Cenozoic Tectonic and Magmatic Evolution of the Mojave Desert: Collaborative Research Between UCB and the University of North Carolina

莫哈韦沙漠的新生代构造和岩浆演化：UCB 和北卡罗来纳大学的合作研究

• 批准号: 8817093
• 负责人: Lang Farmer
• 金额: $ 8.25万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-01-01 至 1991-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8817093&HistoricalAwards=false
• 关键词: Cenozoic; Tectonic; Magmatic; Evolution; Mojave

This is a collaborative study between the University of Colorado and the University of North Carolina on the Nd, Sr, and Pb isotopic, and trace element compositions of Cenozoic mafic-to- silicic volcanic rocks in the Mojave Desert region of southeastern California. The study will use temporal and spatial variations in the geochemical characteristics of the volcanic rocks to constrain models of the tectonic evolution of this region, and to study aspects of the magmatic evolution of the Cenozoic volcanic rocks. Geochemical data from 5Ma basalts will be used to evaluate the age, structure, and composition of the mantle currently underlying this area. The results of this study will be used to test whether pre-Cenozoic mantle lithosphere has been tectonically removed from beneath the continental crust, as suggested by available isotopic data and as proposed in some tectonic models for this region. Geochemical data from older Cenozoic basalts will be used to assess the tectonic setting in which lithosphere removal took place. A similar geochemical data set will be obtained for Miocene intermediate-to-silicic volcanics and will be used to constrain models for the genesis of these rocks. The isotopic compositions of these rocks will also be used to infer aspects of the geochemistry of the lower continental crust, and to define any subsurface boundaries between Precambrian basement terraines with different Nd isotopic characteristics. Overall this study will represent the first comprehensive characterization of the isotope and trace element compositions of Mojave volcanic rocks, and one of the first attempts to apply such data towards constraining tectonic models of the continental lithosphere. The study represents an outgrowth from previous NSF supported research by both of the PIs. Glazner (UNC) will be responsible for sample selection, petrography and trace-element chemistry, and Farmer (UC) will carry out all isotopic determinations.

这是科罗拉多大学和北卡罗来纳大学之间的一项合作研究，内容涉及加利福尼亚州东南部莫哈韦沙漠地区新生代镁铁质至硅质火山岩的 Nd、Sr 和 Pb 同位素以及微量元素组成。 该研究将利用火山岩地球化学特征的时空变化来约束该地区的构造演化模型，并研究新生代火山岩岩浆演化的各个方面。 5Ma 玄武岩的地球化学数据将用于评估目前该区域下方地幔的年龄、结构和成分。 这项研究的结果将用于测试前新生代地幔岩石圈是否已从大陆地壳下方被构造移除，正如现有同位素数据所表明的以及该地区一些构造模型中所提出的那样。 来自较早新生代玄武岩的地球化学数据将用于评估发生岩石圈去除的构造环境。 将为中新世中硅质火山岩获得类似的地球化学数据集，并将用于约束这些岩石的成因模型。 这些岩石的同位素组成也将用于推断下大陆地壳的地球化学方面，并定义具有不同 Nd 同位素特征的前寒武纪基底地形之间的任何地下边界。 总体而言，这项研究将首次全面表征莫哈韦火山岩的同位素和微量元素组成，也是将此类数据应用于约束大陆岩石圈构造模型的首次尝试之一。 该研究是两位 PI 先前支持的 NSF 研究的成果。 Glazner (UNC) 将负责样品选择、岩相学和微量元素化学，Farmer (UC) 将进行所有同位素测定。