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

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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.