DEEP STRUCTURE OF EARTH AND PROBLEMS OF SUPER-DEEP DRILLING

Implementation of a proposed program of super-deep drilling in the U.S.S.R. would solve critical problems in contemporary geology including: a) structure and composition of the basaltic layer, lower granitic layer, definition of the Conrad and Mohorovi?i? discontinuities and relation of forces in the mantle to tectonic processes in the crust, b) differentiation processes leading to earth layering, c) study of granitization and basification, and their relation to ore-deposition, d) hydrothermal solutions and their mineralization and metamorphic effects; gas, fluid, and heat migration within and between mantle and crust, e) pre-Archeozoic development of continents and ocean basins, discovery of pre-Archeozoic rocks, f) definition of representative type sections through the crust. Five sites are proposed: 1) In the epi-Caspian depression to penetrate a sequence of 13–15 kilometers of sedimentaries in an oil province with a steep geothermic gradient, 2) in a polymetallic-ore eugeosyncline of the Urals through 10–12 kilometers of geosynclinal metamorphics and possibly a 3–8 kilometer granitic layer, 3) In the Kem' region of Karelia where the Conrad discontinuity is 8–10 km down in Archeozoic, and possibly older, rocks, 4) in the Kurina depression of Azerbaydzhan where the basaltic.layer occurs beneath a sedimentary-effusive miogeosyncline with a basal granitic layer, all only 5–8 km thick, and 5) on Kunashir in the Kuriles where the Mohorovi?i? discontinuity occurs beneath young volcanics, folded and metamorphic geosynclinal complexes, and a very thin, if any, granitic layer, all only 12 km thick. Super-drilling in the epi-Caspian depression should follow completion of a 7-kilometer hole started in 1961. Projects in Azerbaydzhan, the Urals, and Karelia present the fewest problems of drilling and logistics and should be undertaken as soon as possible. Remoteness and difficult drilling problems will necessitate drilling on Kunashir last. An extensive program of geophysical surveying and development of equipment must be part of the program. —M. Russell