新疆萨瓦亚尔顿金矿床年代学、氦氩碳氧同位素特征及其地质意义

Chronology and Geochemical Characteristics of Helium, Argon, Carbon and Oxygen Isotope in Fluid Inclusion of the Sawayaerdun Gold Deposit, Xinjiang, Northwestern China and their Significance

新疆萨瓦亚尔顿金矿位于西南天山西端,受NNE向脆—韧性剪切带控制。对绢云母化蚀变岩进行了40Ar/39Ar法年龄测定,表明金主成矿时代为三叠纪。根据黄铁矿流体包裹体氦、氩同位素、石英流体包裹体的碳、氧同位素组成,讨论了萨瓦亚尔顿金矿成矿流体的来源。结果表明石英流体包裹体中δ18OSMOW变化于14.51‰~24.2‰,CO2的δ13CPDB变化范围较大,为-8.69‰^+4.98‰,暗示成矿流体中的碳来源于地幔和海相碳酸盐岩。黄铁矿流体包裹体的3He/4He变化较大,为0.04~1.11R/Ra,40Ar/36Ar变化较小,介于301~348。综合分析认为萨瓦亚尔顿金矿的成矿流体为地幔流体和地壳流体混合的产物,以地壳流体为主。

Sawayaerdun gold deposit is located at the western end of Chinese Southwest Tianshan Hercynian orogenic belt. Gold orebodies are controlled by a group of NE-trending brittle-ductile shear zones. ^40Ar/^39Ar age of sericite altered rock from the Sawayaerdun shows that the main stage of gold mineralization occurred in the Triassic. Based on the helium and argon isotope composition of fluid inclusions in pyrite and carbon and oxygen isotope of fluid inclusions in quartz from the Sawayaerdun gold deposit, this paper discusses source of oreforming fluid. The δ^18OSMOW values of quartz range from 14. 51%0 to 24. 2%0. The δ^13CPOB values of fluid inclusions in quartz from the Sawayaerdun gold deposit range from -8. 69%0 to ＋4.98‰, reflecting that the carbon possibly derived from mantle with interaction with marine carbonate rocks. ^3He/^4He ratios of fluid inclusions in pyrite range from 0. 04 to 1.11 Ra, whereas ^40Ar/^36Ar range from 301 to 348. The combined noble gas isotopic data and stable isotopic data imply that the ore-forming fluids of the Sawayaerdun gold deposit were a mixture between mantle-derived fluids and crustal-derived fluids, and the crustal-derived fluids are dominated.