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SHRIMP-RG U-Pb zircon geochronology of mesoproterozoic metamorphism and plutonism in the southwesternmost United States

January 1, 2001

Mesoproterozoic intrusive and granulite‐grade metamorphic rocks in southern California have been inferred to be exotic to North America on the basis of perceived chronologic incompatibility with autochthonous cratonal rocks. Ion microprobe geochronology indicates that zircons in granulite‐grade gneisses, dated at 1.4 Ga using conventional methods, are composed of 1.68–1.80‐Ga cores and 1.19‐Ga rims. These Early Proterozoic gneisses were metamorphosed at extremely high temperatures and moderate pressures during emplacement of the 1.19‐Ga San Gabriel anorthosite complex. The lack of a 1.4‐Ga metamorphic event suggests that Proterozoic rocks in this region, rather than being exotic to North America, may in fact be a midcrustal window into Mesoproterozoic crustal evolutionary processes in southwestern North America.

Citation Information

Publication Year 2001
Title SHRIMP-RG U-Pb zircon geochronology of mesoproterozoic metamorphism and plutonism in the southwesternmost United States
DOI 10.1086/319975
Authors Andrew P. Barth, Joseph L. Wooden, Drew S. Coleman
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Geology
Index ID 70073332
Record Source USGS Publications Warehouse