Sonora Pass intrusive suite
Sonora Pass intrusive suite
Cretaceous, ~84-98 Ma
Occurs in eastern central Sierra Nevada in the Sonora Pass area. One of the Sierra Crest intrusive suites (e.g. Lackey and others, 2008; Hildebrand and Whalen, 2021). Chiefly granodiorite. This unit has yielded zircon U-Pb ages of ~84-98 Ma (Wooden and others, 1999; Lackey and others, 2008; Leopold, 2016). Evernden and Kistler (1970) report biotite K-Ar ages of ~80-86 Ma, as well as a hornblende K-Ar age of ~84 Ma. Macias (1996) reports emplacement pressures of ~2.0 and ~3.5 kbar. Hildebrand and Whalen (2021) report relatively high Nb/Y, La/Yb, and Sr/Y for this unit. Lackey and others (2008) report low zircon d18O (~5-6.5 o/oo VSMOW) and whole-rock d18O (~5-8 o/oo VSMOW) and 87Sr/86Sri values between ~.706-.708. Major plutons: granodiorites of Kinney Lake, China Garden, Mill Creek; Topaz Lake; Fremont Lake, and smaller satellite plutons.