Tectonic Significance of Post-Accretion Rifting of a Mesozoic Island-Arc Terrane in the Northern Sierra Nevada, California

Abstract

This paper presents a new interpretation for the tectonic evolution of the Smartville complex that forms the Western Belt of the foothills metamorphic belt in the northern Sierra Nevada, California. New geological, petrological, and geochronological information suggest that the Smartville complex may form part of an Early Jurassic island-arc terrane that was probably built on a pre-existing oceanic basement. Inferred oceanic basement is represented by multiply deformed and metamorphosed ophiolitic rocks that crop out in the Central Belt north and east of the Smartville complex that are intruded by numerous Lower Jurassic dikes of an incipient island-arc character. Lower Jurassic volcanic and plutonic rocks of the Slate Creek and possibly the Lake Combie complexes in the Central Belt are interpreted as fragments of the early Jurassic arc terrane. Accretion of the ensimatic arc terrane into the continental margin of North America may have occurred along east-vergent thrusting around Middle Jurassic time and...