THE SIN QUYEN CU-FE-AU-REE DEPOSIT ( northern Vietnam ): COMPOSITION AND FORMATION CONDITIONS
I.V. Gas'kova, Tran Tuan Anhb, Tran Trong Hoab, Pham Thi Dungb, P.A. Nevol'koa, and Pham Ngoc Canb
aV.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
bInstitute of Geological Sciences, Vietnam Academy of Science and Technology, 84 Chua Lang, Dong Da, Hanoi, Vietnam
Keywords: Chalcopyrite ores, gold and REE mineralization, chalcopyrite, magnetite, northern Vietnam
Pages: 442-456
Abstract
The Sin Quyen Cu-Fe-Au-REE deposit is localized in the Proterozoic deposits of the Phan Xi Pang zone, northern Vietnam. The mineralization is formed by lenticular and sheet-like bodies occurring concordantly with the host rocks. Seventeen orebodies have been recognized in the deposit, which form an ore horizon up to 140 m in total thickness, about 2 km in strike, and up to 350 m in dip. The ores are of simple mineral composition: Au-rich copper and iron sulfides (chalcopyrite, pyrite, pyrrhotite) and iron oxides (magnetite, hematite). Gold and silver are distributed unevenly in the ores: Their contents vary from hundredths and tenths of ppm to 1.8 ppm. Copper sulfide ores are the main concentrator of gold and silver. All ores are characterized by high REE contents, tens and hundreds of times exceeding the element clarkes. The highest contents have been revealed for Ce and La. Orthite is the main carrier of REE. No correlation between REE and ore elements of sulfide-oxide ores has been revealed, which points to the independent formation of the mineralization.
Orebodies together with the host rocks underwent metamorphism at 500-600 to 630-685?C and 3-7 kbar.
The spatial association of the mineralization with amphibolites (metamorphosed basites) and the mineral composition of ores suggest that the Sin Quyen deposit is of Cyprus volcanogenic type.
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