Pine Hill pluton
Pine Hill pluton
Late Jurassic, ~162-164 Ma
Crops out along Highway 50 east of Folsom. Unfoliated gabbro and gabbro-diorite with minor pyroxenite and diorite. Composed of augite, plagioclase, with magnetite and accessory biotite (which may be an alteration product). Forms a prominent gravity and aeromagnetic high. Includes a lens north of, and separated by, a fault from the main body, but which has similar gravity and magnetic properties. Interpreted as part of the plutonic component of the Smartville Volcanic complex. This pluton has zircon U-Pb ages of ~162-164 Ma (Saleeby, 1982). This unit is described in detail by Springer (1980).