Transcription by Christian Röhr from

KTB Report 90-8, KTB Pilot Hole, Results of Geoscientific Investigation in the KTB Field Laboratory, 0 - 4000.1 m), Edited by the Project Management of the Continental Deep Drilling Programme of the Federal Republic of Germany in the Geological Survey of Lower Saxony, R. Emmermann, H.-G. Dietrich, J. Lauterjung, Th. Wöhrl

KTB-Report, 90-8, B1 - B55, 65 Abb., Hannover 1990

German Continental Deep Drilling Program (KTB) -

Geological Survey of the Pilot Hole "KTB Oberpfalz VB"


C. Röhr, J. Kohl, W. Hacker, S. Keyssner, H. Müller*, J. Sigmund, A. Stroh, G. Zulauf**

D-8486 Windischeschenbach
Federal Republic of Germany

present address:
Mineralogisch-petrographisches Institut
Albertstraße 23b
D-7800 Freiburg i. Br.
Federal Republic of Germany
Geologisch-Paläontologisches Institut
Johann Wolfgang Goethe-Universität
D-6000 Frankfurt/Main
Federal Republic of Germany


B.1 Introduction
B.1.1 Geological setting
B.1.2 Technical data, sampling

B.2 Geological Section of the Pilot Hole
B.3 Gneisses
B.3.1 Petrography
B.3.2 Chemical Composition

B.4 Metabasites
B.4.1 Petrography
B.4.2 Metamorphic evolution
B.4.3 Chemical composition

B.5 Late Dykes
B.5.1 Lamprophyres
B.5.2 Aplites

B.6 Ore Mineralization
B.6.1 Ore mineralization of gneisses
B.6.2 Ore mineralization of metabasic rocks
B.6.3 Ore mineralization of meta-ultramafic intercalations
B.6.4 Conclusions

B.7 Tectonic evolution
B.7.1 Early ductile deformation
B.7.2 Late deformation in the semi-brittle and brittle field
B.7.3 Synopsis of deformation and metamorphism
B.7.4 Implications for tectonics



The KTB pilot hole was drilled through the tectonometamorphic unit of the Zone of Erbendorf-Vohenstrauss (ZEV) at the western margin of the Bohemian Massif (Central Europe) to a depth of 4000 m.

The drilled crust is built up by the following rock sequences:
- monotonous garnet-Al2SiO5-biotite gneisses
- metabasic sequences of amphibolites and meta-gabbros
- interlayering of amphibolites, muscovite-biotite gneisses, biotite-hornblende gneisses and calcsilicate rocks.

Gneisses comprise about 70%, metabasites about 30% of the volume. The rocks underwent polyphase metamorphism. An early stage of high-pressure metamorphism (p > 10 kbar, T around 700 °C) is documented by parageneses and mineral compositions locally preserved in metabasites. Pervasive re-equilibration has taken place under amphibolite facies conditions (p =7 ± 1 kbar, T = 675 ± 50 °C), which are reflected by the bulk of the metabasites and paragneisses. Later partial retrogression under greenschist facies and lower T conditions is pervasive. It has gone to completion in places. Mineralized fissures and cataclasites indicate significant activity of fluids during the late stage evolution.

The foliation of the gneisses dips steeply to SSW down to 3000 m turning towards the E in the deeper part of the section. This structure is interpreted as a large scale open fold with subhorizontal axial plane. The axis plunges gently towards SSE. It formed late, at temperatures below about 500 °C.

A NE-SW trending fault system has caused several stages of cataclasis with conspicuous graphite mineralization. The maximum principle stress direction has rotated from NE to N during compression in the brittle field. During the subsequent late stage of crustal extension the minimum principle stress direction is about E.

Ore mineralizations are generally sparse and of secondary origin, local enrichments correlate with zones of pronounced alteration. The predominant ore minerals pyrite and pyrrhotite and to a lesser extend base metal sulphides are present throughout the section. Pyrrhotite causes most of the magnetic anomalies. Oxides (ilmenite, rutile, and minor magnetite) dominate in the metabasic and meta-ultramafic rocks.

Open fissures containing brines and mineralized with quartz and calcite have been drilled at depth below 3447 m. Near epidote-rich fissures below 3800 m pyrite is replaced by oxidic ore minerals (magnetite, hematite, goethite, and ilvaite).

B.1 Introduction

The continental Deep Drilling Program of the Federal Republic of Germany (KTB) started the pilot hole in September 1987. It reached a final depth of 4000.1 m in April 1989. Core recovery is a total of 3268 m. The main hole will be started in September 1990. It is planned to reach a depth of 10,000 m by the end of 1994.

The drilling site is situated in Eastern Bavaria (Oberpfalz), about 200 km NNE of Munich (Figs. B.1.1, B.1.2), in the exposed basement rocks of the Bohemian Massif, close to its western margin.

Geographical and geological situation

Fig. B.1.1: Geographical and geological situation:
a) Europe, b) outcrops of Variscan orogen in Central Europe and c) the Western Margin of the Bohemian Massif. KTB = drill site, ZEV = Zone of Erbendorf-Vohenstrauss, ZTM = Zone of Tirschenreuth-Mähring, ZTT = Zone of Tepl-Taus.


Geological map of the KTB drilling location

Fig. B.1.2: Geological map of the KTB drilling location, after Stettner in Weber and Vollbrecht (1986).


B.1.1 Geological Setting

The western part of the Bohemian Massif in NE-Bavaria can be subdivided into three Variscan tectono-metamorphic units (Fig. B.1.1): Saxothuringian, Moldanubian and the Zone of Erbendorf-Vohenstrauss. To the west of the NW-SE trending Franconian Line fault system, these crystalline basement rocks are overlain by permo-triassic sediments (Weber and Vollbrecht 1989, Franke 1989):

The Saxothurigian of the Fichtelgebirge consists of Palaeozoic metasediments and mafic and felsic metavolcanic rocks that have suffered a low to medium grade metamorphism at shallow crustal depth. The peak temperatures increase from below 350 °C in the north to more than 600 °C in the south, at the adjacent Moldanubian. The "Zone of Tirschenreuth-Mähring" (ZTM, Schreyer 1966, Stettner 1979, Weber and Vollbrecht 1989) is interpreted as a high temperature shear belt. The age of the low pressure metamorphism was determined to be 320 Ma (Teufel 1988, Kreuzer et al. 1989).

The Moldanubian consists of a presumably Late Proterozoic to Palaeozoic, monotonous, metasedimentary sequence with some intercalated variegated units. It has a polymetamorphic history. Eclogites and associated gneisses reflect an evolution from high to low pressures (Blümel 1983, O'Brien 1989). Small kyanite and garnet inclusions in plagioclase of paragneisses document a former equilibration at intermediate pressures (Blümel 1983). The dominating parageneses with cordierite, K-feldspar and sillimanite reflect a late stage of high temperatures at shallow depth dated as about 320 Ma (Teufel 1988, Kreuzer et al. 1989).

The Zone of Erbendorf-Vohenstrauss (ZEV) has formed from a probably Late Proterozoic to Palaeozoic sequence, transformed to paragneisses, amphibolites, calcsilicate rocks, orthogneisses and metagabbros. The dominating intermediate pressure amphibolite facies overprint has taken place about 380 Ma ago (Teufel 1988, Kreuzer et al. 1989). An earlier metamorphism at higher pressures is locally well documented in metabasites. The ZEV has been interpreted to be part of a large nappe complex covering the Moldanubian and Saxothuringian boundary (Weber and Vollbrecht 1986, 1989). This complex is characterized by the high amount of metabasites and the 380 Ma old intermediate pressure type metamorphism. Other units attributed to this nappe complex are the Münchberg Massif and the Zone of Tepla-Domazlice (Zone of Tepl-Taus, ZTT). The metabasites of the different units show significant differences in their geochemical character (Okrusch et al. 1989).

The drilling site is situated in the northwestern part of the ZEV, about 3 km NW of the small town of Windischeschenbach. The detailed geological map by Stettner (Fig. B.1.2) shows apophyses of the Falkenberg granite, which covers a greater area to the east, in close vicinity to the drill site. To the north, the ZEV is bordered and underlain by the south-dipping "Erbendorf Greenschist Zone", which consists of amphibolites, metagabbros, greenschists, serpentinites and minor metasediments and the "Wetzldorf Unit", which consists of metalydites, quartzites and phyllitic schists. These rocks are considered to be the lower part of the ZEV nappe complex. One major aspect of the project is to drill through the nappe complex to reach the inferred Saxothuringian/Moldanubian collision zone underneath.

B.1.2 Technical data, sampling

Corresponding to the applied drilling techniques the samples available for geological and geochemical investigations are drill cores (diameter: 94 mm), cuttings (grain size 0.1 - 10 mm) and drill flour ("centrifuge samples", 20 µm - 0.1 mm). Down to 1998 m the well is designated as VB1. Due to technical problems at 1998 m depth the lowermost part of the hole had to be abandoned. After back cementation and directional drilling a new hole (VB1a) was started from 1709 m downwards (cf. chapter A for more detailed information concerning drilling techniques and core recovery). A second kick off point is at 3766 m. From there down to 4000 m the hole is designated as VB1b. Cores from VB1a are available down to 3898 m.

For intervals represented only by cuttings and centrifuge samples, the geological profiles had to be constructed from macroscopical and microscopical examination and analyses (chemical, X-ray diffraction) of this material combined with the geophysical borehole logging data. All recovered core material has been reconstructed to its original shape and length followed by itemization and labeling of every piece. Core sections that match together are marked by a straight line. This serves as a reference line for all orientation measurements at the core before the true geographic orientation at the core is reconstructed. Reorientation requires either the evaluation of Formation Micro Scanner and Borehole Televiewer logs or, in case of drillling with orientation marks, determination of the actual dip and orientation of the borehole. Mesoscopic structural analysis was done by measurement of cores or copied wrappings (Fig. B.1.3a). Petrographical and microstructural analysis of the samples is based on about 2500 thin sections and 500 polished sections. Furthermore, chemical and modal analyses were performed on these samples by X-Ray Fluorescence Spectrometry and quantitative X-Ray-Diffractometry. More details about these methods can be found in Schmitz el al. (1989) and in chapter A and C of this volume.

Unrolled cylinder mantle  and normal photograph of two core pieces

Fig. B.1.3: Unrolled cylinder mantle (a) and normal photograph (b) of two core pieces from 455 m. Discordant contact between garnet-biotite-gneiss (GNS) and amphibolite with calcsilicate layers (AMP), at the contact leucocratic mobilisate (MOB).


Geological Survey of KTB Pilot Hole