NEW COMPOUNDS OF IR, OS AND RU WITH SELENIUM, ARSENIC AND TELLURIUM

Abstract

Alluvium of the Zolotaya river in the Western Sayan mountains contains an Os-Ir-Ru association of PGE minerals related to hyperbasites of the Kurtushibin ophiolite belt. Besides the typical minerals of the harzburgite association of ophiolite belts (alloys of Os-Ir-Ru and Pt-Fe), the following compounds have been developed on the primary alloys: (Ir,Os)(As,Te); (Ir,Os)(Te,As); (Ru,Ir,Os)Te; Ir(As,Se,S)2; (Ir,Os)Te2; (Ir,Os)(S,As,Te)2. These phases have not been described previously; for some the synthetic analogues are still unknown. Secondary minerals reveal the hydrothermal replacement features (rims, inclusions, fissures, net-like or frontal replacements). The ratios of Ir, Os and Ru in secondary minerals are inherited from the composition of the primary alloys. Growth of Ir and quartz in which particles of gold are also included and the character of their relations with Ir selenoarsenide suggest that formation of the unusual compounds is related to a quartz-gold ore process superim-posed on the primary hyperbasite paragenesis.