黄铁矿
地质学
热液循环
烟囱(机车)
黄铜矿
地球化学
矿物学
硬石膏
海水
矿物
硫黄
同位素分馏
δ34S
流体包裹体
化学
海洋学
分馏
古生物学
铜
入口
石膏
有机化学
作者
Xingwei Meng,Xiaohu Li,Fong‐Fong Chu,Bin Fu,Jijiang Lei,Zhenggang Li,Hao Wang,Lin Chen
出处
期刊:Geological Magazine
[Cambridge University Press]
日期:2018-05-11
卷期号:156 (06): 989-1002
被引量:19
标识
DOI:10.1017/s0016756818000316
摘要
Abstract Sulphur isotopes can be used as a powerful tool to trace fluid evolution and explore the formation of chimneys. To clarify the in situ S isotopic variations of sulphides at the micro-scale, we analyzed a sulphide chimney collected from the hydrothermal field in the East Pacific Rise 1–2° S using a sensitive high-mass-resolution ion micro-probe for stable isotopes (SHRIMP SI). Three mineral zones can be identified in the chimney: an external outer wall of porous anhydrite and colloform pyrite, an internal middle zone of sub-euhedral pyrite and massive chalcopyrite, and an inner zone of massive pyrite. The δ 34 S V-CDT values of the sulphides fall within the range 1.83–7.51 ‰ (avg. 4.05 ‰, n = 16), and S isotopic values increase from the core (3.09 ‰, n = 3) to the middle (3.78 ‰, n = 11) to the edge (6.99 ‰, n = 2). These results illustrate mineral crystallization processes and the mixing between seawater-derived S and magmatic–hydrothermal fluids during the growth of the chimney. The zones from the edge to the core are characterized by crystal morphologies of colloform/anhedral pyrite to massive pyrite with decreasing δ 34 S values, revealing multi-stage mineral deposition and sulphur isotopic fractionation. In contrast to the increase in δ 34 S values from the core to the edge in one profile (profile A), anomalously low δ 34 S values in fine-grained pyrite relative to chalcopyrite in another profile (profile B) in the middle zone result from S isotopic exchange between seawater SO 4 2− and fluid H 2 S due to different fluid–seawater mixing, possibly caused by variations in permeability and porosity across the chimney.
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