DISTRIBUTION OF SALTS, BRINES AND ORES IN THE SEDIMENTARY COVER

Abstract

Comparison of maps of the distribution of stratiform polymetallic ore deposits with hydrochemical and salt maps shows the almost universal confinement of such deposits both directly to salt-generating basins and to their marginal parts, where subsurface thermal brines were discharged in zones of poleuplifts. Study of fluid inclusions in minerals from these ore deposits has shown that the ore-forming solutions were brines with high contents Cl, Na, Ca and often K. and a low content of SO. The vertical hydrochemical zoning of natural waters and experimental research have enabled a number of investigators to relate the distribution of brines in the sedimentary cover to their instability in the Earth's gravitational field and their tendency to occupy pore space in accordance with their density. The brines of course, could not have remained inert unaltered during their migration through the infrasalt sedimentary rocks. The subsurface brines could also have taken up metals from the crystalline basement rocks, into fractures in which they flowed, and then been driven upward by more concentrated brines in subsequent stages of halogenesis. To substantiate the gravitational hypothesis of formation of ore-bearing solutions, the author discusses using data on the distribution of evaporates, brines and ores in the stratigraphic sections through sedimentary basins.