Collaborative Research: PGE and Pb Systematics in Altered Abyssal Peridotites: Integrating Experiments with Natural Samples

这项工作将验证在橄榄岩蚀变过程中硫化物和金属合金矿物学的变化将调动和分选PGE， Re和Pb相对于其原始岩浆浓度的假设。水热实验将以温度和氧化还原条件为函数约束PGE、Re、Pb在地幔含Ni-Fe-Ru-Re硫化物和金属合金中的溶解度，并评价低硫逸度条件下PGE合金的析出和PGE-Re分馏。该研究的自然样品部分将根据氧化还原、蚀变、硫化物矿化和主要成分（肥沃与枯竭）的作用，限制来自具有良好特征的深海橄榄岩的硫化物、合金和块状岩石中PGE、Re、Pb的分布和分馏。通过整合实验和自然样品数据，本工作将限制蚀变海洋岩石圈再循环过程中PGE、Re、Pb的命运，以及蚀变橄榄岩能否随着时间的推移，在难熔（金属合金）或可动（硫化物）储层之间发展出高度不均匀的187Os/188Os和186Os/188Os比率。该项目是两家美国机构之间的合作项目，将促进新分析技术的技术和专业知识转移到南加州大学新建立的地球化学设施。研究人员将共享一套最先进的仪器，包括FIB-SEM， FE-EMPA, FE-SEM， LA-ICPMS和同步辐射微x射线荧光。收集的所有数据将提交给PetDB和IEDA，并将通过ciw托管的数据存储库向公众提供。来自南加州大学的一名研究生将参加他的博士研究。暴露在海底的蚀变地幔岩石（称为“蛇纹岩化深海橄榄岩”）含有含镍金属相，与次生铂族元素（PGE）含硫矿物（硫化物）和PGE金属块有关。PGEs具有独特的物理和化学性质，对许多技术应用至关重要。因此，它们通常被视为包括航空航天和燃料电池技术在内的广泛行业的战略金属。该研究将极大地促进目前对高温海水蚀变对深海橄榄岩中铂族元素硫化物分布影响的有限认识。此外，深海橄榄岩为了解地球的组成和演化提供了重要的记录。S地幔现在和过去。提出的工作是一个协作的实验和自然样本调查。实验数据将定义与现代深海火山有关的条件下PGE矿物的热力学性质，并评估高温/高压条件下Fe-Ni-Ru-Re硫化物/合金中PGE溶解机制的关键细节。实验结果与自然样品数据相结合，将使我们对海水蚀变对蚀变橄榄岩亲铁、亲铜组分的影响及其对地球Os、Pb同位素非均质性的影响有一个根本性的新认识。地幔。

The proposed work will test the hypothesis that changes in sulfide and metal alloy mineralogy during peridotite alteration will mobilize and fractionate the PGE, Re and Pb relative to their primary magmatic concentrations. Hydrothermal experiments will constrain the solubility of PGE, Re, Pb in mantle Ni-Fe-Ru-Re bearing sulfides and metal alloys as function of temperature and redox conditions, and evaluate PGE alloy exsolution and PGE-Re fractionation under low sulfur fugacity. The natural sample part of the study will constrain the distribution and fractionation of PGE, Re, Pb in sulfides, alloys and bulk rocks from well characterized abyssal peridotites, as function of redox, alteration, sulfide mineralization and primary composition (fertile versus depleted). Through integration of the experimental and natural sample data this work will constrain the fate of PGE, Re, Pb upon recycling of altered oceanic lithosphere and whether altered peridotites can develop, over time, highly heterogeneous 187Os/188Os and 186Os/188Os ratios between refractory (metal alloys) or mobile (sulfide) reservoirs. This project is a collaborative effort between 2 US institutions, and will promote transfer of technology and expertise on novel analytical techniques to a newly established geochemical facility at USC. Researchers will share a suite of state-of-the art instrumentation including FIB-SEM, FE-EMPA, FE-SEM, LA-ICPMS and synchrotron radiation micro-X-Ray fluorescence. All the data collected will be submitted to the PetDB and IEDA, and will be available to the public through a CIW-hosted data repository. A graduate student from USC will participate towards completion of his PhD studies.Altered mantle rocks exposed at the seafloor (called "serpentinized abyssal peridotites") contain Ni-bearing metal phases associated with secondary plantinum-group element (PGE) sulfur-bearing minerals (sulfides) and PGE metal nuggets. PGEs have unique physical and chemical properties that are critical to many technological applications. Thus, they are often regarded as strategic metals in a wide range of industries including aerospace and fuel cell technology. The proposed research will significantly advance the currently limited understanding of the effects of high-temperature seawater alteration on the distribution of plantinum-group element sulfides hosted in abyssal peridotites. Moreover, abyssal peridotites provide an important record for understanding the composition and evolution of Earth?s mantle now and in the past. The proposed work is a collaborative experimental and natural sample investigation. Experimental data will define the thermodynamic properties of PGE minerals at conditions relevant to modern deep-sea volcanoes and assess critical details of PGE solubility mechanisms in Fe-Ni-Ru-Re sulfides/alloys at elevated temperature/-pressure conditions. The combined experimental results and natural sample data will lead to a fundamental new understanding on the effects of seawater alteration on the siderophile and chalcophile composition of altered peridotite and its effect on the Os and Pb isotope heterogeneity in the Earth?s mantle.