Geochemistry and regional correlation of pre-tertiary volcanic rocks in West-Central Nevada

Isolated exposures of late Paleozoic and Mesozoic volcanic rocks in the Walker Lake region of west-central Nevada are tectonically disrupted, and their interrelationships are uncertain. Recent work has resulted in the recognition of several formations: The Pennsylvanian Shamrock, Permian Black Dyke, Triassic Pamlico, and Cretaceous Gold Range. Each of these formations is characterized, with particular emphasis on lithology, petrography, chemistry, and age. Outcrops of pre-Tertiary volcanic rocks of unknown age are similarly characterized, and several units are thereby correlated with known formations. Geochemical data confirm the presumption that the volcanic rocks formed at a convergent plate boundary. Upper Paleozoic volcanic rocks were created in an island arc system which underwent major deformation during the Early Triassic Sonoma orogeny, whereas Mesozoic volcanic rocks were erupted along an active continental margin and deposited in a back arc basin of the Mesozoic Sierran arc system