
|
||
|
|
|
||
|
|
especiallyfor the scientific technicaltreatmentof data from The metabasicunits comprisecoarse-and fine-grained
|
||
|
|
|
||
|
|
drilling projects,includingnumericaland graphicalsoftware garnet-bearingamphibolites(plagioclaseh, ornblendeg, arnet
|
||
|
|
|
||
|
|
packages. KTBase is now available at the andilmenite),massivemetagabbrowsithrelictophitictextures,
|
||
|
|
|
||
|
|
GeoForschungsZentruPmotsdam.A hypertextlink is installed and thin layers (up to 6 m thick) of mafic and ultramafic
|
||
|
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|
||
|
|
on the home pageof the GFZ WWW server(http://www.gfz- metacumulaterocks. Most rock types display chemical
|
||
|
|
|
||
|
|
potsdam.de).
|
||
|
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|
||
|
|
characteristicosf enrichedmid-oceanridge basalts(MORB);
|
||
|
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|
||
|
|
however, normal MORB compositionsalso occur. These
|
||
|
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|
||
|
|
Scientific Results
|
||
|
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|
||
|
|
metabasicunitsperhapsrepresenst licesof formeroceanfloor formedin a backarcenvironmenotr RedSeatypeoceanic
|
||
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|
||
|
|
Crustal Structure and Evolution
|
||
|
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|
||
|
|
basin.
|
||
|
|
The variegatedseriesconsistsof an alternationof massive
|
||
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|
||
|
|
The Oberpfalzis situatedat the westernmargin of the garnetamphibolitesf,ine-grainedbandedamphibolitews ith
|
||
|
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|
||
|
|
BohemianMassif, the largestcoherentsurfaceexposureof layersof calcsilicataensdmarblesh,ornblende-biogtinteisses, basemenrtocksin centralEuropea, ndit encompasspeasrtsof and paragneissesA.mongthe metabasicrocks,alkali basaltic
|
||
|
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|
||
|
|
threefirst-ordertectonometamorphuicnitsof theVariscanfold compositionspredominatewith gradual transitionsinto
|
||
|
|
|
||
|
|
belt: the Saxothuringianth, e Moldanubiana, nd the Tepla- trachyandesiticrocks (hornblendegneisses).These units
|
||
|
|
Barrandian(Plate 2). This basemenbt lock is separatedfrom constitutea metamorphosevdolcano-sedimentasrysociation
|
||
|
|
Pertoo-Mesozoifcorelandsediments(up to 3000 m thick)by with volcaniclastimc aterial,thin lava flows, and pelites the FranconianLineament(FL), a NW-SE trending,deep- interbeddedwith minor marls and limestones.The combination reachingandmultiplyreactivatedsystemof reversefaults.The of turbiditic material with volcanicsand limestoneindicatesa KTB locationis about4 km eastof theFL andjust southof the marinedepositioneanl vironmeinnta tectonicalalyctivesetting.
|
||
|
|
boundarybetweenthe Saxothuringianand Moldanubianunits. All threeof theselithologicunitshavesuffereda pervasive
|
||
|
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|
||
|
|
This boundaryhasbeenregardedas a suturezoneformedby Barrovian-typme etamorphismat upperamphibolitefacies
|
||
|
|
|
||
|
|
closureof an early Paleozoicoceanbasinduringthe Variscan conditions(6-8 kbar and 720øC at peak conditionsin the
|
||
|
|
|
||
|
|
collisionin Devonian/Carboniferotuims es(~400-330Ma).
|
||
|
|
|
||
|
|
paragneisses)c, onnectedwith an intense ductile deformation
|
||
|
|
|
||
|
|
The drill site was located in a small, isolated thatproduceadpenetrativfeoliationW. hereatsheparagneisses
|
||
|
|
|
||
|
|
tectonometamorphiucnit called the ZEV (Zone of Erbendorf- seem to recordprogrademetamorphicevolutionalong the
|
||
|
|
|
||
|
|
Vohenstrau13w),hich representsa variegatedassociationof sillimanite-kyanbitoeundaraynddo not showanysignsof
|
||
|
|
|
||
|
|
paragneisseasndorthogneisseasndmetabasicrockswith minor earlierhigh-pressurevents,the metabasicrockscontainrelics
|
||
|
|
|
||
|
|
metapegmatitesA.ccordingto the resultsof presitestudiesi,n whichclearlydisplaya multistageevolutionfroman early particular lithologic-metamorphiccomparisonswith the high-pressumreetamorphismundereclogitefaciesconditions
|
||
|
|
|
||
|
|
MiJnchbeMrgassiifnthenorthandpreliminairnyterpretatioofn (P> 14kbarT, > ~700øCf)ollowebdyagarnegtranulitfeacies
|
||
|
|
|
||
|
|
conventionallymigratedDEKORP seismicprofiles,the ZEV overprint(P=10-13kbar,T=620-720øCp) riorto thedominant
|
||
|
|
|
||
|
|
had been interpretedas a fiat, bowl-shapedremnantof a amphibolitfeaciesmetamorphism[O'Brienetal., thisissue].
|
||
|
|
|
||
|
|
supracrustal nappe complex straddling the New age determinationsusing a broad spectrumof
|
||
|
|
|
||
|
|
Saxothuringian/Moldanubiabnoundary. In targeting the geochronologmicethodcsonfirmthatthepreVariscaanndearly
|
||
|
|
|
||
|
|
superdeepborehole,it was thereforeexpectedto penetrate Variscanhistoryof the ZEV is muchmore complexthan
|
||
|
|
|
||
|
|
througha 3-5 km thick nappecomplexand to drill into the previousltyhoughatndis distinguishebdyat leastwoseparate
|
||
|
|
|
||
|
|
postulatedsuturezone beneathit.
|
||
|
|
|
||
|
|
metamorphiccycles[O'Brienet al., this issue].The formation
|
||
|
|
|
||
|
|
In fact,howevert,heKTB-HBencounteresdteeplyinclined agesof the metabasicrocksare about485 Ma and nearly
|
||
|
|
|
||
|
|
unitsbelongingto theZEV overtheentiredrilledsectiona, nd contemporaneowuisththeearlyOrdoviciandepositionagl eof
|
||
|
|
|
||
|
|
no evidencesupportingthenappeconcepwt asfound.Figure4 the paragneissprotoliths.The earliestmetamorphicevent
|
||
|
|
|
||
|
|
showsa schematicSW-NE profile throughthe ZEV downto recordedin boththemetabasicrocksandparagneissehsasbeen
|
||
|
|
|
||
|
|
about 10 km which summarizesall availablegeological datedat .•475 Ma, using U/Pb chronologyon zirconand
|
||
|
|
|
||
|
|
information.The drilled crustal segmentconsistsof an monazitea, ndit appearsthat the relict high-pressurmeineral
|
||
|
|
|
||
|
|
alternating sequence of three main lithologic units: paragenesepsreservedin the metagabbrocsanbe attributedto
|
||
|
|
|
||
|
|
paragneissems,etabasiteasnda "variegateds"eriesof gneissesthis Early Ordovician high-pressuremetamorphism.
|
||
|
|
|
||
|
|
and amphibolites.Most rocks show a penetrativefoliation Furthermorteh,edataimplythattherewasonlya veryshort
|
||
|
|
|
||
|
|
whichdipssteeplybetween50øand80øto theSW or NE andis time spanbetweenformationof therocks,theirsubductionto at
|
||
|
|
|
||
|
|
foldedintolarge-scaloepenfoldswithNW-SEtrendingaxes. least40 km, and their subsequenrat pid uplift into shallow
|
||
|
|
|
||
|
|
Theparagneissheasvea ratheruniformcompositioanndare (cool)crustallevels.
|
||
|
|
|
||
|
|
madeup essentiallyof plagioclase(oligoclase)q, uartz,biotite, The second metamorphiccycle, that occurred under
|
||
|
|
|
||
|
|
muscoviteg,arnet,sillimanitea, nd/orkyanite;theycommonly Barrovian conditions,can be bracketedbetween about 405 Ma
|
||
|
|
|
||
|
|
contain flakes of graphite. The protolithsof these rocks (U-Pbagesof zirconsandRb-Sr,K-Ar and4øAr?Aar gesof representa turbidite sequenceof graywackesand pelitic muscovitesa)nd375 Ma (Rb-Sragesof muscovitefromshear
|
||
|
|
|
||
|
|
graywackesinterlayeredat a centimeterto meterscalewhich zones,probablydatingthe regionaldeformation)N. umerousKhas preservedits original compositionalfeatures.Former Ar, 4øAr?Arand Rb-Sr dateson mineralsindicatethat the
|
||
|
|
|
||
|
|
graywackesshow an equigranularquartz-feldsparfabric, drilledbasemenstegmenta, fter coolingto 350-300øCin the
|
||
|
|
|
||
|
|
whereapseliticlayersare coarsearndricherin micaand LateDevonia(n-360Ma),stayeidn theuppecrrusat nde, ven
|
||
|
|
|
||
|
|
typicallydisplaya biotiteflasertextureA. ccordintgo their moreimportanrte,mainetdherefora longtimeperiodwithina
|
||
|
|
|
||
|
|
chemiccahl aracteristthicepsrotolithwsereratheirmmatuarend narrowdepthandtemperatuirnetervalO. nlymarginaalnd
|
||
|
|
|
||
|
|
containa significanatmounot f basalticmaterialT.heywere deepepr artsof theZEV wereaffectedby theCarboniferous
|
||
|
|
|
||
|
|
probabldyepositeadtanactivecontinentmalargin.
|
||
|
|
|
||
|
|
deformatioandlow-pressuhreig, h-temperatmureetamorphism
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
18,187
|
||
|
|
|
||
|
|
EMMERMANNANDLAUTER]UNGK:TBDEEPDRILLHOLE
|
||
|
|
|
||
|
|
i E
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
18,188
|
||
|
|
|
||
|
|
EMMERMANN AND LAUTERJUNG: KTB DEEP DRILL HOLE
|
||
|
|
|
||
|
|
$w
|
||
|
|
Franconian Lineament
|
||
|
|
|
||
|
|
KTB-HB
|
||
|
|
|
||
|
|
NE
|
||
|
|
|
||
|
|
::::::::: .'
|
||
|
|
|
||
|
|
.w•'••:.''"""•'•"ii':•"'•i'•'•.?- ?•' ..•:•ii.•:".:•
|
||
|
|
|
||
|
|
..:.
|
||
|
|
|
||
|
|
Figure4. SchematiScW-NEprofilethroughtheZEV in thesurroundinogfsthe KTB site(no vertical
|
||
|
|
exaggerationT)h.e metamorphsicequencoef theZEV hasa polyphasheistoryw, ithearlyhigh-pressure
|
||
|
|
metamorphiastmabou4t75Ma,andlaterB, arrovian-tympetamorphiastmabou4t00-375Ma.TheFalkenberg granitet,o theNE, intrudedat about310Ma. To theSW areforelandsedimentasryequenceosf Upper CretaceouTs,riassica, ndPermo-Carboniferoaugses.
|
||
|
|
|
||
|
|
(335-325 Ma) which strongly overprinted the neighboring rocksof the variegatedsequenceandareconnectedwith a local
|
||
|
|
|
||
|
|
basement units.
|
||
|
|
|
||
|
|
greenschist facies retrograde overprint. These faults are
|
||
|
|
|
||
|
|
The first evidencefor a commonhistoryof the ZEV and the displacedby reversefaults of possibleCretaceousage, which
|
||
|
|
|
||
|
|
Moldanubian/Saxothuringiaznonesis the emplacementinto all formed under prehnite-actinolite facies conditions. The
|
||
|
|
|
||
|
|
theseunitsof late Carboniferousgraniteswhichoccurredin two youngeststructuralelementsare steepnormal faults probably
|
||
|
|
|
||
|
|
major "pulses",a late tectonicphaseat 335-325 Ma and a relatedto a phaseof grabenformation(Eger Rift) duringthe
|
||
|
|
|
||
|
|
posttectonicphase at 315-305 Ma. The Falkenberggranite, late Oligocene/Miocene(-25-20 Ma).
|
||
|
|
|
||
|
|
whichborderstheZEV ontheNE, hasanageof 311 _+8 Ma Figure 4 depicts the major faults encounteredby the
|
||
|
|
|
||
|
|
(Figure 4). The intrusionof dikes of aplites, calcalkaline superdeepborehole.The most prominentfault system was
|
||
|
|
|
||
|
|
lamprophyre(sdated by *øAr?Ar at -306 Ma) and penetratedbetween6850 m to 7260 m and consistsof a broad
|
||
|
|
|
||
|
|
monzodioritesw, hichcrosscutthe metamorphircocksdownto bundleof individualfault planes.Fissiontrackdataon sphene
|
||
|
|
|
||
|
|
depthsof about7800 m, is closelyrelatedto the granific indicatethat a vertical displacementof more than 3 km took
|
||
|
|
|
||
|
|
magmatism.
|
||
|
|
|
||
|
|
place along this fault system in Cretaceoustime. A second
|
||
|
|
|
||
|
|
The post-Variscahnistoryof theZEV is distinguishebdy major systemoccursbetween7820 m and7950 m, and vertical
|
||
|
|
|
||
|
|
unexpectedlyintense, polyphasedeformation under brittle displacementtherewasat least500 m. Bothsystemsdip steeply
|
||
|
|
|
||
|
|
condition[sWagneretal., thisissue]M. ajordeformatiopnhases to the NE and can be directly correlatedwith the Franconian
|
||
|
|
|
||
|
|
includeintensereversefaultingduringthelateVariscan(.--300 Lineament at the surface.
|
||
|
|
|
||
|
|
Ma) andCretaceou(s.--130-65Maf)ollowedby normalfaulting Fission track studies on apatite, zircon and sphene,in
|
||
|
|
|
||
|
|
duringthe Neogene(<22 Ma). The mostwidespreadbrittle combination with investigations of the Permo-Mesozoic
|
||
|
|
|
||
|
|
elementsin bothboreholesare graphite-bearinlagte Variscan sedimentaryrecordin the westernforelandof the ZEV, provide
|
||
|
|
|
||
|
|
reversefaults.They occurpreferentiallyin paragneisseasnd a detailed picture of the uplift and cooling history of this
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
EMMERMANN AND LAUTERJUNG: KTB DEEP DRILL HOLE
|
||
|
|
|
||
|
|
18,189
|
||
|
|
|
||
|
|
basementblock and indicatethat a rock pile of about 15 km has gaseousinclusionswith admixturesof CH4 and N•, and often
|
||
|
|
|
||
|
|
beenerodedsincetheintrusionof the granites.Major phasesof containinggraphite,formedin connectionwith the late Variscan
|
||
|
|
|
||
|
|
uplift and denudationoccurredduring the late Carboniferous cataclasticdeformation (-300 Ma) and are associatedwith the
|
||
|
|
|
||
|
|
and Permian(> 4000 m), lower Triassic(>1500 m), and during graphite-containinsghearzones.
|
||
|
|
|
||
|
|
the Cretaceous(> 3000 m). All are connectedto prominent 'I-'hedominanttype of fluid inclusionsare highly ........
|
||
|
|
|
||
|
|
stagesof crustalshortening.
|
||
|
|
|
||
|
|
Na(e K, Mg)-CI aqueoussolutionswhoseabundancea, swell as
|
||
|
|
|
||
|
|
A highly unexpectedresult, confirmedby a numberof salinity(upto48 wt % NaCI-CaC•I.•) andCa-contenint,crease
|
||
|
|
|
||
|
|
independenotbservationsis, thelackof anyP-T gradientsdown significantlywith depth. These inclusionsrepresenta young
|
||
|
|
|
||
|
|
to at least8000 m and the uniformityof radiometricages.This (<60 Ma) fluid systemthat probablyinfiltrated in connection
|
||
|
|
|
||
|
|
finding,togetherwith the enormousamountof post-Variscanwith theCretaceousphaseof uplift andfaulting. Subrecentfluid
|
||
|
|
|
||
|
|
uplift andcrustalthickeningr,equiresa processof thrustingand activity is reflectedin low salinity Ca-Na-CI inclusionsonly
|
||
|
|
|
||
|
|
stacking.Henceit appearsthat the superdeephole penetrateda foundin the uppersectionof theborehole.
|
||
|
|
|
||
|
|
pile of steeply inclined thrust slices with the Franconian Secondarymineralsdepositedin faults, veins, and veinlets
|
||
|
|
|
||
|
|
Lineament acting as the frontal ramp. Furthermore,the data documentfluid activity relatedto the brittle deformationof the
|
||
|
|
|
||
|
|
suggestthat the slices were detachedfrom a decollement basementT. heir chemicalcompositionand paragenesems irror
|
||
|
|
|
||
|
|
horizoncoincidingwith the Mesozoicbrittle-ductiletransition the evolution of the respectivehydrothermalsystemsand
|
||
|
|
|
||
|
|
zone.
|
||
|
|
|
||
|
|
constrainthe PT conditionsof eachmajor deformationstage.A
|
||
|
|
|
||
|
|
The geologicstartingmodelprovedto be inaccuratea, ndthe sequencewith decreasingagecanbe establishedfrom actinolite
|
||
|
|
|
||
|
|
newinsightsfrom theKTB resultswill havea strongimpacton throughclinozoisite,epidoteand prehniteto laumontitewhich
|
||
|
|
|
||
|
|
ongoingdiscussionsof the structureand geodynamicsof the reflectsa decreasein temperaturefrom about350øC to 160øC
|
||
|
|
|
||
|
|
CentralEuropeanbasementI.t appearsthattheZEV, becauseof (for laumontite).
|
||
|
|
|
||
|
|
its high-levelcrustalpositionsinceDevoniantimes,has been The ZEV rockscontaina surprisinglylarge amountof free
|
||
|
|
|
||
|
|
shieldedfrom theCarboniferousdeformationandhighheatflow fluids,eitherin the form of hydrocarbon-ric"hdry"gasesor as
|
||
|
|
|
||
|
|
event and thereby preserved important structural and formationwaters.Dry gaseswere only detectedin the gaslogs
|
||
|
|
|
||
|
|
evolutionaryinformationonthepreVariscanandearlyVariscan and couldnot be sampleddirectly.They mainlyconsistof
|
||
|
|
|
||
|
|
history.This historyis characterizebdy a doubleP-T loop,with methane with minor helium and radon and are invariably
|
||
|
|
|
||
|
|
a first, high-pressurleoop as early as Lower Ordovicianand a associatedwith graphitizedfaults. Formationwaterswere first
|
||
|
|
|
||
|
|
secondB, arrovian-typeloopin theDevonianT. he integrationof encounteredat 400 m depth, and they occur very commonly
|
||
|
|
|
||
|
|
these findings into the general geodynamic puzzle of from 3200 m downto thefinal depthin numerousdistinctzones
|
||
|
|
|
||
|
|
reconstructingthe Variscanconsolidationof centralEuropeis of upto severaltensof metersin verticalthicknessB. elow2000
|
||
|
|
|
||
|
|
still a matter for further work. Likewise unexpecteda, nd of m the first salinepeakswere detected,and at 3200 m the first
|
||
|
|
|
||
|
|
considerableconsequencewith respect to geologic models openfissuresand porousalterationzonescontaininghighly
|
||
|
|
|
||
|
|
basedonsurfacemapping,is theintensebrittledeformationand salinefluidswerepenetratedS.ignificanftluidinflow(upto 30
|
||
|
|
|
||
|
|
theenormousamountof thrustfaultingwhichhithertohadbeen m•)occurreadtvarioudsepthlevelsassociatwedithmajofrault
|
||
|
|
|
||
|
|
regardedas impossiblefor an "anorogenic"intraplatesetting, zonesor were stimulatedby draw downtests[Huengeset al.,
|
||
|
|
|
||
|
|
about200 km northof theAlps.
|
||
|
|
|
||
|
|
this issue].
|
||
|
|
|
||
|
|
The most promisingfluid-containingsectionswere studied
|
||
|
|
|
||
|
|
Paleofluids and Recent Fluids
|
||
|
|
|
||
|
|
by in situfluid sampling'andencouragebdy a first successful pumpingtestin the pilot hole,a secondl,ong-termpumping
|
||
|
|
|
||
|
|
Fluidsin the Earth'scrustform oneof the mostimportant experimen(tfromAugustuntilDecember,1991)wasconducted
|
||
|
|
|
||
|
|
topicsof contemporargyeosciencea,ndthe superdeepdrill hole in theopen-holesectionof theKTB-VB.460 m3of brineswith
|
||
|
|
|
||
|
|
offersmanynew andsurprisinginsightsinto fluid processeisn about70 g/L TDS and270 m3 of gaseswerepumpedto the
|
||
|
|
|
||
|
|
the past and at present.One of the surprisesfor interpreting surface and continuouslyanalyzed (the "4000 m fluid").
|
||
|
|
|
||
|
|
metamorphicrocksis that,despitethepolymetamorphihcistory Simultaneousmonitoringof the KTB-HB showedthat fluids of
|
||
|
|
|
||
|
|
of the various metamorphicunits and the strongDevonian thetwo boreholescommunicatedthrougha networkof fractures
|
||
|
|
|
||
|
|
medium-pressureoverprint, the primary oxygen and sulfur whichconnectedtheopen-holesectionof thepilotholewiththe
|
||
|
|
|
||
|
|
isotopicpatternsof the protolithshave been preserved.This intervalbetween3000m and6000m of thesuperdeehpole.
|
||
|
|
|
||
|
|
implies that metamorphismtook place under nearly closed- The composition of the formation waters changed
|
||
|
|
|
||
|
|
systemconditionsat low water/rockratios and was not, as has systematicallywith depth,and the followinggeneralvertical
|
||
|
|
|
||
|
|
oftenbeenpostulateda,ccompaniebdy pervasivefluid flow.
|
||
|
|
|
||
|
|
sequencewas established:(1) an upper zone of normal
|
||
|
|
|
||
|
|
The inventory of paleofluids from the ZEV rocks groundwaterextending down to at least 650 m, (2) an
|
||
|
|
|
||
|
|
encompassegsasesandaqueoussolutionstrappedin nanogram intermediatezone of low-salinity,NaCl-dominatedformation
|
||
|
|
|
||
|
|
quantitiesas fluid inclusionsmainly in quartz [MOller et al., watersdownto about3200m, and(3) ,moderatetloyhighly
|
||
|
|
this issue].Severalgenerationsand typesof inclusionscan be salineCa-Na-C1basemenbt rineswitha pronounceidncreasein
|
||
|
|
|
||
|
|
distinguisheadndrelatedto distinctgeodynamipcrocessesT.he salinityandCacontenwt ithdepth.Type2 probablyrepresentas
|
||
|
|
|
||
|
|
oldestfluid generationpreservedprobablyrepresentsgaseous formationwaterwhichis evolvinginto type 3 by water/rock
|
||
|
|
|
||
|
|
remnantsfrom the Devonian metamorphismand consistsof interaction.
|
||
|
|
|
||
|
|
water-freeN2-bearinginclusions(with CH,•or CO2)whichhave Table2 summarizetshemajoranalyticaldataof the"4000m
|
||
|
|
|
||
|
|
the highestdensities(about750 kg/m3).Moderatelysaline fluid"(representativoef types)which,at atmospheripcressure,
|
||
|
|
|
||
|
|
NaC1-KCI-MgCaIq2ueouisnclusion(4s-8wt % NaCI•.),which releasedabout0.8 L/L gasesthai weredissolvedunderin-situ
|
||
|
|
|
||
|
|
areconspicuouselynrichedin theuppersectionof theborehole conditionsT.he gasphaseconsistsof 67.0%N2, 31.6%CH4,
|
||
|
|
|
||
|
|
(above4500 m), representa fluid systemthat accompaniedthe 0.52% He, 0.14% At, and0.04% CO2.Chemicaal ndisotopic
|
||
|
|
|
||
|
|
lateCarboniferougsraniticintrusion(s-330 Ma). CO•-dominant datashowthat nitrogenand methanewerederivedby thermal
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
18,190
|
||
|
|
|
||
|
|
EMMERMANN AND LAUTERJUNG:KTB DEEPDRILL HOLE
|
||
|
|
|
||
|
|
Table 2. The "4000 m Fluid"
|
||
|
|
|
||
|
|
Brine Data
|
||
|
|
|
||
|
|
Element
|
||
|
|
Na K
|
||
|
|
Li
|
||
|
|
Ca
|
||
|
|
Mg
|
||
|
|
Sr Ba
|
||
|
|
Mn Zn
|
||
|
|
Cu
|
||
|
|
|
||
|
|
mg/L
|
||
|
|
7160 231
|
||
|
|
2.4
|
||
|
|
15700
|
||
|
|
2.2
|
||
|
|
244 1.5
|
||
|
|
0.13 0.01
|
||
|
|
0.02
|
||
|
|
|
||
|
|
s7Sr/•6Sr 0.7095
|
||
|
|
|
||
|
|
•SO
|
||
|
|
|
||
|
|
-5%o
|
||
|
|
|
||
|
|
•D
|
||
|
|
|
||
|
|
- 10%o
|
||
|
|
|
||
|
|
Ele•nent
|
||
|
|
|
||
|
|
•ng/L
|
||
|
|
|
||
|
|
AI Fe
|
||
|
|
SiO2
|
||
|
|
CI
|
||
|
|
Br
|
||
|
|
F
|
||
|
|
SO4 PO4 HCO,
|
||
|
|
TDS
|
||
|
|
pH Eh
|
||
|
|
|
||
|
|
<0.015 0.3
|
||
|
|
54.0
|
||
|
|
44100
|
||
|
|
417
|
||
|
|
3.8
|
||
|
|
307 0.5 45
|
||
|
|
68260
|
||
|
|
8.3(in-situ5.3-5.8) -150 (mY)
|
||
|
|
|
||
|
|
Gas Data
|
||
|
|
Element
|
||
|
|
N, CH,
|
||
|
|
He Ar
|
||
|
|
CO,
|
||
|
|
|
||
|
|
vol %
|
||
|
|
67.0 31.6
|
||
|
|
0.52 0.14
|
||
|
|
0.04
|
||
|
|
|
||
|
|
•N 3Herlie
|
||
|
|
|
||
|
|
+0.30,60 6x 10'6
|
||
|
|
|
||
|
|
decompositioonf organicmaterialof a marinesedimentary 10'• m2,whichareseveroarl derosfmagnituhdieghetrhanthe
|
||
|
|
|
||
|
|
source(paragneissprotoliths).The He.isotopicsignatureis matrixpermeabilitoiefstherockassmeasureindthelaboratory
|
||
|
|
|
||
|
|
dominatedby radiogeniccrustalhelium, with lessthan 3% of undersimulateidn situcondition[sHuengeestal., thisissue].
|
||
|
|
|
||
|
|
mantle component which probably originates from the Theformatiopnressurdeseterminefodrthebrine-containing
|
||
|
|
|
||
|
|
metabasicrocks[M6ller et al., thisissue].
|
||
|
|
|
||
|
|
zonesat differentintervalsshowa progressiviencreasewith
|
||
|
|
|
||
|
|
The chemical compositionof the 4000 m fluid, and depthto a maximumvalue of 105 MPa for the fluids at 9 km.
|
||
|
|
|
||
|
|
especiallyits Ca dominanceh, igh Sr contentand Br/C1ratio Thegradienot f meanformationpressuries about11 MPa/km
|
||
|
|
resemblesthatof otherbasemenbt rines (e.g.,in theCanadian andis nonlinear,probablybecausoef a stepwisiencreasien shield,[seeFrape and Fritz, 1982]). Variouslinesof evidence salinitywithdepthI.nflowbehaviodruringthetestsandother
|
||
|
|
suggesthat this brine wasoriginallyrich in NaC1andthat its evidenciendicatetshatthebrine-containiznognesrepresenat highcontentsof Ca andSr werederivedfromexchangewith hydraulicallyopen systemwhich is under hydrostatic
|
||
|
|
wallrockfeldsparsat 250øC-300øCT. here are no indicationsof conditions.
|
||
|
|
|
||
|
|
contaminationby recentmeteoricwaters.
|
||
|
|
|
||
|
|
Application of several independent chemical
|
||
|
|
|
||
|
|
geothermometers suggests that the 4000 m brine has GeophysicalStructuresand Phenomena
|
||
|
|
|
||
|
|
experienceda temperatureof about 160øC (equilibrium
|
||
|
|
|
||
|
|
temperature)a, lthoughits in situ temperatureis only 119øC. Crustalseismicstructure.Calibrationof crustalseismic This fluid probablycame from a deeperlevel (-5500 m, structureandunderstandinogf thenatureof reflectorswasone
|
||
|
|
correspondingto 160øC) and was "pumped"by tectonic oftheforemoosbt jectivoesftheKTBprogramTo. achievtehis, processeisntoitspresenpt ositionA. ltogethert,heexistingdata a combinatioonfdifferengteophysiceaxlperimenwtsascarried supportthe contentionof M6ller et al. [this issue] that the outto definethepositionandspatiadl istributioonf reflective precursorfluids of this brine were ultimately derived from elemenatsndtounravethl eirmessabgyedirectlpyrobintgheir (evaporitic)Permo-Mesozoicsedimentsin the westernforeland petrophysiccaolm, positioannadlstructurparlopertieWs.iththis of the ZEV and migratedinto their presentpositionin informationa,ndby comparintghe observeadndmodeled
|
||
|
|
|
||
|
|
connectionwith Cretaceousuplift and deformationby dynamicwavefield,constrainotsnthedecisivelementosf the
|
||
|
|
|
||
|
|
infiltration along the deep reachingfault systemsof the seismicresponsefunctionwerederived.
|
||
|
|
|
||
|
|
Franconian Lineament.
|
||
|
|
|
||
|
|
The KTB drill hole was sitedat the intersectionof two
|
||
|
|
|
||
|
|
Information on in situ permeabilitiesand hydraulic seismipcrofilesD, EKORP-a4ndKTB8502,wherepresite
|
||
|
|
propertiesof the basement,which are critically neededfor investigationhsadindicateadnumbeor f reflectorastaccessible
|
||
|
|
|
||
|
|
understandingand modelinghydrodynamicprocessesc,ome depths[Harjeset al., thisissue].To obtaina moredetailed
|
||
|
|
|
||
|
|
from a number of borehole experiments.These include seismicimageof the KTB surroundinags3-D seismic drawdownd, rill stemandinjectiontestsconductedat different experime(nIStO89w) asconductiend1989c, overinagnareaof depthlevelsand two very successfukley experimentsa: drill 19x 19kmcentereodnthedrillsite[Harjesetal.,thisissue]. stem test and a combined fluid injection and hydraulic Analysiosf theresultsfromtheISO89experimenletdto an experimenct,arriedoutin theopen-holbeottomsectionof the interpretivgeeologic-tectonmicodelof the crust,a cross superdeepborehole.The resultsobtainedrevealthe existenceof sections, hownin Figure5. Westof the ZEV blockseismic
|
||
|
|
a numberof distinct,hydraulicallyconnectedzonesthat are imagesreflectstructureosf theforelandsedimentasn, dwithin relatedto majorfaultsystemsandextenddowntoat least9 km. thebasementwt,omaingrouposf reflectoarsrepresenOt.ne In situpermeabilitiewsithinthesezonesarebetween10'•7m2and groupis planars, teeplyinclined(steepelementsS,E), and
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
sw
|
||
|
|
|
||
|
|
EMMERMANN AND LAUTERJUNG: KTB DEEP DRILL HOLE
|
||
|
|
|
||
|
|
18,191
|
||
|
|
|
||
|
|
8
|
||
|
|
|
||
|
|
o
|
||
|
|
|
||
|
|
KI'B
|
||
|
|
|
||
|
|
o
|
||
|
|
|
||
|
|
eeeeeeeeeeeeeeee %eeeeeeeeeeeeee
|
||
|
|
|
||
|
|
e:© ß ©©ee
|
||
|
|
|
||
|
|
ß
|
||
|
|
|
||
|
|
ß
|
||
|
|
|
||
|
|
eeee©eeeee
|
||
|
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|
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|
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eeeeeeeeeeeeeeeeee
|
||
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|
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|
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eeeeeeeeeeeeeeeee©e
|
||
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|
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ß
|
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|
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|
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|
|
ß
|
||
|
|
|
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|
|
eeeeeeeeee
|
||
|
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|
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|
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eeeeeee
|
||
|
|
|
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|
|
eee
|
||
|
|
|
||
|
|
ß
|
||
|
|
|
||
|
|
.I
|
||
|
|
|
||
|
|
15
|
||
|
|
km Figure 5. Interpretationof the seismicprofile KTB 8502. Reflectingelementscanbe dividedinto two groups: steeplyinclinedreflectors(SE1-SE4)andsubhorizontarleflectors(B, G, andR) The darklyshadedzonebounded by thesubhorizontarleflectorsis the"Erbendorbf ody."
|
||
|
|
|
||
|
|
extendsdownto about10 km. The secondgroupof reflectorsis seismograms.Comparison of these with the measured
|
||
|
|
|
||
|
|
subhorizontalandis "bundled"in thedepthinterval>8.5 to 12 seismogramsshowsa fairly goodagreementO. n theotherhand,
|
||
|
|
|
||
|
|
'km. This latter groupmarksa zoneof high seismicreflectivity syntheticseismogramscalculatedusing seismicimpedance
|
||
|
|
|
||
|
|
which,basedon wide-anglereflectionseismicsi,s immediately valuesderivedfrom compositionadlatameasuredon cuttingsin
|
||
|
|
|
||
|
|
underlaibnya high-velociztyone(V•> 7 km/s)T. hisprominent the field laboratoryyielded only very small amplitudes.This
|
||
|
|
|
||
|
|
mid crustal phenomenon, which combines high seismic resultprovesthat the seismicreflectivityof the SEI is not due
|
||
|
|
|
||
|
|
reflectivity and high P wave velocity, is called the Erbendorf to lithologiccontrastbut is mainly causedby the effectsof
|
||
|
|
|
||
|
|
body(darkshadingonFigure5).
|
||
|
|
|
||
|
|
cataclastic deformation.
|
||
|
|
|
||
|
|
Most of the steeplyinclined reflectorscan be tracedto the Altogether,the geophysicarlesultscombinedwith "ground
|
||
|
|
|
||
|
|
surfaceandrelatedto known major fault systemsT. he strongest truth" from the boreholehave shownthat steep-angleseismic
|
||
|
|
|
||
|
|
of these reflectors is the so-called SE1 reflector, which strikes reflectionprofiling, at least in this basementregion, mainly
|
||
|
|
|
||
|
|
SE-NW and dips 55ø to the NE, has a considerablelateral depictsthe effects of brittle faulting and imagesthe young
|
||
|
|
|
||
|
|
extent, and crosscutsall lithologic boundaries.It can be deformationpattern of the upper crust. Faulting is also
|
||
|
|
|
||
|
|
correlateddirectly to the FranconianLineamentat the surface obviouslyresponsiblefor a 2-3 km verticaldisplacemenotf the
|
||
|
|
|
||
|
|
andclearlyrepresentsits depthcontinuationT. he SE1 reflector subhorizontalreflectors belonging to the Erbendorf body
|
||
|
|
|
||
|
|
was predictedto 'occur between6600 and 7100 m in the (Figure 5). This body may well be a metabasicrelict of a
|
||
|
|
|
||
|
|
borehole,and in fact, the most prominentcataclasticfault paleosubductionzone, or a sliver of dense rock emplaced
|
||
|
|
|
||
|
|
bundleof the KTB, consistingof at least four major fault tectonicallyduringthe Variscancollision.It is thereforea key
|
||
|
|
|
||
|
|
planesw, asdrilledin thedepthintervalbetween6850and7260 elementin the geodynamicinterpretationof theentirebasement
|
||
|
|
|
||
|
|
m. Calculationssuggesthatthecontrastof seismicimpedance region,butmoreinterpretivework,andperhapsevenadditional
|
||
|
|
|
||
|
|
betweenthe wallrocksand the permeable,fluid-bearing,and experimentsw, ill beneededto understandfully its nature.
|
||
|
|
|
||
|
|
mineralizedfaultzonecanproducetheobservedreflectivity.
|
||
|
|
|
||
|
|
In thecourseof theinterpretivwe orksummarizeadbovet•he
|
||
|
|
|
||
|
|
On thebasisof thesefindings,a'specialseismicexperiment KTB seismic group developeda promising new processing
|
||
|
|
|
||
|
|
was designed whose major goal was to quantitatively methodof true-amplitude,prestackmigrationwhichrepresents understansdeismicreflectorsin the crystallinebasementan importantgeneraladvancein seismicdataprocessingT. his
|
||
|
|
|
||
|
|
[Harjes et al., this issue].The spatial orientationof the methodis basedon a generaldiffractionconceptinsteadof a
|
||
|
|
|
||
|
|
reflectingelementSE1wasdefinedaspreciselyaspossiblea, nd reflectionconceptandprovidesa quantitativeandgeometrically
|
||
|
|
|
||
|
|
thegeometryof theseismicexperimenwt asoptimizedin order correctreconstructioonf thereflectivitydistributionwith depth.
|
||
|
|
|
||
|
|
to achievemaximumresolutionT. hentheseismicimpedanceof Plate 3 showsa sectionof the KTB 8502 profile which was
|
||
|
|
|
||
|
|
the rock section between 6500 and 7500 m was calculated from reprocessewdith thismethod.Comparisonwith Figure5 shows
|
||
|
|
|
||
|
|
borehole measurementsand transformed into synthetic theinterpretivepowerof thenew method.
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
18,192
|
||
|
|
|
||
|
|
EMMERMANN AND LAUTERJUNG:KTB DEEPDRILL HOLE
|
||
|
|
|
||
|
|
Geoelectrics. In the last decade many electromagnetic favorablefreeenergyvalueat therelevantemperature3: CH4q'
|
||
|
|
|
||
|
|
surveysof continentalbasementregionshave revealeddeep- 2FeS+ 2H•SO4 • 3Cq'2FeS:+8H20.
|
||
|
|
|
||
|
|
seatedzonesof highelectricalconductivitywhosenatureis still In summaryt,heresultsobtainedoncoremateriaal ndfrom
|
||
|
|
|
||
|
|
enigmatic.Suggestedcausesof thesefeaturesare the presence various borehole measurements indicate that the basement
|
||
|
|
|
||
|
|
of saline fluids, interconnectedfilms of graphite or sulfide sectiond, espitetheubiquitouosccurrencoef salinebrinesh, as,
|
||
|
|
|
||
|
|
mineralizations,or some combinationof these.The European in generala, relativelyhighelectricresistivitwy hichincreases GeotraverseProject (EGT) proved the existenceand large downwardfrom 103k• m at surfaceto 10•k•m at 9 km depth.
|
||
|
|
|
||
|
|
extent of such layers at midcrustal levels in the central Intermediatediscretezonesof low to very low resistivity(1 to
|
||
|
|
|
||
|
|
EuropeanVariscancrust [ERCEUGTGroup, 1992], and they 100 k• m) are in most casesclearly relatedto graphite-
|
||
|
|
|
||
|
|
were also foundduringKTB site selectionstudiesin both the containingshear zones. Graphite (__+sulfidesth)erefore
|
||
|
|
|
||
|
|
SchwarzwaldandOberpfalzregions.
|
||
|
|
|
||
|
|
determinestheelectricalbehaviorof thiscrustalsegment,andit
|
||
|
|
|
||
|
|
Magnetotelluric surveys and long-period magnetic field appeartshatgeoelectricmalethodcsanimagetectonicprocesses
|
||
|
|
|
||
|
|
variations indicated a zone of high electrical conductivity andcanbe usedto tracepaleoshearzones.
|
||
|
|
|
||
|
|
underlyingthe KTB drill site at about 10 km, which has a Gravimetry and Magnetics.The KTB superdeebporehole
|
||
|
|
|
||
|
|
pronouncedanisotropywith maximumconductivityvaluesin wassitedona strongmagnetiacnomalyandgravityhigh,andit
|
||
|
|
|
||
|
|
theN-S direction.After completionof thesuperdeepboreholea, was expected that borehole geophysicsand laboratory
|
||
|
|
|
||
|
|
large-scaledipole-dipoleexperiment(Plate 4), the first of its measuremenotsf rocksamplesobtainedduringdrillingwould
|
||
|
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|
||
|
|
kind, wascarriedoutto investigatetheextentandpropertiesof give importantnew insightsinto interpretationof such
|
||
|
|
|
||
|
|
this high-conductivityzone [ELEKTB group, this issue],The anomaliesP. late5 showsa new,high-resolutio3n-D gravity
|
||
|
|
|
||
|
|
resultconfirmedthe expectationthat the boreholereachedthis map of the KTB surroundingswhich portrays the density
|
||
|
|
|
||
|
|
zoneandthat the electrodeat 9065 m depthwasindeedlocated distributionT. he pronouncedgravitylow in theNE corresponds
|
||
|
|
|
||
|
|
within a layer of highconductivityT. he positionof thislayerat to the Falkenberggranite,and the strongpositiveanomaliesat
|
||
|
|
|
||
|
|
9 kin roughlycoincideswith the postulatedbasaldetachment the KTB site are due to metabasicbodies.However,despitea
|
||
|
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|
||
|
|
horizon which is related to the post-Variscancrustal thrust relativelylargedensitycontrasbt etweenthemajorrocktypesof
|
||
|
|
|
||
|
|
stack.
|
||
|
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|
||
|
|
the ZEV (paragneisse2s740 kg/m3 and metabasite2s890
|
||
|
|
|
||
|
|
Extensivesufacemeasurementswith a variety of electrical kg/m3)t,heirsteepdips,interlayerinagndcomplexstructure
|
||
|
|
|
||
|
|
methodscarriedout in the KTB surroundingsduringthe presite make lithologic interpretationof the gravity pattern very
|
||
|
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|
||
|
|
surveyandthepilot phaserevealedtheexistenceof shallowlow difficult. A partialsolutionto thisproblemcanbe achievedby a
|
||
|
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|
||
|
|
electricalresistivityanomaliesandconfirmedthat the drill site combinationof gravity data with results of geomagnetics
|
||
|
|
|
||
|
|
wascloseto thecentreof an unusuallylargesurfaceanomalyof [Bosumet al., this issue].
|
||
|
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|
||
|
|
the electric self-potential(about-600 mV) extendingNW-SE. The magnetic data give independentinformation about
|
||
|
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|
||
|
|
That is, the drill site is situated on a "geobattery"which lithology (inventoryof ferri-magneticminerals)and can also
|
||
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|
||
|
|
probablydrawsits energyfrom redox potentialdifferencesin portray tectonicfeatures,like mineralizedshear zones. The
|
||
|
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|
||
|
|
the subsurface,with graphite-coatedcataclasticshear zones KTB superdeephole penetratedmany magnetic anomalies,
|
||
|
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|
||
|
|
actingas electronconductingbridges.The modelpresentedby which have a vertical extent of some meters up to about
|
||
|
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|
||
|
|
Stoll et al., [1995] providesa generalexplanationof the nature hundredmeters.One of the mostimportantof theseanomalies,
|
||
|
|
|
||
|
|
and source of the observed anomalous electric fields. It is with a strongdecreaseof the magneticfield intensity, occurs
|
||
|
|
|
||
|
|
supportedby downholemeasurementsof the self-potentialand nearthe surface.Below about1200 m the total magneticfield
|
||
|
|
|
||
|
|
the redoxpotentialobtainedfrom speciallydevelopedlogging intensityincreasessystematicallywith depthwith a gradientof
|
||
|
|
|
||
|
|
tools.
|
||
|
|
|
||
|
|
up to 200 nT/km, which is muchhigherthan the undisturbed
|
||
|
|
|
||
|
|
Hence it appearsthat graphiteis of specialimportancein Earth'smagneticfield would produce(about22 nT/km). This
|
||
|
|
|
||
|
|
producingthe observedgeoelectricphenomena.Among the result requiresa magneticbody at depth, the exact nature of
|
||
|
|
|
||
|
|
ZEV rocks, the paragneissescontainprimary graphitewhose which, however, remains unknown.Unfortunately,the deep
|
||
|
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|
||
|
|
crystallinityindicatestemperaturesof about700øC, in accord section of the superdeep hole was cased before a high-
|
||
|
|
|
||
|
|
with the temperaturesof peak metamorphismT. his graphite temperature modification of the magnetometer tool was
|
||
|
|
|
||
|
|
representsoriginal organic material in the protolithsand is developed.Thereforethe intervalbetween6000 m and 8600 m
|
||
|
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|
||
|
|
finely dispersedso that it does not contributeto the overall wasonly measuredby a SchlumbergeGr PIT inclinometertool,
|
||
|
|
|
||
|
|
electrical conductivity. More important for electrical whose resolution is about 100 times poorer than the
|
||
|
|
|
||
|
|
conductivityis the secondarygraphite,which is ubiquitousin magnetometertool. Nevertheless, the deep magnetic data
|
||
|
|
|
||
|
|
cataclasticshearzones,whereit is always associatedwith iron obtainedwith this tool documentthat the strongestmagnetic
|
||
|
|
|
||
|
|
sulfides and ohiorite. This graphite often forms a quasi- anomalyencounteredin the boreholeoccursbetween7300 m continuous coating along shear planes and is locally and 7900 m.
|
||
|
|
|
||
|
|
concentratedin millimeter-thick layers which constitutegood Surprisingly,pyrrhotiteturnedout to be the main carrier of
|
||
|
|
|
||
|
|
electrical conductors over hundreds of meters.
|
||
|
|
|
||
|
|
rock magnetismin the drilled sequenceand is responsiblefor
|
||
|
|
|
||
|
|
All the evidencesuggeststhat thisgraphitewasprecipitated mostof the observeddownholemagneticanomalies.Magnetite
|
||
|
|
|
||
|
|
from hydrocarbon-bearinfgluidsat about400øCand2 kbar. A plays only a very subordinaterole and is restrictedto a few
|
||
|
|
|
||
|
|
possiblemodeof formationis describedby the reactionCHn+ distinctintervals.It is particularlyenrichedin somepartsof the
|
||
|
|
|
||
|
|
CO2 • 2C + 2H20. This reactionrequiresa relativelyhigh variegatedseries(marbleandcalcsilicate-bearinagmphibolites)
|
||
|
|
|
||
|
|
activation energy, which could be providedby mechanical, between7320 and 7800 m, where it producesthe magnetic
|
||
|
|
|
||
|
|
tribochemical effects in connection with brittle deformation. anomaly mentioned above, which is about 2 orders of
|
||
|
|
|
||
|
|
Alternatively, since graphiteis intimately associatedwith Fe magnitudehigherthananyof thosegeneratedby pyrrhotite.
|
||
|
|
|
||
|
|
sulfides,a reactioninvolvingmethaneandsulfatein the system The pyrrhotitecontentin paragneisseasndmetabasicrocksis
|
||
|
|
|
||
|
|
C-O-H-Fe-S could also be considered, which has a lower, more very similar and mostly below 1 wt %. Enrichmentsup to
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
18,193
|
||
|
|
|
||
|
|
EMMERMANN AND LAUTERJUNG:KTB DEEPDRILL HOLE
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
18,194
|
||
|
|
|
||
|
|
EMMERMANN AND LAUTERJUNG: KTB DEEP DRILL HOLE
|
||
|
|
v
|
||
|
|
r n ¾I
|
||
|
|
|
||
|
|
Plate 4. Schematicsetupof the dipole-dipoleexperimentcarriedout at the final depthof 9101 m. Electric currentwasinjectedat variabledistancesfrom the drill site on two perpendiculapr rofiles.The electricalfield wasmeasuredby two probesat thebottonsof thesuperdeepholeandthepilot hole.The first resultsconfirmthat thesuperdeepholepenetratedinto thehigh-conductivitylayerpredictedto lie at 10ñ1km (shadedband).
|
||
|
|
|
||
|
|
KTB
|
||
|
|
0'-.
|
||
|
|
|
||
|
|
-15--o0• -25.
|
||
|
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|
||
|
|
-30. SW
|
||
|
|
-35 -
|
||
|
|
s
|
||
|
|
-40 •
|
||
|
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|
||
|
|
-45 -
|
||
|
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|
||
|
|
-50 -.
|
||
|
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|
||
|
|
448O•
|
||
|
|
4490
|
||
|
|
|
||
|
|
"•
|
||
|
|
|
||
|
|
/ 5540
|
||
|
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|
||
|
|
/ 5530
|
||
|
|
|
||
|
|
4500 •
|
||
|
|
|
||
|
|
/ 5520
|
||
|
|
|
||
|
|
/•i/ot4o5e14t•52e00 r•e/•/ sso5o 510
|
||
|
|
|
||
|
|
453O
|
||
|
|
|
||
|
|
549O
|
||
|
|
|
||
|
|
Plate5. Three-dimensiongaral vitymapof theKTB surroundingssh,owingthegravityhighat thedrill site causedby metabasiteosf theZEV, andthepronouncegdravitylowsrelatedto theFalkenbergranite(F) to the
|
||
|
|
NE andtheforelandsediments(S) to the SW:
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
EMMERMANNANDLAUTERJUNGK: TBDEEPDRILLHOLE
|
||
|
|
|
||
|
|
18,195
|
||
|
|
|
||
|
|
iii
|
||
|
|
|
||
|
|
ml i
|
||
|
|
|
||
|
|
i i
|
||
|
|
|
||
|
|
iii
|
||
|
|
|
||
|
|
i i
|
||
|
|
|
||
|
|
i
|
||
|
|
|
||
|
|
Dme)•o0t.h............T...emperat.u..r.e..3..0..0...
|
||
|
|
|
||
|
|
•:.'. •
|
||
|
|
|
||
|
|
....
|
||
|
|
|
||
|
|
o
|
||
|
|
|
||
|
|
•.' •
|
||
|
|
|
||
|
|
2000
|
||
|
|
|
||
|
|
--'-'-,•,
|
||
|
|
|
||
|
|
..............
|
||
|
|
|
||
|
|
:'•.\..••.•. _ • . ,
|
||
|
|
|
||
|
|
4000
|
||
|
|
..
|
||
|
|
|
||
|
|
....... !
|
||
|
|
|
||
|
|
!
|
||
|
|
|
||
|
|
'' '• • '-"'" ••',t•'•
|
||
|
|
|
||
|
|
.....
|
||
|
|
|
||
|
|
•___'._'._ k ',. •......•........
|
||
|
|
|
||
|
|
'. '. '. 'k',-- T(Gradti2e8nfWkm)
|
||
|
|
|
||
|
|
6000 .,. . ....,.. .., . . .•
|
||
|
|
|
||
|
|
..
|
||
|
|
|
||
|
|
. ., T•mperal:u•e•redi
|
||
|
|
|
||
|
|
, ,
|
||
|
|
|
||
|
|
(cacOlated19•6) , _
|
||
|
|
|
||
|
|
" •'
|
||
|
|
|
||
|
|
•1, • lit••u,•nt
|
||
|
|
|
||
|
|
• ß ; %•
|
||
|
|
|
||
|
|
&/• II
|
||
|
|
|
||
|
|
8000 ................
|
||
|
|
|
||
|
|
• '. "
|
||
|
|
|
||
|
|
---
|
||
|
|
|
||
|
|
•
|
||
|
|
|
||
|
|
ß
|
||
|
|
|
||
|
|
•
|
||
|
|
|
||
|
|
,
|
||
|
|
|
||
|
|
ß
|
||
|
|
|
||
|
|
• Finacl repht9'101m • '. •....m,..•
|
||
|
|
|
||
|
|
'
|
||
|
|
|
||
|
|
•.measu4r8•dhafter
|
||
|
|
|
||
|
|
.....
|
||
|
|
|
||
|
|
•th. elast:gir•:u•...•.ati•
|
||
|
|
|
||
|
|
10000 .........
|
||
|
|
|
||
|
|
• '. '.,..
|
||
|
|
|
||
|
|
Plate 6. Diagramshowingthe predictedandmeasuredtemperatureast depthin the KTB site.The curves outlinedin yellowshowthepredictedthermagl radienftrompresitestudies(with lo and20 envelopesT).his predictiotnurnedouttobemuchtoolow.Thebluelinefromsurfacteo4000m showsthemeasuretdemperature profilein thepilothole.Bottomholetemperature(BsHT)atdifferenst tageosf drillingthesuperdeehpoleare shownbyredsquareasndthesecorrespontdo a constangtradienotf 28 K/km.The temperaturaet finaldepth (red dot) was measured48 hoursafter drilling ceasedT. he red shadedfield showsthe temperatureprofile
|
||
|
|
predictedfrom the6000 m BHT andbasedon 31 K/km and28 K/kin.
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
18,196
|
||
|
|
|
||
|
|
EMMERMANNAND LAUTERJUNG:KTB DEEPDRILL HOLE
|
||
|
|
|
||
|
|
severalweight percentare typical for hornblendegneissesand wasalsodesignedw, hichprovideda wealthof newinformation
|
||
|
|
|
||
|
|
all major shear zones. Since it was known from laboratory aboutthe thermalstructureof the drilledsegmenat ndled to
|
||
|
|
|
||
|
|
experiments that pyrrhotite occurs in at least two low- improved methodsof handling downholetemperature
|
||
|
|
|
||
|
|
temperaturepolymorphs, a monoclinic ferrimagnetic and a measurementsT. able 3 presentsa summaryof values for
|
||
|
|
|
||
|
|
hexagonalantiferromagneticmodification,and that the Curie thermalconductivityand heat production.Rock foliationand
|
||
|
|
|
||
|
|
temperatureof this mineral is around 300øC the superdeep microcracksare responsiblefor significantanisotropyin
|
||
|
|
|
||
|
|
borehole offered an ideal opportunity to study the in situ thermalconductivit(yupto 20%), withhighesvt aluesparallel
|
||
|
|
|
||
|
|
magnetomineralogical properties of this hitherto poorly to foliation.The distributionof heatproductionwith depth
|
||
|
|
|
||
|
|
investigatedmineral[Kontnyet al., thisissue].
|
||
|
|
|
||
|
|
reflectslocallithologiesT.he data,in generals, howa slight
|
||
|
|
|
||
|
|
Among the most important results of this study is that decreasbeutdefinitelydo notconfirmthewidelycitedlaw of
|
||
|
|
|
||
|
|
frequently, both monoclinic and hexagonalpyrrhotite occur an exponentiadlecreasoef heatproductionwithdepth(Figure
|
||
|
|
|
||
|
|
together,mostlyin intimateintergrowthsw, ith the monoclinic 6).
|
||
|
|
|
||
|
|
polymorph being dominant in metabasic units. Hexagonal Geothermadlatafromthesuperdeebporeholeareconsistent
|
||
|
|
|
||
|
|
pyrrhotite is the stable phase at higher temperatures(above withtheresultsandpredictionfsromthepilothole.Withinthe
|
||
|
|
|
||
|
|
about 220øC) and it predominates below 8000 m. The upper1500m thetemperaturegradientincreasedfrom 20 K/km
|
||
|
|
|
||
|
|
observations of monoclinic pyrrhotite grains with relict to about 28 K/km at 1500 m and remained at that value down to
|
||
|
|
|
||
|
|
hexagonalcoresindicatelow-temperaturetransformationfrom the final depth.On that basis,the undisturbeedquilibrium
|
||
|
|
|
||
|
|
an originally hexagonal phase during uplift and cooling. temperatureat 9100 m is about265øC.Within uncertaintyt,he
|
||
|
|
|
||
|
|
Accordingto experimentalfindingsthe Curie temperatureof verticalheatflow densityw, hichis theproducot f temperature
|
||
|
|
|
||
|
|
hexagonapl yrrhotitemightbe aslow as260øC.It is well known gradientand vertical thermalconductivityi,s also constant
|
||
|
|
|
||
|
|
from laboratorymeasurementsthat the magneticsusceptibility below 1500 m, with a mean value of around 85 mW/m'.
|
||
|
|
|
||
|
|
increasesstrongly at temperaturesjust below the Curie Estimationof thecontributioonf thecumulativheeatproduction
|
||
|
|
|
||
|
|
temperature(the Hopkinsoneffect), and one of the open rateto theverticalheatflow densityshowsthattheupper6 km
|
||
|
|
|
||
|
|
questionsrelevantto the boreholemagneticstudiesis whether of the penetratedbasemenot nly provideabout10% of the
|
||
|
|
|
||
|
|
the Hopkinsoneffect contributessignificantlyto the observed calculatedheatflowdensityvalueof 85 mW/m'at 1.5km. If
|
||
|
|
|
||
|
|
anomalousdepth gradientin the magneticfield intensity,or this value is typical for the crust, then a shift in the thermal
|
||
|
|
|
||
|
|
whetherthe magnetite-containinlgayer is sufficientto produce gradienttolowervaluesmustoccurwellbelow10kmdepth.
|
||
|
|
|
||
|
|
this phenomenon.
|
||
|
|
|
||
|
|
The results of thermal studies in the two boreholes raise a
|
||
|
|
|
||
|
|
The geopotentialfields, electric, gravity, and magnetic, number of basic questionsabout the heat budgetin the
|
||
|
|
|
||
|
|
provide complementaryinformation. Whereas geoelectrics continentaclrust.Oneof theproblemsis howtoexplainthelow
|
||
|
|
|
||
|
|
mainlyimagetectonicfeaturesandgravityprovideslithological thermalgradientin theuppermost1500m, andhowto reconcile
|
||
|
|
|
||
|
|
information,geomagneticscarry informationaboutboth. The the--25mW/md' eficiitn heatflowdensitbyetweetnheupper
|
||
|
|
|
||
|
|
combined evaluation of data from the three sources, now and lower boreholesectionsT. hree alternativesare currently
|
||
|
|
|
||
|
|
underway, will contribute to a detailed 3-D geologic discussedw, hichmayworkin concert:(1) topography-enhanced
|
||
|
|
|
||
|
|
reconstructionof theKTB surroundings.
|
||
|
|
|
||
|
|
heat advection by groundwater flow; (2) paleoclimatic
|
||
|
|
|
||
|
|
Geothermalstudies.Evaluationof thegeothermadl atafrom perturbationof thesteadystatetemperaturefield dueto changes
|
||
|
|
|
||
|
|
the KTB pilot hole providedthe highly unexpectedresultthat of the meansurfacetemperature(e.g., in connectionwith the
|
||
|
|
|
||
|
|
the thermalgradient(21 K/km) and verticalheat flow density last ice age); and (3) disturbancesof the steady state
|
||
|
|
|
||
|
|
(55mW/m')metthepredictevdaluesonlyintheupper1000m. temperaturefield due to lateral refraction of heat flow in a
|
||
|
|
|
||
|
|
Both parametersthenincreasedrapidly to about 1500 m, after compositionallyandstructurallyvery heterogeneoussubsurface
|
||
|
|
|
||
|
|
which almost constantgradientsof 28 K/km and heat flow [Clauser et al., this issue].
|
||
|
|
|
||
|
|
valuesof 85 mW/m'prevailedT.hetemperatuirne thepilot Modeling of available data prove that both groundwater
|
||
|
|
|
||
|
|
hole at 4000 m was 119øC and lay well above even the upper advectionand paleoclimaticeffects are able to producethe
|
||
|
|
|
||
|
|
error limit calculated from the data obtainedby the shallow- measurednear-surfacethermal gradient and heat flow, but the
|
||
|
|
|
||
|
|
drilling geothermalstudies(Plate 6).
|
||
|
|
|
||
|
|
exactcontributionof eachprocesscannotyet be quantified.In
|
||
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|
||
|
|
The desireto explainthe failed prognosisled to an ambitious any case, the observationsclearly demonstratethat external
|
||
|
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|
||
|
|
research effort [Clauser et al., this issue]. The KTB field lab factorsinfluencethe near-surfacetemperaturefield in the crust,
|
||
|
|
|
||
|
|
carried out a large numberof measurementson core material and this suggeststhat values of geothermalgradientand heat
|
||
|
|
|
||
|
|
andcuttingsto determinestatisticallysoundvaluesfor thermal flow from shallowdrill holesin crystallineterranestend to be
|
||
|
|
|
||
|
|
conductivity,heatdiffusion,andheatproductionto be usedin systematicallytoolow.
|
||
|
|
|
||
|
|
thermal modeling. An extensivegeothermallogging program Another set of problemsis raised by the surprisinglyhigh
|
||
|
|
|
||
|
|
Table 3. Parameters Used for Geothermal Calculations
|
||
|
|
|
||
|
|
Paragneisses HornblendeGneisses
|
||
|
|
|
||
|
|
ThermalconductivityW, /m K Heatproductionla, W/ms Naturalgammaactivity,c/skg Potassium,wt %
|
||
|
|
Uranium,ppm Thorium,ppm
|
||
|
|
|
||
|
|
1.50+ 0.19 51 ñ 5 3.4 ñ 0.2
|
||
|
|
2.24 ñ 0.25
|
||
|
|
2.8 ñ 0.4 7.9 ñ 1.0
|
||
|
|
|
||
|
|
1.15ñ 0.11 39 ñ 5
|
||
|
|
2.8 ñ 0.2 1.9 ñ 0.22
|
||
|
|
2.0 ñ 0.2 5.7 ñ 0.8
|
||
|
|
|
||
|
|
Amphibolites
|
||
|
|
0.53 ñ 0.28 23 ñ 7 2.6 ñ 0.2
|
||
|
|
0.88 ñ 0.42 1.0ñ 0.6 2.5 ñ 1.5
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
EMMERMANNANDLAUTERJUNGK' TBDEEPDRILLHOLE
|
||
|
|
|
||
|
|
18,197
|
||
|
|
|
||
|
|
.
|
||
|
|
'""'"•' "':.....
|
||
|
|
|
||
|
|
ß.:..:.•",'. .:•;•'.•......
|
||
|
|
ß..'...:.:,.•v..:•,•_..•..•::-•'l,.'.';.-•.:.;.. .....:•œ.-.•.g,-?.2.'.'.,:.:•.
|
||
|
|
.: '•. ß .,t.,. ß
|
||
|
|
|
||
|
|
at the KTB site well correspondsto the averagebackground
|
||
|
|
valueofabou8t 0mW/m2insoutherGnermany.
|
||
|
|
Rheology and Stress Field. A key target of the KTB programfrom the very beginningwas the studyof the stateof stressin the Earth'scrustandthe rheologicalbehaviorof rocks
|
||
|
|
|
||
|
|
....
|
||
|
|
|
||
|
|
under_in situ conditions down to mid crustal levels. Current
|
||
|
|
|
||
|
|
understandinogf the rheologyof the continentacl rustis based
|
||
|
|
|
||
|
|
primarily on laboratorystudiesof rock strengthundergreatly
|
||
|
|
|
||
|
|
•......'.' .•,•A?•..:.•:.,:•.
|
||
|
|
|
||
|
|
simplified conditions.These studiesindicate that two major processescontrolthe mechanicalbehaviorof crustalrocks:(1)
|
||
|
|
|
||
|
|
"ß• •.. .:,•..•!".'"'
|
||
|
|
|
||
|
|
. ..
|
||
|
|
|
||
|
|
In upper crustallevels, deformationcausesbrittle failure and rock strengthis limited by frictional strengthof preexisting
|
||
|
|
|
||
|
|
faults. Becausethe frictional strengthincreaseslinearly with
|
||
|
|
|
||
|
|
'?';'tg•;•:-.':.:-.'
|
||
|
|
|
||
|
|
confining pressure,the strengthof the crust correspondingly increaseswith depth. (2) At greater depth, beyond a certain
|
||
|
|
|
||
|
|
.r•: •'.:,.
|
||
|
|
|
||
|
|
temperatureand at low strainrates,rock strengthis determined by flow laws and decreasesexponentiallywith furtherrise in
|
||
|
|
|
||
|
|
temperature.
|
||
|
|
|
||
|
|
......'., .•/,
|
||
|
|
|
||
|
|
ß
|
||
|
|
|
||
|
|
ß
|
||
|
|
|
||
|
|
ß(.'-d:•.-',•...•ß. .
|
||
|
|
|
||
|
|
....;..?..'•a:.v.,.. .
|
||
|
|
|
||
|
|
ß....:: ,
|
||
|
|
|
||
|
|
.•..[.;.,...
|
||
|
|
|
||
|
|
' •:;Z•..:......
|
||
|
|
|
||
|
|
ß ...''....:12.[. :......:... ß ,..
|
||
|
|
|
||
|
|
_
|
||
|
|
|
||
|
|
. . ß-.' ..s.•&-•.::'
|
||
|
|
|
||
|
|
'::'-"'"' ß....•..:;•.-•j¾.:...:.:.
|
||
|
|
|
||
|
|
ß
|
||
|
|
|
||
|
|
The change from brittle to ductile (plastic) behavior, commonlyreferredto as the brittle-ductiletransition,depends on factors such as, among others, rock mineralogy, fluid content, and strain rate. Therefore, in nature a more or less
|
||
|
|
broadtransitionzonecanbe expected.Most modelsof rheology are basedon the mechanicalpropertiesof quartzbecauseof its abundancien continentacl rustalrocks.Accordingto the "quartz
|
||
|
|
|
||
|
|
model"(Figure7), thereis a linearbuildupof differentialstress
|
||
|
|
|
||
|
|
with depthin the crustto the brittle-ductiletransitionat about
|
||
|
|
|
||
|
|
300øC,after which rock strength,and thus the magnitudeof
|
||
|
|
|
||
|
|
0.0
|
||
|
|
|
||
|
|
1.0
|
||
|
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|
||
|
|
2.0
|
||
|
|
|
||
|
|
3.0
|
||
|
|
|
||
|
|
"stored"stressf,allsexponentially. Obviously,thereare shortcomingisn sucha simplemodel.
|
||
|
|
|
||
|
|
HPR [laW/m3]
|
||
|
|
|
||
|
|
Apart from uncertaintiesin the physical-mechanicaplroperties of mineralsandrocks,a morefundamentapl roblemis that the
|
||
|
|
|
||
|
|
Figure 6. Diagram showingthe changesin heat production thresholdtemperaturefor ductileflow is criticallydependenotn
|
||
|
|
|
||
|
|
values,as measuredby laboratoryexperimentsand downhole strainrate,andrealisticstrainrates(10'•ns'• to 10'• s'•) are
|
||
|
|
|
||
|
|
logging, with depth in the superdeepborehole.The commonly unattainablein the laboratory.On diagramslike Figure 7, the
|
||
|
|
|
||
|
|
cited exponentialdecreasein heat productionwith depthis not confirmedby thesedata.Instead,onefindsintervalsof constant
|
||
|
|
|
||
|
|
expectednaturalsituationis thereforedepictedas a continuous
|
||
|
|
|
||
|
|
averageheat production(vertical lines) which correlate with transitionfrom thebrittleto theductileregime.
|
||
|
|
|
||
|
|
lithologicchanges.
|
||
|
|
|
||
|
|
With a basaltemperatureof about265øC,theKTB superdeep
|
||
|
|
|
||
|
|
hole has penetratedinto depthsin which the brittle-ductile
|
||
|
|
|
||
|
|
transitioncan be expected,and thusa uniqueopportunityis
|
||
|
|
|
||
|
|
available to study this fundamentalregion in situ. The most
|
||
|
|
valueof 85 mW/m2for theheatflowdensityat 8 kmdepth. importantelementsof thesestudiesare the determinationof the
|
||
|
|
|
||
|
|
Extrapolationof the temperaturegradient measuredin the stresstensorwith depth and the structuralanalysisof rocks
|
||
|
|
|
||
|
|
superdeephole using conventionalmodels for the lower crust fromdepthapproachingthetransitionzone.Fromthebeginning
|
||
|
|
|
||
|
|
and assuming conductive heat flow leads to predicted of the KTB program, geoscientistsand engineers worked
|
||
|
|
|
||
|
|
temperatureswell above800øCand heat flow densitiesof 55 to closely together to develop an integratedstressmeasurement
|
||
|
|
80mW/m2at thecrust/mantbleoundariny 30kmdepthT, here strategy that involved a number of different methods and
|
||
|
|
|
||
|
|
is no evidencefor partial meltingat this depthfrom seismic experimentswhosecommongoal was to establisha continuous
|
||
|
|
|
||
|
|
data, and there are also other reasons to expect lower temperaturefsor thecrust/mantleboundaryT. hereforeonemust questionthe model assumptionsI.s there an additionalheat
|
||
|
|
source in the crust below the drill site? Could the Erbendorf
|
||
|
|
|
||
|
|
stressprofile from the surfaceto the final depth.Theseinclude modified hydraulic fracturing tests and analysis of borehole breakoutsand drilling-inducedtensile fractures[Brudy et al., this issue].
|
||
|
|
|
||
|
|
bodybe responsiblefor highheatproductionor are thereeven The magnitude of the least horizontal principal stress
|
||
|
|
|
||
|
|
significantheatinputsfrom exothermahl ydrationreactionsin component(S•) was determined by conventionalhydraulic the middle and lower crust?Is the assumptionof conductive fracturing experiments in the pilot hole (14 experiments
|
||
|
|
|
||
|
|
heattransportincorrect,and can fluid convectionrelatedto the between800 m and 3000 m), and by two modified hydraulic
|
||
|
|
|
||
|
|
FranconianLineamentexplainthedilemma?
|
||
|
|
|
||
|
|
fracturing experimentsat 6018 and 9070 m depth in the
|
||
|
|
|
||
|
|
Theseand other ideaswill be explorednumericallyand superdeephole.Theseexperimentsyieldedinprecisevaluesfor
|
||
|
|
|
||
|
|
additionalconstraintsare expectedfrom plannedgeothermal themaximumhorizontasl tresscomponen(tS•t),andthereforea experimentsin the KTB "Deep Crustal Laboratory."The new methodwas developedto estimatethe magnitudeof proposedidea that the thermal anomaly around the Tertiary from a combinedanalysisof boreholebreakoutsand drillingEgerRift, to thenorthof thedrill site,is thecauseof thehigh inducedtensilefracturesof the boreholewall. Assumingthat heatflow densitycanbe discountedbecausethevaluemeasured the vertical stressS,., whose value was calculatedfrom the
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
18,198
|
||
|
|
|
||
|
|
EMMERMANN AND LAUTERJUNG: KTB DEEP DRILL HOLE
|
||
|
|
|
||
|
|
differential stress
|
||
|
|
,
|
||
|
|
|
||
|
|
',
|
||
|
|
|
||
|
|
criteriom for friction-
|
||
|
|
|
||
|
|
',,,••r ..•" controlslelidding
|
||
|
|
|
||
|
|
\,
|
||
|
|
|
||
|
|
transitionI alß,
|
||
|
|
|
||
|
|
.•. •=10'•e
|
||
|
|
|
||
|
|
range /.•':'•,, "britptleastircansition"
|
||
|
|
|
||
|
|
--300 øC
|
||
|
|
|
||
|
|
,,•,,"
|
||
|
|
|
||
|
|
,, .......
|
||
|
|
|
||
|
|
•= 10-14
|
||
|
|
|
||
|
|
KTB
|
||
|
|
|
||
|
|
/
|
||
|
|
|
||
|
|
-
|
||
|
|
|
||
|
|
depth (z)
|
||
|
|
T = f(z) p = f(z)
|
||
|
|
|
||
|
|
flloafwoqwruartzite strainrate• as indicated[s-•]
|
||
|
|
(dislocationcreep)
|
||
|
|
|
||
|
|
Figure 7. Schematicdiagramshowingthe dependenceof crustalrheology(basedon the behaviorof quartzite) on pressure(depth)andtemperatureandthe magnitudeof differentialstress[Stoeckhert1, 994]. The final depth of the KTB borehole(9101) reachedthe zoneof transitionalbrittle-ductilebehavior.
|
||
|
|
|
||
|
|
lithology of the drilled sectionand density of the respective hundredsof metersfrom the injectionzonein the depthrange
|
||
|
|
|
||
|
|
rock types,is a principalstresscomponenta, continuousprofile between8 and9 km [ZobackandHarjes, thisissue].
|
||
|
|
|
||
|
|
of the complete stress tensor down to about 9 km was The inducedseismicitywasrecordedby a surfacenetworkof
|
||
|
|
|
||
|
|
established.
|
||
|
|
|
||
|
|
70 stationsandwith a three-componengteophonetooldeployed
|
||
|
|
|
||
|
|
The combined results of all stress measurements indicate that at 4 km depthin thepilot hole.Clusteranalysisshowedthatthe
|
||
|
|
|
||
|
|
thedirectionof S, is remarkablyuniformat N160øE+10ø over events were concentratedat two different depth levels, both almostheentireinvestigateddepthrangefrom3 km to 9 km, abovethe injectionzone and extendingabout 1 km from the
|
||
|
|
|
||
|
|
andit correspondwsell with theN146øEregionalorientationof borehole.Fault planesolutionsof the seismiceventsindicatea S, in centralEuropeT. he only significancthangeof Ss with strike-slipcharacter,andthisdocumentsthatthecrustat 8-9 km
|
||
|
|
deptihsa shifot fabou6t0ø,toN220øWat,7200mwhichis stillin a stateof frictioneaql uilibriuHmo.wevetrh,e
|
||
|
|
|
||
|
|
coincidwesiththelowermofasut ltplaneof theSE1fault compleatbesenocfeinduceedarthquankeeas9r 030mdepth,
|
||
|
|
|
||
|
|
bundlVea. lueosfthemagnituodfSe,at6018mand9070m couplwediththeobservatthioatntheseismeivcenctslustering
|
||
|
|
|
||
|
|
depth in the superdeephole are 111 MPa and 183 MPa, at a depthof about8.7 km, indicatesan abruptchangeof the
|
||
|
|
|
||
|
|
respectively,andthe estimateddifferentialstressesare between stressstate,and markedlylower shearstressessuggesthat the
|
||
|
|
|
||
|
|
180 MPa and 147 MPa. Apart from theuppermosst ectionof the bottomof theboreholemay benearthebrittle-ductiletransition.
|
||
|
|
|
||
|
|
drill hole downto about1000 m, whereS. appearsto be the A different approachto identifying directly the current
|
||
|
|
|
||
|
|
leastprincipasl tresst,hestressmagnitudeosbtainedfromS,,Ss
|
||
|
|
|
||
|
|
brittle-ductiletransitionzone comesfrom combiningdata on the presentstateof stresswith the resultsof microscopicand
|
||
|
|
|
||
|
|
andSv(-240 MPa at 9100 m) indicatestrike-slipconditions(S, <S,< S.).
|
||
|
|
|
||
|
|
submicroscopitcexturalstudiesof minerals,especiallyquartz, in the suspectedepthrange[Dresenet al., thisissue].Because
|
||
|
|
|
||
|
|
The datasupporthe hypothesisthatthe stateof stressin the the rate of processeswhich control quartz texturesincreases
|
||
|
|
|
||
|
|
brittle crust is limited by the frictional equilibrium on exponentiallywith increasingtemperaturei,t wasexpectedthat
|
||
|
|
|
||
|
|
preexisftainuglatsndthatthecontineunptaplcerusatctassa significcahnat ngienstexturfaelaturwesouladppeoarn
|
||
|
|
|
||
|
|
stresgsuidaendiscapabolfetransmitftoinrgceosfhundreodf sapproachthinetgransitizoonneT.herefoqrueartfzromcutting
|
||
|
|
|
||
|
|
megapasccaolsm, paratbolethosexertebdy plate-drivisnagmplteaskeqnuasi-continuboeulosw7ly000mwasanalyzed
|
||
|
|
|
||
|
|
processes.
|
||
|
|
|
||
|
|
by opticalmicroscopyandtransmissioenlectronmicroscopyI.n
|
||
|
|
|
||
|
|
The urgentquestionof whetherthe brittle-ductiletransition general,the quartzmicrotexturesare similar within the depth
|
||
|
|
|
||
|
|
wasencountereidn the KTB superdeephole canbe answered interval 7-9 km; however, there are systematicqualitative
|
||
|
|
|
||
|
|
with a definite"maybe."One of the mostimportantlinesof changes with depth. These include an improved spatial
|
||
|
|
|
||
|
|
evidencecomesfrom a large-scalehydraulicfracturingand organizationof dislocationsd, ecreaseof dislocationdensity,
|
||
|
|
|
||
|
|
fluid injectionexperimenct onductedin theuncasedbottomhole and submicroscopifcluid inclusionsand indicatean increasing
|
||
|
|
|
||
|
|
sectionat theconclusioonf drillingandwasespeciallydevoted rate of thermallyactivatedrecoveryprocessesT. hesefindings,
|
||
|
|
|
||
|
|
to testingthe brittle-ductiletransitionhypothesisW. ithin 25 like those of the hydaulic fracturing and fluid injection
|
||
|
|
|
||
|
|
hours2,00m3ofluidwereinjecteidntothecrusat tabou9t030 experiments,indicatethat the superdeephole might have, in
|
||
|
|
|
||
|
|
m and some 400 microearthquakewsere triggereda few fact, reachedthepresent-daybrittle-ductiletransitionzone.
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
EMMERMANN AND LAUTERJUNG: KTB DEEP DRILL HOLE
|
||
|
|
|
||
|
|
18,199
|
||
|
|
|
||
|
|
Deep Crustal Laboratory: A TelescopeInto the
|
||
|
|
Earth's Interior
|
||
|
|
|
||
|
|
levels. This was done using a combinationof hydraulic fracturingtestswithanalyseosf compression(barleakoutsa)nd
|
||
|
|
|
||
|
|
tensilefailures (drilling-inducedfractures)of the borehole
|
||
|
|
|
||
|
|
A detailedpictureof thecrustalsectionandits propertieshas walls.Thestudyhasshownthatthebrittleuppercrustis strong,
|
||
|
|
|
||
|
|
been assembled from the field experiments, laboratory "stress-loadeda,"nd capableof sustainingand transmitting
|
||
|
|
|
||
|
|
investigationsand boreholemeasurementsof the KTB main forcesof plate-drivinmg agnitudeT.hegeneratioonf hundreds
|
||
|
|
|
||
|
|
phase.Duringthenext5 yearsof thefinal phase,supplementary of microearthquakbesy extremelysmall increasein pore
|
||
|
|
|
||
|
|
experimentsare plannedusingthe globally uniqueassociation pressur(e< 1 MPa)indicatetshatstresslevelsthroughouthte
|
||
|
|
|
||
|
|
of two deep boreholesinto the crystalline basementwith a brittlecrustarenearits frictionalstrengthandthatonly a small
|
||
|
|
|
||
|
|
separationof 200 m.
|
||
|
|
|
||
|
|
stressincreaseis necessartyo inducefailure.Thesefindings
|
||
|
|
|
||
|
|
Two main objectives of this so-called "Deep Crustal provethevalidityof experimentaldlyerivedtheoreticasltress
|
||
|
|
|
||
|
|
Laboratory" have been defined: (1) The discrimination of profilesa,ndconfirmthatcrustasltrengtihn situdependosnthe
|
||
|
|
|
||
|
|
geophysicalsignalsgeneratedby deep-seatedprocessesand by frictionasl trengthon preexistingfa, vorablyorientedfractures
|
||
|
|
|
||
|
|
shallow events. Conventionaldeep-soundingmethodscan be with coefficientsof frictionin therangeof 0.6 to 1.0 [Byerlee,
|
||
|
|
|
||
|
|
interfered with by effects induced at the Earth-Atmosphere 1978].
|
||
|
|
|
||
|
|
interfaceand disturbedby structuresand processesat shallow The brittle-ductile transition. The lack of induced
|
||
|
|
|
||
|
|
depth. (2) Determinationof equilibriumvalues of physical microearthquakebselowabout9 km suggesttshatthebottomof
|
||
|
|
|
||
|
|
parametersandtheirlong-periodvariationswithtimeanddepth. thesuperdeepboreholeis closeto thepresent-daybrittle-ductile
|
||
|
|
|
||
|
|
Theseobjectiveswill be tackledby deploymentof instruments transition.This hasbeenconfirmedby detailedstudyof quartz
|
||
|
|
|
||
|
|
at variousdepthandtime intervals.
|
||
|
|
|
||
|
|
microstructureisn gneissesw, herestrainis partitionedbetween
|
||
|
|
|
||
|
|
Altogether,threegeneraltypesof experimentsare planned: brittle fracture, solution/precipitationcreep, and plastic flow.
|
||
|
|
|
||
|
|
(1) Stationary registrationof time-dependentvariations of Measurementsof the dislocation density in quartz, which
|
||
|
|
|
||
|
|
physical parameters at different depths under "natural" decreasestowardthe bottomof the borehole,yield differential
|
||
|
|
|
||
|
|
boundaryconditions:plannedinvestigationsincludelong-term stressesof about 140 MPa, which approximatelyequal the
|
||
|
|
|
||
|
|
measurementosf the seismicity,tidal effects,deformation,and confining pressureat that depth. Thus the emprical Goetze
|
||
|
|
|
||
|
|
naturalelectromagnetiecvents(in addition,depthprofilesof criterion also indicatesthat plastic flow contributesto rock
|
||
|
|
|
||
|
|
equilibriumfield valueswill be registered(e.g., temperature, deformationat final depths[Dresenet al., thisissue].
|
||
|
|
|
||
|
|
heat production)),(2) experimentsu, niqueor repeated,with Crustal fluids and rock permeability. Mixturesof aqueous
|
||
|
|
|
||
|
|
defined changes in boundary conditions (e.g., downhole and gaseousfluids are widespreadin the upper9 km of the
|
||
|
|
|
||
|
|
measurements of seismic surface vibrations and active electrical continental crust sampled by the KTB. Fluids are mostly
|
||
|
|
|
||
|
|
experimentsor hydraulic/fluidtests),(3) cross-holexperiments confined to faults and fractures, and these were encountered,
|
||
|
|
|
||
|
|
(the useof two holesallowsspecificexperimentsto investigate even at bottom hole depths,in numerousdistinct zonesup to
|
||
|
|
|
||
|
|
hydraulicconnectivityandfluid pathwaysaswell asanisotropy severaltensof metersthick. The permeabilityof thesezonesis of physicalparameters(e.g., seismicwave-propagationu)nder of the orderof 10"s to 10'•7m2, which is severalordersof
|
||
|
|
|
||
|
|
naturalconditions)A. particularbenefitof the closeproximity magnitudehigher than the matrix permeability of the rocks.
|
||
|
|
|
||
|
|
of the two deep boreholesis the ability to perform seismic Formationpressuresdeterminedin brine-containingzonesshow
|
||
|
|
|
||
|
|
cross-hole experiments with higher frequencies and thus a nonlinear increase with depth, probably due to stepwise
|
||
|
|
|
||
|
|
improvedspatialresolutionT. his typeof experimentswill close increasesin salinity.The formationpressureof 103 MPa at 9
|
||
|
|
|
||
|
|
the gap in scale factor between laboratory measurements km is near-hydrostaticT. his, and the fact that experiments
|
||
|
|
|
||
|
|
(centimeterrange),boreholemeasurement(sdezimeterrange), proveda hydraulicconnectionbetweenthe pilot hole and the
|
||
|
|
|
||
|
|
seismicfield experiments(kilometerrange) and seismology main hole, indicates that fluid pathways are highly
|
||
|
|
|
||
|
|
(100-1000 km range).
|
||
|
|
|
||
|
|
interconnected.
|
||
|
|
|
||
|
|
Finally,it is plannedto expandintoa 3-D triangulararrayby The compositionof the fluids varies systematicallywith
|
||
|
|
|
||
|
|
sinkinga thirdholedownto about1000m andtherebycreatea depth:groundwaterin the upperlevels,NaCl-dominatedfluids
|
||
|
|
|
||
|
|
greatly improved"telescope"into Earth's interior. With this of low salinityat intermediatedepths,andhighlysaline,Ca-Na-
|
||
|
|
|
||
|
|
configurationthe DeepCrustalLab will providea platformfor C1basemenbt rinesbelowabout3200 m. The lattercontainhigh
|
||
|
|
|
||
|
|
high-resolutioninvestigationsof anisotropyand transport amountsof dissolvedgas (~0.dL/L of brine), mainly nitrogen
|
||
|
|
|
||
|
|
propertiesin thevicinityof thesiteandwill greatlyimprovethe and methane,which is derivedby thermaldecompositioonf
|
||
|
|
|
||
|
|
discriminationbetweendeep-seateadndnear-surfaceeffectsand organicmaterialin the paragneissprotoliths.Data suggesthat
|
||
|
|
|
||
|
|
processes.
|
||
|
|
|
||
|
|
Permo-Triassicevaporitesin the sedimentarybasinwestof the
|
||
|
|
|
||
|
|
drill site are the ultimate source of the brines, which have
|
||
|
|
|
||
|
|
Conclusions
|
||
|
|
|
||
|
|
infiltratedthebasemenatlongdeep-reachinfgaultsystemsdown to at least 10 km depth.
|
||
|
|
|
||
|
|
In this paper we attemptedto summarizethe scientific Graphite and geoelectricanomalies.Despitetheubiquitous
|
||
|
|
|
||
|
|
advancesgainedby the continentaldeep drilling program,the presenceof salinebrines,the electricalresistivityincreasesi,n
|
||
|
|
|
||
|
|
KTB,withrespetcotallofthemajorresearcthhemeSs.omoef generaflr,om103C]matsurfacteo l0sC]mat9 kmdepths.
|
||
|
|
|
||
|
|
theresultws illhaveth6irgreatesimt pacitn advancinreggionalLocal anomalies, at various depths, with extremely low
|
||
|
|
|
||
|
|
studies, whereasothers are of general significance.In this resistivity(1 to 100fi m) areclearlyrelatedto graphite-bearing
|
||
|
|
|
||
|
|
conclusionwe pick out thoseaspectsof the KTB scientific shearzones.Graphitein suchshearzonesis interconnectedover
|
||
|
|
|
||
|
|
programwhichareprincipallyof globalimportanceandwhich distancesof hundredsof meters, and this phenomenon
|
||
|
|
|
||
|
|
couldnot havebeenobtainedwithoutdrilling.
|
||
|
|
|
||
|
|
obviouslydeterminesthe electricalresponseof the basement.
|
||
|
|
|
||
|
|
Stress field. A continuousprofile of the complete stress Before drilling, a prominentlow-resistivitylayer of regional
|
||
|
|
|
||
|
|
tensor has been obtained from the surface down to midcrustal extentwaspostulatedat about10 + 1 km depth.This zonewas
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
18,200
|
||
|
|
|
||
|
|
EMMERMANN AND LAUTERJUNG: KTB DEEP DRILL HOLE
|
||
|
|
|
||
|
|
the target of a dipole-dipoleexperimentconductedin the The complexity of the drilled crustalstructuresinspiredthe
|
||
|
|
|
||
|
|
boreholeaftercessationof drilling. It turnsout thatthebottom development of a new seismic processingmethod (true
|
||
|
|
|
||
|
|
depthof the KTB is well within this majorconductorw, hose amplitude,prestackmigration) and demonstratedthe need to
|
||
|
|
|
||
|
|
positioncoincideswith a postulatedbasaldetachmenzt one of consider3-D aspectsin seismicimaging. The new method
|
||
|
|
|
||
|
|
the post-Variscanthrusts(Mesozoicbrittle-ductiletransition). providedhigh-resolutioinmagesof themidcrustandlowercrust
|
||
|
|
|
||
|
|
An importantimplicationof thesefindingsis that geoelectric at the KTB site. It has been and will continue to be used for
|
||
|
|
|
||
|
|
surveyscouldbeusedto mappaleosheazronesandthushelpin reprocessingand reinterpretationof existing seismic records,
|
||
|
|
|
||
|
|
tectonic reconstructions.
|
||
|
|
|
||
|
|
for example, the DEKORP data, and thus holds great promise
|
||
|
|
|
||
|
|
Thermal structureof the crust.A majorlessonof theKTB for newinsightsintothedeepstructureof crystallinebasement.
|
||
|
|
|
||
|
|
is that geothermaldata obtainedfrom shallowwells shouldbe
|
||
|
|
|
||
|
|
usedwith greatcautionin makinggeothermapl rognosesT.he Looking Back thermasl tructuroef theuppermos1t500m of thecrustis highly
|
||
|
|
|
||
|
|
disturbedI.n thisintervalthe geothermagl radientis about21 As this paper goesto press,we look back on 19 yearsof
|
||
|
|
|
||
|
|
K/km and the heat flow reachesvalues of about 55 mW/m2. involvemenitn theKTB programs, tartingin the first planning
|
||
|
|
|
||
|
|
Both parametersthenincreaserapidly to about27.5 K/km and stagesin 1977, to thecessationof drilling in 1994, andon to the
|
||
|
|
|
||
|
|
85mW/m2,respectivealyn,dremainclosetothoselevelsright final phase of on-site experimentationin the Deep Crustal
|
||
|
|
|
||
|
|
responsiblefor the near-surfaceeffects: heat advectionby LaboratoryT. he successof theKTB programdependedonclose
|
||
|
|
|
||
|
|
topographically induced groundwater flow and surface cooperationamong diverse groups including ministries and
|
||
|
|
|
||
|
|
temperaturefluctuationsdue to paleoclimate.The effect of agencies, management teams and engineering units from
|
||
|
|
|
||
|
|
paleoclimateis dominant.In particular,the last ice age is industry and academia,and not least the scientists,those
|
||
|
|
|
||
|
|
responsiblefor a perturbationof up to severaldegreesin the assignedto the KTB field laboratoryand scientistsfrom
|
||
|
|
|
||
|
|
present-daytemperaturedistributionof the upper4 km. Below universities and researchinsitutes. It might be useful to
|
||
|
|
|
||
|
|
about2000 m, advectionis negligibleandheattransporct anbe summarize,from ourcurrentperspectivew, hatwe believewere
|
||
|
|
|
||
|
|
describedby a purelyconductivemodel.
|
||
|
|
|
||
|
|
the key elementsfor the successof the German Continental
|
||
|
|
|
||
|
|
The KTB has fostereda numberof importantadvancesin Deep Drilling Program and what we would probably do
|
||
|
|
|
||
|
|
interpretingand modelingheat flow data. For example,the differentlya secondtime.
|
||
|
|
|
||
|
|
intimatealternationof gneissand metabasiteunitswith near- The singlemostimportantfactorwasthe continuingsupport
|
||
|
|
|
||
|
|
vertical contactswas ideal for studyingthe effects of lateral andparticipationfrom the geosciencecommunityin Germany,
|
||
|
|
|
||
|
|
refractionof heat flow and for developingnew modelswhich both from the professionalsocietiesand steeringcommittees
|
||
|
|
|
||
|
|
take theseeffectsinto account.The large amountof datafrom and from the leadingindividualsin most branchesof the solid
|
||
|
|
|
||
|
|
loggingand from laboratorymeasurementcslearly refutedthe earthscienceswhoparticipatedin theprogram.Thisbroadbasis
|
||
|
|
|
||
|
|
widely held assumptionthat heat-producingelements are of supportresultedfrom a long conceptfinding phase,which
|
||
|
|
|
||
|
|
strongly concentratedin the upper crust and then decrease lastednearly7 years,andduringwhichthe fundamentaal spects
|
||
|
|
|
||
|
|
exponentially with depth. Instead, the data show that heat andgeneralphilosophyof thedrilling programwerediscussed.
|
||
|
|
|
||
|
|
productionis controlledby lithology,and thereis only a very The resultof thisphasewasa rich anddiverseresearchprogram
|
||
|
|
|
||
|
|
slightoveralldecreasewith depth.
|
||
|
|
|
||
|
|
which combined the key issues of the various geoscience
|
||
|
|
|
||
|
|
Seismicstructure. The seismicprogramemployeda broad disciplinesinvolved. This hard won scientificconsensusin the
|
||
|
|
|
||
|
|
spectrum of studies, which covered scale lengths from geosciencecommunity helped to keep the debateson site
|
||
|
|
|
||
|
|
kilometers to a few centimeters. These included 2-D and 3-D, selectionat a professionallevelandto ensurethatall disciplines
|
||
|
|
|
||
|
|
near-vertical and wide-angle seismic surveys, VSP were equally involved in the selection decision and in the
|
||
|
|
|
||
|
|
measurements,and more sophisticatedsurface-to-borehole ensuingresearch.
|
||
|
|
|
||
|
|
experiments. These were complemented by petrophysical It was clear from the beginningthat a superdeepdrilling
|
||
|
|
|
||
|
|
laboratorystudiesunderin situ conditions,drill core analyses, programwould exceedthe limits of existing technology.This
|
||
|
|
|
||
|
|
anda varietyof boreholemeasurements.
|
||
|
|
|
||
|
|
technicalchallengeand the strongsupportfrom the German
|
||
|
|
|
||
|
|
The 3-D experiment, the first of its kind in crystalline industry were prerequisitesfor KTB to be consideredfor
|
||
|
|
|
||
|
|
basement,revealed a numberof pronounced,steeplydipping funding as a large-scalenationalresearchinitiative. From the
|
||
|
|
|
||
|
|
reflectorsin the uppercrust. The most prominentof thesewas total budgetof $350 nilIlion US, 50 million were earmarkedfor
|
||
|
|
|
||
|
|
penetrated,as predicted, at a depth of about 7000 m. The scientific projects and an equal sum was allocated to the
|
||
|
|
|
||
|
|
reflectoris a deep-reachingfault systemconsistingof a 400 m industry for R&D projects. The drilling industry was also
|
||
|
|
|
||
|
|
thickgroupof shearzones.The physicalparametersresponsible funded for constructionof a completelynew drill rig, which
|
||
|
|
|
||
|
|
for the observedreflectivity were quantified by integrated involved a number of technical innovations.This greatly
|
||
|
|
|
||
|
|
modeling of data from surface experiments, borehole improvedthe competitivestanceof theGermandrilling industry
|
||
|
|
|
||
|
|
measurementsand laboratorystudies.
|
||
|
|
|
||
|
|
internationally.
|
||
|
|
|
||
|
|
Altogether,the seismicprogramdemonstratedthat most of Approvalfor a fully equippedmodernfield laboratoryon site
|
||
|
|
|
||
|
|
the reflectionsregisteredin the upper crust originatefrom was hard foughtin the planningstagebut it provedto be
|
||
|
|
|
||
|
|
fracturezonesand faults and that lithologicboundariesare of indispensibleand shouldbe includedin any futureprojectsof
|
||
|
|
|
||
|
|
little importance.This is due to the fact that impedance thiskind. The field laboratorystaffcarriedouta broadspectrum
|
||
|
|
|
||
|
|
contrastsproducedby faultingare muchhigherthanthosedue of investigationws hichprovidedthenecessarybackgroundata
|
||
|
|
|
||
|
|
to lithological variations. Furthermore, although the for the numerousresearchprojectsat universitiesand other
|
||
|
|
|
||
|
|
petrophysicasl tudiesand VSP data clearly indicatedseismic institions. An information stream from quasi-continuous
|
||
|
|
|
||
|
|
anisotropyof the rocks,the anisotropyeffect wasfoundnot to analysis of cuttings and drilling fluid (including dissolved
|
||
|
|
|
||
|
|
contributesignificantlyto thereflectivityof thecrust.
|
||
|
|
|
||
|
|
gases),combinedwith datafrom boreholeloggingprovidedthe
|
||
|
|
|
||
|
|
21562202b, 1997, B8, Downloaded from https://agupubs.onlinelibrary.wiley.com/doi/10.1029/96JB03945, Wiley Online Library on [08/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
|
||
|
|
|
||
|
|
EMMERM•N AND LAUTERJUNG' KTB DEEP DRILL HOLE
|
||
|
|
|
||
|
|
18,201
|
||
|
|
|
||
|
|
basisfor an optimumbalancebetweenloggingandcoring,and
|
||
|
|
|
||
|
|
also gave the engineersrapid feedback in case of technical
|
||
|
|
|
||
|
|
problems.
|
||
|
|
|
||
|
|
A lesson learned while drillin• the vilot hole was that the
|
||
|
|
|
||
|
|
_
|
||
|
|
|
||
|
|
_
|
||
|
|
|
||
|
|
DallmeyerR, . D., W. Frankea, ndK. Weber(Eds.)P, re-PermianGeology of CentralatutWesternEurope,604 pp.,Springer-VerlaNge, w York,
|
||
|
|
1995.
|
||
|
|
DresenG, ., J. DuysterB, . St'OckherRt,. Wirth, andG. Zulauf,Quartz
|
||
|
|
|
||
|
|
project managementmust have a clearly defined chain of
|
||
|
|
|
||
|
|
ContinentaDleepDrillingProgramKTB,J. GeophysR.es.,thisissue
|
||
|
|
|
||
|
|
commandandresponsibilityandthatdecisionmakingmustgive ELEKTB Group,KTB and the electricalconductivitoyf the crust,J.
|
||
|
|
|
||
|
|
equal weight to the concernsof the geoscientistsand thoseof
|
||
|
|
|
||
|
|
GeophysR. es.,thisissue
|
||
|
|
|
||
|
|
the engineeringteam.Thereforethe go-aheadfor
|
||
|
|
|
||
|
|
the superdeep
|
||
|
|
|
||
|
|
EmmetmannR,., The KTB pilothole:Tectonicsettingt,echnicadl ataand firstresultsi,n TheGermanContinentaDl eepDrilling Program,edited
|
||
|
|
|
||
|
|
hole by the Ministry for Researchand Technology was byR. EmmetmananndJ. Wohlenberg52, 7-553,Springer-VerlaNge, w
|
||
|
|
|
||
|
|
conditionalon reorganizationof the projectmanagementT. he
|
||
|
|
|
||
|
|
York, 1989.
|
||
|
|
|
||
|
|
new, and ultimatelysuccessfulm, anagemenst chemeconsisted Emmetmann,R., and H.J. Behr, Location for the superdeepborehole
|
||
|
|
|
||
|
|
of three directorates: geoscience, borehole logging and experimentation,and engineering.The final decisionswere
|
||
|
|
|
||
|
|
confirmedT,ectomq•hysic1s3,9, 339-340,1987. EmmetmannR,., andJ. LauterjungD, oubleX-rayanalysisof cuttingsand
|
||
|
|
rock flour:A powerfultool for rapidand reliabledeterminatioonf
|
||
|
|
|
||
|
|
madeby a projectmanagerwith experiencein all threeareas, boreholelithostratigraphSyc,i.Drill., 1,269-282, 1990.
|
||
|
|
|
||
|
|
andhisresponsibilitywasto weightheoftendiverginginterests ERCEUGTGroupA, nelectricarlesistivitcyrustasl ectionfromtheAlpsto
|
||
|
|
|
||
|
|
of the threedirectorates.He was advisedby an expert panel theBalticSea(centraml gmenot f theEGT), Tectonophysic2s0,7, 123-
|
||
|
|
|
||
|
|
made up
|
||
|
|
|
||
|
|
from
|
||
|
|
|
||
|
|
leading scientistsand
|
||
|
|
|
||
|
|
industry representatives.
|
||
|
|
|
||
|
|
139, 1992.
|
||
|
|
FrapeS.K., andP.Fritz,Thechemistrayndisotopiccompositionf saline
|
||
|
|
|
||
|
|
This managemenst tructureintegratedindustryexperienceand groundwatefrsomtheCanadianShieldG, eochi•nC. osmochimAc. ta,
|
||
|
|
|
||
|
|
geoscienceconcernsat the decision-makinglevel, and it
|
||
|
|
|
||
|
|
48, 1617-1627, 1982.
|
||
|
|
|
||
|
|
ensureda balanceddistributionof financesand manpowerfor Harjes,H. P.,et at.,Originandnatureof crustarleflectionsR:esultsfrom
|
||
|
|
|
||
|
|
drilling, coring,logging,andthe boreholeexperiments.
|
||
|
|
|
||
|
|
integratesdeismicmeasuremenattstheKTB superdeedprillingsite,J.
|
||
|
|
|
||
|
|
In retrospectw, e believethatthe time givenfor the planning
|
||
|
|
|
||
|
|
GeophysR. es.,thisissue HuengesE, ., B. Enge.•r,J. Erzinger,W. Kesselsa,nd J. Ktick,The
|
||
|
|
|
||
|
|
phase(7 years) and the presite investigations(2 years) was permeablcerust:Geohydraulpicropertiedsownto 9100 m depthJ, .
|
||
|
|
|
||
|
|
necessaryand sufficient. For the purposeof site selection, GeophysR. es.,thisissue.
|
||
|
|
|
||
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however,it wouldhavebeenbetterto havedrilled a technically simple, 2-3 km hole at each site instead of several shallow boreholes(< 500 m).
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KontnyA, ., G. FriedrichH,.J.Behr,H. deWallE, .E.Horn,P. M611ear,nd G. Zulauf, Formationof ore nfineralsin metamorphicrocksof the GermanContinentadleepdrillingsite(KTB), J. GeophysR. es.,this
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issue.
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M611erP, ., et at., Paleo-andrecentfluidsin the uppercontinentaclrust-
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AcknowlegmentsW. e are especiallyindebtedto R. Trumbullfor his
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ResultsfrowntheGern•anContinentadl eepdrillingProgram(KTB), J.
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constructivediscussionasndcritiqueof themanuscriptW. e alsothankU.
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GeophysR. es.,thisissue.
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Harmsfor contributionsto the text and for providingsomeof the figures. The GermanFederalMinistryfor ResearchandTechnologyfinancedand gave full supportto the KTB program.The authorsthank the Deutsche Forschungsgemeinschafoftr continuousfundingof the coordinationof
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O'Brien, P. J., J. Duyster,B. Grauert,W. SchreyerB, . St'0ckherta,nd K. Weber, Crustal evolutionof the KTB drill site:From oldestrelicsto the
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lateHercyniangranitesJ,. GeophysR. es.,thisissue. Pechnig,R., G. Zimmermann,S. Haverkamp,J. Wohlenberg,and H.
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BurckhardtI,ntegratedloginterpretatioin theGermanContinentadl eep
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the scientificprogram(Em 23/14) and for supportingthe scientistsand
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drilling Program:Lithology,porosity, and fracturezones,J. Geophys.
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techniciansof the field laboratory(Em 23/19). Finally, specialthanksare due to the Universityof Giessenfor providingfacilitiesfor coordination of theprogramandadministrativesupportfor thefield laboratory.
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Res., this issue Stoeckhert, B., The "brittle-ductile transition" in the KTB borehole: A
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tentative prognosis,KTB Rep. 94-2, 25-34, Nieders,•ichsisches Landesdamftor BodenforschH.,annoverG, ermany,1994.
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Stoll,J., J. BigalkeandE.W. Grabnet,Electrochemicmalodellingof self-
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References
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potentiaal nomaliesS, urv.Geophys.1, 6, 107-120,1995. Wagner,G. A., et al., Post-Variscatnhermalandtectonicevolutionof the
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KTB siteanditssurroundingsJ,. GeophysR. es.,thisissue
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Borm,G., B. EngeserB, . HoffersH, .K. Kutter,andC. Lempp,Borehole Zoback,M.D., andH.-P. Harjes,Injection-induceedarthquakeasndcrustal
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stressat9 km depthattheKTB deepdrillingsite,GermanyJ, . Geophys.
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Bosum,W., U. Casten,S.C. Fieberg,1. Heydr, and H.C. Soffel,Three-
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Res., this issue
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dimensionainlterpretatioonf theKTB gravityandmagneticanomalies,
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J. GeophysR. es.,thisissue
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Brudy,M., M.D. Zoback,K. Fuchs,F. Runm•el,andJ. Baumg'tirtner,
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Estimationof the completestresstensorto 8 km depthin the KTB
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R. Emmermannand J. Lauterjung,GeoForschungsZentmPmotsdam,
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this issue
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potsdam.de)
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ByefleeJ,.D,,FrictionofrocksP, ureAppl.Geophys.,11661,5-629,1978.
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Clauser,C., et at., The thermalregimeof thecrystallinecontinentaclrust: (ReceivedFebruary14, 1996;revisedDece•nber18, 1996;
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ImplicationfrsomtheKTB,J. GeophysR.es.t,hisissue
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acceptedDecember18, 1996.)
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