GSA Connects 2021 in Portland, Oregon

Paper No. 194-1
Presentation Time: 2:30 PM-6:30 PM


GUNNING, Kellie1, GASCHNIG, Richard1, DOE, Michael2 and GOODGE, John W.3, (1)Department of Environmental, Earth and Atmospheric Sciences, University of Massachusetts Lowell, 1 University Dr, Lowell, MA 01854, (2)Colorado School of Mines, Golden, CO 80401, (3)Department of Earth and Environmental Sciences, University of Minnesota Duluth, 1114 Kirby Drive, Heller Hall 229, Duluth, MN 55812

The configuration of the Mesoproterozoic supercontinent Columbia is still debated, with models placing East Antarctica in differing positions against western North America. This research tests the SWEAT model that places East Antarctica next to the southwestern part of North America. We focus on U-Pb age and trace element analysis of detrital zircons, monazite, and rutile in Mesoproterozoic Hess Canyon Group in Arizona. We supplement this with similar data from Neoproterozoic-Paleozoic rocks in the Transantarctic Mountains (TAM), as these provide information on basement sources in the Antarctic interior.

Arizona samples yield zircon ages from 1.45-1.8 Ga, with a concentration of grains at ca. 1.6 Ga. Detrital zircon ages from the TAM samples vary and include Grenville-age grains but most share major populations between 1.5 and 1.8 Ga. Trace elements from these zircons show a net decrease in Gb/Yb, U/Yb, and Nb/Yb, and a net increase in Eu/Eu* from 1.8 Ga to 1.5 Ga, suggesting that the younger grains came from a less evolved source. Arizona samples mimic the TAM with a more subdued trend during this period. Based on similarities, these combined zircon ages suggest that the two basins shared a detrital source region during this period, some of which is likely on East Antarctica. Monazites from the TAM samples have ages at 1.2 and 1.5 Ga, and those from Arizona form a continuum from 1.5-1.7 Ga, indicating shared metamorphic event around 1.5 Ga. Detrital rutile grains found in one Antarctic sample also show evidence of a Neoproterozoic/early Paleozoic metamorphic event, probably the Ross Orogeny. Together, our new age and trace element data from detrital mineral suites are consistent with the SWEAT configuration for Columbia.

Future work will entail analysis of Hf isotopes in zircon and Pb isotopes in detrital feldspar to provide a more comprehensive evaluation of the sources of the minerals in order to constrain the placement of the continental blocks.