Petrographic composition of diamond-bearing Carnian formations of the Bulkur anticline the north-eastern Siberian Platform

Abstract

Research subject. Diamondiferous explosive detrital and sedimentary volcanoclastic rocks of the Carnian base of the Upper-Triassic confined to the west flank of the Bulkur Anticline in the north-eastern Siberian Platform. Aim. To identify diamondiferous features of Carnian rocks. Materials and methods. The materials collected by the authors while performing prospecting and evaluation works by the OOO Arctic Mining Company in 2022-2023 were used. The materials were represented by field observation results and mineral-petrographic studies. Rock types were defined by petrographic analysis in thin sections using a Leica DM2700P microscope and known classifications. Diamonds and accessory minerals were distinguished from steam sediment samples and described at the central analytical laboratory of the Vilyuysk Geosurvey Expedition, PJSC Alrosa. The estimation of diamond and pyrope content in core- and bulk samples (CPT) was performed considering their direct correlation. Results. The highest concentrations of diamonds were found to be localized in rocks in the west flank of the Bulkur Anticline. These formations were detected in lapilli tuffs, xenotuff breccia and orthotuffites. Paratuffites and tuff aleuro-sandstones exhibit a lesser diamond potential. Conclusions. The diamond potential of rocks of the Carnian base correlates well with the pyrope content and saturation of volcanoclastic materials. Tuff aleuro-sand-stones of the Bulkur member in the Osipay base and overlying shell deposits are considered potentially diamondiferous. Diamondiferous formations possess considerable thickness and productive efficiency, thus assuming a substantial increase in the diamond prospective potential in the Russian Arctic.