Origin of Dongguashan Stratabound Cu-Au Skarn Deposit in Tongling: Restraints of Sulfur Isotope
详细信息
- 责任者：Xu Xiaochun (School of Resources and Environmental Engineering ; Heifei University of Technology ; Hefei 230009 ; China) ; Yin Tao
- 刊名：Acta Petrologica Sinica
- 出版年：2010
- 卷期：26(9)
- 关键词：铜矿 ; copper ores ; 金矿 ; gold ores ; 硫同位素 ; sulfur isotopes ; 安徽 ; Anhui Province
- 页码：p.2739-2750
- 图表：8 illus., 4 tables, 87 refs.
- 分类号：1001
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
Dongguashan Cu-Au deposit is one of representative and typical deposits in Tongling,Anhui Province,China.The upper orebodies of the Dongguashan deposit are obviously hosted in the Carboniferous limestone.They are mainly stratabound skarn-type orebodies in bedded or bedded-like.The lower orebodies are rigidly controlled by the magmatic intrusions and the contact zones between the magmatic intrusions and wallrocks,and developed in veins or venlet-disseminated.The ore types of the upper stratabound skarn orebodies are mainly quartz-sulfides who contain copper and gold.δ34S values of sulfur-bearing minerals in the ores suggested sulfur isotope equilibrium reached in hydrothermal systems.Contrasting to the sulfur isotope composition of typical deposits in the world,the δ34S values of sulfide and the δ34S values of sulfate of the Dongguashan deposit are respectively different from Sedex-type deposit and VHMS-type deposit,while both values of the Dongguashan deposit are closed to porphyry deposit.Based on mineral paragenesis,physicochemical conditions and the reservoir effect of sulfur isotope given by Zheng and Hoefs（1993）,it is indicated that H2S is the most effective sulfur-bearing species in the sulfide stage（XH2S>0.99）,which suggested that the reservoir effect of sulfur isotope would hardly influence the δ34S∑S values of hydrothermal system.Applying the Ohmoto’s medol,it is obtained that the Δ34S values for sulfur fractionation between hydrothermal solution and magmatic melt range from 0‰ to +5‰.So the sulfur isotope composition of hydrothermal solution come from magma could range from +0.3‰ to 12.0‰ according to the sulfur isotope composition of whole magamatic rocks.Δ34S values for sulfur fractionation between sulfate and hydrothermal solution range from +5.0‰ to +19.0‰ in high temperature（600~350 ℃）from silicate stage to oxide stage.Δ34S values for sulfur fractionation between pyrite and hydrothermal solution range from-1‰ to 0‰ in high temperature（450~350 ℃）,0‰ to +1.5‰ in low temperature（350~200 ℃）,from oxide stage to sulfide stage.So that the theoretical δ34S values of sulfur isotope composition of sulfur-bearing minerals crystallized from hydrothermal solution are basically consistent with the actual δ34S values of ore minerals in Dongguashan deposit,which indicate that the sulfur of ore minerals should derived from magma.Combined with the pioneers’ researches on regional and ore deposit geology,it is suggested that the Dongguashan deposit was a stratabound Cu-Au skarn deposit which closely related to the Yanshanian magmatism.The relative high δ34S values of the magma and its related hydrothermal solution imply that the magma hybridized sulfate developed widely in regional sedimentary.Although the regional sedimentary rocks experienced sedimentation from sea water and reduction caused by anaerobic bacteria in diagenetic stage,but there is no sulfur isotopic evidence conserved for the Dongguashan deposit experienced Hercynian submarine depositional mineralization.