Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Kobussen, A. F. Articles by Shee, S. R. Search for Related Content GeoRef GeoRef Citation

Ghosts of lithospheres past: Imaging an evolving lithospheric mantle in southern Africa

¹ Geochemical Evolution and Metallogeny of Continents, Australian Research Council National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109, Australia
² Shee & Associates Pty. Ltd., Glen Iris, VIC 3146, Australia

Group II (143–117 Ma) and Group I kimberlites (108–74 Ma) intrude across the southwest boundary of the Kaapvaal craton, sampling the same volume of the subcontinental lithospheric mantle (SCLM) in two time slices. Major and trace element analyses of 3699 peridotitic garnet xenocrysts were used to construct paleogeotherms for 17 kimberlite localities, and to place each garnet at its depth of origin. The Ti contents of each garnet and the calculated X_Mg of its coexisting olivine were projected onto a southwest-northeast section across the craton boundary, and splines were used to interpolate between the virtual boreholes in each age group. The sections show that the cratonic SCLM extends at least 75 km southwest of the mapped craton boundary, suggesting a dipping contact. Marked differences between the time-slice sections show that between 117 and 108 Ma the SCLM on both sides of the craton boundary was heated and chemically refertilized by infiltrating asthenosphere-derived melts, thinning the depleted layer by ~40 km. The thermal and geochemical changes record a significant tectonothermal event that may be related to changes in the stress field associated with opening of the South Atlantic, or with mantle upwelling.

Key Words: South Africa • lithosphere evolution • lithosphere structure • mantle xenocrysts • mantle garnets

This article has been cited by other articles:

				C. Bonadiman, Y. Hao, M. Coltorti, L. Dallai, B. Faccini, Y. Huang, and Q. Xia Water contents of pyroxenes in intraplate lithospheric mantle European Journal of Mineralogy, June 1, 2009; 21(3): 637 - 647. [Abstract] [Full Text] [PDF]