Early Proterozoic Crustal Evolution: Geochemical and Neodymium Isotopic Evidence from Sedimentary Rocks

一种研究陆源污染的有效方法 沉积岩是通过岩相学， 常量和微量元素地球化学、矿物化学和Nd- 同位素研究 这些数据提供了关键证据， 种源的组成和平均年龄。 使用此 的方法，重要的限制提供了模型， 地壳的组成、生长和演化。 构造问题 沉积岩的形成和再循环历史也可以 处理。 同位素证据表明， 地壳生长发生在北元古代早期， 美国约1.9-1.7 Ga。 澳大利亚和欧洲的证据 表明这一幕地壳生长可能是全球性的 意义 在这里，建议检查岩相， 两种沉积物的地球化学和Nd同位素组成 这些序列大约在这个时候沉积，包括 Chelmsford Formation（切姆斯福德地层）1.85安大略萨德伯里地区的Ga） 和瓦迪托-奥尔特加集团（CA。1.7新北方 墨西哥 切姆斯福德组为近源浊积岩单元 沉积在早期发展的Penokean 造山运动瓦迪托-奥尔特加集团是 西南地区地壳生长过程中沉积的沉积岩 美国约1.9 - 1.7 Ga。 通过这项研究， 可能对地壳的性质施加重要的限制， 在早元古代的生长和演化。 比较 与地球历史上其他时期的地壳形成事件 （特别是在太古代-元古代边界）将有助于 测试当前的地壳演化模型。

A powerful approach to the investigation of terrigenous sedimentary rocks is through combined study of petrography, major and trace element geochemistry, mineral chemistry and Nd- isotopic study. Such data provide critical evidence regarding the composition and mean age of he provenance. Using this approach, important constraints are provided for models of crustal composition, growth and evolution. Questions of tectonic setting and recycling history of sedimentary rocks can also be addressed. Isotopic evidence indicates that an important period of crustal growth occurred during the early Proterozic of North America at about 1.9-1.7 Ga. Evidence from Australia and Europe suggests this episode of crustal growth may have been of global significance. It is here proposed to examine the petrographical, geochemical and Nd-isotopic composition of two sedimentary sequences which were deposited at about this time, including the Chelmsford Formation (ca. 1.85 Ga) of the Sudbury region, Ontario and the Vadito - Ortega Groups (ca. 1.7 Ga) of northern New Mexico. The Chelmsford Formation is a proximal turbidite unit deposited in response to early development of the Penokean Orogeny. The Vadito - Ortega Groups are representative of sedimentary rocks deposited during crustal growth in southwestern U.S.A. at about 1.9 - 1.7 Ga. From this study, it will be possible to place important constraints on the nature of crustal growth and evolution during the early Proterozoic. Comparisons with crust-forming events at other times in earth history (particularly at the Archean - Proterozoic boundary) will help to test current models of crustal evolution.