CRUSTS OF WEATHERING AS BASIC SUPPLIERS OF TERRIGENOUS MATERIAL DURING FORMATION OF ANCIENT DIAMONDIFEROUS PLACERS

Abstract

On the example of Mesozoic deposits of one of the main diamondiferous regions of the Siberian platform, basic suppliers of terrigenous material into the ancient diamondiferous placers under formation and their occurrences have been characterized. Special attention has been paid to characteristics of local sources of allothigenous material removal to sedimentation basins of the said period, the main of which were Middle-Late Triassic crusts of weathering on terrigenous-carbonate rocks, formations of trappean origin (dolerites, tuffs, tufogene thick layers) and kimberlites. Comparatively short transfer of weathering products and their accumulation mainly in freshwater continental basins determined weak hydrothermal effect of environment on allothigenous minerals. The received specific features of the mineral composition of various rocks' crusts of weathering have been recommended for application during paleogeographical reconstructions in diamondiferous regions, to determine source areas of terrigenous material, in particular. The stated recommendations have been implemented when assessing material from local sources of drift (including diamondiferous material as well) to continental (Irelyakh and Ukugut suites) and coastal (Pliensbachian and Toarcian stages) deposits of MaloBOtuobinsky region, where primary and placer diamond deposits are successfully mined.