Мінеральні ресурси України (Nov 2021)
About characteristics of diamonds from ancient sedimentary thick layers of marginal parts of platforms
Abstract
Basing on carried out complex investigations’ opinion about various features of diamonds from a number of perspective sites of Tunguska diamondiferous sub-province has been confirmed. Among the sites some territories of Baikitsk and South-Tunguska areas are most perspective. Sufficient influence on formation of ancient diamond placers here has been exerted by Pre-Cambrian phase of kimberlite magmatism in Prisayanie and other similar structures of the Siberian platform, from where crystals were carried to Irkutsk amphitheatre. An opinion has been passed about confinedness of rounded diamonds’ areas of distribution to the fields of Pre-Cambrian terrigenous formations’ development, which allows forecasting discovery of high-productive bodies in marginal parts of ancient platforms, as well, that has been confirmed on the example of East-European platform. Results of diamonds investigation allow assuming possibility of thermal impact on crystals in conditions of ancient secondary collectors of trappean formation magmatic initiations, which led to transition of green pigmentation spots into brown spots. The received typomorphic features of diamonds of the discussed sedimentary thick layers can be used for restoration of exogenous history on the path from their sources to the places of modern location in placers, which is very important for determination of source areas of diamondiferous material. Judging by the presence of balasses in placers of the Nizhnyaya Tunguska viver basin carbonado in the upper river basin of the Vilyuy river and Tunguska type balasses in the Sredne-Marchinski diamant rayon (SMDR) typical rounded diamonds and tri gontriotahedra of the ist species, the demolition of such diamonds could reach the yunction zone of the Tunguska syneclise and Anabar (Anabariskhe anche-Anechariche river Trung). According to a number of typomorphic features, the studied to a number of typomorphic features, the studied diamonds are close to the resip crystals of the Urals and Middle Timan, but their distrinction is characterized by a higher (not less than 3–5 times) content of laminar crystals of a number of octahedron-rhombododecahedron which testifies to the polygenesis of their root sources (no less than two fields of the Precambrian phrase and one for the Mesozoic phase of magmatism). Typomorphic features of diamonds are important for paleographic reconstructions of the spread of ancient prolific deposits. The mineralogical zoning of the peacer diamond area by typomorphic features of diamonds opens up the possibility of localizing promising areas and searching for the source of this mineral, which is much more stable under exogenous conditions compared to other mantle formations.
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