Ultramafic rocks at the center of the Vredefort structure: Further evidence for the crust on edge model

Research Article| October 01, 1999 Ultramafic rocks at the center of the Vredefort structure: Further evidence for the crust on edge model Marian Tredoux; Marian Tredoux 1Department of Geological Sciences, University of Cape Town, Private Bag, Rondebosch 7700, South Africa Search for other works by this author on: GSW Google Scholar Rodger J. Hart; Rodger J. Hart 2Schonland Research Center, University of the Witwatersrand, P.O. Box 3, Wits 2050, South Africa Search for other works by this author on: GSW Google Scholar Richard W. Carlson; Richard W. Carlson 3Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, D.C. 20015, USA Search for other works by this author on: GSW Google Scholar Steven B. Shirey Steven B. Shirey 3Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, D.C. 20015, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Marian Tredoux 1Department of Geological Sciences, University of Cape Town, Private Bag, Rondebosch 7700, South Africa Rodger J. Hart 2Schonland Research Center, University of the Witwatersrand, P.O. Box 3, Wits 2050, South Africa Richard W. Carlson 3Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, D.C. 20015, USA Steven B. Shirey 3Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, D.C. 20015, USA Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1999) 27 (10): 923–926. https://doi.org/10.1130/0091-7613(1999)027<0923:URATCO>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Marian Tredoux, Rodger J. Hart, Richard W. Carlson, Steven B. Shirey; Ultramafic rocks at the center of the Vredefort structure: Further evidence for the crust on edge model. Geology 1999;; 27 (10): 923–926. doi: https://doi.org/10.1130/0091-7613(1999)027<0923:URATCO>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Ultramafic rocks from the center of the Vredefort structure previously have been interpreted either as Early Proterozoic igneous rocks genetically related to the Bushveld complex, or as Archean upper mantle rocks. Re-Os isotopic data from these rocks display very low 187Os/188Os and 187Re/188Os, suggesting that they are not magma chamber cumulates, but rather the residues of melt extraction, similar in Re-Os systematics to subcontinental lithospheric mantle. Whole-rock Re depletion model ages for two samples are 3.3 and 3.5 Ga, indicating that the postulated melt extraction event must have occurred in the Archean. On the basis of these data we conclude that the ultramafic rocks are not related to the Bushveld event, but rather represent upper mantle that rebounded to crustal levels following an impact event. This conclusion strengthens evidence for a model whereby the rocks exposed in the core of the Vredefort structure represent the lower parts of a crust on edge profile that possibly contains a paleo-Moho very near the Earth's surface. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.