The tertiary magmatic sweep, Nevada, and early proterozoic tholeiitic/alkaline/peralkaline plutonism, Northwest Territories

该项目的目标是a)更好地了解过去4000万年来美国西部侵位的火成岩的来源，以及b)调查与加拿大西北地区南部古老的超级大陆解体有关的火成岩活动。在过去的4000万年里，美国西南部，特别是内华达州，火山活动剧烈，伴随着地壳的伸展和断裂。火山活动有条不紊地从东北向西南横扫内华达州，推测是法拉隆板块俯冲到北美地下的结果。我们对火山作用如何与俯冲板块或地壳伸展联系在一起，火山岩的来源是什么，以及这种火成活动在多大程度上对内华达州同期的金矿化负责，我们知之甚少。我们试图确定岩浆的来源，无论是在地幔中还是在地壳中(或两者都有)，并更好地描述火山活动席卷内华达州北部和西部的时间。在西北地区，大约20亿年前，一个火成岩侵入杂岩沿着大奴湖的东臂侵位，携带着富含Nb、Ta和稀土元素的岩石，这些元素对工业都很重要。这些侵入体标志着该地区历史上的一个新时期，在经历了一段长时间的地质沉寂之后，一块古老的大陆大陆被分裂成碎片，使这些侵入体得以浮出地表。了解侵入岩的地球化学和成因，以及它们之间的关系，将改进经济上重要的稀土矿物的成因模式，并增加该地区更多矿化的勘探工作。

The goals of this project are to a) better understand the sources of igneous rocks emplaced during the last 40 million years in the western United States, and b) investigate igneous activity associated with breakup of an old supercontinent in the southern Northwest Territories of Canada. The past 40 million years has been a time of intense volcanic activity in the southwestern United States, particularly Nevada, accompanied by stretching and faulting of the crust. Volcanism swept methodically from northeast to southwest across Nevada, presumably a result of the subduction of the Farallon Plate beneath North America. We understand very little of how volcanism was linked to the subducting plate or crustal stretching, what the sources for the volcanic rocks were, and to what degree this igneous activity was responsible for contemporaneous gold mineralization in Nevada. We seek to identify the sources of magmas, either in the mantle or in the crust (or both), and better describe the timing of the sweep of volcanism across northern and western Nevada. In the Northwest Territories, an igneous intrusive complex was emplaced along the East Arm of Great Slave Lake around 2 billion years ago, carrying with it rocks rich in Nb, Ta, and rare earth elements, all important to industry. The intrusions mark a new period in the history of the region, where, after a long period of geological quiescence, an old continental landmass was split into fragments that allowed these intrusions to rise to the surface. Understanding the geochemistry and origin of the intrusions and the relationships between them will improve models for the origin of the economically important rare earth minerals and add to the exploration effort for more mineralization in the area.