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Comprehensive Study of the Lu-Hf Radiogenic Isotope Systematics of Normal and Hotspot Affected Mid-Ocean Ridge Basalts

正常和热点影响的洋中脊玄武岩 Lu-Hf 放射性同位素系统学的综合研究

基本信息

批准号：
9818969
负责人：
Jean - guy Schilling
金额：
$ 19.98万
依托单位：
University of Rhode Island
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
1999
资助国家：
美国
起止时间：
1999-03-15 至 2003-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=9818969&HistoricalAwards=false
关键词：
Comprehensive Study Lu Hf Radiogenic

项目摘要

A comprehensive documentation and study of 176Hf/177Hf isotope ratio variation of mid-ocean ridge basalt (MORB) glasses from the URI dredge rock collection will be conducted. The collection focuses on unusually elevated mid-ocean ridge segments affected by nearby hotspots and underlying mantle plumes. About 300-400 samples from some 300 different sampling localities will be studied. Possible correlations, or decoupling, will be sought between the radiogenic Lu-Hf isotope system with that of Pb, Sr, Nd, and He isotope systems, and other geochemical parameters previously established on the very same basalt glasses. The study should provide new constraints on the depth and mode of melting and extent of garnet involvement beneath mid-ocean ridge segments affected by hotspots such as Jan Mayen, Iceland, Azores, Sierra Leone, St Helena and Tristan da Cuhna in the Atlantic, the Galaggos and Easter in the Pacific, and the Afar in the Gulf of Aden-Red Sea region. Greater insights should also be gained on suboceanic mantle geochemistry, length scales of heterogeneities, and mantle dynamics. The study will be done in collaboration with Dr. Janne Blichert-Toft and Dr. Francis Albarede, from the Ecole Superieure de Lyon, France, where the 176Hf/177Hf ratio measurements will be made by plasma source multi-collector mass spectrometry, after Hf has been separated at URI.

将对大洋中脊玄武岩(MORB)玻璃的176Hf/177Hf同位素比值变化进行全面的文献记录和研究。收集的重点是受附近热点和下伏地幔热柱影响的异常抬高的大洋中脊部分。将对来自约300个不同采样点的约300-400个样本进行研究。在放射性成因的Lu-Hf同位素系统与铅、锶、钕和氦同位素系统之间，以及之前在同一玄武岩玻璃上建立的其他地球化学参数之间，将寻求可能的关联或解耦。这项研究应对受热点影响的大洋中脊之下的石榴石融化的深度和方式和范围提供新的制约因素，这些热点包括大西洋的Jan Mayen、冰岛、亚速尔群岛、塞拉利昂、圣赫勒拿和特里斯坦-达库纳，太平洋的加拉戈斯和复活节，以及亚丁湾-红海地区的阿法尔。还应对海底地幔地球化学、非均质性的长度尺度和地幔动力学有更多的了解。这项研究将与法国里昂高等学院的Janne Blichert-Toft博士和Francis Albarde博士合作完成，在URI分离出HF后，将使用等离子体源多收集器质谱仪测量176 Hf/177 Hf比率。