Characteristics of Stable Isotopic Compositions and Its Geological Significances of the Yangla Copper Deposit, Northwestern Yunnan Province
详细信息
- 责任者：Chen Siyao (State Key Laboratory of Geological Process and Mineral Resources ; China University of Geosciences ; Beijing 100083 ; China) ; Gu Xuexiang
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(4)
- 关键词：铜矿 ; copper ores ; 稳定同位素 ; stable isotopes ; 云南 ; Yunnan Province
- 页码：p.1290-1300
- 图表：illus., 3 tables, 42 refs.
- 分类号：1001
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
The Yangla copper deposit is locate in the middle part of the Jinshajiang belt. It was formed due to the westward subduction of the Jinshajiang oceanic basin and collisional orogeny during Mid-Late Triassic. Ore bodies are typically layered or bedded and closely related to the acidic plutons. Ore bodies are trinity controlled by the pluton, stratum and structure and have obvious feature of the skarn deposit. The stable isotopic compositions of marble and various kinds of minerals in different stages have been analyzed respectively. The results show that the δ18OSMOW values of the garnet which is the major mineral of the skarn is 6.7‰, indicating that the oxygen isotopic compositions of skarn may inherit directly from the acidic plutons. The δD values of the quartz in main mineralization are varied from -112‰～-77‰ and the δ18OH2O values are varied from -2.42‰～4.85‰, which reflects that the main compositions of ore-forming fluids was magmatic water and accompanied with input of meteoric water. The δ13CPDB values of -5.2‰～-1.7‰ and the δ18OSMOW values of 12.7‰～20.1‰ for the calcite shows that the carbon and oxygen of calcite are sourced mainly from magma and less from marble. The δ13CPDB values of 3.6‰～5.0‰ and the δ18OSMOW values of 21.2‰～25.4‰ for marble indicate that the marble was re-crystallized from the oceanic carbonate. And as the distance between marble and ore-body decreases, the δ13C values and δ18O values have a trend reducing constantly, which shows that during the process which the ore-forming fluids metasomatiled marble, the fluids with low δ13C values and δ18O values occurred isotope exchange with marble and made the δ13C values and δ18O values of marble decrease, and the nearer distance between marble and ore-body was, the more intense the isotope exchange was. The δ34S value of ore sulfides varied from -6.9‰～2.5‰ and were focused from -2‰～1‰, showing that the sulfur of the sulfides is probably from magma. Summarize the discussions above and combine the geological characteristics of the deposit, we believe that the Yangla copper deposit is a typical skarn deposit.
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