(also called exogene deposits), mineral deposits associated with ancient and modern geochemical processes on the earth’s surface. They form on the earth’s surface; in the thin upper layers of the earth’s crust, including tables of ground water and partly stratal underground water; and on the bottom of swamps, lakes, rivers, seas, and oceans.
Supergene deposits are formed by mechanical and biochemical transformations and differentiations of inorganic substances of endogenic origin. Four groups of deposits are distinguished: residual, infiltration, placer, and sedimentary. Residual deposits are formed by the loss of soluble inorganic compounds from the weathering crust and the accumulation of poorly soluble residue of economic importance (nickel, iron, and manganese ores, and magnesite, bauxite, and kaolin). Infiltration deposits form by precipitation from underground water, below the earth’s surface, of valuable soluble substances (ores of uranium and copper, as well as native sulfur). Placer deposits are created by the accumulation of heavy and tough valuable minerals (gold and platinum; minerals of titanium, tungsten, and tin) in the friable deposits of slopes, rivers, and shores. Sedimentary deposits are formed during the process of accumulation of precipitates at the bottoms of marine and continental reservoirs (coal, combustible shales, petroleum, combustible gas, salts, phosphorites, gravel, sands, clays, limestones, cement, gypsum, jasper, and tripoli, and ores of iron, manganese, aluminum, uranium, copper, and vanadium). Supergene mineral deposits have great industrial significance.
REFERENCESSmirnov, V. I. Geologiia poleznykh iskopaemykh, 2nd ed. Moscow, 1969.
Strakhov, N. M. Osnovy teorii litogeneza, vols. 1-3. Moscow,1960-62.
V. I. SMIRNOV