CALIBRATION OF THE MONAZITE FISSION-TRACK THERMOCHRONOMETER ON AN EXHUMED FAULT BLOCK, WHITE MOUNTAINS, CALIFORNIA

Monazite fission-track (MFT) has an estimated closure temperature (TC) of ≤50 – 25 °C and presents itself as a promising new method for dating low-magnitude erosion in the upper-crust (<2 – 1 km). However, significant challenges remain deciphering the role of geochemistry, surface processes, and ambient temperature annealing on MFT cooling ages. In order to have confidence in MFT as a tool for resolving relief forming processes, we require both laboratory and empirical calibration. Similar calibration studies have been undertaken for more established thermochronometric methods. Stockli et al. (2000) performed multi-method apatite (U-Th-Sm)/He and apatite fission-track in the White Mountains, California, U.S.A. and provided empirical evidence for the presence of an exhumed apatite partial annealing zone and partial retention zone. The White Mountains are a tilted fault block generated by high-angle normal faulting during Miocene development of the Basin and Range province across the western U.S.A. Here, we present our initial work to emulate the Stockli et al. (2000) study by collecting twelve samples for MFT from the same localities in the White Mountains, CA. Due to the low temperature sensitivity modelled for MFT, there is a possibility that recent more recent surface processes, such as Pliocene – Pleistocene paleoclimate change, may exert a primary control on ages. To address this, we collect additional samples from the prominent river valleys which drain off the White Mountains. Results from this study will have important implications on applicability of MFT to date relief forming processes and shed light on the role of paleoclimate in shaping the modern topography of the Basin and Range province.