Mount Whitney Intrusive Suite
Mount Whitney Intrusive Suite
Late Cretaceous, ~83-92 Ma
Occurs along crest of southern Sierra Nevada. One of the Sierra Crest intrusive suites (e.g. Lackey and others, 2008; Hildebrand and Whalen, 2021). Chiefly granodiorite, in most places porphyritic, and granite. Zircon (and one sphene) U-Pb ages of 83-92 Ma (Chen and Moore, 1982; Lackey and others, 2008; Davis, 2010; Sisson and Moore, 2013); hornblende K-Ar and Ar-Ar ages of 80-90 Ma and biotite K-Ar and Ar-Ar ages of 78-83 Ma (Evernden and Kistler, 1970; Davis, 2010), as well as a zircon Ar-Ar age of 91 Ma and zircon U-Th/He ages of 75 and 84 Ma (Davis, 2010). Aluminum in hornblende emplacement pressures range from 0.2-3.5 kbar (Chapman and others, 2012). 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 relative to Vienna Standard Mean Ocean Water [VSMOW]) and whole-rock d18O (~5-8 o/oo VSMOW) and 87Sr/86Sri values between ~.706-.708. Major plutons: Paradise Granodiorite, granite of Carroll Creek, granite of White Mountain, granodiorite of Castle Creek, granodiorite of Chagoopa, granodiorite of Mitchell Peak, granite of Mount Kaweah, granodiorite of Mountain Home, granodiorite of Sugarloaf, granodiorite of White Divide, Paradise Granodiorite, Pyramid pluton, and Whitney Granodiorite. One of the largest and youngest plutonic suites in the eastern Sierra Nevada.