PROTEROZOIC GEOCHRONOLOGICAL AND ISOTOPIC BOUNDARY IN NW ARIZONA

U-Pb ages determined from zircon, sphene, and apatite in conjunction with Pb isotopic analyses of alkali feldspar establish a regional geochronological framework and constrain the location of a major north-trending Proterozoic crustal boundary in northwestern Arizona. Two regions west of the boundary (Hualapai Mountains and Lost Basin Range-Garnet Mountain) are characterized by complex U-Pb zircon systematics, evidence for inheritance of an older zircon component (1.8-2.3 Ga), and elevated 207Pb/204Pb from feldspars compared to the east. We interpret the boundary to be a suture related to convergence of terranes c1.68-1.70 Ga which was reactivated by younger uplift. -from Authors