The intermetallic compound Ni3Au and gold-nickel solid solutions in metalliferous sediments of the triassic chert formation in Sikhote-Alin in the Far East

Abstract

The intermetallic compound Ni3Au and Au-Ni solid solutions (native nickel Au and Au-bearing native Ni) were found in the contact metamorphosed metalliferous sediments of the Triassic chert formation in Sikhote-Alin. The metalliferous rocks are characterized by high contents of Au, Ag, and PGE, as well as the presence of diverse minerals of precious metals. Nickel gold (Au0.91-0.88 Ni0.09-0.12) is found as grains and crystals (3 to 4 im in size) in Au-bearing cherts with hematite, which are conventionally defined as “itabir-ites” and in the altered siliceous rocks of the Dal’nerechensky district (the upper reaches of the Gornya River). The nickel gold is associated with copper Au, pure native Au (Au1.00), and Au-Ag and Au-Ag-Pb solid solutions (Au0.86/0.84Ag0.14_0.16 and Au0.78Ag0.19Pb0.03, respectively). The Au-bearing Ni is found in the metamorphosed carbonaceous mudstones and Au-bearing “itabirites” of the Shirokopadninsky area (Olgin-sky district). The Au content varies from 6.09 wt % (Ni0.98Au0.02) to 11.30 wt % (Ni0.96Au0.04) in some Au-bearing Ni grains (about 10—15 im in diameter) taken from the metamorphosed mudstones. The grains of Au-bearing Ni (Co0.001_0.00Au00.2-0.17 Ni 0.98_0.83) in the “itabirites” are also characterized by their heterogeneous composition and the fine impregnation of the Ni3 Au intermetallic compound (Ni2.99Au1.01 based on the microprobe analysis).