Petrogenesis of Proterozoic Anorogenic Granites in the Central United States

这项拟议工作的目标是调查1.1至1.8Ga造山花岗岩的起源和构造环境，这些花岗岩构成了美国中部地壳的一大部分。这项研究将利用Nd、Sr、Pb和O的同位素变化和微量元素模式来阐明花岗岩源区的性质、岩浆形成过程和岩浆演化。来自横跨北美大陆的600-1000公里宽的带的非造山花岗岩。它们侵位于1.1-1.8Ga之间的几个幕间，具有区别于其他类型花岗岩的主要和微量元素化学。关于非造山花岗岩的化学和构造来源的假设是非常多样化的，并包含了相反的极端。一个全面的同位素和化学数据库将有助于限制这种可能性。这项研究集中在威斯康星州、密苏里州和德克萨斯州的四个建筑群。它们都有已知的U-Pb年龄，并且每一个都具有岩石学和化学特征。将针对特定的钚进行特别详细的采样和研究。这种方法既可以研究特定岩体中的岩浆成因细节，也可以比较不同地壳省份和侵入幕之间的深成岩浆。这两种观察尺度都需要识别和解释非造山岩浆成因的主要特征。

The objective of the proposed work is to investigate the origin and tectonic setting of 1.1 to 1.8 Ga anorogenic granites that make up a large part of the crust in the central United States. The study will employ isotopic variations in Nd, Sr, Pb and O, and trace element patterns to elucidate the nature of granite source regions, the process of magma genesis, and the evolution of the magmas. Anorogenic granites from a 600-1000 km-wide band that extends across the North American continent. They were emplaced during several episodes between 1.1 and 1.8 Ga, and have a major and trace element chemistry that distinguishes them from other types of granites. Suggested hypotheses regarding both the chemical and tectonic sources of anorogenic granites are exceedingly diverse and encompass antithetic extremes. A comprehensive isotopic and chemical data base would help constrain the possibilities. This study focusses on four complexes located in Wisconsin, MIssouri, and Texas. All have known U-Pb ages, and each is petrographically and chemically characterized. Specific plutons will be targeted for especially detailed sampling and study. This approach allows study of both details of magma genesis in a specific pluton, and the comparison of plutons among different crustal provinces and intrusive episodes. Both scales of observation are required to identify and explain the main features of anorogenic magma genesis.