Primary fluid exsolution in porphyry copper systems: evidence from magmatic apatite and anhydrite inclusions in zircon
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Primary fluid exsolution in porphyry copper systems: evidence from magmatic apatite and anhydrite inclusions in zircon Jin-Xiang Li 1,2
&
Guang-Ming Li 3 & Noreen J. Evans 4 & Jun-Xing Zhao 3 & Ke-Zhang Qin 3 & Jing Xie 1
Received: 7 July 2019 / Accepted: 31 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Introduction It is well known that ore-forming melts associated with porphyry Cu deposits were oxidized and enriched in chlorine (Cl), sulfur (S), and water (e.g., Streck and Dilles 1998; Cooke et al. 2005; Richards 2011; Wang et al. 2018). In fact, the effective partitioning of Cl and S into exsolved fluids is a very important process in the formation of porphyry Cu systems (e.g., Sillitoe 2010; Richards 2011). However, the timing of primary fluid exsolution and the behavior of Cl and S during late-stage magma evolution are still poorly understood. Apatite, a common accessory phase in igneous rocks, incorporates oreforming elements (S, F, and Cl) into its crystal structure (e.g., Piccoli and Candela 2002; Zhang et al. 2012). Importantly, apatite trapped as inclusions in other igneous minerals can record the original volatile content of the magma (e.g., Scott et al. 2015; Stock et al. 2016, 2018; Zhu et al. 2018), eliminating diffusion effects associated with late-stage melts and/or fluids (Brenan 1993; Kusebauch et al. 2015). Additionally, magmatic anhydrite is an important indicator of S-rich and oxidized melts
Editorial handling: P. Hollings Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00126-020-01013-4) contains supplementary material, which is available to authorized users. * Jin-Xiang Li [email protected] 1
Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
2
Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China
3
Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
4
School of Earth and Planetary Sciences, John de Laeter Center, Curtin University, Perth, WA 6945, Australia
(e.g., Luhr 2008; Xiao et al. 2012; Masotta and Keppler 2015; Hutchinson and Dilles 2019), such as those related to porphyry Cu deposit formation (Audétat 2004; Richards 2011; Sun et al. 2015). However, magmatic anhydrite is rare in ore-forming magmatic intrusions, possibly due to dissolution by late-stage exsolved fluids (Chambefort et al. 2008). Previous studies on anhydrite inclusions and apatite phenocrysts in ore-bearing and fresh igneous rocks suggest that anhydrite crystallization could be an important process in reducing S contents during magma evolution (Streck and Dilles 1998; Chambefort et al. 2008). This study investigates apatite and anhydrite inclusions in zircon from ore-forming intrusions in the Duolong porphyry CuAu deposit, central Tibet (Fig. 1). Petrography and chemical analyses of apatite and anhydrite i
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