Active near-surface mobilisation of slab-derived geochemical signatures by hyperalkaline waters in brecciated serpentinites
Active near-surface mobilisation of slab-derived geochemical signatures by hyperalkaline waters in brecciated serpentinites
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角砾蛇纹岩中超碱性水对板片衍生的地球化学特征的主动近地表动员
DOI：
10.1016/j.chemgeo.2023.121822
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发表时间：
2024
期刊：
影响因子：
3.9
通讯作者：
Evans A
中科院分区：
文献类型：
--
作者：
Evans A
塞浦路斯特罗多斯岛上不寻常的超碱性大气地面沃茨，来自阿尔忒弥斯底辟的高度变形和完全蛇纹化的超镁铁质角砾岩岩体，具有高盐度（25-30%的海水总溶解固体）和一些最高记录的天然沃茨pH值（11 - 13）。这些沃茨中溶解的Na、K、Li、B、Ba、Rb、Cs、Cl和SO 4浓度升高，离子/氯化物比率大大高于海水，海洋气溶胶的贡献较小。例如，K浓度与海水值相似。水稳定同位素比值显示了广泛的水-岩作用，87 Sr/86 Sr以岩石为主（0.705），明显低于海水。这些罕见的流体与地表和浅层地下沃茨形成对比，这些水排出超镁铁质Troodos地幔序列，pH值为8.5-9，大气稳定同位素比，87 Sr/86 Sr类似于早中新世海水（0.7085）和低溶解盐，尽管离子/氯化物比也大于海水。高pH值和盐度的组合是不寻常的蛇绿岩和这些超碱性沃茨是最相似的端元流体从蜿蜒的泥火山在马里亚纳弧前。雨水迅速过境梯田的石棉尾矿对特罗多斯大多类似于表面沃茨，但显示轻微污染的盐成分。我们认为，蛇纹岩中含有高度可溶性盐的包裹体在隆升和底辟作用期间或采矿活动期间的粉碎作用中受到构造变形的影响。提出了一个多阶段的过程，其中碱和其他特征从特罗多斯地块下方停滞的俯冲板片中释放出来，并注入地幔楔。其中一些岩石已被底辟隆起和侵蚀带到地表，在那里，构造变形或采矿活动使现代大气沃茨能够在近地表调动板片衍生的地球化学特征。
Unusual hyperalkaline meteoric groundwaters on Troodos massif, Cyprus, issue from highly deformed and completely serpentinized ultramafic brecciated rock masses of the Artemis Diapir and have high salinity (25–30% seawater total dissolved solids) and some of the highest recorded pH values (11−13) for natural waters. These waters have elevated dissolved Na, K, Li, B, Ba, Rb, Cs, Cl and SO4with ion/chloride substantially above seawater ratios, overprinting minor contributions from marine aerosols. For example, K concentrations are similar to seawater values. Water stable isotope ratios imply extensive water-rock interaction and87Sr/86Sr is rock-dominated (0.705) and significantly lower than seawater. These rare fluids contrast with surface and shallow ground waters draining the ultramafic Troodos Mantle Sequence that have pH of 8.5–9, meteoric stable isotope ratios,87Sr/86Sr similar to early Miocene seawater (0.7085) and low dissolved salts albeit with ion/chloride ratios also greater than seawater. The combination of high pH and salinity is unusual in ophiolites and these hyperalkaline waters are most similar to end-member fluids emanating from serpentine mud volcanoes in the Mariana forearc. Rainwater rapidly transiting terraces of asbestos mine tailings on Troodos mostly resemble the surface waters but show slight contamination by a saline component. We propose that inclusions within the serpentinite that contain highly soluble salts have been made accessible by tectonic deformation during uplift and diapirism, or comminution during mining activity. A multistage process is proposed whereby alkali and other signatures have been released from the stalled subducting slab beneath the Troodos massif and have infused the mantle wedge. Some of these rocks have been carried to the surface by diapiric uplift and erosion, where tectonic deformation or mining activities have enabled the near-surface mobilisation of slab-derived geochemical signatures by modern meteoric waters.
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通讯作者：
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DOI：
--
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1987
期刊：
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DOI：
--
发表时间：
2016
期刊：
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