Resumen de Low temperature thermochronology of metamorphic core complexes: case studies from the Basin and Range Province, southwestern USA.
Timothy J. Carter, Barry P. Kohn, Andrew J.W. Gleadow, David A. Foster, D.X. Belton, J.D. Woodhead
Metamorphic core complexes in the southwestern USA are the product of mid-Tertiary extension, which preceded the later classical “Basin and Range ” type extension responsible for the present-day physiography of the area. Previous apatite fission track thermochronology on these terranes has yielded estimates of the palaeogeothermal gradient, the angle of low-angle faults while active, and the timing and rate of slip along the fault surface. However, the relatively low uranium concentrations and young ages ofsamples studied resulted in large uncertainties. New (U-Th)/He data provide tighter constraints on the latest-stage tectonic histoiy of two core complexes: the Harcuvar and Chemehuevi Mountains. The results suggest a higher slip rate than previously reported, as well as evidence for a change in slip rate during extension.
