Genesis of the Guanfang Copper Deposit in the Yunxian-Jinggu Volcanic Arc, Western Yunnan: Evidences from Fluid Inclusions and Geochronology
详细信息
- 责任者：Chen Li (Chengdu Institute of Geology and Mineral Resources ; Chengdu 610081 ; China) ; Wang Liquan
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(4)
- 关键词：铜矿 ; copper ores ; 云南 ; Yunnan Province
- 页码：p.1279-1289
- 图表：illus., 2 tables, 22 refs.
- 分类号：1001
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
The Guanfang copper deposit is located in the north part of Yunxian-Jinggu volcanic arc. Disseminated Cu ores and veinlets are hosted in the Xiaodingxi Formation almond-shaped basalt, basaltic breccia and associated fractures. We first report a precise zircon U-Pb age of 234.3±0.8Ma of the basalt from the Xiaodingxi Formation. This age indicates that the Xiaodingxi Formation is Middle Triassic, different with previously accepted of Late Triassic. Petrography, microthermometry and Laster Raman spectra studies on fluid inclusions in quartz and calcite indicate that at least two mineralizing episodes occurred in the Guanfang Cu deposit: the volcanic-subvolcanic hydrothermal mineralization during Middle Triassic and the groundwater hydrothermal (possibly genozoic) overprinting. In combination with the evolution history of the Yunxian-jinggu volcanic arc, we conclude that the Middle Triassic Xiaodingxi basalt and Manghuai rhyolite formed bimodal volcanic rock assemblage. The Guanfang Cu deposit occurs in the mafic volcanic rocks in rift basin with marine-continent-alternating sedimentary conditions. It has VHMS features in the early mineralization stage. Due to lack "brine pool", the place that hydrothermal ore-forming fluids accumulation, the Guangfang Cu deposit only occurs veinlet, networks and breccia bodies in volcanic path at the deposit bottom but no massive stratiformed ore bodies at the surface. The deposit overprinted by groundwater hydrothermal fluids at the late mineralization stage.
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