DETRITAL ZIRCON GEOCHRONOLOGY AND SOURCES OF NEOPROTEROZOIC-LOWER CAMBRIAN SILICICLASTIC STRATA, WHITE-INYO RANGE, EAST-CENTRAL CALIFORNIA

The North American continental margin has experienced considerable Phanerozoic tectonic disruption; proper recognition of correlative lithotectonic packages across major transcurrent structures is critically important to understanding the tectonic evolution of the margin. Detrital zircon geochronology of upper Proterozoic to lower Paleozoic miogeoclinal assemblages from the White-Inyo Mountains permits evaluation of: 1) the age and provenance of these metasediments and 2) a model for truncation of the passive margin along a large magnitude (~400 km) Cretaceous dextral shear zone (i.e., the Mojave-Snow Lake hypothesis). U-Pb ages of detrital zircons from the oldest unit exposed in the White-Inyo Mountains, the Neoproterozoic Wyman Formation, reflect ultimate derivation from the adjacent 1.75-1.80 Ga Yavapai continental basement, with subsidiary sources in both the 1.40 Ga Yavapai-Mazatzal anorogenic granitoids and the 2.5-2.6 Ga North American craton. In addition to these primary sources, grains extracted from the Wyman Formation, the uppermost Proterozoic Reed Dolomite (Hines tongue member), and clastic strata of the Lower Cambrian Deep Springs, Campito, Poleta, and Harkless formations contain variable proportions of 1.0-1.3 Ga zircon. These grains may have been derived from either the SW Grenville province or, alternatively, from ca. 1.08 Ga diabase sills in the Crystal Spring Formation of Death Valley. Minor populations of 0.7-0.5 Ga zircon permit speculation regarding a possible non-Laurentian source for these grains. In aggregate, U-Pb age probability plots from the White-Inyo section are similar to those of the stratigraphically equivalent Stirling and Wood Canyon formations in the Death Valley region as well as metamorphic pendants in the Snow Lake block of the central Sierra Nevada batholith. These pendant rocks are separated from White-Inyo Mountains strata by a belt of eugeoclinal assemblages; hence, correlation of White-Inyo and Snow lake assemblages requires a fault on the east side of the Snow Lake block. We suggest that the Snow Lake block represents footwall assemblages of a Cretaceous low-angle normal fault system that connects at depth with White-Inyo strata. This model requires a few tens of km of offset, in contrast to the hundreds of km required by the Mojave-Snow Lake hypothesis.