Peculiarities of composition and possible source of PGE minerals from the placer gold deposit of the Taymen’ river (Western Priokhotsk Region, Russia)

Abstract

Coarse platinoid-chromite intergrowths in association with native gold, as well as with Au‐(Ag)‐Cu and Au‐(Cu,Ag)‐Pd alloys, first discovered in the Taymen’ river alluvial sediments have been investigated. Identification of the essentially isoferroplatinum-ferrichromite composition of these intergrowths in the presence of native metal, intermetallic and chalcogenide phases of specific composition within the platinum matrix allowed the authors to connect genetically the origin of these intergrowths with platinum-bearing alkaline-ultrabasic massifs of the Chad-Konder type. Products of destroying similar rocks presumably accumulated in the Taymen’ river placer. Analogues of these circular intrusive rocks are now apparently overlapped by Mesozoic and Cenozoic rocks including Quaternary unconsolidated sediments. The revealed typomorphism of Pt‐Fe alloys, platinoid chalcogenides, and chromespinellides from the Taymen’ river gold placer allows one to prospect the Au‐(Cu)-Pt‐Cr mineralization occurrence formerly unknown in the subregion of the central part of Western Priokhotsk region. Special attention is focused on the peculiarities of the compositions of natural Pt‐Fe alloys, platinoid chalcogenides, and chrome-spinellides due to their well-known capabilities to indicate formation affiliation of the source rocks. In particular, this is important while typing the root supply sources of platinum-bearing placers, especially in regions with unknown endogenous platinoid sources. Such a situation appeared in connection with our discovery of large lumpy platinum-chromite intergrowths in the alluvial gold placer of the river Taymen’ (northeast of Khabarovsk krai). The Taymenskoye deposit of placer gold is situated to the southeast from the Lantar part of the Dzhugdzhur autonomous type anorthosite massif [1]. To the southwest, the deposit joins with the gold-bearing placer of the Lantar’ River valley. The Lantar’ and Taymen’ valleys are separated from the Sea of Okhotsk by the Pri