Investigation of High Precision Os Measurements on Lavas From Iceland and the Austral Islands

对冰岛和南方群岛熔岩进行高精度 Os 测量的调查

• 批准号: 0000908
• 负责人: Alan Brandon
• 金额: $ 9.39万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-09-01 至 2002-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0000908&HistoricalAwards=false
• 关键词: Investigation; Precision; Os; Measurements; Lavas

BrandonEAR-0000908Recent work has shown that coupled enrichments in 186Os/188Os and 187Os/188Os for some Hawaiian lavas is consistent with the hypothesis of core-mantle interaction within the Hawaiian plume source. If this is correct, then these are perhaps the most robust geochemical data to date, that show some plumes originate in the D" region of the deepest part of the mantle. Alternatively, these data could instead be consistent with entrainment of ancient recycled crust provided certain conditions hold. As a further test of these hypotheses, high precision 186Os/188Os and 187Os/188Os data for lavas from Iceland and the Austral Islands will be obtained. These two suites are ideal for subsequent testing of the roles of core-mantle interaction and ancient crustal recycling in generating radiogenic Os compositions in plumes because of the following. Seismic evidence suggests that Iceland plume originates from D" just above the core-mantle boundary. It is a high 3He hotspot with active volcanism in a relatively fixed position for at least 60 million years. Taken together, these observations support a deep mantle origin for the Iceland plume where core-mantle interaction may occur. Some Austral Islands lavas have 187Os/188Os that are too high to be produced by reasonable models for entrainment of outer core into plume sources. Therefore, the these lavas can be used to make a rigorous test of the role of ancient crustal recycling for potentially producing radiogenic 186Os/188Os in plume-derived lavas. The ultimate result of this study will be to provide a greater understanding of the significance of chemical exchange between the outer core and plume sources, the role of crustal recycling to produce Os isotopic signatures in plumes, and the use of coupled enrichments of 186Os/188Os and 187Os/188Os to constrain the depths of origin of plumes.

Brandonear-0000908的工作表明，夏威夷熔岩的耦合浓度与某些夏威夷熔岩的耦合富集与夏威夷羽流源内的核心 - 披风相互作用的假设是一致的。如果这是正确的话，那么这些也许是迄今为止最强大的地球化学数据，这表明一些羽流起源于地幔最深部分的D“ d”区域。另外，这些数据可以与在某些条件下的融合夹带一致。作为某些条件的夹带。作为对这些假设的进一步测试，对这些假设的进一步测试，对186os/188 os and 188 obl and iCENDER and 1888888888888888888888888888888888888888888年份。这两个套件非常适合随后测试核心 - 螺栓相互作用和古代地壳回收在羽毛形成中产生放射性OS组成的作用，这是由于以下情况。 这是一个高3HE热点，在至少6000万年中，具有相对固定的位置有活跃的火山症。 综上所述，这些观察结果支持了可能发生核心固定相互作用的冰岛羽流的深层地幔。 一些澳大利亚岛的熔岩有187OS/188OS，这些熔岩太高，无法通过合理的模型而生产，以使外部芯夹在羽流源中。 因此，这些熔岩可用于对古代地壳回收的作用进行严格测试，以在羽流衍生的熔岩中产生潜在的186OS/188OS。 这项研究的最终结果将是对外部核心和羽流源之间化学交换的重要性，在羽毛中产生OS同位素特征的作用，以及使用186OS/188OS和187OS/188OS限制Plumes plumes of Plumes的深度的作用。