TRIASSIC DIAMONDIFEROUS TUFFACEOUS-SEDIMENTARY ROCKS IN THE ARCTIC ZONE OF SIBERIA
S.A. Grakhanov1,2, V.F. Proskurnin1, O.V. Petrov1, N.V. Sobolev3,4
1A.P. Karpinsky All-Russian Research Geological Institute, Srednii pr. 74, St. Petersburg, 199106, Russia
2AO ALMAR-ALMAZY ARKTIKI, ul. Chernyshevskogo 8/2, office 207.1, Yakutsk, Sakha Republic, 677000, Russia
3V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
4Novosibirsk State University, ul. Pirogova 1, Novosibirsk, 630090, Russia
Keywords: Diamond, deposit, placer, Triassic, Arctic zone of Siberia
Abstract
In the Arctic zone of Siberia, large diamond occurrences have been discovered in volcaniclastic, sedimentary-volcaniclastic, volcanosedimentary, and sedimentary rocks of the upper Ladinian strata and the base of the Carnian (Triassic) strata. They are confined to the Primorye mineragenic zone, which is traced along the Laptev Sea water area from the western Verkhoyansk area to eastern Taimyr. We have first identified a specific range of diamonds in these deposits. Among the rounded crystals of varieties I, II, V, and VII, there are grains with a light carbon isotope composition and high nitrogen contents. They have no analogues in typomorphic features in the known primary deposits of Yakutia but are completely similar to diamonds in the Rhaetian, Early Jurassic, Late Jurassic, Early Cretaceous, Neogene, and Quaternary commercial placers and placer occurrences, which suggests their formation as a result of the erosion of Triassic sources.
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