The chemical and isotopic characteristics of erupted magmas from regions bounding distinct tetonophysical provinces provide insights into relationships between magma generation and evolution, crust/mantle evolution, and tectonic development. the southwestern United Stated, particularly the Colorado Plateau - Basin and Range region, yields opportunities to investigate these relationships. Preliminary investigations of mafic lavas from the Springerville volcanic field, east-central Arizona, suggest that this field marks a portion of the Colorado Plateau - Basin and Range transition zone and is underlain by distinct mantle and crustal reservoirs. Two mantle sources have been identified, but elucidation of the nature of interactions between these sources, or between derivative melts, and the characterization of additional crustal or mantle reservoir input awaits further detailed trace element and multi-isotope investigations. This project will build on recently published and acquired field, petrographic, chronologic, and chemical data through more detailed chemical and multi-isotope (Sr,Nd, Pb, O) studies of lavas from the entire Springerville compositional spectrum. The ultimate goal is to define the character of the subcontinental mantle beneath the Springerville portion of the transition zone and to define the range of petrogenetic processes acting within this region. This will lead to a more complete understanding of the effects that the tectonic state of the lithosphere have on the nature of mantle reservoir development and interaction, and the petrogenetic processes giving rise to chemical and isotopic diversity in continental volcanic suites.
