Named for exposures on summit of Mitchell Peak, its type locality, in northwestern part of Triple Divide Peak 15' quad, Tulare Co, CA. Is youngest and most extensive unit of Mitchell Intrusive Suite (new). Exposed in much of Triple Divide Peak quadrangle, and also occurs in adjacent Marion Peak 15' quadrangle where it was formerly called granodiorite of Mitchell Peak by Moore (1978). Consists of older coarse-grained and younger fine-grained facies. Coarse-grained facies porphyritic with potassium feldspar phenocrysts (3-4 cm); foliated. Fine-grained facies also porphyritic and finer grained than most Sierra Nevada granitic rocks; groundmass minerals are 1-2 mm; phenocrysts mainly potassium feldspar and quartz (2-4 cm); has pronounced near-vertical foliation; contains abundant angular blocks of coarse-grained facies and pipes and dikes of orbicular granodiorite; Pb-U age about 91 Ma. Intrudes into and largely surrounded by granodiorite of Castle Creek. Assigned to Cretaceous.

Source: GNU records (USGS DDS-6; Menlo GNULEX).