| Autor: |
Feng, Kai, Fan, Hong-Rui, Groves, David I., Yang, Kui-Feng, Hu, Fang-Fang, Liu, Xuan, Cai, Ya-Chun |
| Předmět: |
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| Zdroj: |
Mineralium Deposita; Feb2020, Vol. 55 Issue 2, p293-308, 16p |
| Abstrakt: |
The Daliuhang gold deposit (> 20 t gold) is located in the central Penglai-Qixia belt of the giant Jiaodong gold province, eastern China. The ore-hosting Guojialing granodiorite and pegmatite were formed at 129.0 ± 0.6 Ma and 126.2 ± 0.6 Ma, respectively. Syn-ore monazite, with a U–Pb age of 120.5 ± 1.7 Ma, represents the timing of gold mineralization. Given at least 5 m.y. between magmatism and mineralization, a genetic relationship to magmatic-hydrothermal activity is negated. Noble gas isotopes of pyrite have crust-mantle-mixed 3He/4He (1.13 to 1.50 Ra) and air-like 40Ar/36Ar (327–574). Together with the broadly positive correlation between 3He and 36Ar, it is inferred that the initial ore-forming fluids were deeply sourced from the sedimentary wedge overlying the subducted plate and overlying mantle during early Cretaceous paleo-Pacific plate subduction. The pre-ore and post-ore pyrites have low δ34S values (3.7–5.6‰ and 5.3–6.4‰, respectively), whereas ore-related pyrites have higher δ34S values, especially in As–Au-rich domains (7.8–8.3‰). These positive δ34S values also suggest that the initial ore fluid and some of the sulfur component were derived via subduction-related devolatilization. The elevated δ34S values of the ore-related pyrite are partly ascribed to mass fractionation and partly to a contribution from sulfur leached from crustal host rocks. This interpretation is also supported by neodymium isotope ratios of monazite (εNd (~ 120 Ma) = − 13.7 to − 11.6), which correlate well with the ore-hosting Guojialing granodiorite. This study highlights the combined roles of deeply derived fluids and intense interaction with upper crustal rocks in the formation of Jiaodong gold deposits. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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