U-Pb geochronology of the Acasta Gneiss Complex in Northwest Canada

The Acasta Gneiss Complex in Northwest Canada contains the oldest dated rocks in the world. The gneisses range in age from 4.03-3.6 Ga, as determined by U-Pb dating of zircons (Bowring and Williams 1999). U-Pb dating of xenocrystic cores in these zircons indicates a cryptic record of continental crust older than 4.0 Ga. In this study, zircons were selected and characterized from thirteen samples of Acasta Gneisses. Many of the zircons contain xenocrystic cores mantled by younger domains. U-Pb geochronological data were collected using laser ablation inductively coupled plasma mass spectrometery (LA-ICPMS). Twelve of the samples show evidence for two distinct crystallization events, one which formed the cores and another in which the mantle domain overgrew the cores. The oldest cores were dated at >4.0 Ga. This provides additional evidence for pre-4.0 Ga crust formation in the late Hadean.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Safipour, Roxana G

Advisor dc:contributor.advisor

• Samuel Bowring.

• Earth, Atmospheric, and Planetary Sciences.

Statement dc:rights

• MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/114375

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/114375