Specific Features of Hydrothermal and Hypergene Alterations of Micaceous Kimberlites

Abstract

Basing on complex research of accessory and rock-forming minerals of kimberlite rocks of pipes Udachnaya, Nyurbinskaya and Botuobinskaya, the processes of secondary mineral formation have been determined in details. The products of kimberlite rocks alteration have been studied, the scheme of initial minerals transformation has been constructed, typomorphic features of final weathering products have been revealed, the profile of kimberlite rocks’ weathering crust of Nakyn field has been established. It was shown that saponite in Yakutian kimberlite pipes has a hydrothermal origin that make it possible to use it during prospecting of kimberlite bodies under certain conditions. Complex comparative investigation of ancient weathering crusts of rocks of various chemical and mineralogical composition allowed tracing specific features of their hypergene alteration and typomorphic indications of eluvial products that is very important for solving a number of applied tasks. It is possible to differentiate at the structural level the same varieties of primary minerals in redeposited weathering products of various rocks, as well as identify secondary stratified silicates, differing in the last case either by character of octahedral positions’ occupation in their structure, either by the way of mutual superposition of individual silicate layers or by their polytypic character. That is why redeposited in ancient sedimentary thick layers products of various types of weathering crusts preserve structural and chrystallochemical features in relation to the minerals of eluvial strata, allowing tracing the ways of terrigenous material transport into sedimentation basins (including diamondiferous material