Chemical and boron isotopic variations of tourmaline deciphering magmatic-hydrothermal evolution at the Gejiu Sn-polymetallic district, South China
文献类型：期刊论文
| 作者 | Guo, Jia4; Xiang, Lu4; Zhang, Rongqing1,5; Yang, Tao5; Wu, Kai2; Sun, Weidong3
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| 刊名 | CHEMICAL GEOLOGY
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| 出版日期 | 2022-03-30 |
| 卷号 | 593页码:20 |
| 关键词 | Tourmaline Mineral chemistry Boron isotope Magmatic-hydrothermal evolution Gejiu Sn-polymetallic district South China |
| ISSN号 | 0009-2541 |
| DOI | 10.1016/j.chemgeo.2021.120698 |
| 通讯作者 | Zhang, Rongqing(rqzhang@nju.edu.cn) |
| 英文摘要 | The world-class Gejiu Sn-polymetallic district (southwest China), with ca. 3.27 Mt Sn metal, is a magmatic-hydrothermal deposit associated with the Late Cretaceous biotite granites; however, the magmatic and hydrothermal processes involved in its formation remain poorly understood. Tourmaline is a ubiquitous phase in the Gejiu district, and here we employ in-situ major, trace element, and boron isotope compositions of tourmaline to investigate the source and evolution of the mineralizing fluid, and late-magmatic and hydrothermal processes related to ore formation. Based on petrographic observations, four types of tourmaline are identified: i) latemagmatic tourmaline (Tur I) disseminated in the biotite granites, ii) hydrothermal tourmaline (Tur II) from quartz veins with fracture-filling structure in the biotite granites, iii) hydrothermal tourmaline (Tur IIIa-1, IIIa-2 and Tur IIIb-1, IIIb-2) from fluorite-quartz veins with typical replacement texture against the greisenized granites, among which Tur IIIb-2 is directly related to cassiterite formation, and iv) hydrothermal tourmaline (Tur IV) from sulfide-calcite veins hosted by proximal skarn. Tourmaline (Tur Ito Tur III) from the granites belongs mostly to the alkali group and schorl-dravite solid-solution series, with Fe/(Fe + Mg) ranging from 0.83-1.00 for Tur I, 0.68-1.00 for Tur II, and 0.19-1.00 for Tur III, respectively. By contrast, Tur IV belongs mostly to the vacancy group and has foitite-Mg-foitite composition, with Fe/(Fe + Mg) of 0.10-1.00. Large variations of Fe/(Fe + Mg) as well as Na/(Na + Ca) in hydrothermal tourmaline (Tur II to Tur IV), are related to different degrees of interaction between B-rich fluids with host rocks (solidified granite or carbonate). Most trace elements in tourmaline do not correlate with Fe/(Fe + Mg) and Na/(Na + Ca) ratios, implying the trace element compositions are predominantly controlled by melt/fluid compositions and local fluid-rock reactions. Relative to late-magmatic Tur I, hydrothermal tourmaline (Tur II to Tur IV) is enriched in Sr and depleted in Nb, Ta, and (REE + Y), whereas their Li, Be, Sc, V, and Sn concentrations are largely overlapped. The delta B-11 values in different types of tourmaline fall in a narrow range from -17.8 to -13.7 parts per thousand, in favor of B-rich fluids episodically exsolved from the granitic melt. Tin enrichment in both late-magmatic and hydrothermal tourmaline grains, especially in those (Tur IIIb) from Sn-mineralized veins, is related to magmatic differentiation and late-stage fluid exsolution. Among all types of tourmaline, Tur IIIb-2 coexisting with cassiterite has elevated Fe3+/(Fe3+ + Fe2+) ratios (mean 0.23), indicating that cassiterite precipitated under relatively oxidized conditions. The distinct chemical (i.e. high Mg, Ti, V, Sc, Sr, and Sn contents) and B-isotope compositions (slightly lower delta B-11 values of -17.8 to -15.0 parts per thousand) in syn-ore Tur IIIb-2, combined with the co-occurrence of liquid- and vapor-rich inclusions triggered by fluid boiling in Sn-mineralized veins, suggest that fluid boiling and acid-consuming reaction could be major processes triggering cassiterite precipitation in the quartz vein and greisen. Overall, the chemical and B-isotope signatures of tourmaline are ideal tracers to unravel the magmatic-hydrothermal evolution in the Gejiu Sn-polymetallic district, which could be further employed as a potential prospecting guide for Sn-W deposits. |
| 资助项目 | National Natural Science Foundation of China[42102108] ; Fundamental Research Funds for the Central Universities[DLTD2104] |
| WOS研究方向 | Geochemistry & Geophysics |
| 语种 | 英语 |
| WOS记录号 | WOS:000768027500001 |
| 出版者 | ELSEVIER |
| 源URL | [http://ir.qdio.ac.cn/handle/337002/178612]  |
| 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 | Zhang, Rongqing |
| 作者单位 | 1.Nanjing Univ, Frontiers Sci Ctr Crit Earth Mat Cycling, Nanjing 210023, Peoples R China 2.Northwest Univ, Dept Geol, State Key Lab Continental Dynam, Xian 710069, Peoples R China 3.Chinese Acad Sci, Ctr Deep Sea Res, Inst Oceanol, Qingdao 266071, Peoples R China 4.Chengdu Univ Technol, Coll Earth Sci, Chengdu 610059, Peoples R China 5.Nanjing Univ, Sch Earth Sci & Engn, State Key Lab Mineral Deposits Res, Nanjing 210023, Peoples R China |
| 推荐引用方式 GB/T 7714 | Guo, Jia,Xiang, Lu,Zhang, Rongqing,et al. Chemical and boron isotopic variations of tourmaline deciphering magmatic-hydrothermal evolution at the Gejiu Sn-polymetallic district, South China[J]. CHEMICAL GEOLOGY,2022,593:20. |
| APA | Guo, Jia,Xiang, Lu,Zhang, Rongqing,Yang, Tao,Wu, Kai,&Sun, Weidong.(2022).Chemical and boron isotopic variations of tourmaline deciphering magmatic-hydrothermal evolution at the Gejiu Sn-polymetallic district, South China.CHEMICAL GEOLOGY,593,20. |
| MLA | Guo, Jia,et al."Chemical and boron isotopic variations of tourmaline deciphering magmatic-hydrothermal evolution at the Gejiu Sn-polymetallic district, South China".CHEMICAL GEOLOGY 593(2022):20. |
入库方式： OAI收割
来源：海洋研究所
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