S. R. Krainov, B. N. Ryzhenko, and E. V. Cherkasova
Vernadsky Institute of Geochemistry and Analytical Chemistry (GEOKhI), Russian Academy of Sciences, ul. Kosygina 19,
Moscow, 119991 Russia
e-mail: ruzhenko@geokhi.ru
Received August 20, 2003
Abstract—Empirical materials on the distribution of ore-forming elements (Zn, Pb, Fe, Mn, and Cu) in chlo-
ride brines and the thermodynamic simulations of geochemical processes leading to the accumulation of these
elements in such brines were analyzed together to demonstrate that (1) high concentrations of ore-forming ele-
ments are generated in chloride brines of the Cl–Na–Ca and Cl–Ca–Na geochemical types, which evolve in
compliance with the “calcic trend,” and the geochemistry of bivalent ore-forming elements in these brines is
similar to the geochemistry of Ca at corresponding Eh and pH; and (2) chloride brines with high concentrations
of ore-forming elements can be produced at a certain combination of boundary conditions, including high R/W
ratios and interaction temperatures in the rock–water systems and, particularly, long durations of these interac-
tions. Because of this, the most active concentrators of ore elements are ancient (Paleozoic) relict marine brines
that underwent preliminary evaporative concentrating and were deeply metamorphosed in the host rocks (par-
ticularly terrigenous clayey rocks). Thermodynamic simulations were utilized to quantify the effects of differ-
ent lithologies on the genesis of chloride brines with high concentrations of ore elements. These data are used
to formulate a hypothesis explaining the genesis of stratiform base-metal ore formations: chloride ore-forming
brines mobilize ore elements from terrigenous (clayey) rocks in salt basins, and these elements are precipitated
in the form of sulfides under certain thermodynamic boundary conditions in carbonate rocks. The precipitation
of sulfides of the ore-forming elements can be maintained by the material of the carbonate rocks themselves,
without inflow of sulfide ions from outside.
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