PETROGENESIS AND MAGMATIC RELATIONSHIPS OF CRETACEOUS LARAMIDE IGNEOUS ROCKS OF SOUTHEAST ARIZONA

Connections between volcanic and plutonic sequences can provide insight into the mechanisms of magma generation, evolution, and eruption. Our investigation focuses on the geochemical signatures of igneous rocks associated with the Laramide Orogeny in southeast Arizona, which provides a geochemical fingerprint to help constrain the relationship between a suite of volcanic and plutonic rocks. Furthermore, these data may elucidate processes concerning the evolution and genesis of source magma. Several contemporaneous plutonic and volcanic sequences are found within close proximity, however, an unequivocal genetic link between these intrusive and extrusive rocks remains incomplete. Additionally, the details concerning magma generation within this area is enigmatic. Volcanic and plutonic rocks of Cretaceous to early Tertiary age were collected from several locations in southeast Arizona in the Galiuro, Dripping Springs, and Sierrita Mountains during the spring of 2018. Three distinct sets of coexisting igneous rocks were collected. The first set includes the Galiuro Mountains Late Cretaceous igneous suite, which consists of tuff, lava, and flow breccia, and potentially coeval plutonic rocks of the Copper Creek Granodiorite. The second set includes the Williamson Canyon volcanics, which consists of andesite, tuff, volcanic breccia, and volcanic conglomerate, and possibly associated plutonic rocks. The third set includes the Red Boy Rhyolite and Ox Frame volcanics and the associated plutonics, including the Harris Ranch Monzonite. Although previous work in this region has established age connections between most of the rocks chosen (Guthrie, 1994; Titley et al., 1986), a direct connection between volcanic and plutonic series remains inconclusive. The geochemical and petrographic analyses of these samples will lead to a better understanding of the relationship between these igneous units, as well as the volcanic history of southeast Arizona. The geochemistry of the bulk rocks will be determined by x-ray fluorescence/ inductively coupled plasma mass spectrometry. The results of this study may also lead to a better understanding of spatial and temporal relations between source magma(s), as well as the geochemical evolution of these magma(s).