DOI:10.19762/j.cnki.dizhixuebao.2020210
 
Ore forming fluid characteristics of orogenic gold deposits in the Indus Yurlung Zangbo suture zone: constraints from He Ar isotope geochemistry
Author NameAffiliationE-mail
ZHAO Xiaoyan 1) MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing, 100037 zxy19890926@163.com 
YANG Zhusen 1) MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing, 100037  
ZHANG Xiong 2) Beijing Institute of Geology for Mineral Resources, Beijing, 100012  
PEI Yingru 3) Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing, 100037  
Abstract:The Yurlung Zangbo orogenic gold metallogenic belt is a newly established collisional orogenic gold metallogenic belt in the Tibetan Plateau. The metallogenic fluid is a set of CO2 H2O NaCl CH4 N2 system that is mainly composed of metamorphic water. In order to explore the influence of mantle component on mineralization, two large scale orogenic gold deposits, the Bangbu deposit and the Nianzha deposit in the Indus Yurlung Zangbo suture zone (IYS) are selected as the research objects for He Ar isotopic analyses. The results show that the concentration ranges of He and Ar isotopes in fluid inclusions of pyrite from the gold bearing quartz vein of the Bangbu deposit are narrow with 3He/4He=0. 59~0. 70 Ra, 40 Ar/ 36 Ar=365. 1~423. 1 respectively. The 3He/4He and 40 Ar/ 36 Ar values of the two melnikovite samples are 0. 11 Ra, 0. 19 Ra and 302. 1, 305. 9. The 3He/4He and 40 Ar/ 36 Ar of pyrite in quartz polymetallic sulfide vein of the Nianzha deposit are 0. 27~0. 60 Ra and 370. 2~1777. 9 respectively. The ore forming fluid of the orogenic gold deposits in the IYS is a mixture of crustal and mantle fluid whose crustal end member is mainly metamorphic water. The contribution of mantle components in the Bangbu gold deposit and Nianzha gold deposit are 12. 8%~15. 2% and 5. 7%~13. 0% respectively, which is obviously different from the Au Sb mineralization in the southern Tibetan detachment system. The ore forming fluid of Au Sb deposit in the detachment system of southern Tibet is mainly characterized by the modified saturated atmospheric water, without the contribution of mantle component.
keywords:He Ar isotope  metamorphic fluid  Mantle component  orogenic gold deposit  Indus Yurlung Zangbo suture zone
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