Au-bearing gabbro-tonalite-granodiorite-granite plutons of the urals: Age, geochemistry, and magmatic and ore evolution

Abstract

Gabbro-tonalite-granodiorite-granite (GTGG) plutons productive for gold are suprasubduc tion intrusive bodies formed at an Andean type active continental margin 410-380, 365-355, and 320-290 Ma ago. The Devonian plutons are situated in the southeastern marginal continental zone, whereas the Carbon iferous plutons occur in the northwestern zone. All GTGG plutons are mantle-crustal. Their formation started with hydrous basic magmatism and was accompanied by such magmatism up to the final stage. Man tle derived amphibole gabbro and diorite experienced partial melting (anatexis) in the lower crust under a pressure of 6-10 kbar, giving birth to the tonalite-granodiorite members of the GTGG series. The latter, in turn, were involved in anatexis with the formation of adamellite and granite, immediately accompanied by hydrothermal gold mineralization. The multistep anatexis is the main petrogenetic process responsible for the gold resource potential of GTGG plutons. In the process of anatexis occurring under high fluid saturation, gold was repeatedly removed from rocks into fluid, facilitating its concentration in ore deposits.

Devonian-Carboniferous Magmatism and Metallogeny in the South Ural Accretionary-Collisional System

“…The rocks have U-Pb [Grabezhev, Ronkin, 2011;Fershtater, 2013Fershtater, , 2015Grabezhev, 2014] and Sm-Nd [Kosarev et al, 2014] ages from 418 to 399 Ma (Lochkovian -Emsian). Similar ages were obtained for many intrusions with island arc trace-element signatures [Fershtater et al, 2010;Fershtater, 2013Fershtater, , 2015 and the author's data on Voznesenka and Karagaykul [Kosarev et al, 2014] which represent Early Devonian (D 1 lh-e 1 ) magmatism.…”

Mercury spikes as evidence of extended arc-volcanism around the Devonian–Carboniferous boundary in the South Tian Shan (southern Uzbekistan)

“…In fact, volcanic activity appears to have been waning at the end of the Devonian Period in the east Magnitogorsk zone, but was still occurring 82 . Additionally, dating of sulphide mineralisation in the Urals volcanic-hosted massive sulphide deposits (362 ± 9 and 363 ± 1 Ma; 80 ) and intrusive magmatism in the Ural Platinum Belt, where continental-margin gabbro–tonalite–granodiorite magmatism was initiated at ~ 365–355 Ma 83 , 84 , include the time interval of the end-Devonian crisis. Many pyroclastic rocks related to volcanism within an intra-oceanic arc occur around the D–C boundary at Baruunhuurai Terrane, Mongolia 85 ; however, precise biostratigraphic data are not available for this interval.…”