GEOCHEMICAL AND MAGMATIC RELATIONSHIPS OF LATE CRETACEOUS TO LATE TERTIARY IGNEOUS ROCKS FROM SOUTHEAST ARIZONA

Contiguous Tertiary igneous sequences in southeast Arizona associated with the Laramide Orogeny and post-orogenic extension are considered co-magmatic, yet a genetic link between these intrusive and extrusive rocks and details concerning magma generation remain ambiguous. This project aims at examining the geochemical signatures of representative samples from these sequences to help constrain the genetic relationships between these rocks. These data will additionally provide insight into the magma generation, evolution, and eruption associated with these rocks. Furthermore, this study will be compared with the data and findings of Murray et al. (2019), which was a collaborative study focused on Late Cretaceous to Early Tertiary igneous rocks from the same study area. Four distinct sets of Tertiary igneous rocks were collected from outcrops in the Picacho Mountains, the Galiuro Mountains, the White Canyon Wilderness, the Sierrita Mountains, and the Superstition Mountains in southeast Arizona. The first set includes the Picacho Mountain volcanics, consisting of basalt and dacite, and the Galiuro Mountain volcanics, consisting of porphyritic and devitrified dacite. The second set includes the White Canyon Wilderness volcanics, consisting of ignimbrite, tuff, vitrophyre, and potentially coeval quartz diorite. The third set includes plutonics associated with the Sierrita Mountain volcanics. The fourth set includes the Superstition Mountain volcanics, including tuff and potentially coeval porphyritic granodiorite. Although previous work has age-dated most of these rocks to the Middle Tertiary and performed basic petrographic analysis (Shafiqullah et al., 1976; Nealey and Sheridan, 1989; Spencer and Reynolds, 1989; Dickinson, 1991; Dickinson, 1995), the petrography is incomplete and more importantly there is no trace element geochemical analyses; this produces inconclusive genetic and magmatic relationships. Geochemical analysis will be performed by bulk-rock inductively coupled plasma optical emission/mass spectrometry to provide major, minor, and trace element compositions. This study will better constrain the precise relationship between these igneous sequences and may also provide a better understanding of the magmatic and volcanic activity associated with the Laramide Orogeny.