LAURENTIA MESOPROTEROZOIC ANOROGENIC GRANITES: REASSESSING THE AGE AND ORIGIN OF A-TYPE GRANITES ACROSS ARIZONA

A prominent Mesoproterozoic magmatic episode across North America resulted in multiple granitic intrusions known as the anorogenic(A)-type magmatic belt. Granites are commonly formed during orogenic processes (e.g., subduction, continental collision). However, A-type granites are unique because they are not clearly associated with regional orogenic events, raising the question of what processes–and magma sources–were involved in their formation. We studied 16 Proterozoic A-types granites exposed throughout the three distinct crustal provinces of Arizona, including the Mojave, Yavapai, and Mazatzal, to determine their ages and identify differences in magmatic sources (i.e., proportion of crust versus mantle contribution). Some A-type granites of northern Arizona associated with the Yavapai and Mojave crustal province have been dated to ca.1.4 Ga; however, similar A-type granitic intrusions in southern Arizona within the Yavapai and Mazatzal province have yet to be studied in detail. Three main objectives of this project include: (1) characterize the granites based on their mineralogy and modal abundances, (2) constrain the crystallization age of samples through U-Pb zircon geochronology, and (3) determine the magmatic source(s) and understand crust-mantle interaction(s) based on combined Lu-Hf (i.e., initial ε¹⁷⁶Hf) and oxygen (i.e., δ¹⁸O) zircon isotopic values. Combined, this dataset will provide a better understanding of A-type granite petrogenesis and better elucidate the magmatic and tectonic history of Laurentia during the Mesoproterozoic.