SUPPRESSION OF VOLCANISM DURING RAPID EXTENSION IN THE BASIN AND RANGE PROVINCE, UNITED-STATES

Continental extension and volcanism are generally thought to be comple mentary. Stratigraphic and structural data from some highly extended p arts of the Basin and Range province reveal instead that rapid extensi on appears to have suppressed volcanism, This relation may reflect enh anced crystallization of midcrustal magmas during extension resulting from exsolution of magmatic volatiles, increased interaction of magmas with meteoric water, and dispersal of magma into smaller bodies, Some rift environments may thus be characterized by voluminous synextensio nal plutonism with little or no concomitant volcanism.