STACKED DETACHMENT FAULTS IN THE SUPRASTRUCTURE OVER A BURIED DIAPIRIC CORE, CURRANT GAP, WHITE PINE RANGE, EAST-CENTRAL NEVADA: EVIDENCE FROM MAPPING, GEOPHYSICAL, AND ISOTOPE GEOCHEMICAL STUDIES

GPS-assisted, fine-scale mapping supports a series of stacked, coalescing detachment faults as the major tectonic structure in the White Pine Range. The White Pine detachment (WPD), rooted in the Mississippian Chainman Formation, has been documented previously in the range and in adjoining Railroad Valley. The deeper “Currant Gap Detachment” (CGD), probably rooted in the Cambrian Lincoln Peak Formation, outcrops in a small area. These detachments within ductile units of a brittle suprastructure were triggered by ductile extension within a thermally weakened infrastructure. A similar structural style is considered ubiquitous in eastern Nevada and points to regional ductile extension.

In Currant Gap, lower Cambrian units (CGD lower plate) are separated from Ordovician and younger units (upper plate) by a bifurcate zone of silicified carbonate (called by us “SC rock”) overlain by tectonic breccia. The SC rock is distinct from jasperoid and consists of a mottled gray-white quartzite (previously mistaken for Ordovician Eureka Quartzite) that extends as a vein network into an adjoining carbonate host.  This highly resistant material forms steep cliffs and erosional remnants cutting into Cambrian Pole Canyon Formation. The breccia forms gentle, rounded slopes with no in-place outcrops; the ground is strewn with small chips of many lithologies, including what appears to be indurated shale. Similar breccia has been observed in the WPD, and in a similar detachment in the Schell Creek Range. In addition to the SC rock and breccia, the CGD zone has small (100-300m) blocks of Ordovician and Devonian rocks, as well as jasperoid, in a chaotic melange-like arrangement.  Low d¹⁸O (<0‰) carbonate veins indicate that meteoritic fluids traveled through the low-angle CGD.

East of Currant Gap, a relatively narrow zone splays to the west into the aforementioned melange and merges to the east into the WPD. This zone was previously mapped as the Currant Summit strike slip fault, but evidence for its continuation west into Currant Gap is lacking. The zone may be a normal fault connecting the WPD and CGD, or its east end may be where the two detachments coalesce. Seismic refraction data there show a 10m thick layer of Chainman resting on a hard, nearly horizontal surface (probably Cambrian) with no evidence of significant lateral separation.