LATE MESOZOIC-EARLY TERTIARY FOLDING AND FAULTING IN THE WHITE PINE RANGE, EASTERN NEVADADA

The Griffon gold mine in the south-central White Pine Range of eastern Nevada is a sediment-hosted, disseminated deposit in an area underlain by folded and faulted shallow marine strata of Devonian through Permian age. Surface geologic mapping and drill data from mineral exploration determined the following sequence of deformational events, beginning after the deposition of Permian strata: (1) A minor episode of normal faulting that formed WNW-striking faults. (2) Mesozoic (pre-Early Cretaceous?) contraction that formed north-trending, open folds and possible local thrust faults. This event correlates with contraction in the Central Nevada Thrust Belt. (3) Low-angle normal faulting that juxtaposed Mississippian strata over Devonian through Mississippian strata. (4) Gold mineralization that occurred primarily within the hanging-wall of the low-angle normal fault(s). (5) A weak normal faulting event that formed NE-striking faults. (6) Normal faulting that produced ENE-striking faults with variable displacements, locally greater than 100 meters. (7) A period of faulting that involved several faults with strikes between N and NW. These faults display variable dips, between 55° and vertical, and possibly include both normal and strike-slip displacements. Movement along these faults either rotated an existing fold ~75° from the dominant orientation or formed a new fold by transpression. It is unclear how many periods of movement are represented by these faults. (8) Low-angle normal faulting along the Blackrock Fault, a major structure in the southern part of the range. Previous workers interpreted this fault to have been active between 31.3 and 14.3 Ma. Several of the faulting events at Griffon have not been reported in other portions of the range. Although absolute ages of these deformational events are poorly constrained, cross-cutting relationships indicate that both high- and low-angle normal faulting occurred in the Late Cretaceous-early Tertiary time frame. Since this remains a rather enigmatic period in much of the Basin and Range province, these local observations provide some insight on regional patterns of deformation.