Известия высших учебных заведений: Геология и разведка (May 2019)
Comparative characteristics of indicator minerals of kimberlites and new perspectives diamond of the Ygyatta diamondiferous region (Western Yakutia)
Abstract
The new data on the composition of kimberlite indicator minerals (KIM) — pyropes and picroilmenites — of the first kimberlite body T-54-14, opened in 2015 in the Syuldyukar kimberlite field by the geologists of ALROSA PJSC, during the verification of the anomaly T-54-14, have been given. The pyropes of the kimberlite body T-54-14 are rep-resented mainly by the differences of the lherzolite paragenesis, the concentration of pyropes of the diamondiferous dunite-harzburgite paragenesis is low and does not exceed 1,8%. Among the picroilmenites the low-chromium varieties prevail, with the content of magnesium 5—9 wt. % MgO, the low-magnesium high-chromium varieties are absent. The comparison data with KIM of Khatyryk (Syuldyukar field) and Vostochny (Ygyatta field) high-contrast halos, allocated within the Ygyatta diamondiferous region, have been provided. The pyropes from the Khatyryk halo are close in composition to the pyropes of the kimberlite body T-54-14, but show a higher concentration of manganese — 0,5 wt.% MnO. The picroilmenites from the Khatyryk halo are distinguished mainly by the presence of high-chromium high- and low-magnesium varieties. KIM from the Vostochny halo also have differences in the composition in comparison with the KIM of the kimberlite body T-54-14. A higher concentration of wehrlite (10%) and diamondiferous duniteharzburgite (7%) pyropes has been established, pyropes have a lower (0,45 wt.%) concentration of MnO, high-chromium low-magnesium varieties of picroilmenites have been identified. The presence of high-contrast halos of IMK, significant differences in the mineral composition, direct findings the diamonds and pyropes without marks of mechanical wears in the sedimentary Carbon and Permian deposits with low reservoir properties indicate a high pros-pect for the discovery of a industrial diamonds kimberlites in the Ygyatta region.
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