Systematic variations of trace element and sulfur isotope compositions in pyrite with stratigraphic depth in the Skouriotissa volcanic-hosted massive sulfide deposit, Troodos ophiolite, Cyprus
Systematic variations of trace element and sulfur isotope compositions in pyrite with stratigraphic depth in the Skouriotissa volcanic-hosted massive sulfide deposit, Troodos ophiolite, Cyprus
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DOI：
10.1016/j.chemgeo.2015.12.012
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发表时间：
2016-03
期刊：
影响因子：
3.9
通讯作者：
M. Keith;K. Haase;R. Klemd;S. Krumm;H. Strauss
中科院分区：
文献类型：
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作者：
M. Keith;K. Haase;R. Klemd;S. Krumm;H. Strauss
Troodos蛇绿岩代表了保存最完好的现代海洋地壳化石类似物之一，包括许多火山携带的块状硫化物矿床。Skouriotissa矿床可分为网状矿带和上覆块状硫化物透镜体，后者被含金属沉积物覆盖，代表了以前的硫化物-海水界面。黄铁矿是这些矿石中主要的硫化物矿物。黄铁矿微量元素组成随地层深度（低至~ 150mbsf）有系统的变化，可能反映了流体温度的变化和相分离的影响（Co、Ni、Se、Te、Bi和Cu）。热液带精炼（Zn、Sb和Pb）和海底流体-海水混合（Mo）是控制黄铁矿化学的重要过程。块状含硫化物闪锌矿和自形黄铁矿可能形成于热流体（~ 400℃），而胶状黄铁矿的出现表明沉淀温度较低（< 400℃）。相似的δ18O石英-流体平衡温度（~ 400°C）表明，在最后150 m流体上升到海底的过程中，Skouriotissa流体并没有明显冷却。深网状黄铁矿的δ34S组成（−1.4‰）表明，斯古里奥提沙热液体系中加入了一个同位素轻的岩浆挥发相（< 0‰）。在进一步的流体上升过程中，白垩纪海水（δ34S = 18 ~ 19‰）增加了38%左右，形成了正δ34S值（6.1‰）的网状黄铁矿。此外，Skouriotissa与现代海底喷口系统和块状硫化物矿床之间的化学和结构相似性表明，Skouriotissa热液系统具有现代类似物。
The Troodos ophiolite represents one of the best-preserved fossil analogs of modern oceanic crust and includes numerous volcanic-hosted massive sulfide deposits. The Skouriotissa deposit can be separated into a stockwork ore zone and an overlying massive sulfide lens that is covered by metalliferous sediments representing the former sulfide–seawater interface. Pyrite is the dominant sulfide mineral within these ores. The trace element composition of pyrite varies systematically with stratigraphic depth (down to ~ 150 mbsf) probably reflecting fluid temperature variations and effects of phase separation (Co, Ni, Se, Te, Bi and Cu). Metal remobilization due to hydrothermal zone refining (Zn, Sb and Pb) and fluid-seawater mixing at the seafloor (Mo) represent further important processes controlling the pyrite chemistry. Massive sulfide-hosted sphalerite and euhedral pyrite probably formed from hot fluids (~ 400 °C), while the occurrence of colloform pyrite indicates lower precipitation temperatures (< 400 °C). Similar δ18O quartz-fluid equilibration temperatures (~ 400 °C) in the stockwork zone suggest that the Skouriotissa fluids did not cool significantly during the final 150 m of fluid ascent to the seafloor. The δ34S composition of deep stockwork pyrite (− 1.4‰) suggests that an isotopically light magmatic volatile phase (< 0‰) was added to the hydrothermal system of Skouriotissa. During further fluid ascent about 38% of Cretaceous seawater (δ34S = 18–19‰) was added leading to the precipitation of stockwork pyrite with positive δ34S values (6.1‰). In addition, the chemical and textural similarities between Skouriotissa and modern seafloor vent systems and massive sulfide deposits suggest that the Skouriotissa hydrothermal system has a modern analog.