Ore-Forming Fluid Studies of Tongyu Gold Deposit, Shaanxi Province
详细信息
- 责任者：Xu Yanming (Faculty of Earth Resource ; China University of Geosciences ; Wuhan 430074 ; China) ; Zhou Zonggui
- 刊名：Mineral Deposits
- 出版年：2013
- 卷期：32(5)
- 关键词：金矿 ; gold ores ; 流体包裹体 ; fluid inclusions ; 陕西 ; Shaanxi Province
- 页码：p.1011-1025
- 图表：9 illus., 5 tables, 31 refs.
- 分类号：1001
- issnNo：ISSN0258-7106
- isbnNo：CN11-1965/P
摘要
The Tongyu gold deposit,lying in southern North China platform,is tectonically located in western Xiao Qinling gold metallogenic belt.Ore bodies,hosted in metamorphic rocks of Achaean Taihua Group,occur as sheets,veins and lenses.Wall rock alteration is well developed in the gold deposit;there are carbonatization, sericitization,silicification,choritization etc.The authors approximately calculated the density,pressure,depth on the basisof studiesof petrography and microscopic differential thermometry of fluid inclusions as well as components and H-O isotopic compositionsof the fluids.Homogenization temperaturesof fluid inclusionsof the three stages are 280~360℃,190~330℃and 150~290℃respectively,with salinitiesof 3%~11%,3%~15%and 1%~11%.The liquid part of the fluid inclusion mainly contains Na+,K+,Ca2+.Cl-is the anion of the highest value,and SO2-4takes the second place.The gas phase composition primarily contains H2O,CO2and N2,followed by a small amount of O2and CH4.The fluid inclusions are characterized by slight reduction. Mineralization took place at intermediate temperature.Based on fluid inclusion studies,the authors consider that the ore-forming hydrothermal fluid is of low salinity.The ore-forming pressures are from 78 MPa to 220 MPa,suggesting that the depth ranges from 3 km to 8 km.(D values vary in the range of-44.4‰ ~-81.8‰,and δ18O(H2O)in the range of 0.01‰ ~6.65‰.TheδD-δ18O isotopic diagrams show that the early stage was dominated by magmatic water or mixed magmatic water,whereas at the late stage there was some addition of atmospheric precipitation.The authors have reached the conclusion that Au in the ore-forming fluid mainly migrated in the form of Au(HS)-2,followed by Au2S(HS)2-2.