A HISTORY OF STABILIZATION AND MODIFICATION OF CRATONIC NORTH AMERICAN CRUST OF THE EASTERN SNAKE RIVER PLAIN, IDAHO USING THERMOCHRONOLOGY OF DEEP CRUSTAL XENOLITHS AND BASEMENT EXPOSURES

Granulite xenoliths erupted in Neogene basalts of the Eastern Snake River Plain (ESRP) can be used as windows into the origin and thermal evolution of the Archean lower crust of southern Idaho. Using a combination of LA-ICPMS and ID-TIMS methods, U-bearing accessory minerals in xenoliths from the northern margin of the ESRP are analyzed to interpret a regional thermochronologic history from the Precambrian through the Tertiary. Overgrowth domains of zircons in the xenoliths are interpreted to identify and date distinct thermal events that affected the lower crust. LA-ICPMS analysis of zircons from Square Mountain yield ages between 3.4 and 2.8 Ga and are interpreted to be the crystallization age of the lower crust of this region. Domains yielding ages of 2.5 Ga and 47.6 Ma are interpreted to be metamorphic events. Ages of xenoliths from Spencer-Kilgore, ID and Craters of the Moon National Monument and Archean granulite from basement outcrop at House Mountain, ID will also be presented.