Molybdenum in Basalt-Hosted Seafloor Hydrothermal Systems: Experimental, Theoretical, and Field Sampling Approaches
Molybdenum in Basalt-Hosted Seafloor Hydrothermal Systems: Experimental, Theoretical, and Field Sampling Approaches
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DOI：
10.1016/j.gca.2023.05.018
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发表时间：
2023-06
影响因子：
5
通讯作者：
G. Evans;L. A. Coogan;B. Kacar;W. Seyfried
中科院分区：
文献类型：
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作者：
G. Evans;L. A. Coogan;B. Kacar;W. Seyfried
海底热液喷口是全球海洋钼和其他与生物有关的过渡金属的潜在来源，补充了大陆径流。在这里，我们使用的实验，理论和现场采样的方法相结合，以调查的行为，钼在玄武岩托管海底热液系统，提供深入了解的过程中控制钼浓度的热液流体，并获得估计喷口流体钼浓度和通量。这项研究的结果表明，从350 °C、500 bar热液玄武岩蚀变实验中产生的反应流体含有775-801 nmol/kg Mo，因此与最近收集的天然海底喷口流体的时间序列相当，后者在302 °C时含有200-220 nmol/kg Mo，在281-282 °C时含有29-30 nmol/kg Mo（Evans等人，2023年）。对本研究中产生的实验蚀变玄武岩和最初从皮托深裂谷收集的蚀变洋壳的其他天然样品进行的基于同步加速器的分析表明，存在与微量硅铝榴石一致的富钼颗粒。Mo：Cu比率在自然喷口流体和近喷口沉积物陷阱样品从主奋进领域的比较表明，喷口流体钼很容易纳入浮力羽流颗粒和平流出近喷口领域，类似于以前的质量平衡研究在这个区域Cu.Thermodynamic计算的钙铝榴石溶解度的背景下，矿物缓冲热液和比较与自然和实验热液流体表明，高温喷口流体含有30-1500 nmol/kg钼。热液Mo通量是现代Mo收支的一个次要组成部分，但在1.24Ga前的“大氧化事件”和广泛的氧化大陆风化之前，热液Mo通量约占同期大陆风化通量的0.3-200倍。总的来说，确定热液喷口作为富钼羽流颗粒的来源，并有可能扩散到更广泛的海洋环境中，这对关于生命和地球环境共同进化的假设具有重要意义，特别是缺氧的太古宙海洋中钼的形式和可用性，其中钼依赖酶途径被认为已经出现并随后演变。
Seafloor hydrothermal vents represent potential sources of Mo and other biologically relevant transition metals to the global ocean, complementing continental runoff. Here, we use a combination of experimental, theoretical, and field-sampling approaches to investigate the behavior of Mo in basalt-hosted seafloor hydrothermal systems to provide insight into the processes controlling Mo concentrations in hydrothermal fluids and to derive estimates of vent fluid Mo concentrations and fluxes. Results of this study demonstrate that reaction fluids generated from 350 °C, 500 bar hydrothermal basalt alteration experiments contain 775–801 nmol/kg Mo and are thus comparable to a recently collected time series of natural seafloor vent fluids that contained 200–220 nmol/kg Mo at 302 °C and 29–30 nmol/kg at 281–282 °C (Evans et al., 2023). Synchrotron-based analyses of experimentally altered basalt produced in this study and additional natural samples of altered oceanic crust originally collected from Pito Deep Rift reveal the presence of Mo-rich particles consistent with trace molybdenite. Comparisons of Mo:Cu ratios in natural vent fluids and near-vent sediment trap samples from Main Endeavour Field indicate that vent fluid Mo is readily incorporated into buoyant plume particles and advected out of the near-vent field, analogous to previous mass balance studies of Cu in this region.Thermodynamic calculations of molybdenite solubility in the context of mineral-buffered hydrothermal fluids and comparisons with natural and experimental hydrothermal fluids suggest that high-temperature vent fluids contain 30–1500 nmol/kg Mo. While a minor component of the modern Mo budget, hydrothermal Mo fluxes are estimated to have constituted 0.3–200× the contemporaneous continental weathering fluxes prior to the ∼2.4 Ga ago “Great Oxidation Event” and widespread oxidative continental weathering. Overall, identification of hydrothermal vents as a source of Mo-rich plume particles with potential for dispersal into the wider marine environment has significant implications for hypotheses regarding the co-evolution of Life and Earth’s environments, specifically the form and availability of Mo in anoxic Archean-Eon oceans, where Mo-dependent enzymatic pathways are thought to have emerged and subsequently evolved.