Study on Fluid Inclusions from the Luojiahe Copper Deposit in Zhongtiao Mountains Region
详细信息
- 责任者：Jiang Yuhang (Key Laboratory of Mineralogy and Metallogeny ; Guangzhou Institute of Geochemistry ; Chinese Academy of Sciences ; Guangzhou 510640 ; China) ; Luo Yong
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(7)
- 关键词：铜矿 ; copper ores ; 流体包裹体 ; fluid inclusions ; 中条山 ; Zhongtiao Mountains
- 页码：p.2583-2592
- 图表：5 illus., 1 table, 38 refs.
- 分类号：1001
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
Luojiahe copper deposit is located in the Luojiahe tectonic-erosion window,southeastern of Zhongtiao rift. Cu- mineralization occurs in the metamorphic volcanic-sediments of the Songjiashan Formation which is covered by Mesoproterozoic andesitic rocks of the Xiyanghe Group. This paper focuses on the study of fluid inclusions in ore-bearing quartz veins which are intergrowth with ore-body,to discuss the features of ore-forming fluids and the implications for Cu-mineralization. Based on systematically petrographic observation,fluid inclusions are classified into five types by phases: Pure vapor inclusions ( I-type) ,pure aqueous inclusions ( II- type) ,vapor-rich inclusions ( III-type) ,aqueous-rich inclusions ( IV-type) and daughter mineral-bearing inclusions ( V-type) . II-type and IV-type inclusions are dominant in the upper orebody,and I-type and V-type inclusions are dominant in the lower orebody. The coexistence of V-type with I-type inclusions shows the features of boiling assemblage. Microthermometry data indicates that there are two different systems of CaCl 2 -NaCl-H 2 O system ( IVa1-type) and NaCl-H 2 O system ( IVa2-type) in the liquid-rich aqueous inclusions ( IVa types) ,corresponding to the upper quartz veins and the lower quartz veins. Both homogenization temperature ( T h ) and salinity of the two types are different,indicating that the ore-forming fluids might originate from two different fluid sources. The T h of IVa1-type range from 100℃ to 208℃ and salinities range from 10. 24% to 20. 45% NaCleqv. It is suggest that the fluid of IVa1-type is hot brine derived from sea water. In contrary,the IVa2-type is from magmatic fluid,with T h of 151 ～ 306℃ and salinities of 3. 39% ～ 15. 07% NaCleqv,respectively. T h and salinities of the V-type inclusions are in range of 175 ～ 300℃ and 30. 7% ～ 38. 16% NaCleqv. In this regards,we can infer that hot brine and magmatic fluids have different influences to Cu-mineralization. The former extracted metal elements from volcanic rocks,and then precipitated when loss of temperature and pressure. The later released metal elements by phase separation. Laser-Raman microspectroscopy analyses show that the vapour phase of the fluid inclusions is composed of H 2 O and a few CO 2 . Regarding the regional tectonic setting,fluids channel,mechanism and the features of ore-forming fluids,we conclude that the Luojiahe Cu deposit is a volcanic-associated massive sulfide deposit of Precambrian.