Both California and Peru have or have had significant gold deposits because of their proximity to where two tectonic plate boundaries meet. Off the California coast there is the Pacific Plate and the North American Plate which meet at the San Andreas Fault but there also is the Farallon Plate which apparently has subducted somewhat below the North American Plate. Off Peru, the Nazca Plate is subducting under the South American Plate and which has caused the Andean orogeny.