| WANG Yejian,HAN Xiqiu,QIU Zhongyan. 2017. Source and nature of ore-forming fluids of the Edmond hydro-thermal field, Central Indian Ridge: evidence from He-Ar isotope composition and fluid inclusion study. Acta Oceanologica Sinica, 36(1):101－108 |
| Source and nature of ore-forming fluids of the Edmond hydro-thermal field, Central Indian Ridge: evidence from He-Ar isotope composition and fluid inclusion study |
| 中印度洋脊Edmond热液区成矿流体属性与来源:来自流体包裹体和He-Ar同位素的证据 |
| Received:March 25, 2016 Revised:June 14, 2016 |
| DOI：10.1007/s13131-016-0963-1 |
| Key words:fluid inclusion helium and argon isotopes phase separation massive sulfides Central Indian Ridge |
| 中文关键词: 流体包裹体 He-Ar同位素 相分离 块状硫化物 中印度洋脊 |
| 基金项目:The National Natural Science Foundation of China under contract No. 41306056; the China Ocean Mineral Resources R&D Association Project under contract No. DY125-12-R-03; the Scientific Research Fund of the Second Institute of Oceanography, SOA under contract No. JG1308. |
| Author Name | Affiliation | E-mail | | WANG Yejian | Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China | yjwang@sio.org.cn | | HAN Xiqiu | Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China | xqhan@sio.org.cn | | QIU Zhongyan | Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China | |
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| Abstract: |
| To understand the source and nature of the ore-forming fluids of the Edmond hydrothermal field on the Central Indian Ridge, we studied the He-Ar isotope composition and fluid inclusions of the hydrothermal precipitates. Our results show that the sulfide samples contain noble gases He, Ne, Kr, and Xe with their abundances in between those of air-saturated water (ASW) and mid-ocean ridge basalt (MORB). The 3He/4He ratio varies from 1.3 to 8.7 Ra(n=10, average:5.1 Ra), whereas the 40Ar/36Ar ratio is from 285.3 to 314.7 (n=10, average:294.8). These aa results suggest that the He was derived from a mixture of MORB with variable amounts of seawater, but the Ar in the ore-forming fluids trapped in the sulfides is predominantly derived from seawater. The fluid inclusions of barite have a wide range of homogenization temperatures and salinities varying from 163℃ to 260℃ and 2.6 wt% to 8.5 wt% NaCl equiv., respectively. It is suggested that the ore-forming fluids were produced by phase separation, which agreed with the present-day vent fluid study. |
| 中文摘要: |
| 本文通过对热液产物的流体包裹体及其He-Ar同位素组成研究，来揭示中印度洋脊Edmond热液区成矿流体的属性和来源。结果显示，硫化物流体包裹体中的He、Ne、Kr和Xe等稀有气体的丰度位于大气饱和水（ASW）和洋中脊玄武岩（MORB）之间。其3He/4He比值分布在1.3至8.7 Ra，平均值为5.1 Ra（n=10）；其40Ar/36Ar比值在285.3至314.7之间，平均值为294.8（n=10）。该结果表明硫化物成矿流体中的He来源于MORB与海水不同程度的混合，而Ar主要来源于海水。测温学结果显示，重晶石流体包裹体的均一温度和盐度分布范围较大，分别为163℃至260℃、2.6至8.5 wt% NaClequiv.。这暗示了热液区的成矿流体受控于相分离作用，与前人对喷口流体的研究结论相吻合。 |
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