University of New Mexico
Archean detrital zircons in the Proterozoic Vishnu Schist of the Grand Canyon, Arizona : implications for crustal architecture and Nuna reconstructions
Abstract
dc:description.abstractU-Pb dating of 1035 detrital zircons from twelve spatially-distributed samples of the Paleoproterozoic Vishnu Schist reveals a bimodal 207Pb/ 206Pb age probability diagram with peaks at 1.8 Ga and 2.5 Ga. Surprisingly, only 13% of detrital zircon ages overlap with the published depositional age range of 1750–1741 Ma. The similarity of the age distributions in all samples constrains possible suturing of crustal blocks to pre-Vishnu Schist deposition rather than during the peak 1710-1680 Ma deformation. Of all grains analyzed, 15% overlap at 2σ with the 1.84 ± 1 Ga Elves Chasm orthogneiss of western Grand Canyon. This supports field evidence that Vishnu Schist was deposited on 1.84 Ga arc basement rather than in a juvenile 1.75 Ga arc setting. Archean grains of 3.8–2.5 Ga comprise 30% of all grains. A comparison of the > 2.2 Ga ages from the Vishnu Schist (495 grains) with compilations of zircon ages from other cratons does not support provenances in the Wyoming, South China, or Siberian cratons; instead sources may be located in Gawler craton of Australia, North China craton, or Antarctica. If the detrital zircons were far-traveled, this is a new constraint for viable reconstructions of the Nuna supercontinent. However, given the high percentage of pre-1.8 Ga zircons, unexposed proximal basement sources are more likely, resulting in a model by which Vishnu sediments were derived from Mojave crust that consists of Archean and 1.9-1.8 Ga crust, now in the subsurface, that was unroofed during Vishnu deposition.
Degree
thesis:*- Name thesis:degree_name
- Earth and Planetary Sciences
- Level thesis:degree_level
- Masters
- Discipline thesis:degree_discipline
- Department of Earth and Planetary Sciences
- Year
- 2010
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Shufeldt, Owen Philip
- Contributors dc:contributor
-
- Karlstrom, Karl E.
- Crossey, Laura
- Asmerom, Yemane
- Whitmeyer, Steven
Subjects
dc:subject × 2Rights
- Language dc:language
- English
Identifiers
dc:identifier.*- OAI identifier oai:identifier
- oai:digitalrepository.unm.edu:eps_etds-1080