TESTING CORRELATION OF THE GOLDEN BEAR AND COSO DIKES IN EASTERN CALIFORNIA: IMPLICATIONS FOR DIKE EMPLACEMENT AND TECTONIC RECONSTRUCTION SINCE 83 MA

Studies of distinctive c.a. 83 Ma quartz monzonite porphyry dikes and the 102 Ma leucogranite plutons they intrude, along with other data, suggest 65 km of offset sub-parallel to the Owens Valley, CA since dike emplacement. These rocks are the Golden Bear Dike and Independence Pluton of the Sierra Nevada, correlated to the Coso dike swarm and Cactus Flat leucogranite of the Coso Range. Corroborating evidence for such a reconstruction includes: 1) Sr isotope 0.706 isopleth within the Sierra Nevada batholith, 2) Permian and Triassic structural features of the White and Inyo Mountains, CA, and 3) offset Independence Dike swarm. However, paleomagnetic evidence complicates the simple piercing-point hypothesis because the polarities of the correlated rocks are: normal for the sampled Golden Bear dike locality and reversed for the Coso dikes sampled thus far. Indeed the single, thick, very long, continuous Golden Bear dike is different in areal extent compared to the discontinuous Coso dike swarm, which spans a wide swath along strike, as many separate dikes. Consequently, similarity in age, chemistry, and wall rock of the two dike sets may simply be coincidental. Alternatively, the difference in polarity may reveal west-to-east progressive emplacement across the C34n-C33r boundary at 83.5±0.7 Ma. Current studies will assess the reason for the opposite polarity of these correlated dikes.