Hydrothermal oxidation of Os
Hydrothermal oxidation of Os
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DOI：
10.1016/j.gca.2019.04.019
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发表时间：
2019-06
影响因子：
5
通讯作者：
D. Foustoukos
中科院分区：
文献类型：
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作者：
D. Foustoukos
进行了一系列热液金刚石砧室实验，以研究在 500°C 至 1000°C 温度范围和类似于上地幔/下地壳环境 (29-1343MPa) 的压力下，Os 和 Ir 在盐水和氧化热液中的迁移率与流体 pH 值的函数关系。通过拉曼振动光谱在原位条件下实时监测反应液的成分。结果表明，在氧化还原条件 (∼+5 ΔFMQ) 和超过 850°C 的温度下，形成了 Os双键 O 挥发性水物质。这些物质是在低压条件（<150MPa）下从均质流体中分离出来的不混溶相中检测到的。根据之前的实验和理论研究，原位观察到的含锇物种归因于 OsO4(g) 的存在。因此，Os 在高温/高压岩浆液中的挥发性传输可能包括氧化物水性物质以及 Os-Cl 络合。 Ir-H2O 实验中在 700–800°C 和 543–793MPa 压力下形成的 H2(aq) 提供了 Ir 氧化的可能证据。实验数据支持板片衍生流体通过以含 Cl 和氧的挥发性水复合物形式增强 Os 的迁移性，在交代捕虏体中相对于原始上地幔成分产生升高的 Os/Ir 比的作用。
A series of hydrothermal diamond anvil cell experiments was conducted to investigate the mobility of Os and Ir in saline and oxidizing hydrothermal fluids as function of fluid pH at temperatures ranging from 500 °C to 1000 °C and pressures resembling upper mantle/lower crust environments (29–1343 MPa). The composition of reactant fluids was monitored in real time and at in situ conditions by Raman vibrational spectroscopy. Results revealed the formation of Osdouble bondO volatile aqueous species under oxidizing redox conditions (∼+5 ΔFMQ) and at temperatures exceeding 850 °C. These species were detected in an immiscible phase separated from the homogeneous fluid at low pressure conditions (<150 MPa). Based on previous experimental and theoretical studies, the Os-bearing species observed in situ are attributed to the presence of OsO4(g). Volatile transport of Os in high temperature/pressure magmatic fluids, therefore, may include oxide aqueous species along with Os-Cl complexation. Possible evidence of Ir oxidation was provided by the formation of H2(aq)in Ir-H2O experiments at 700–800 °C and pressures of 543–793 MPa. Experimental data support the role of slab-derived fluids in yielding elevated Os/Ir ratios in metasomatized xenoliths relative to primitive upper mantle composition through the enhanced mobility of Os in the form of Cl- and oxygen-bearing volatile aqueous complexes.