Shingle Springs complex
Shingle Springs complex
Early Jurassic
Equivalent to the Bear Mountains ophiolitic mélange of Saleeby (1982). Mafic amphibolite-facies hornblende schist, probably metabasalt but entirely recrystallized. Locally includes gneiss and migmatite. Locally includes felsic metavolcanics as quartz-rich schist, metasedimentary rocks as mica-actinolite schist, pelitic phyllite and quartzite, metalimestone as calcite-chlorite schist and marble. Interleaved with serpentinite, serpentinite-matrix mélange, and metaserpentinite as cummingtonite-schist. Early Jurassic age is the metamorphic age, based on a hornblende K-Ar age of ~190 Ma (Behrman, 1977). Protolith age is uncertain, but a metaplagiogranite in an amphibolite block in serpentinite-matrix mélange has yielded a zircon U-Pb age of ~300 Ma (Saleeby, 1982). Interpreted by Saleeby (1982) to be dismembered and metamorphosed Paleozoic ophiolite. Locally divided into: