Geochemistry and petrology of protosulfide melts in an ore-bearing apophysis of the Yoko-Dovyren intrusion

Pshenitsyn, I.V.; Ariskin, A.A.; Nikolaev, G.S.; Korost, D.V.; Yapaskurt, V.O.; Kislov, E.V.; Sobolev, S.N.; Kubrakova, I.V.; Tyutyunnik, O.A.

Авторы: Pshenitsyn I.V., Ariskin A.A., Nikolaev G.S., Korost D.V., Yapaskurt V.O., Kislov E.V., Sobolev S.N., Kubrakova I.V., Tyutyunnik O.A.
Журнал: Geochemistry International
Том: 60
Номер: 3
Год издания: 2022
Издательство: Maik Nauka/Interperiodica Publishing
Местоположение издательства: Russian Federation
Первая страница: 235
Последняя страница: 255
DOI: 10.1134/S0016702922030065
Аннотация: The paper presents results of petrological and geochemical studies of sulfide-bearing rocks from a bottom apophysis in the central part of the Yoko-Dovyren massif, northern Transbaikalia, Russia. It is composed of plagioperidotite and was sampled in a bulge up to 300 m thick throughout the whole vertical section,from its upper to lower contact. The observed diversity of sulfide-bearing rocks is subdivided into four types:(1) picrodolerite with droplet-shaped sulfides, (2) olivine gabbronorite with sulfides varying from dropletshaped to irregular globules, (3) olivine gabbronorite with larger globules and patchy net-textured domains,and (4) net-textured ores. These varieties occur in the basal zone of the apophysis, in the interval up to 30 m inward from the lower contact. Petrographic features of these rocks correspond to olivine ortho- and mesocumulates, with the only exception of the quenched picrodolerite with an ophitic groundmass. The association of sulfides (pyrrhotite, chalcopyrite, pentlandite, and cubanite) has a pretty little varying composition, except only a relative decrease in the proportion of chalcopyrite in samples with more than 5% sulfides. The resultsof X-ray computed tomography show an increase in the sulfide connectivity in the rocks (from 25 to 95%)with increasing sulfide abundance. These characteristics, supported by visualized 3D models, allowed us to identify a morpho-structural trend tended from the rocks with sulfide droplets to the net-textured ores. Thefirst ever data were obtained on the chemostratigraphy (PGE and tellurium) of rocks composing this apophysis. Covariations of Au, Pt and Pd with S and Te indicate that the precious metals have a single sulfide precursor. The 100%-sulfide compositions calculated for these rocks indicate that the most primitive and PGE rich sulfides correspond to droplets it the lowerest part of the apophysis, whereas the net-textured ores are depleted in these elements. The geochemical estimates are supported with COMAGMAT-5 modeling which made it possible to calculate the average Au, PGE, and Te contents in the protosulfide melt (in ppm): 2.9 Au,14.4 Pt, 25.1 Pd, and 44.3 Te. Results of the geochemical studies of different fragments of the net-textured ores reveal a heterogeneity in the form of domains relatively enriched in copper, PGE, and tellurium, whosecharacteristic size is a few dozen centimeters. This can be considered as a signature of the porous migration and accumulation of the crystallization products of the original sulfide liquid at the subsolidus stage of cooling down the ore-bearing cumulates.
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Geochemistry and petrology of protosulfide melts in an ore-bearing apophysis of the Yoko-Dovyren intrusionстатья

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