Talc-dominated seafloor deposits reveal a new class of hydrothermal system.
Talc-dominated seafloor deposits reveal a new class of hydrothermal system.
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DOI：
10.1038/ncomms10150
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发表时间：
2015-12-22
影响因子：
16.6
通讯作者：
Murton BJ
中科院分区：
文献类型：
--
作者：
Hodgkinson MR;Webber AP;Roberts S;Mills RA;Connelly DP;Murton BJ
Von Damm Vent Field（VDVF）位于开曼群岛中部扩张中心的侧翼，轴向裂谷以西13公里，位于辉长岩和橄榄岩基底内。与任何其他活动喷口区不同，VDVF的热液沉淀物中含有85-90%的硅酸镁矿物，即滑石。热液流体从3米高、1米直径的烟囱和其他孔中排出，温度高达215 °C，金属浓度低，相对于海水，pH值中等（5.8），氯化物浓度高（667 mmol kg−1）。在这里，我们表明，VDVF喷口流体是由海水与镁铁质和超镁铁质基底沉淀滑石与海水混合的相互作用。VDVF的热通量测量值为487±101 MW，与已知最强大的岩浆驱动热液系统相当，可能代表了一种重要的离轴海洋地壳冷却模式，以前没有在全球模型中得到承认或解释。 Von Damm Vent气田含有85-90%的滑石，热液流体在215 °C下具有不寻常的化学性质。在这里，作者表明，海水与热液流体混合的矿物学结果和热量输出可能代表了一种在全球模型中没有完全考虑的地壳冷却模式。
The Von Damm Vent Field (VDVF) is located on the flanks of the Mid-Cayman Spreading Centre, 13 km west of the axial rift, within a gabbro and peridotite basement. Unlike any other active vent field, hydrothermal precipitates at the VDVF comprise 85–90% by volume of the magnesium silicate mineral, talc. Hydrothermal fluids vent from a 3-m high, 1-m diameter chimney and other orifices at up to 215 °C with low metal concentrations, intermediate pH (5.8) and high concentrations (667 mmol kg−1) of chloride relative to seawater. Here we show that the VDVF vent fluid is generated by interaction of seawater with a mafic and ultramafic basement which precipitates talc on mixing with seawater. The heat flux at the VDVF is measured at 487±101 MW, comparable to the most powerful magma-driven hydrothermal systems known, and may represent a significant mode of off-axis oceanic crustal cooling not previously recognized or accounted for in global models. The Von Damm Vent Field comprises 85–90% talc, with hydrothermal fluids of unusual chemistry at 215 °C. Here, the authors show that the mineralogy results from seawater mixing with hydrothermal fluids and the heat output may represent a mode of crustal cooling not fully accounted for in global models.