On the relation between the rare-earth — rare-metal and gold ore mineralization and fault-block tectonics of the Ukrainian Shield. 1

Abstract

The paper, which is the first of a series of articles on the relation of metallogeny and fault-block tectonics of the Ukrainian Shield (USh), summarizes data on the chemical-mineralogical composition and the exact location of deposits, ore occurrences and points of increased rare-earth — rare-metal and gold mineralization, which are combined into eight groups: TR, U and Th, W and Mo, Be and Sn, Ta, Nb and other rare metals, zir-con and monazite (Zr), Au, F. They are compared with the scheme of the fault-block structure of the shield constructed from the results of tectonophysical studies. A detailed description of the fault zones of the USh has been given and many of them are shown to be composed of packets of a budinized and cataclasized varicoloured complex: metamorphosed basites and ultrabasites, calciphyres, quartzites, gneisses, micas, skarns, plagioclasites, quartz-feldspar rocks and silicification zones. The formation of such packages of the varicoloured complexes is associated with shear processes in wide (from 7 to 20 km) fault zones, accompanied by tectonic stratification of the basement rocks, dynamometamorphism, diaphthoresis, metasomatism, etc. The age of the fault zones of the USh and correlation with the formation of ore mineralization are considered in this article. It is emphasized that the rock complexes of the Precambrian faults are brought to the surface from considerable depths and are determined by the conditions of deep stress metamorphism and granitization during shifts, therefore they cannot be compared with complexes of modern faults. However, the structural parageneses of Precambrian faults in their geometric relationships are close to those obtained from the results of physical experiments on brittle-plastic and plastic materials. This makes possible to determine the nature of the stress-strain state of the Earth’s crust during the process of fault formation and the parameters of the stress fields. It is established that 94 % of all deposits and ore occurrences are located within fault zones, the area of which occupies about 22 % of the USh area. The obtained data refine the known metallogenic maps of the USh and allow reducing the priority areas in four to five times when planning future mapping and prospecting works for the groups of deposits under consideration.