Exploration of the Deep Continental Crust - Böcker

Drilling deep into the earth holds a fascination for earth scientists derived in part from the fact that the drill hole is the ultimate test of a hypothesis. When surface exploration methods have been fully uti­ lized and all the geological inferences drawn about the structure be­ neath the surface, we must finally drill to sample directly the third dimension of the crust of the earth. The drill is thus the tool of choice of the energy and minerals re­ sources industry. Because of high cost, drilling has been only sparing­ ly used for solving fundamental problems in the earth sciences. But now, having used the quite sophisticated methodology of exploration geophysics, the exciting structural detail emerging from seismic re­ flection profiling in particular has led several nations to begin a major program of scientific drilling to solve some of the major prGb­ lems in the earth sciences. Hhat is described in this volume are the blueprints for national re­ search programs in France, the Federal Republic of Germany, Japan and the United States. The Soviet Union has already embarked on a major drilling effort, the results of which are soon to be published. Results, of course, are still few, and this first volume is more concerned with the problems to be solved.

The Second International Symposium on Observation of the Continental Crust Through Drilling (supported by the Alfred Wegener Foundation, the Federal Ministry of Research and Technology, the German Research Society and the Inter-Union Commission on the Lithosphere) took place in Seeheim (Odenwald) and included a discussion on the Continental Deep Drilling Programme of the Federal Republic of Germany. This sym- posium was regarded as the continuation of a course agreed upon in Tarrytown in 1984. Here, the scientific contents and technical con- cepts of the technically complex and expensive experiments of conti- nental drillings were carefully coordinated before the national commit- tees carne to practical decisions. In Seeheim, rather than in Tarrytown, the methods of technical realization were in the foreground, as the results of scientific projects, e. g. , the NAGRA or the Salton Sea Scien* tific Drilling Project, were evaluated, supplementing industrial ultra- deep drilling experience. The presentation and discussion of the Con- tinental Deep Drilling Project of the Federal Republic of Germany was also granted ample scope with nine lectures and sixty posters.The con- tents of the KTB presentation have been summed up in two contributions and included in this volume. The conference centered on three major subjects: The National- Prograrrunes and Aspects of Geoscience: H. Vidal, FRG; H. Riesen- huber, FRG; E. Seibold, FRG; K. Fuchs, FRG; Cl. Megnien, F; R. S. An- drews, USA; F. G. Stehli, USA; E. A. Kozlovsky, USSR; E. V.

The articles in this volume were selected from a series of reports delivered in the So­ viet Union at Yaroslavl during the International Seminar "Super-deep drilling and deep geophysical research", which was organized and held in August 1988 by the Ministry of Geology of the USSR, jointly with the Inter-Union Commission on the Lithosphere. One of the most important problems of modem geology, is the state and prospects of further development of deep continental structure investigations, was discussed at the seminar with the participation of 245 scientists and specialists from 19 countries. At the plenary and sectional meetings of the seminar, 83 reports were delivered, discussions on the most interesting problems were organized, the exchange of ideas between the leading scientists a round table took place in discussion. The distinctive feature of the present collection of articles is the wide scope of the investigation of the Earth's crust. The reports elucidate such subjects of world impor­ tance as (1) achievements in implementation of major scientific programs investi­ gating deep Earth structure and plans for their further materialization; (2) theoretical problems of carrying out geological-geophysical explorations and drilling operations; and (3) new approaches to the study of the Earth's interior. The results of deep inves­ tigations of individual countries and organizations are considered, and concrete tech­ nical elaboration, methods of work execution, etc. are discussed.

The present book is devoted to the study of the deep Earth's interior structure, one of the most important problems of Earth sciences today. The drilling of the Kola superdeep well inaugurated a new stage in the study of the Precambrian continental crust. The well was sunk in the northeastern part of the Baltic Shield, in an area where the Precambrian ore-bearing structures, typical of the ancient platform basements, are in juxtaposition with each other. To the present the well has been drilled to a depth of 12 km, has traversed the full thickness of the Proterozoic complex and a considerable part of the Archean stratum, and is still be­ ing worked on. This book reviews the principal results of investigations to a depth of 11,600 m; these are described in three sections: geology, geophysics, and drilling. The book begins with a general review of the history, the present state of knowledge, and trends of further investigations in the field of study of the Earth's interior and superdeep drilling. The first section of the book considers the geology of the vicinity of the Kola superdeep well and describes its geological section based on a detailed examination both of the cores and the near-borehole area.

Third International Symposium on Observation of the Continental Crust through Drilling

The drilling site of the KTB is located on the western margin of the Bohemian Massif, a few kilometers south of the structurally important Saxothur ing ian/Moldanubian boundary of the central European Hercynian orogene and several kilometers east of one of the most important Permian-Mesozoic strike-slip zones of central Europe, the Franconian line. The borehole will be drilled in the Moldanubian segment (Fig. 1). o ~-:::--...~ . . -. . -. D Il1O , Fig. l: Geological map of the Central Europe Variscides and location of borehole From geographical and political points of view, the drill site is located in northern Bavaria in the Oberpfalz province near the towns of Windischeschenbach and Erbendorf about 40 km southeast of Bayreuth. TARGETS AND RESEARCH TOPICS 'The Continental Deep Drilling program of the Federal Republic of Germany (KTB) is a project of basic geoscientific research. The program and goals of this project have been set by a board of the Senate Commission on Geosciences of the German Research Foundation (DFG). The technical concept of the drilling, sampling, coring and logging programs corresponds to these goals.The upper limit of the budget of 450 million DM is approved by the Federal Ministry of Research and Development (Bundesministerium fuer Forschung und Technologie).

In October 1986 the German Minister for Research and Technology (Bundesminister fUr Forschung und Technologie), Dr. H. Riesenhuber, officially announced that the super-deep borehole of the Continental Deep Drilling Program of the Federal Republic of Germany (KTB) would be drilled in the Oberpfalz area of Northern Bavaria. The site selection was based on a recommendation from the Deutsche Forschungsgemeinschaft (DFG) made after an evaluation by the Project Management of the technical and financial risks involved. This decision was preceded by a conference held from September 19 to 21, 1986 in Seeheim/Odenwald at which the results of the site studies in the Oberpfalz and the Schwarzwald were presented and thoroughly debated. The models and scientific targets resulting from these investigations formed the basis for a vote by the DFG Senate Commission for Geoscientific Interdisciplinary Research which was taken immediately after the conference. After evaluation of all scientific and technical aspects, the members of the commission voted almost unanimously for the Oberpfalz site. It was, ho",'ever, strongly emphasized that both locations had a wealth of attractive research objectives and that despite clear-cut differences in some major aspects scientifically the two could be regarded as more or less equivalent. Both'locations would be excellent sites for research drilling and would certainly cor.

Terrestrial Heat Flow and the Lithosphere Structure summarizes current problems of analyzing related data. The individual chapters are written by leading scientists in geothermics, and are arranged in three sections: - General Lithospheric Geothermics - Regional Lithospheric Geothermics - Worldwide Heat Flow Density Studies. Emphasis is laid on the interrelations between lithospheric structure and local heat flow fields.