Contact metamorphism in Santa Rosa Range, Nevada

The metamorphic rocks of the Santa Rosa Range of N.-central Nevada represent a sequence of Upper Triassic (and Jurassic?) sediments that was 20,000 ft. thick before it was strongly folded, metamorphosed, locally faulted, and intruded by granitic stocks. Each of the 6 formations is dominantly metapelitic, although quartzitic, calcareous, and dolomitic rocks are widespread. All the rocks were converted to metamorphic assemblages of quartz, albite, muscovite, chlorite, and carbonates before and during the regional folding. The 9 stocks consist mainly of sodic granodiorite, but adamellite, trondhjemite, and tonalite are locally abundant. Early chilled apophyses show the magmas originally contained few if any crystals, and structural relationships prove the stocks are dominantly cross-cutting (stoped?) bodies. This study emphasizes the influence of magmatic water on contact-metamorphic reactions; the relationships suggest that the rapid rate of heating by intrusive magma may be the most significant characteristic of contact, as compared to regional metamorphism.