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Both Precambrian (~1.0 Ga) and/or Late Cretaceous-early Tertiary ages have been proposed based on radiogenic isotope methods (i.e., K/Ar, Ar) used to determine ages of non-sulfide vein minerals.Here we report the first Re-Os geochronological data on arsenopyrite (aspy) extracted from a quartz-siderite vein from the 4000 ft. Arsenopyrite formed during the late stages of massive siderite precipitation — the main gangue mineral of the Ag-rich veins.Siderite formation was closely followed by that of Ag-rich tetrahedrite and/or galena.Minor aspy also precipitated during tetrahedrite deposition.Six arsenopyrites closely related to Au mineralization of the Maoling gold deposit are dated by Re-Os technique and define a Re-Os isochron with an age of 2316± 40 Ma, which suggests that the deposit was formed in the Paleoproterozoic era rather than in the Indosinian period as some early researchers suggested.High initial 187Os/188Os ratio of 1.32±0.48 indicates a crustal derivation of the ore-forming material of the deposit, which may be derived from rocks of the Gaixian formation of the Liaohe Group.Development of Re-Os geochronology for crustal matrices has been ongoing since 1998 in the laboratory.This work has resulted in major advancements in the direct isotopic dating of crustal sulfide minerals, petroleum source-rocks, and natural hydrocarbons, using Re-Os isotopes.
For sulfide minerals, Re-Os geochronology has direct application to the timing and duration of hydrothermal ore deposit formation.
Among these, the Carlin-like deposits are relatively rare, as compared to the typical orogenic gold deposits.
The Yunnan–Guizhou–Guangxi “golden triangle” in southwestern China is one of the few important areas for Carlin-like gold deposits.
The Ag-rich sulfide ore (tetrahedrite & galena) is mainly hosted by steeply-dipping siderite-quartz veins intersecting folded quartzite and siltstone from the Ravalli Group of the Mesoproterozoic Belt Supergroup.
The age of mineralization in the district has been controversial since the first geological studies.