GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 23-17
Presentation Time: 9:00 AM-5:30 PM


NOLAN, Tristan Q.1, GEHRELS, George E.1, PECHA, Mark1 and SUNDELL, Kurt E.2, (1)Department of Geosciences, University of Arizona, Gould-Simpson Building #77, 1040 E 4th St, Tucson, AZ 85721, (2)Department of Geosciences, University of Arizona, Tucson, AZ 85721

The Catalina Mountains contain several major granitic suites, including the ca. 1.4 Ga Oracle Granite, 55-40 Ma Wilderness Suite, and 25 Ma Catalina Granite. However, several anomalous zircon ages did not correspond to any of these, indicating some alternate zircon provenance. Detrital zircons retrieved from Sabino Canyon stream sediments yield ages of ca. 2.2 Ga, 1.4 Ga, 45 Ma, and 25 Ma, with regions of distinct ages present in a single crystal. Zircons from the Wilderness suite show complex zonation, with cores of ca. 1.4 Ga and 150 Ma surrounded by ca. 55-40 Ma rims that have highly variable U concentrations and U/Th values. CL textures of the rims are highly variable, and suggest both igneous and metamorphic processes of zircon growth. The ca. 2.2 Ga and 150 Ma ages are anomalous for the Catalina Mountains. Possible Jurassic-Cretaceous plutonic sources of the ca. 150 Ma zircons are present in southern Arizona, but not in the Catalina Mountains. The 2.2 Ga crystal is even more anomalous, as there are few sources for igneous zircon of that age in southwestern North America. The most likely source is Australia, which may have been next to southwestern North America during Paleoproterozoic time, and would have allowed for sediment transport between the two land masses. The zircon could have been incorporated into the ca. 1.7 Ga Pinal Schist, incorporated into the ca. 1.4 Ga Oracle granite, and then weathered into Sabino Canyon sediments.