气候变化领域集成服务门户(CCPortal): Prograde metamorphism provides gold and base metals to orogenic gold deposits in southern Tibet: Insights from thermodynamic modeling

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DOI	10.1016/j.jseaes.2023.105766
	Prograde metamorphism provides gold and base metals to orogenic gold deposits in southern Tibet: Insights from thermodynamic modeling
	Ding, Zhengpeng; Sun, Xiaoming; Zhong, Richen; Yu, Chang; Miao, Fengyu; Yang, Chengye; Ran, Menglan; Liu, Ying; Wu, Zhongyang; Su, Yue
发表日期	2023
ISSN	1367-9120
EISSN	1878-5786
卷号	255
英文摘要	The metamorphic devolatilization model is presently the most widely accepted model for the formation of orogenic gold deposits. According to this model, Au is likely derived from metamorphic rocks that experienced metamorphism from greenschist to amphibolite facies. Nevertheless, in recent years, some researchers have suggested that Au may have originated from different source regions, such as the mantle. As one of China's most significant orogenic gold provinces, the Indus-Yarlung Zangbo suture zone (IYZSZ) in southern Tibet plays a critical role in this discussion. Orogenic gold deposits within the IYZSZ are typically hosted in Triassic metasedimentary rocks called the Langjiexue group. This paper aims to investigate the suitability of metasedimentary rocks of the Langjiexue group as a source region of Au and base metals. Furthermore, we also examine whether the metamorphic devolatilization model is applicable to the IYZSZ. Our study involves reporting the mineral compositions and evolution of metamorphic zones (chlorite to sillimanite zones) in metasedimentary rocks obtained from the IYZSZ and providing detailed petrographic descriptions of these rocks. Thermodynamic modeling based on metamorphic mineral compositions was used to reveal the behaviors of H2O, Au, S, Cu, Pb, and Zn within prograde metamorphism. Our modeling results proved that the breakdown of chlorite and muscovite, both of which are the main mechanisms of Au and base metals release in metasedimentary rocks, occurs under different geothermal gradients. Given the observed metamorphic mineral compositions, it is the breakdown of chlorite that is the predominant reaction responsible for releasing Au and base metals under the real geothermal gradient of lower crustal metasedimentary rocks (similar to 25 degrees C/km). This gradient is capable of releasing at least 1.5 ppb Au, 5.2 ppm Cu, 4.3 ppm Pb, 5.0 ppm Zn, and 20 ppm S (as part of the bulk rock) into the ore fluids. Through the mass balance calculations, we found that over 4.05 t of Au, 14,040 t of Cu, 11,600 t of Pb, and 13,500 t of Zn can be mobilized from 1 km(3) of metasedimentary rocks. Therefore, lower crustal metasedimentary rocks can play a significant role in contributing to Au and base metals in the IYZSZ and other metasediment-hosted orogenic gold deposits worldwide.
关键词	Orogenic gold deposits Thermodynamic modeling Metasedimentary rocks Progressive metamorphic zones Metamorphic devolatilization model Southern Tibet
英文关键词	STRUCTURAL GEOMETRY; HIMALAYAN OROGEN; WORLD-CLASS; MINERALIZATION; DEVOLATILIZATION; EXHUMATION; GENESIS; SYSTEMS; ROCKS; GEOCHRONOLOGY
WOS研究方向	Geosciences, Multidisciplinary
WOS记录号	WOS:001034300600001
来源期刊	JOURNAL OF ASIAN EARTH SCIENCES
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/282944
作者单位	Sun Yat Sen University; Sun Yat Sen University; Sun Yat Sen University; University of Science & Technology Beijing
推荐引用方式 GB/T 7714	Ding, Zhengpeng,Sun, Xiaoming,Zhong, Richen,et al. Prograde metamorphism provides gold and base metals to orogenic gold deposits in southern Tibet: Insights from thermodynamic modeling[J],2023,255.
APA	Ding, Zhengpeng.,Sun, Xiaoming.,Zhong, Richen.,Yu, Chang.,Miao, Fengyu.,...&Su, Yue.(2023).Prograde metamorphism provides gold and base metals to orogenic gold deposits in southern Tibet: Insights from thermodynamic modeling.JOURNAL OF ASIAN EARTH SCIENCES,255.
MLA	Ding, Zhengpeng,et al."Prograde metamorphism provides gold and base metals to orogenic gold deposits in southern Tibet: Insights from thermodynamic modeling".JOURNAL OF ASIAN EARTH SCIENCES 255(2023).