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

本文将对URI挖泥岩收集的中洋脊玄武岩（MORB）玻璃的176Hf/177Hf同位素比值变化进行全面的记录和研究。这些资料集中在受附近热点和地幔柱影响的异常升高的洋中脊段。将研究来自约300个不同采样地点的约300-400个样本。将寻求放射性成因的Lu-Hf同位素系统与Pb、Sr、Nd和He同位素系统之间可能的相关性或解耦合，以及之前在同一玄武岩玻璃上建立的其他地球化学参数。这项研究应该为受热点影响的洋中山脊段（如大西洋的扬马扬、冰岛、亚速尔群岛、塞拉利昂、圣赫勒拿岛和特里斯坦达库纳群岛、太平洋的加拉戈斯群岛和伊斯特群岛、亚丁湾-红海地区的阿法尔群岛）下的石榴石融化的深度和模式以及涉及的范围提供新的限制。在海底地幔地球化学、非均质长度尺度和地幔动力学方面也应获得更深入的认识。该研究将与来自法国里昂高等学院的Janne Blichert-Toft博士和Francis Albarede博士合作完成，在URI分离Hf后，将通过等离子体源多收集器质谱法测量176Hf/177Hf比率。

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.