气候变化领域集成服务门户(CCPortal): Volatile variations in magmas related to porphyry Cu-Au deposits: Insights from amphibole geochemistry, Duolong district, central Tibet

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DOI	10.1016/j.oregeorev.2018.03.019
	Volatile variations in magmas related to porphyry Cu-Au deposits: Insights from amphibole geochemistry, Duolong district, central Tibet
	Li, Jin-Xiang; Qin, Ke-Zhang; Li, Guang-Ming; Evans, Noreen J.; Zhao, Jun-Xing; Yue, Ya-Hui; Xie, Jing
通讯作者	Li, JX (通讯作者)
发表日期	2018
ISSN	0169-1368
EISSN	1872-7360
起始页码	649
结束页码	662
卷号	95
英文摘要	Ore-forming fluid exsolution in a shallow magma chamber is a critical step in the formation of porphyry Cu +/- Mo +/- Au deposits but one for which direct evidence is rarely found. Here, CI abundance, major-trace element content and H isotope analysis of amphibole in diorite and barren granodiorite porphyry samples from the Duolong porphyry-epithermal Cu-Au district are presented in order to reveal processes associated with fluid exsolution and magma evolution. Low-Al Mg-hornblende formed in ore-bearing diorite at - 750-860 degrees C and similar to 80-200 MPa. On primitive mantle-normalized diagrams, these low-Al amphibole grains have slightly convex upward REE patterns with distinctly negative Eu anomalies and negative anomalies in Pb, Sr, Eu, Zr, Hf, and Ti anomalies, suggesting crystallization from the same arc magma after plagioclase and magnetite crystallization. A large variation in estimated melt H2O (similar to 6 to 3 wt%) and CI content (0.09-0.38 wt%), as well as low 8D values (-103 to - 113%o) indicate that the magma underwent large-scale fluid exsolution, contributing to the formation of Duolong Cu-Au mineralization. Additionally, amphibole from a barren granodiorite porphyry shows two distinct populations, distinguished by their A1 content. This intrusion has low-Al amphibole (Mghornblende) which formed at similar conditions to low-Al amphiboles in the diorite (790-870 degrees C and similar to 100-230 MPa), whereas high-Al amphibole (tschermakite) formed at similar to 880-970 degrees C and degrees 210-400 MPa. Some high-Al amphibole phenocrysts have slightly convex REE patterns with no negative Eu anomalies, a depletion in Nb, Zr, and Hf, and positive Sr, Ba, and Pb anomalies, likely consistent with amphibole crystallization from more mafic basaltic-andesitic melts. Low-Al amphibole in the granodiorite porphyry shows different compositional trends compared to those in the diorite, suggesting that they crystallized from different magmas. Considering the evidence for mafic magma replenishment suggested by the positive correlation between Al-IV and Mg# values in high-Al amphibole, the low-Al amphibole in the barren granodiorite porphyry likely crystallized from a new hybrid magma with mafic to intermediate-felsic magma compositions. Meanwhile, smaller variations in CI content (0.08-0.24 wt%) in low-Al amphibole was dominantly controlled by magma evolution (shown by variable Mg#) rather than fluid exsolution. Thus, the low 8D values (-102 to -122%o) were likely inherited from evolved dioritic magmas that underwent fluid exsolution. Importantly, the CI compositional variation of amphibole has a potential application as a powerful tool to identify ore-bearing and barren intrusions within porphyry Cu +/- Mo +/- Au deposits.
关键词	HYDROTHERMAL ORE-DEPOSITS MOUNT ST-HELENS ZIRCON U-PB HYDROGEN ISOTOPE MELT INCLUSIONS NORTHERN TIBET WESTERN TIBET ARC MAGMAS CRETACEOUS GRANITOIDS TECTONIC IMPLICATIONS
英文关键词	Amphibole; H isotope; Fluid exsolution; Duolong; Tibet
语种	英语
WOS研究方向	Geology ; Mineralogy ; Mining & Mineral Processing
WOS类目	Geology ; Mineralogy ; Mining & Mineral Processing
WOS记录号	WOS:000432760500037
来源期刊	ORE GEOLOGY REVIEWS
来源机构	中国科学院青藏高原研究所
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/259196
推荐引用方式 GB/T 7714	Li, Jin-Xiang,Qin, Ke-Zhang,Li, Guang-Ming,et al. Volatile variations in magmas related to porphyry Cu-Au deposits: Insights from amphibole geochemistry, Duolong district, central Tibet[J]. 中国科学院青藏高原研究所,2018,95.
APA	Li, Jin-Xiang.,Qin, Ke-Zhang.,Li, Guang-Ming.,Evans, Noreen J..,Zhao, Jun-Xing.,...&Xie, Jing.(2018).Volatile variations in magmas related to porphyry Cu-Au deposits: Insights from amphibole geochemistry, Duolong district, central Tibet.ORE GEOLOGY REVIEWS,95.
MLA	Li, Jin-Xiang,et al."Volatile variations in magmas related to porphyry Cu-Au deposits: Insights from amphibole geochemistry, Duolong district, central Tibet".ORE GEOLOGY REVIEWS 95(2018).