Unnamed Pt(Cu0.67Sn0.33) from the Bolshoy Khailyk River, Western Sayans, Russia, and a Review of Related Compounds and Solid Solutions

Andrei Y Barkov,Luca Bindi,Gennadiy I Shvedov,Robert F Martin,Chi Ma,Erick A Juárez-Arellano,Nobumichi Tamura

doi:10.3390/min11111240

Abstract

We describe a potentially new species of a platinum cupride–stannide mineral (PCSM) of composition Pt(Cu0.67Sn0.33). It occurs in a placer deposit in the River Bolshoy Khailyk, southern Krasnoyarskiy kray, Russia. A synthetic equivalent of PCSM was obtained and characterized. The PCSM occurs as anhedral or subhedral grains up to 15 μm × 30 μm in association with various platinum-group minerals, Rh–Co-rich pentlandite and magnetite, all hosted by a placer grain of Cu–Au–Pt alloy. Synchrotron micro-Laue diffraction studies indicate that the PCSM mineral is tetragonal and belongs to the inferred space-group P4/mmm (#123). Its unit-cell parameters are a = 2.838 (3) Å, c = 3.650 (4) Å, and V = 29.40 (10) Å3, and Z = 1. The c:a ratio calculated from the unit-cell parameters is 1.286. These characteristics are in good agreement with those obtained for specimens of synthetic Pt(Cu0.67Sn0.33). A review on related minerals and unnamed phases is provided to outline compositional variations and extents of solid solutions in the relevant systems PtNi–PtFe–PtCu, PdCu–PdHg–PdAu, PdHg–PtHg, and AuCu–PtCu. The PCSM-bearing mineralization appears to be related genetically with an ophiolitic source-rock of the Aktovrakskiy complex of the western Sayans. The unnamed phase likely crystallized from microvolumes of a highly fractionated melt rich in Cu and Sn.

Highlights

The placer deposits of the River Bolshoy Khailyk, western Sayans, in the Ermakovskiy district, southern Krasnoyarskiy kray of Russia [1] are known for assemblages of platinumgroup minerals (PGM) and associated PGE–Au phases
The platinum cupride–stannide mineral (PCSM) grains are hosted by a composite grain of (Au,Pt)Cu alloy recovered in a remote placer deposit along the Bolshoy Khailyk river
The unnamed species of PGM investigated at Bolshoy Khailyk is analogous, both compositionally and structurally, to synthetic Pt(Cu0.67Sn0.33) obtained and characterized by Juarez-Arellano et al [2]

Summary

Introduction

The placer deposits of the River Bolshoy Khailyk, western Sayans, in the Ermakovskiy district, southern Krasnoyarskiy kray of Russia [1] are known for assemblages of platinumgroup minerals (PGM) and associated PGE–Au phases. We focus here on a potentially new species of a platinum cupride–stannide mineral (PCSM) of composition Pt(Cu0.67Sn0.33); we describe its properties and characteristics. This mineral is closely related to synthetic Pt(Cu0.67Sn0.33), a phase recognized recently in the ternary system Pt–Cu–Sn [2]. These include tetraferroplatinum, PtFe, and tulameenite, Pt2CuFe [4,5], both important sources of Pt in various parageneses of Pt–Fe alloy minerals, e.g., [6] We explore how these minerals and phases can be grouped on the basis of the degree of order of constituent metals in the relevant structures

Methods

Discussion

Conclusion