Ongoing research focuses on the Cenozoic magmatic and tectonic history of the southern U.S. Cordillera, specifically in southeastern Arizona. I am interested in magmatic processes including petrogenetic mechanisms and source identification of anatectic magmas during the Laramide Orogeny, and how anatexis might play a role in cordilleran tectonics. I am also interested in mid-Cenozoic extension of the southern Basin and Range following the Laramide Orogeny. I employ multiple thermochronologic techniques to determine the timing of extension and exhumation of metamorphic core complexes during the Oligocene–Miocene and a later sequence of extension and exhumation during the Miocene. Projects that may materialize one day include Ti stable isotope analyses of rocks and minerals (titanite and magnetite) from the Tuolumne Batholith to examine Ti isotope fractionation mechanisms on the mineral, rock, and pluton scale.
Thermochronology of the Pinaleño Mountains, SE Arizona
Paleocene–Eocene Peraluminous Granites in Metamorphic Core Complexes
In the Pinaleño Mountains of southeastern AZ, a weakly-peraluminous granodioritic–granitic suite of rocks intruded into mafic–intermediate Proterozoic igneous rocks from 58 to 52 Ma, similar to other Cenozoic granites exposed in core complexes throughout Arizona. The Relleno suite, exposed in the Pinaleño Mountains, represents another intrusion of anatectic granites in the U.S. Cordillera and suggests that magmatic temperatures were hot enough to partially melt mafic crustal rocks
(A map of the southern Arizona anatectic suite, Adam pointing out granitic dikes in a 1.1 Ga diabase in Ash Creek Canyon in the Pinaleño Mountains, SE Arizona, and a spessartine cumulate(?) in peraluminous Eocene granites in the Catalina Mountains (with my field assistant, Guadalupe).
(U-Th)/He Thermochronology of Secondary Fe- and Mn-Oxides
Hematite and other Fe- and Mn-oxides are common secondary minerals in faults, fractures, and veins in the upper crust and potentially record information about the timing and or conditions of fluid movement through or deformation of their host rocks. These phases are difficult to date by most radioisotopic techniques, but relatively high concentrations of U and Th make the (U-Th)/He system a promising approach if cooling, crystallization, and U-uptake effects on ages can be accurately interpreted. Using petrographic, spectroscopic, and thermochronologic analyses of Fe- and Mn-oxides in faults, fractures, and veins we try to understand the potential of these phases and to constrain the timing of deformation or fluid flow and their relationship to magmatic, hydrothermal, and/or tectonic activity in the southern Basin and Range (In collaboration with ANGL).
Stable Isotopes of Titanium
Non-traditional stable isotopes (those of transition metals, alkali earth metals, etc.) have become an increasingly important analytical tool for geochemists and petrologists. I study titanium isotope ratios in Ti-bearing minerals from a suite of rocks in the zoned Tuolumne Intrusive Complex (part of the Sierra Nevada Batholith) to determine the effects of assimilation, fractional crystallization, and potential magma mixing in magmatic arcs, how whole rock and mineral δ49Ti may track magmatic differentiation, as well as isotope fractionation and partitioning processes (In collaboration with Dr. Vali Memeti).
Syn-Collisional Magmatism in the Pamir Orogeny
The Vanj complex displays a range of SiO2 (54–75 wt.%) and isotopic compositions (−7 to −3) εNd(i), 0.706 to 0.710 87Sr/86Sr(i), −3 to +1 zircon εHf(i), 6.0 to 7.6 zircon δ18O(VSMOW), which reflects some juvenile mantle input and subsequent assimilation or mixing with the Central/South Pamir terrane lower crust. The Vanj complex is speculatively interpreted to be the consequence of a mantle drip or small delamination event that was induced by India–Asia collision. The age, geochemistry, outcrop pattern, and tectonic position of the Vanj magmatic complex suggest that it is part of a series of magmatic complexes that extend for >2500 km across the Pamir and northern Qiangtang terrane in Tibet. All of these complexes are located directly south of the Tanymas–Jinsha suture zone, an important lithospheric and rheological boundary that focused mantle lithosphere deformation after India–Asia collision.