V.A. DUSHIN, S.G. SUSTAVOV, D.I. PROKOPCHUK, A.K. TRUTNEV, V.S. KOZMIN (URSMU)

First discovery of a diamond from Lower Permian deposits in the area of the Sylva River headwaters (Sverdlovsk Region)

The article deals with the first discovery of a diamond in Lower Permian bedrock in the Sylva River headwaters within the eastern wing of the Yuryuzan-­Sylva depression. The work is based on results of authors’ studies, generalization of materials, both on the diamond potential of the Cis­Ural Trough and the West Ural structural megazone, and on geology and petrography of the host rock assemblages, their structural and tectonic position in the zone of influence of the Main West Ural Thrust. The paper uses results of studies on a TESCAN VEGA LMS scanning electron microscope with an Xplore 30 energy­dispersive attachment from Oxford Instruments and a URS­55 X­ray unit in an RCD chamber in the URSMU laboratory. The mineralogical and petrographic study of coarse clastic rocks hosting the diamond, identified as tuff breccias, showed their fluid­magmatic genesis, as evidenced by the textural, structural and mineralogical features of the rocks, including drop­shaped elliptical volcanic­glass segregations, pulp­like finely dispersed nature of the groundmass (binding material), ungraded, weakly rounded to acute­angled fragments of igneous and sedimentary rocks, occurrence of such accessories as kyanite, rutile, monazite, zircon, apatite, titanite, gold, chrome spinel, moisso-nite, magnetic and glass microspherules. The data obtained indicate the probable phreatic volcanism, which led to the transportation of the diamond and its satellites to a weakened activated zone in the forefront of the Main West Ural Thrust.
Keywords: diamond, tuff breccia, tuffizite, microspherule, Yuryuzan­Sylva depression, Main Western Ural Thrust