Platinum Group Element Analysis of Komatiites

为了更好地了解铂族元素(PGE)的地幔地球化学特征和186Os-187Os同位素研究提供的信息，我们提出用精密同位素稀释电感耦合等离子体质谱(ICPMS)技术测定全球科马提岩的铂族元素丰度。根据本实验室的结果，该分析技术已成功地应用于科马提石中PGE的测定。拟议的地点包括来自下列绿岩带的科马提岩：Barberton(南非)；Kamennoozero、Vetreny、Oenia(波罗的海盾牌)；Belingwe(南非)；Abitibi(加拿大)；Kambalda(澳大利亚)；Gorgona(加勒比)。所有样品都可以从我们的收藏中获得，或者将从其他地球化学研究，特别是以前的Os同位素研究中慷慨地提供。这些包括贫氧化铝和未贫氧化铝的科马提岩，以及球粒和超球粒的初始含伽马-187Os的科马提岩。我们建议的研究目标是：1.专注于建立科马提岩经历极高程度部分熔融期间的PGE行为规律，并为未来的工作建立一个框架，包括苦味熔岩和原生玄武岩熔体；2.确定太古代地壳物质的PGE组成，这可能是显生宙溢流玄武岩和奥里伯岩俯冲地壳的来源；3.研究每个科马提岩源区(大概是太古宙下地幔)的PGE组成，以寻找其不均一性的线索，以及对太古宙地幔动力学的影响；以及4.寻找太古宙地柱中核-地幔相互作用的证据，包括这种外核派生信号长期变化的证据。这个项目的成功完成将使我们能够确定这种方法是否可以用于更好地理解由苦苦岩和原生玄武岩采样的源区的地幔过程，从而扩展我们的框架，包括对地幔进行更大的时空采样。该项目还支持俄罗斯地球化学家伊戈尔·普赫特尔继续访问美国，他是波罗的海盾牌四个科马提岩地点的广泛研究的持有者和热心学生，以前非俄罗斯科学家无法进入。

HumayunEAR-0106974To better understand the mantle geochemistry of platinum group elements (PGE) and the information returned by 186Os-187Os isotopic studies, we propose to determine the PGE abundances of a global suite of komatiites by a precise isotope dilution ICP-MS technique. Based on results in this lab, this analytical technique has been successfully applied for the determination of PGEs in komatiites. Proposed localities include komatiites from the following greenstone belts: Barberton (S. Africa); Kamennoozero, Vetreny, Onega (Baltic Shield); Belingwe (S. Africa); Abitibi (Canada); Kambalda (Australia); and Gorgona (Caribbean). All samples are available in collections held by us, or will be generously provided from other geochemical studies, particularly previous Os isotopic studies. These include both alumina-depleted and alumina-undepleted komatiites, and both chondritic and suprachondritic initial gamma-187Os-bearing komatiites.Our intellectual goals for the proposed study are to: 1. Focus on establishing the rules of PGE behaviour during the extremely high degrees of partial melting experienced by komatiites, and establish a framework for future work that would include picritic lavas and primary basaltic melts; 2. Determine the PGE composition of Archean crustal materials, which are possible sources of subducted crust for Phanerozoic flood basalts and OIB lavas; 3. Study the PGE composition of each komatiite source region, presumably the Archean lower mantle, for clues to its heterogeneity, with implications for mantle dynamics in the Archean; and 4. Search for evidence of core-mantle interaction in Archean plumes, including evidence for secular changes in such outer core derived signatures.Successful completion of this project will enable us to determine whether this approach can be applied to better understand mantle processes in source regions sampled by picrites and primary basalts, and thereby extend our framework to include a larger spatiotemporal sampling of the mantle. This project also supports the continued US visit of Russian geochemist, Igor Puchtel, the holder and dedicated student of an extensively studied suite of four komatiite localities in the Baltic Shield previously inaccessible to non-Russian scientists.