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Description
The Rainbow Rock Quarry is part of the footwall of the Truckhaven Fault and has been a gold and silver mining prospect for over one hundred years. It is situated along the north edge of Wonderstone Wash in the northwestern Seventeen Palms USGS 7.5 minute quadrangle, located in the southeastern section of the active San Andreas Fault system. This region is characterized by seismic activity, continental rifting, volcanism, hydrothermal alteration, rapid sedimentation and active precious metal deposition. The Truckhaven Fault zone strikes ~N65°E and separates a Cretaceous quartz monzonite footwall from Plio-Pleistocene Canebrake Conglomerate and Palm Spring Formation in the hanging wall. Well-developed slickenlines at one locality document sinistral normal slip on the Truckhaven Fault. The fault zone dips southeast and hosts sites of alteration mostly in hanging wall rocks, including gold and silver mineralization and argillization. To the southwest of Rainbow Rock is the source of Wonderstone Wash. The goal of this project was to conduct a field investigation of the area where the Truckhaven Fault strikes into the West Salton Detachment and determine the relationship between these two faults. Several exposures of hydrothermal alteration were observed in this area in addition to reverse faulting and metamorphic amphibolite rocks were studied in thin section to better understand the rocks that may represent the footwall of the West Salton Detachment. By illustrating the architecture of these two faults, we hope to understand the kinematics during their activity, in order to question whether they remain active, or accommodation has been relieved by the San Jacinto Fault system.
