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

拟议的工作将测试的假设，在橄榄岩蚀变过程中硫化物和金属合金矿物学的变化将动员和压裂的铂族元素，铼和铅相对于其原始岩浆浓度。通过水热实验研究PGE、Re、Pb在地幔Ni-Fe-Ru-Re硫化物和金属合金中的溶解度随温度和氧化还原条件的变化规律，评价低硫逸度条件下PGE合金的出溶和PGE-Re分馏。研究的天然样品部分将限制铂族元素，铼，铅的分布和分馏的硫化物，合金和散装岩石的特点深海橄榄岩，作为功能的氧化还原，蚀变，硫化物矿化和主要成分（肥沃与枯竭）。通过整合实验和天然样品数据，这项工作将限制PGE的命运，Re，Pb的循环蚀变的海洋岩石圈，以及是否蚀变橄榄岩可以开发，随着时间的推移，高度不均匀的187 Os/188 Os和186 Os/188 Os的比例之间的耐火（金属合金）或移动的（硫化物）水库。该项目是两个美国机构之间的合作努力，并将促进新的分析技术的技术和专业知识转移到南加州大学新成立的地球化学设施。研究人员将分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。南加州大学的一名研究生将参与完成他的博士研究。暴露在海底的蚀变地幔岩（称为“蛇纹化深海橄榄岩”）含有与第二铂族元素（PGE）、含硫矿物（硫化物）和PGE金属块有关的含镍金属相。铂族元素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。拟议的研究将大大推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的影响的有限认识。此外，深海橄榄岩提供了一个重要的记录，了解地球的组成和演化？现在和过去都是。拟议的工作是一个合作的实验和自然样本调查。实验数据将确定PGE矿物在现代深海火山相关条件下的热力学性质，并评估PGE在高温/高压条件下Fe-Ni-Ru-Re硫化物/合金中溶解机制的关键细节。结合实验结果和天然样品数据将导致一个根本的新的认识，海水蚀变的影响，亲铁和亲铜组成的蚀变橄榄岩和它的影响，在地球上的Os和Pb同位素的不均匀性？的斗篷。

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.