Structure and Emplacement of Cretaceous Plutons in Northwest Yosemite National Park, California

Abstract

The ~103-98 Ma Yosemite Valley Intrusive Suite, younger Granodiorite North of Tuolumne Peak, and ~97 Ma Yosemite Creek Granodiorite intrude plutonic and metasedimentary host rocks of the central Sierra Nevada batholith. Precambrian to Cambrian metasedimentary rocks separate the Yosemite Valley Intrusive Suite from the younger (94-85 Ma) Tuolumne Intrusive Suite and are interpreted to represent the original extent of the older suite. The Mt. Hoffman granodiorite and Taft Granite of the Yosemite Valley Intrusive Suite record evidence of the development of magma chambers, whereas the Tuolumne Peak and Yosemite Creek granodiorites were likely constructed via several small increments, and a sizable magma chamber did not form. Accommodation of magma was probably facilitated by a combination of processes, but there is only direct evidence for minor stoping. The dominant northwest-striking magmatic foliation in the Mt. Hoffman granodiorite records regional northeast-southwest shortening strain. Variations in strike of magmatic foliation in the Taft Granite likely results from a combination of regional strain and internal processes within a magma chamber.