Serpentinite mélange with ultramafic and mafic igneous rocks
Serpentinite mélange with ultramafic and mafic igneous rocks
Early Jurassic or older
Forms a discontinuous belt along and northeast of the Melones fault between Angels Camp and Mariposa plus an isolated outcrop at the San Joaquin Valley margin south of the Kaweah River. Largely interleaved with units MRDGS and MRDPH. Deformed and dismembered blocks of serpentinized harzburgite, gabbro, and serpentinite. Local minor basalt layers. Includes thin, lensoidal diorite plutons, one correlated with the ~163 Ma Cobb Creek pluton of the Don Pedro intrusive suite (unit Gdp) (Morgan, 1976). Also includes felsic dikes and conspicuous mariposite-bearing quartz veins. Mariposite from this unit has yielded a K-Ar age of ~123 Ma (Evans and Bowen, 1977), probably marking hydrothermal mineralization related to formation of gold-bearing quartz veins along the Melones fault. This unit possibly represents oceanic crust that formed the basement of the Don Pedro terrane.