Collaborative Research: Sr-Nd-Pb-Hf Isotope Studies of Deep Crustal Xenoliths from the Southwestern U.S.A. and Northern Mexico

9318687卡梅伦私人投资公司建议对得克萨斯州西部戴维斯山脉-大本德地区和墨西哥奇瓦瓦的卡马戈玄武岩油田的麻粒岩相包体进行岩石学、地球化学、锶-钕-铅-氢同位素和常规的U/铅锆石研究。此外，他们还将分析新墨西哥州基尔伯恩洞中含有石榴石的变质岩残留物的Hf同位素组成。基尔伯恩洞和其他地点的遗迹只有有限的ND(0)变化，但176Lu/177Hf比值范围很大，包括极值(0.5)。从含石榴石残岩中熔体提取的Hf模式年龄应该比基于ND的模式年龄更明确。这将是第一次系统地研究下地壳捕虏体，整合了锶、钕、铅和氢同位素，也将是迄今为止最详细的常规铀/铅锆石研究。尽管这项合作工作的直接目标是研究下地壳，但加州大学圣克鲁斯分校的工作人员将在麦迪逊大学获得最先进的HF同位素分析方面的宝贵经验，包括联合开发新标准和尖峰。这种方法将使加州大学圣克鲁斯分校能够有效地启动一个关于Hf同位素工作的计划。

9318687 Cameron The PIs propose to make a combined petrologic, geochemical, Sr-Nd-Pb-Hf isotope and conventional U/Pb zircon study of granulite facies xenoliths from the Davis Mountains-Big Bend region of west Texas and the Camargo basalt field in Chihuahua, Mexico. In addition, they will analyze garnet- bearing metaigneous restites from Kilbourne Hole, New Mexico, for their Hf isotope compositions. Restites from Kilbourne Hole and the other locations have only limited variation in Nd(0) but a wide range of 176Lu/177Hf ratios including extreme values (0.5). Hf model ages for melt-extraction from garnet-bearing restites should be far less ambiguous than model ages based on Nd. This will be the first systematic study of lower crustal xenoliths that integrates Sr, Nd, Pb, and Hf isotopes, and it will be by far the most detailed conventional U/Pb zircon study to date. Although the immediate goal of this collaborative effort is the study of the lower crust, U.C. Santa Cruz workers will gain valuable experience at U.W. Madison in state-of-the-art Hf isotope analysis, including joint development of new standards and spikes. This approach will allow U.C. Santa Cruz to efficiently start-up a program in Hf isotope work.