A Petrographic, Geochemical and Isotopic Study of the 780 Ma Gunbarrel Large Igneous Province, Western North America

On the western margin of North America lie dykes, sills and volcanic rocks which define a magmatic episode at 780 Ma. These units are collectively termed the Gunbarrel Large Igneous Province (LIP) and share remarkably similar petrographical, geochemical and isotopic signatures indicating a single homogeneous source. The Irene and Huckleberry metavolcanic rocks of Washington State were correlated to the Gunbarrel LIP based on similar ages, but were found to not be related based on geochemistry and isotopic analysis. The timing of the Gunbarrel LIP coincides with the break-up of Rodinia, and Gunbarrel samples were compared to coeval magmatism from South China to test the “Missing Link” reconstruction model. While some mafic dykes have similar Nd isotopic ratios, no definitive correlations could be found between the different magmatic events. Finally, LIPs play a key role in housing various economic deposits and the Gunbarrel magmas show potential for being a Ni-Cu-PGE target.