Geology Commons^™

Petrogenesis Of The 91-Mile Peridotite In The Grand Canyon: Ophiolite Or Deep-Arc Fragment?, S. J. Seaman, M. L. Williams, K. E. Karlstrom, P. C. Low

Geosciences Department Faculty Publication Series

Recognition of fundamental tectonic boundaries has been extremely difficult in the (>1000-km-wide) Pro-tero-zoic accretionary orogen of south-western North America, where the main rock types are similar over large areas, and where the region has experienced multiple postaccretionary deformation events. Discrete ultramafic bodies are present in a number of areas that may mark important boundaries, especially if they can be shown to represent tectonic fragments of ophiolite complexes. However, most ultramafic bodies are small and intensely altered, precluding petrogenetic analysis. The 91-Mile peridotite in the Grand Canyon is the largest and best preserved ultramafic body known in the southwest United …