Tectonic controls on porphyry copper formation in the western USA

The Basin and Range Province is a hyperextended piece of the crust previously thickened by orogenesis. The region is also notable for its porphyry copper deposits, which mainly formed towards the end of crustal compression. However, due to the extreme dissection of the landscape by subsequent extension, spatial and temporal constraints on crustal shortening and its relationship to porphyry copper formation are limited. Across much of the province, compressional features are poorly preserved, but metamorphic core complexes offer a window into the pre-extensional history. Contractional structures and exhumed remnants of the middle to lower crust preserved will be used to constrain patterns of pre-extensional crustal thickness and the timing and duration of compression to investigate potential links to porphyry copper formation. This project aims to determine spatial and temporal patterns in the magnitude and longevity of pre-extensional compression within the Basin and Range Province to compare with patterns of porphyry copper formation. Objectives: 1: Contractional structures preserved within a selection of metamorphic core complexes will be identified and characterised to constrain the pre-extensional paleostress field. 2: Geothermobarometry and Lu-Hf garnet geochronology will be used to determine the magnitude and timing of maximum burial in a selection of key metamorphic core complexes. Maximum burial depths will serve as a proxy for crustal thickness, elucidating temporal and spatial patterns of crustal thickening. 3: In-situ Rb-Sr dating of syn-tectonic mica or U-Pb dating of zircons within contractional structures will place absolute constraints on fault motions, allowing the student to build a spatial and temporal picture of compression across the region that can be compared with porphyry copper mineralisation.