Evolution of ore-forming fluids and formational mechanism for gold deposits in the southern Bei Shan, Xinjiang-Gansu border area of China.

	Evolution of ore-forming fluids and formational mechanism for gold deposits in the southern Bei Shan, Xinjiang-Gansu border area of China.
	Liu, W ; Pan, XF
刊名	ACTA PETROLOGICA SINICA
	2006
卷号	22 期号:1 页码:171-188
关键词	fluid inclusion stable isotopes convective circulation pervasive infiltration Au deposits from the southern Bei Shan
ISSN号	1000-0569
文献子类	Article
英文摘要	Gold deposits in the southern Bei Shan, Xinjiang-Gansu border area of China, constitute the biggest gold mineralization zone in the northwestern China. The Xinjinchang, the Laojinchang, and the Xiaoxigong gold deposits were selected from the southern Bei Shan for this study. On the basis of investigation of deposit geology and petrography, we conducted microthermometric and microlaser Raman spectrometric analyses for the gangue quartz-hosted fluid inclusions, H and C isotope measurements of quartz- and ore pyrite-hosted inclusion H2O, CO2 and CH4, and quartz O and pyrite S isotope measurements. Fluid inclusions from the 3 deposits include CO2+CH4-rich, aqueous, and (HO)-O-2-CO2+CH4 types. For the Xiaoxigong, homogenization temperatures of fluid inclusions vary mainly from 270 to 450 degrees C; a number of aqueous inclusions yield high-salinity (16.43%similar to 18.63% NaCl equiv.), whereas a majority of aqueous inclusions and all CO2+CH4-rich inclusions represent the medium to low salinity (2.8%similar to 13.6%) fluid. For the Xinjinchang, homogenization temperatures of fluid inclusions vary mainly from 210 degrees C to 346 degrees C; a number of fluid inclusions have trapped the high-salinity (10.98%similar to 14% NaCl equiv.) fluid, whereas a number of aqueous inclusions and a great majority of CO2+CH4-rich inclusions represent the medium to low salinity (2.9%similar to 8.81% NaCl equiv.) fluid. For the Laojinchang, however, homogenization temperatures of aqueous inclusions vary mainly from 141 degrees C to 400 degrees C, and salinity ranges from 1.4% to 8.28% NaCl equiv. Simulation of O-18/O-16 and D/H exchange between meteoric-derived water and country rocks gave meaningful results. Ore-forming fluid that precipitated the early auriferous sulfide-quartz vein in the Xiaoxigong, has delta D and delta O-18 that correspond to relatively high water/rock ratios (w/r) (approximate to 0.01 to 0.05) and are buffered by the K-feldspar granite. Sulfide delta S-34 for the auriferous quartz vein is close to that for the K-feldspar granite from the Xiaoxigong. These characteristics suggest convective circulation of hydrothermal fluid around granitic magma body. With cooling and solidification of the magma intrusion, convection of hydrothermal fluid collapsed and changed to discrete, pervasive infiltration and leaching through various country rocks within the Xiaoxigong deposit. Correspondingly, ore-forming fluid that resulted in formation of the ore of alteration rock type in the Xiaoxigong, has delta D that corresponds to low w/r (0.005 similar to approximate to 0.01), and relatively low but variable delta O-18 hence indicating buffering by local rocks of the Mid-Proterozoic felsic schists. Pyrite delta S-34 for the ore of alteration rock type is close to that for the Mid-Proterozoic felsic schists from the Xiaoxigong. Ore-forming fluids from the Xinjinchang and the Laojinchang deposits exhibit delta D and delta O-18 that correspond to w/r=0.004 similar to 0.01 and w/r=0.007 to 0.02, respectively, and show affinity to the magmatic water or the country rocks of diabase and dacite from the Lower Permian Zhesi formation. In addition, pyrite delta S-34 that varies from -2.58 parts per thousand to -6.32 parts per thousand for the Xinjinchang and the Laojinchang indicates multiple derivations for sulfur from the diahase and dacite, and the carbonaceous slate.
WOS关键词	OXYGEN-ISOTOPE EXCHANGE ; T-X CONDITIONS ; HYDROTHERMAL ALTERATION ; OROGENIC GOLD ; CARBON-DIOXIDE ; SYSTEMS ; WATER ; MINERALIZATION ; INCLUSIONS ; AUSTRALIA
WOS研究方向	Geology
语种	英语
出版者	SCIENCE PRESS
WOS记录号	WOS:000235920900018
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/67113]
专题	中国科学院地质与地球物理研究所
通讯作者	Liu, W
作者单位	1.Chinese Acad Sci, Key Lab Mineral Resources, Inst Geol & Geophys, Beijing 100029, Peoples R China 2.Chinese Acad Sci, State Key Lab Lithospher Evolut, Inst Geol & Geophys, Beijing 100029, Peoples R China
推荐引用方式 GB/T 7714	Liu, W,Pan, XF. Evolution of ore-forming fluids and formational mechanism for gold deposits in the southern Bei Shan, Xinjiang-Gansu border area of China.[J]. ACTA PETROLOGICA SINICA,2006,22(1):171-188.
APA	Liu, W,&Pan, XF.(2006).Evolution of ore-forming fluids and formational mechanism for gold deposits in the southern Bei Shan, Xinjiang-Gansu border area of China..ACTA PETROLOGICA SINICA,22(1),171-188.
MLA	Liu, W,et al."Evolution of ore-forming fluids and formational mechanism for gold deposits in the southern Bei Shan, Xinjiang-Gansu border area of China.".ACTA PETROLOGICA SINICA 22.1(2006):171-188.