Named for St. Kevin Lake and adjoining St. Kevin mining district, Lake Co, CO, Southern Rocky Mountain region. These rocks were assigned to Silver Plume Granite by Stark (1935) and to Silver Plume? Granite by Behre (1953). Occurs in a batholith about 25 mi long and 12 mi wide centered near crest of Sawatch Range west of Leadville. Many satellitic bodies are north and east of the batholith. Comprises four main facies: 1) trachtyoid hybrid a coarse-grained inhomogenous rock that is mostly quartz monzonite; 2) normal, a light-gray to pink even-grained to markedly porphyritic biotite-muscovite granite or quartz monzonite; 3) granodiorite which is porphyritic to seriate porphyritic, fine to medium grained and weakly foliated; and 4) fine-grained, a gray fine-grained equigranular massive to weakly foliated biotite-muscovite quartz monzonite. A coarse porphyritic facies formerly assigned to Hell Gate Porphyry (not used) is considered part of St. Kevin. Is of Precambrian age.

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

Occurs in a small batholith and in many irregular bodies in north half of Sawatch Range. Listed with granitic rocks and gabbro of circa 1,400 m.y. (Precambrian Y) age group.

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

Is one of ten named and several unnamed lithodemic units assigned to the Berthoud Plutonic Suite (new). Occurs in a batholith about 25 mi long and 12 mi wide in northern Sawatch Range in the Southern Rocky Mountain region. Extends full width of range into Mosquito Range on west, and Elk Mountains on east. Composed of an inhomogeneous assemblage of two-mica rocks ranging from granite to granodiorite. Is one of the most thoroughly dated granites of CO. Age determined from Rb-Sr isochron plot of 1,432 +/-60 m.y.; concordia plot of U-Th-Pb ratios in zircons about 1,400 +/-40 m.y.; K-Ar on mica of 1,210-1,358 m.y.

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