The La Pesta pluton is a 1400 km2 pluton in the eastern zone of the Peninsular Ranges batholith. The Sacotone Springs area is part of a roof pendant near the center of the pluton that contains igneous and sillimanite-grade metasedimentary rock. The metasedimentary rocks consist of sillimanite-bearing schists, gneisses, and quartzites whose grade is consistent with that found in adjacent areas. Temperature and pressure conditions were approximately 650° C and 4 kb. The plutonic rocks north and west of Tule Mountain are sphene-hornblende-biotite tonalities that have strong foliation, abundant dark inclusions and a low magnetic susceptibility. Dikes of leucogranite with both pegmatitic and aplitic textures cut the metasedimentary and older igneous rocks but terminate at the contact with the Las Pesta pluton. The tonalitic rocks are probably western zone rocks despite the low magnetic susceptibility. Their magnetism may have been destroyed during the emplacement of the La Pesta pluton. They represent the eastern most exposures of the western zone rocks. The leucogranite dikes are most likely products of anatexis of the metasedimentary package, which happened during the emplacement of the La Posta pluton.
