Evolution of Ore-Forming Fluids in the Anqing Copper-Iron Deposit, Anhui Province, and Its Ore-Forming Implications
详细信息
- 责任者：Dong Yucui (State Key Laboratory of Geological Processes and Mineral Resources ; School of Earth Sciences and Resources ; China University of Geosciences ; Beijing 100083 ; China) ; Zhang Zhiyu
- 刊名：Geological Journal of China Universities
- 出版年：2013
- 卷期：19(2)
- 关键词：铜矿 ; copper ores ; 铁矿 ; iron ores ; 安徽 ; Anhui Province
- 页码：p.245-258
- 图表：illus., 3 tables, 56 refs.
- 分类号：1001
- issnNo：ISSN1006-7493
- isbnNo：CN32-1440/P
摘要
Anqing copper-iron deposit is one of the most important skarn-type deposits along the Middle and Lower Yangtze River metallogenic belt.In this study,the ore-forming fluids of this deposit are systematically researched by analyzing their properties,and evolution,and discussing the ore-forming mechanism.The petrographic observation of fluid inclusions shows that inclusions of the deposit consist of I-type daughter mineral-bearing three-phase inclusions(L+V+S),II-type gas-liquid two-phase inclusions(L+V),and a few Ⅲ-type gas-phase inclusions(V).Diopside and garnet during the pneumatolytic-hydrothermal period contain a relatively small number of fluid inclusions which are mainly I-type;while quartz and calcite during the hydrothermal period developed large quantities ofⅡ-type inclusions.The results of laser Raman microprobe analysis and microthermometry of fluid inclusions show that ore-forming fluids could be approximated as an unsaturated NaCl-H 2 O system.From the early skarn stage to the carbonate stage,ore-forming fluids experienced a continuous evolution from high temperature(456.1~578.1℃),high salinity(39.37%~54.79% NaCleq) conditions to low temperature(112.3~312.4℃),low salinity(7.59%~31.75% NaCleq) conditions.During this evolution of water-rock interaction,boiling and mixing of magmatic hydrothermal and meteoric water occurred,respectively.The water-rock interaction and boiling in early skarn stage was related to the diagenesis of skarn.Boiling and mixing in quartz-sulfide stage may be a significant mechanism for the formation of chalcopyrite.Hydrogen and oxygen isotopic studies indicate that ore-forming fluids during the pneumatolytic-hydrothermal period is composed mainly of magmatic water with an increasing proportion of meteoric water into the fluids from the quartz-sulfide stage to the carbonate stage during the hydrothermal period.
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