The Longs Peak-St. Vrain batholith is a compound granite mass of pre-Cambrian age, which intrudes highly metamorphosed schists and gneisses, mostly of sedimentary origin, in the Front Range of the southern Rocky Mountains in Colorado. It is the purpose of this paper to describe the batholith and outline its relationships to the enclosing schists and, as far as known, to the other large granite batholiths which make up a major part of the great pre-Cambrian mosaic of the Front Range.1
Field work was begun by the senior author in 1921 and 1922 along the Big Thompson River valley between the foothills and the continental divide. At that time the term “Longs Peak” was applied to the chief granite of the area, and the Mount Olympus granite was identified.2 Intermittent field work from 1924 to 1931 permitted the mapping of the Longs Peak part of the batholith and the identification . . .