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The AAPG/Datapages Combined Publications Database

Utah Geological Association

Abstract


Proceedings of the First International Conference on the New Basement Tectonics, 1974
Pages 555-564

The Importance of Lineaments in the Tectonic Evolution of the Earth’s Crust and in the Occurrence of Ore Deposits in Middle Europe

A. Pilger

Abstract

Most European geologists feel that the cardinal or fundamental lineaments on the surface of the globe originated in Precambrian time and even earlier, with the beginning of the Earth’s crust. These trends have been a part of the early tectonic evolution of the crust, resulting in the present tectonic network of the Precambrian basement. They have been revived from time to time during geologic ages, strongly influencing the tectonic history of the continents, including that of geosynclines. Frequently, they cross all younger structures and may show some unexpected evidence for their existence within these younger areas.

The cardinal lineaments run straight for long distances, over hundreds and even thousands of kilometers, outlining sharp boundaries of tectonic units and of continental or subcontinental blocks. Their accompanying subordinate structures, as well as the lineaments of a second order, exhibit mutual tectonic relationships with regard to the younger structures encountered. Certainly, important lineaments also came into being in later geologic times, for instance in connection with the Hercynian orogeny or with Mesozoic and Cenozoic plate tectonics, but such lineaments often follow the older tectonic directions.

The Precambrian basement of Middle Europe is insufficiently exposed and has been too often altered by later tectonic events, magmatism or anatexis to permit extensive research with regard to the origin of lineaments. This explains the difficulty in ascertaining for this region the connection between basement tectonics and lineaments, while such work can be undertaken best in areas like Finland, North America, etc. It remains possible, however, to follow the evolution of lineaments through time and to compare their effects on successive tectonic stages. Research studies of the internal textures of lineaments, most important in theory as well as in practice, have to be made with the aid of Petrofabric Analysis (there are, for instance, shearing axes in OkI and hkO positions, bisecting rectangular sets of fissures and fractures); they will give an insight into the origin of lineaments and their relationships with the encountered structures.

Many ore deposits occur along lineaments, preferentially accompanying lineaments of a second order. Whereever a lineament crosses a coal field, for example. Its strong network of shearing fissures and fractures can make mining quite difficult, yet, on the other hand, it may greatly increase the amount of pore spaces to permit a better circulation of hydrothermal fluids and bring about some deposition of ore.


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