Platinum Group Element Analysis of Komatiites

为了更好地了解铂族元素（PGE）的地幔地球化学和186 Os-187 Os同位素研究所提供的信息，我们建议采用精确同位素稀释ICP-MS技术测定全球科马提岩套的PGE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岩中铂族元素的测定。建议的地点包括来自以下绿岩带的科马提岩：巴伯顿（S。非洲）; Kamennoozero，Vetreny，Onega（波罗的海盾牌）; Belingwe（S。非洲）、阿比提比（加拿大）、坎巴尔达（澳大利亚）和戈尔戈纳（加勒比）。所有样品都可在我们的收藏品中获得，或将从其他地球化学研究中慷慨提供，特别是以前的Os同位素研究。这些包括氧化铝贫化和氧化铝未贫化科马提岩，以及钙长石和超球粒陨石初始γ-187 Os轴承科马提岩。重点是建立PGE行为的规则，在极高程度的部分熔融经历科马提岩，并建立一个框架，为未来的工作，将包括苦橄熔岩和原生玄武岩熔体; 2。确定太古代地壳物质的铂族元素组成，这些物质可能是古生代溢流玄武岩和OIB熔岩俯冲地壳的物质来源;研究每个科马提岩源区（可能是太古代下地幔）的铂族元素组成，以寻找其不均匀性的线索，并对太古代地幔动力学产生影响;在太古宙羽状岩中寻找核幔相互作用的证据，包括这种外核衍生签名的长期变化的证据，该项目的成功完成将使我们能够确定这种方法是否可以应用于更好地了解苦橄岩和原生玄武岩采样的源区地幔过程，从而扩展我们的框架，包括更大的地幔时空采样。该项目还支持俄罗斯地球化学家Igor Puchtel继续访问美国，Igor Puchtel是波罗的海地盾四个科马提岩地点的广泛研究套件的保持器持有者和专门的学生，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.