VOLCANOGENIC-SEDIMENTARY DEPOSITS (EN: volcanogenic-sedimentary deposits; DE: vulkanogene Sedimentlagerstatten; FR: gites volcano-sedimentaires; ES: depósitos volcanico-sedimentarios; RU: вулканогенно-осадочные месторождения) are the depositions of the useful minerals, which have been formed as the result of the inflow, into the basins of the ancient and modern seas and oceans, of the mineral products, which are formed during the eruptions of the volcanoes at the bottom of the sea, on the islands, and along the shores, and as the result of the sedimentation of these products in the form of the layers, slabs, and nodules.
The volcanogenic components of the useful minerals could inflow onto the areas of the accumulation of the sediments within the solutions of the volcanic gas and hot waters of the volcanic origin, within the adsorbed state on the surface of the volcanic ash, during the decomposition of the cooled lavas and ashes by the sea water, as the consequence of the leaching and removal from the lava rocks and ashes by the volcanic gaseous and liquid solutions. There belong to the volcanogenic-sedimentary deposits the large tabular depositions of the iron and manganese ores, which have been formed of the silicates, carbonates, oxides and hydroxides of these metals, and also the pyrite ores, to the composition of which there belong the sulfide compounds of iron, copper, and zinc, and sometimes of lead, barium, and calcium. There may serve as the examples of such deposits the iron ore deposits of the Transuralia, and the copper deposits of the Ural mountains (Gajskoe, Degtyarskoe, and others). They believe, that certain deposits of the bauxites, phosphorites, and uranium also are the volcanogenic-sedimentary deposits. These deposits are embedded within the strata of the rocks, which are consisting of the cooled lavas, ashes, and layers of the siliceous rocks, which are alternating with the normal marine sediments, namely, with the schists, sandstones, and limestones.
Among the volcanogenic-sedimentary deposits, there are known the depositions of the different geological ages, namely, since the most ancient (pre-Cambrian) till the youngest (modern). It is believed, that the accumulations of the nodular ores of iron and manganese at the bottom of the Pacific, Atlantic, and Indian oceans (see the "Ferromanganese concretions" article), which are containing the admixture of cobalt, nickel, molybdenum, platinum, and other valuable metals, also have been formed from the products of the underwater eruptions of the young volcanoes.
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