Reconstructing volatile exsolution in a porphyry ore-forming magma chamber: Perspectives from apatite inclusions
文献类型：期刊论文
| 作者 | Huang, Wenting1,5,6; Stock, Michael J.1; Guyett, Paul C.1,4; Xia, Xiao-Ping5,6; Liang, Huaying5,6; Sun, Weidong3 ; Lai, Chun-kit2
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| 刊名 | AMERICAN MINERALOGIST
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| 出版日期 | 2024-08-27 |
| 卷号 | 109期号:8页码:1406-1418 |
| 关键词 | Porphyry deposit apatite inclusions volatile exsolution diffusional re-equilibration |
| ISSN号 | 0003-004X |
| DOI | 10.2138/am-2023-8963 |
| 通讯作者 | Xia, Xiao-Ping(xpxia@gig.ac.cn) |
| 英文摘要 | Porphyry-type deposits in the shallow crust (3-5 km) are formed from metal-rich fluids exsolved from underlying magma chambers (5-15 km). However, a direct volatile record of the fluid exsolution in the magma chamber is commonly lacking. Here, we analyze the compositions of apatite inclusions (in biotite and plagioclase phenocrysts and fully/partly included in zircon microphenocrysts) and the apatite in groundmass from the largest Cretaceous Luoboling porphyry Cu-Mo deposit in South China. In combination with thermodynamic models, we reconstructed the volatile behavior in the ore-forming magma. The analyzed apatites are magmatic in origin, without hydrothermal overprint, as indicated by their homogeneous cathodoluminescence (CL) and higher Cl and REE contents than typical hydrothermal apatite. Apatite inclusions fully enclosed in zircon show decreasing XClAp/XOHAp $\begin{array}{} \displaystyle X_{\mathrm{Cl}}<^>{\mathrm{Ap}} / X_{\mathrm{OH}}<^>{\mathrm{Ap}} \end{array}$ (1.5-0.1) with increasing XFAp/XOHAp $\begin{array}{} \displaystyle X_{\mathrm{F}}<^>{\mathrm{Ap}} / X_{\mathrm{OH}}<^>{\mathrm{Ap}} \end{array}$ (0.4-3.3) and XFAp/XClAp $\begin{array}{} \displaystyle X_{\mathrm{F}}<^>{\mathrm{Ap}} / X_{\mathrm{Cl}}<^>{\mathrm{Ap}} \end{array}$ (0.5-21), and display a steep drop in XClAp $\begin{array}{} \displaystyle X_{\mathrm{Cl}}<^>{\mathrm{Ap}} \end{array}$ at approximately constant XOHAp $\begin{array}{} \displaystyle X_{\mathrm{OH}}<^>{\mathrm{Ap}} \end{array}$ in the ternary F-Cl-OH plot. These trends follow the modeled compositional trajectories of isobaric, H2O-saturated crystallization, indicating volatile exsolution during or before zircon crystallization in the magma chamber. Groundmass apatite crystals, phenocryst-hosted apatite inclusions, and apatite inclusions that are partially enclosed by zircon microphenocrysts have comparable volatile compositions, with much higher XFAp/XOHAp $\begin{array}{} \displaystyle X_{\mathrm{F}}<^>{\mathrm{Ap}} / X_{\mathrm{OH}}<^>{\mathrm{Ap}} \end{array}$ (1.7-78.8) and XFAp/XClAp $\begin{array}{} \displaystyle X_{\mathrm{F}}<^>{\mathrm{Ap}} / X_{\mathrm{Cl}}<^>{\mathrm{Ap}} \end{array}$(2.3-37.5) but lower XOHAp $\begin{array}{} \displaystyle X_{\mathrm{OH}}<^>{\mathrm{Ap}} \end{array}$ and XClAp $\begin{array}{} \displaystyle X_{\mathrm{Cl}}<^>{\mathrm{Ap}} \end{array}$ than those fully enclosed in zircon. Compositional similarities between these crystals in different textural associations indicate that the phenocryst-hosted apatite inclusions do not preserve their original volatile records at the time of entrapment, and the volatile compositions were overprinted by later re-equilibration with the residual melt and the exsolved magmatic fluids. Given the porphyry magma is highly oxidized, and sulfides phases would be unstable in such circumstance, we suggest that volatile exsolution in the magma chamber is essential for Cl and Cu-Mo extraction from the melts and therefore the porphyry mineralization. In this study, only zircon-hosted apatite inclusions appear to best record the magmatic volatile compositions in a porphyry system. Therefore, using apatite hosted in other minerals or groundmass compositions to unravel magma volatile contents in porphyry Cu systems should be conducted with caution. |
| WOS关键词 | CU-MO DEPOSIT ; LA-ICP-MS ; FUJIAN PROVINCE ; PARTITION-COEFFICIENTS ; THERMODYNAMIC MODEL ; HYDROTHERMAL ZIRCON ; ZIJINSHAN OREFIELD ; OXYGEN FUGACITY ; JACK HILLS ; FLUID |
| 资助项目 | National Natural Science Foundation of China[42072088] ; National Key R&D Program of China[2018YFA0702600] ; China Scholarship Council (CSC) Scholarship[202104910197] ; Frontiers for the Future grant[20/FFP-P/8895] ; Science Foundation Ireland ; Geological Survey Ireland ; SFI Research Centre for Applied Geosciences, Ireland (iCRAG)[13/RC/2092_2] |
| WOS研究方向 | Geochemistry & Geophysics ; Mineralogy |
| 语种 | 英语 |
| WOS记录号 | WOS:001282862600011 |
| 出版者 | MINERALOGICAL SOC AMER |
| 源URL | [http://ir.qdio.ac.cn/handle/337002/186192]  |
| 专题 | 海洋研究所_深海极端环境与生命过程研究中心 |
| 通讯作者 | Xia, Xiao-Ping |
| 作者单位 | 1.Univ Dublin, Trinity Coll Dublin, Dept Geol, Dublin 2, Ireland 2.Fortescue Met Grp Ltd, Global Project Generat & Targeting, East Perth, WA 6004, Australia 3.Chinese Acad Sci, Ctr Deep Sea Res, Inst Oceanol, Qingdao 266071, Peoples R China 4.Univ Coll Dublin, SFI Res Ctr Appl Geosci, iCRAG, Dublin 4, Ireland 5.CAS Ctr Excellence Deep Earth Sci, Guangzhou 510640, Peoples R China 6.Chinese Acad Sci, Guangzhou Inst Geochem, Guangzhou 510640, Peoples R China |
| 推荐引用方式 GB/T 7714 | Huang, Wenting,Stock, Michael J.,Guyett, Paul C.,et al. Reconstructing volatile exsolution in a porphyry ore-forming magma chamber: Perspectives from apatite inclusions[J]. AMERICAN MINERALOGIST,2024,109(8):1406-1418. |
| APA | Huang, Wenting.,Stock, Michael J..,Guyett, Paul C..,Xia, Xiao-Ping.,Liang, Huaying.,...&Lai, Chun-kit.(2024).Reconstructing volatile exsolution in a porphyry ore-forming magma chamber: Perspectives from apatite inclusions.AMERICAN MINERALOGIST,109(8),1406-1418. |
| MLA | Huang, Wenting,et al."Reconstructing volatile exsolution in a porphyry ore-forming magma chamber: Perspectives from apatite inclusions".AMERICAN MINERALOGIST 109.8(2024):1406-1418. |
入库方式： OAI收割
来源：海洋研究所
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