2026-09-20T09:42:13Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/1143752022-01-13T07:53:59Zcom_1721.1_7582com_1721.1_7581col_1721.1_131024
Samuel Bowring.
Safipour, Roxana G
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences.
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
n-cn---
2018-03-27T14:19:48Z
2018-03-27T14:19:48Z
2009
2009
http://hdl.handle.net/1721.1/114375
1028993474
Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 58-59).
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.
by Roxana G. Safipour.
S.B.
136 pages
eng
Massachusetts Institute of Technology
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.
http://dspace.mit.edu/handle/1721.1/7582
Earth, Atmospheric, and Planetary Sciences.
U-Pb geochronology of the Acasta Gneiss Complex in Northwest Canada
Thesis
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<Abstract>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.</Abstract>
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