JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 102, NO. B8, PAGES 18,179-18,201, AUGUST 10, 1997

The German Continental Deep Drilling Program KTB:
Overview and major results
Rolf EmmermannandJ6mLauterjung
GeoForschungsZentPruomtsdamP,otsdamG, ermany
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.

Introduction

requireclosecooperationbetweengeoscientistasndengineers,a

prerequisitewhichdevelopedintoa fruitful symbiosisL. ike any

In October1994, after 1468daysof drilling, the superdeep expedition to uncharted regions, the KTB project was

boreholeof the GermanContinentaDl eep Drilling Program meticulouslyplannedto foreseeand minimizepotentialrisks.

KTB (KontinentalesTiefbohrprogrammder Bundesrepublik Thusthe projectproceededin distinctphasesa, fter eachof

Deutschlandr)eacheditsfinaldepthof 9101 m at a temperature whicha fundamenttaelevaluatiownasmadeandstrategiewsere

of ~265øC. The main phaseof the KTB was then concluded redefinedA.ftera preparatorpyhase(1982-1984a) nda phaseof

with threemajorexperimentsin the uncasedbottomsectionof presiteinvestigationasndsiteselection(1985-1986),the KTB

the hole: a dipole-dipoleexperiment,a draw-downtestand a pilotphasebeganin 1987.Thisinvolvedsinkinga pilotholeto

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

KTB was terminated as scheduledon December 31, 1994.

1990).The resultsof thepilot phasehada majorimpacton

The KTB was the largest and most expensiveresearch scientificand technicalplanningof the superdeephole

programin the geoscienceesver undertakenin Germany.The CHauptbohrung"K, TB-HB), and providedthe basisfor the Federal Ministry for Researchand Technologycommitteda officialgo-aheafdorthemainphaseA. pprovawl asgiventothe

total of 528 million DM (~$350,000,000U.S.) to the project, designand constructioonf a specializeddrill rig with a

fromtheplanningphasein 1982throughto completionin 1994. maximumcapacityof 12 km, the targetdepthwassetat the

A KTB projectgroupe, stablisheadt theGeologicaSlurveyof temperatulreevelof 300øC(expecteadtabout10km),a budget

LowerSaxony,Hannoverw, asresponsiblfeor thetechnicaal nd wasdetermineda,nd a time framefor the main phasewas

operational realization of the program. The Deutsche limitedto December31, 1994.The year 1995 wascommitted

Forschungsgemeinscha(fDt FG) oversaw and coordinatedall for siteshut-dowanndfinaldataevaluationa,ndonJanuary1,

KTB-relatedscientificactivities.At onetime or anotherduring 1996, the GeoForschungsZentrPumotsdam(GFZ) took over

this period, more than 700 scientistsand technicianswere responsibilitfyor the final phase.In thisphase,the two drill

employedin KTB-relatedwork.

holes,whicharesome200 m apart,will beusedovera 5-year

KTB fully deservesthe term "superdeepadventure"because periodas a deepcrustallaboratoryfor in situ scientificand

it advancedthe frontiersof many geoscientificand technical technicalexperiments.

fields.It wasclearfrom the very beginningthatsuccesswould

Copyfight1997by theAmericanGeophysicaUl nion
Papernumber96JB03945. 0148-0227/97/96JB-03945509.00

Realization of an Idea
In 1977 the Senate Commission on Geoscientific Research of
theDeutscheForschungsgemeinschafifrtst discussedtheideaof investigatingthe continentalcrust by meansof a superdeep

18,179

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EMMERMANN AND LAUTEPOUNG: KTB DEEP DRILL HOLE

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EMMERMANN AND LAUTERJUNG: KTB DEEP DRILL HOLE

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borehole.At that time, conceptualmodelsof the makeupand Collapse of the Variscan orogen started in the late

evolution of the continentalcrust were primarily based on Carboniferous(~300 Ma) andwasenhancedby mantle-induced

interpretationof the geological record, interpretationof crustalextensionand magmaticactivity which heraldedthe

geophysicalimages obtained from various deep-soundingbreak-upof thenewlyassemblePdangeaT.hisepisodecreateda

methodsa, ndapplicationof laboratorydatafromexperimental multitudeof Permian(300-250 Ma) bimodal volcanic suites,

petrologyandgeochemistrtoy realrocks.The commissiofnelt intramontanebasinsandgrabenstructuresm, anyof whichare

thatfurtherprogressrequired"groundtruth"thatcouldonlybe wrench-relatedD. uringthe Alpine orogeny(~100-30 Ma) the

obtainedby direct observationthroughdrilling. From the region was affected by compressionaalnd transpressional

beginningt,hereforet,wo fundamentagl oalsof globalrelevance tectonicswhich were followedby yet anotherstageof rifting

weresingledout:(1) calibrationof crustalgeophysicsa,nd(2) andgrabenformationin theTertiary(since~25 Ma). Manyof

studyof thecrustalstressfield andtherheologicablehaviorof theseeventswere accompaniedby magmatismand enhanced

the crust.In the ensuingyears,discussionws ithin the whole hydrothermaalctivity,causingthe formationof widespread

geosciencceommunityled to a muchbroadedr efinitionof the mineralization.

conceptof continentasl uperdeedprilling. In 1984the official This multiply reworkedcentralEuropeancrustis relatively

proposatlo establishtheKTB wassubmitteadndfive priority thin (~30 km) andextremelyheterogeneousb,oth laterallyand

areasweredefined:(1) thenatureof geophysicasltructuresand vertically. It is distinguishedby regionally variable but

phenomenas:eismicreflectorsand electrical,magneticand generally high heat flow values, complex gravimetric and

gravimetricanomalies;(2) the crustalstressfield and the magnetic patterns, pronounced seismic reflectivity, the

brittle-ductiletransition:orientationand magnitudeof stresses occurrenceof high-andlow-velocitylayers,andzonesof high

as a function of depth; (3) the thermal structureof the electricalconductivityat differentdepths.

continentalcrust: temperaturedistribution,heat flow, heat

productiona,ndheattransport(;4) crustalfluidsandtransport processesfl:uid systemsf,luid sourcesa,ndfluid movements;Site Selection: A Difficult Decision

and(5) structureandevolutionof thecentralEuropeanVailscan basement: properties, deformation mechanisms, and geodynamicosf a multiply reactivatedcontinentacl rustal
environment.

Altogether,more than 40 potentialdrill siteswere initially suggestedb,utonlyfoursurvivedthefinal definitionof project objectives,and the first main selectionconferencein 1983

narrowed the choice to two final candidates, the Schwarzwald

From technicacl onsiderationsa,ndbasedon theexpectation and Oberpfalzregions.As existingknowledgewas inadequate

of importantchangesin rheologyandreactionkineticsabove to decide betweenthe two, a 2-year programof geological,

about250øC,the targetwassetat the 250ø-300øCtemperature petrologicala, ndgeophysicasltudieswasstartedin eachregion.

window. This temperaturetarget was combined with the The results were discussed at a final selection conference in

objectiveof penetratingat least8000 m into the continental September1986, attendedby over 200 geoscientistosf all

crust.

disciplines.

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

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

the central Europeancrust. Perhapsbecauseof its relatively young age (typically < 500 Ma), this crustal type differs fundamentallyfrom that sampledby the Russiansuperdeep

from shallow-drillingstudiescarried out in both regions especiallyfor thispurposeindicatedthatthetargettemperature of 250ø-300øCmight be encounteredat 7 km depth in the

boreholeKola SG3. Neverthelessc, entralEuropeancrusthasa Schwarzwald,whereasit could lie about 5 km deeperin the

complexhistory and has been repeatedlyaffectedby major Oberpfalz.Therefore,taking the original depthcriterioninto

compressionaalndtensionalprocessesIt. waslargelyformedor reshapedduring the Variscan orogeny(~400-300 Ma), which wasan importantsteptowardthe assemblyof Pangea(at ~300

account,the DeutscheForschungsgemeinschasfetlectedthe Oberpfalz site for the superdeepborehole [Emmermannand Behr, 1987]. The specificscientificattractionsof this site were

Ma).

seento be (1) its locationin the suturezone betweentwo first-

The Variscan belt represents a collage of arcs and microcontinentsresulting from collision of the Old Red Continent(Laurentia+ Baltica + East Avalonia) with Armorica

order units of the Variscanorogen;(2) the existenceof an appealingand testablegeologicmodelwhich had far-reaching

implicationsfor crustalarchitectureand geodynamics(;3) the

and Gondwana.An important rifting phasein Cambrian and Ordoviciantimes(~500 Ma) first separatedthe microplatesof
East Avalonia and Armorica from mainland Gondwana and

occurrenceof marked gravity, magnetic,and electrical selfpotential anomalies; (4) the expected presenceof seismic

reflectors at drillable depths and of an electrical high-

createdlargeareasof thinnedcontinentalor evenoceaniccrust. conductivitzyoneat 10 __1 km; and(5) thechanceto testfor

The crustalblocksinvolved beganto convergein Ordovician thermal and geochemicalinfluencesfrom the nearbyTertiary

time (by ~450 Ma) and were finally weldedtogetherduring a Eger rift.

prolongedstageof collisionin the Devonianand Carboniferous

(400-300 Ma) to form thepresent-dayVariscides.Incorporation

of magmaticarcs and back arc basins,long-distancenappe Two-Step Drilling Concept

transport, a final stage of low-pressure,high-temperature

metamorphism, and voluminous intrusion of late to Sincethegeologicabl oundaryconditionsandtheirimpacton

postorogenigcraniteshavedonemuchto obscurethe recordof the technicalrequirementfsor reachingthe envisageddepth

oceansopeningandclosing.

targetwerenotknownsufficientlyt,heKTB conceptwasbased

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18,182

EMMERMANN AND LAUTERJUNG: KTB DEEP DRILL HOLE

on drilling two holes,first a pilot hole as a sortof "fact-finding about1.5wt % DEHYDRIL-HT,a synthetich,ectoritc-typLei,-

mission"andthenthesuperdeepholeitself.

bearingNa-Mg silicatewhichyieldeda thixotropics, olid-free,

Main objectives of the pilot phase were to acquire a highly lubricantmud system.Later, due to its electrolyte

comprehensive set of geoscientific data from core sensitivityc,orrosivebehaviori,nstabilityat hightemperatures,

investigations,cuttingsanalyses,and boreholemeasurements and other factors,it was continuouslmy odifiedby adding

with which to develop the methodologyrequiredfor optimal HOSTADRILLa, norganicpolymera,ndNaOHplusNa•CO•to

evaluation of the superdeephole and to test the geological fix a pH valueof 10 to 11. With increasingtemperaturien the

prognosesM. oreover, the pilot hole would reducethe needfor deeperpartsof the KTB-HB (below7100 m) and owingto

samplingand loggingin the upper,largecalibersectionof the continuingsmallinfluxesof salineformationwaters,a steady

superdeephole and would provide the information on rock deteriorationin rheologicalpropertiesand water-binding

propertiesanddrillability, boreholestability,potentialgain and capacityrequireda partialreplacemenbty addinga mixtureof

loss zones,temperatureprofile, etc., critically neededfor the different commercial polymers (KEMSEAL, MILTEMP,

technicalplanning.

PYROTROL). Furthermore, in order to reduce borehole

The KTB pilot hole was spuddedon September27, 1987. instabilitietshemudweightwasraisedfrom 1.06kg/L to 1.40

The conceptdevelopedby the KTB engineers,which was to kg/L by addingbarite(seeTable 1 for a summaryof fluid

modify a conventionadl rill rig from industryand to combine systemsusedat variousstages).

rotarydrilling andwire line coringtechniquest,urnedout to be After completionof the pilothole,a 1-yearmeasuringand

very successfulW. ith a high-speedtopdriverotatingsystemand experimentationprogram was conducted,which included a

using an internal and externalflush-jointed5 V2inch mining comprehensiveloggingprogram,14 hydrofracmeasurements

drill stringwith 6 inch thin-kerfeddiamondcorebits,560 days and a large-scalethree-dimensiona(l3D) seismic reflection

of drilling and logging were needed to achieve a basement survey,coveringan areaof 19 x 19 km aroundthe drill site. In

penetrationof 4000 m, and a total of 3564 m of excellent April 1990 the hole was caseddownto 3850 m, leavingan

quality cores was recovered.By applying straight vertical openholesectionof 150m. Thepilotphasewasthencompleted drillingcapabilitiesthistechniquehasa depthpotentialof 5 to 6 with a first short-termpumptest,whichyielded71 m3 of

km andthusmaybe of specialimportancefor futurecontinental basemenbtrineswith highamountosf N2 andCH4 fromthe

researchdrilling to intermediatedepths.

uncased bottom zone.

A prerequisitefor the successof the drilling techniquewas The main resultsof the pilot phase[Emrnermann1, 989],

the developmentof a new water-baseddrilling fluid system, whichdeterminedthetechnicacloncepftor thesuperdeehpole,

which was undertakenin close cooperationbetween KTB were (1) the considerablyhigher than expectedgeothermal

engineersand geochemists.This system met all technical gradientw, hichled to a definitionof thedepthtargetat 10 km

requirementsw, asenvironmentallysafeand,for the first time, (correspondintogabout300øC);(2) thelithologicheterogeneity

alloweda quantitativegeoscientificmonitoringof the drilled andthecontinuoussteepinclinationof rockunits,whichcaused basementT. he startingcompositionwasa mixtureof waterwith severe deviation of the hole out of the vertical and resulted in
developmentof a vertical drilling strategy;and (3) the

frequencyof cataclasticshear zones and fluid inflow zones

Table 1. Drilling Fluid SystemsUsedin theKTB Main Hole

which, in combinationwith the high horizontaldifferential stressesl,ed to the expectationthat boreholeinstabilitieswould

Borehole section

DrillingFluid System

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

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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,

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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

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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

experimentfsie,ld investigationans,d externasl cientificcover administration tasks, telecommunication facilities,

investigations.

databasemanagementa, nd software modulesdeveloped

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18,186

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

on the home pageof the GFZ WWW server(http://www.gfz- metacumulaterocks. Most rock types display chemical

potsdam.de).

characteristicosf enrichedmid-oceanridge basalts(MORB);

however, normal MORB compositionsalso occur. These

Scientific Results

metabasicunitsperhapsrepresenst licesof formeroceanfloor formedin a backarcenvironmenotr RedSeatypeoceanic

Crustal Structure and Evolution

basin.
The variegatedseriesconsistsof an alternationof massive

The Oberpfalzis situatedat the westernmargin of the garnetamphibolitesf,ine-grainedbandedamphibolitews ith

BohemianMassif, the largestcoherentsurfaceexposureof layersof calcsilicataensdmarblesh,ornblende-biogtinteisses, basemenrtocksin centralEuropea, ndit encompasspeasrtsof and paragneissesA.mongthe metabasicrocks,alkali basaltic

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

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

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18,187

EMMERMANNANDLAUTER]UNGK:TBDEEPDRILLHOLE

i E

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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

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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

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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

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sw

EMMERMANN AND LAUTERJUNG: KTB DEEP DRILL HOLE

18,191

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.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.

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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

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

horizon which is related to the post-Variscancrustal thrust relativelylargedensitycontrasbt etweenthemajorrocktypesof

stack.

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

surveyandthepilot phaserevealedtheexistenceof shallowlow difficult. A partialsolutionto thisproblemcanbe achievedby a

electricalresistivityanomaliesandconfirmedthat the drill site combinationof gravity data with results of geomagnetics

wascloseto thecentreof an unusuallylargesurfaceanomalyof [Bosumet al., this issue].

the electric self-potential(about-600 mV) extendingNW-SE. The magnetic data give independentinformation about

That is, the drill site is situated on a "geobattery"which lithology (inventoryof ferri-magneticminerals)and can also

probablydrawsits energyfrom redox potentialdifferencesin portray tectonicfeatures,like mineralizedshear zones. The

the subsurface,with graphite-coatedcataclasticshear zones KTB superdeephole penetratedmany magnetic anomalies,

actingas electronconductingbridges.The modelpresentedby which have a vertical extent of some meters up to about

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

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

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

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18,193

EMMERMANN AND LAUTERJUNG:KTB DEEPDRILL HOLE

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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.

-30. SW
-35 -
s
-40 •

-45 -

-50 -.

448O•
4490

"•

/ 5540

/ 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:

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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

The desireto explainthe failed prognosisled to an ambitious any case, the observationsclearly demonstratethat external

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

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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

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

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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.

however,it wouldhavebeenbetterto havedrilled a technically simple, 2-3 km hole at each site instead of several shallow boreholes(< 500 m).

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
issue.

M611erP, ., et at., Paleo-andrecentfluidsin the uppercontinentaclrust-

AcknowlegmentsW. e are especiallyindebtedto R. Trumbullfor his

ResultsfrowntheGern•anContinentadl eepdrillingProgram(KTB), J.

constructivediscussionasndcritiqueof themanuscriptW. e alsothankU.

GeophysR. es.,thisissue.

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

O'Brien, P. J., J. Duyster,B. Grauert,W. SchreyerB, . St'0ckherta,nd K. Weber, Crustal evolutionof the KTB drill site:From oldestrelicsto the
lateHercyniangranitesJ,. GeophysR. es.,thisissue. Pechnig,R., G. Zimmermann,S. Haverkamp,J. Wohlenberg,and H.
BurckhardtI,ntegratedloginterpretatioin theGermanContinentadl eep

the scientificprogram(Em 23/14) and for supportingthe scientistsand

drilling Program:Lithology,porosity, and fracturezones,J. Geophys.

techniciansof the field laboratory(Em 23/19). Finally, specialthanksare due to the Universityof Giessenfor providingfacilitiesfor coordination of theprogramandadministrativesupportfor thefield laboratory.

Res., this issue Stoeckhert, B., The "brittle-ductile transition" in the KTB borehole: A
tentative prognosis,KTB Rep. 94-2, 25-34, Nieders,•ichsisches Landesdamftor BodenforschH.,annoverG, ermany,1994.

Stoll,J., J. BigalkeandE.W. Grabnet,Electrochemicmalodellingof self-

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