Collaborative Research: Relationship between Ultramafic Rocks and Crustal Sutures in the North American Southwest

美国西部大陆岩石圈的大部分拼装时间为1.8~1.6Ga，但其构造样式存在争议，特别是具有不同前寒武纪特征的地块或地体可能主要是通过正交和顺序俯冲并置的，或者主要机制可能是扭压平移。该项目将详细研究超镁铁质岩石的赋存状态，这些岩石似乎在空间上与前寒武纪地块的边界有关，因此表明存在俯冲。海底蛇绿岩地球化学特征将大大加强这一选择，而如果没有这种选择，将指向包括走滑组装在内的其他选择。预计结果将影响对美国西部大部分大陆岩石圈如何组装的理解。

0003477Karlstrom0003479SeamanMuch of the western United States continental lithosphere was assembled from 1.8 to 1.6 Ga, but the tectonic style of assembly is controversial, in particular the blocks or terranes of different precambrian characteristics may have been juxtaposed primarily by orthogonal and sequential subduction or the major mechanism may have been transpressional translation. This project will examine the geochemistry in detail of occurrences of ultramafic rocks that seem to spatially be associated with boundaries of precambrian blocks, thus suggesting subduction. A sea-floor ophiolitic geochemical signature would considerably strengthen this option whereas absence would point to alternatives including strike-slip assembly. Results are expected to influence understanding on how the continental lithosphere of much of the western United States was assembled.