187Re-187Os, 190Pt-186Os, 34S/32S Isotopic Systematics of the Subcontinental Mantle of the Western United States

美国西部次大陆地幔的 187Re-187Os、190Pt-186Os、34S/32S 同位素系统学

• 批准号: 9804909
• 负责人: Richard Walker
• 金额: $ 14.4万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-09-01 至 2000-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9804909&HistoricalAwards=false
• 关键词: 187Re; 187Os; 190Pt; 186Os; 34S

9804909Walker The timing of melt extraction in the subcontinental lithospheric mantle (SCLM) underlying regions of Proterozoic and Phanerozoic crust in the western United States is largely unknown. Distinctions between metasomatism of the SCLM via fluids and melts derived from subducting slabs, and the processes resulting in formation of OIB-type mantle domains, remain unclear. As a first step to alleviate some of the ambiguity, recent investigations have identified several compositional parameters that are unique to subduction-related metasomatism. These include high oxygen fugacities relative to oceanic and cratonic mantle, suprachondritic 187Os/188Os, and heavy 34S/32S. Some OIB-type mantle domains may have suprachondritic 186Os/188Os ratios. Therefore, these data combined with other geochemical parameters may discern between subduction zone metasomatism and OIB-type compositional enrichments within the SCLM. To address the timing of melting and the processes that modified the SCLM associated with Proterozoic and Phanerozoic crust, we will obtain 187Re-187Os, 190Pt-186Os and 34S/32S isotopic data on mantle xenoliths from the western United States. We will use negative thermal ionization mass spectrometry to obtain Os isotopic data. Bulk rock S isotopic data will be obtained using gas source mass spectrometry, and in situ S isotopes will be obtained by secondary ionization mass spectrometry.

9804909 Walker在美国西部的proterorogic和phanerokoic Crust的底部岩石圈地幔（SCLM）中熔体提取的时机在美国西部是未知的。 SCLM通过流体和从俯冲板上得出的熔体以及导致OIB型地幔结构域形成的过程之间的区别尚不清楚。 作为减轻某些歧义的第一步，最近的研究已经确定了几个组成参数，这些参数是与俯冲相关相关的相关化合物所独有的。 这些包括相对于海洋和克拉通地幔的高氧散发性，上线187OS/188OS以及重量的34/32s。 某些OIB型地幔域可能具有186OS/188OS比率。 因此，这些数据与其他地球化学参数相结合，可以辨别俯冲带代理和SCLM内OIB型组成富集。 为了解决熔解的时间以及修改与properorogic和phanerozoic Croust相关的SCLM的过程，我们将获得来自美国西部的地幔Xenoliths的187RE-187OS，190PT-186OS和34S/32S同位素数据。 我们将使用负热电离质谱法来获得OS同位素数据。 将使用气源质谱法获得大量岩石同位素数据，并通过次级电离质谱法获得原位的同位素。