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Structural controls on melt segregation and migration related to the formation of the diapiric Schwerin Fold in the contact aureole of the Bushveld Complex, South Africa

By
Luke Longridge
Luke Longridge
School of Geosciences, University of the Witwatersrand, Johannesburg, PVT Bag 3, Wits, 2050, South Africa, Email: luke.longridge@wits.ac.za
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Roger L. Gibson
Roger L. Gibson
School of Geosciences, University of the Witwatersrand, Johannesburg, PVT Bag 3, Wits, 2050, South Africa, Email: luke.longridge@wits.ac.za
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Paul A. M. Nex
Paul A. M. Nex
School of Geosciences, University of the Witwatersrand, Johannesburg, PVT Bag 3, Wits, 2050, South Africa, Email: luke.longridge@wits.ac.zaUmbono Group of Companies, Isle of Houghton, Johannesburg, South Africa
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Published:
October 01, 2010

Partial melting of metapelitic rocks beneath the mafic–ultramafic Rustenburg Layered Suite of the Bushveld Complex in the vicinity of the periclinal Schwerin Fold resulted in a structurally controlled distribution of granitic leucosomes in the upper metamorphic aureole. In the core of the pericline, subvertical structures facilitated the rise of buoyant leucosome through the aureole towards the contact with the Bushveld Complex, with leucosomes accumulating in en-echelon tension gashes. In a subhorizontal syn-metamorphic shear zone to the southeast of the pericline, leucosomes accumulated in subhorizontal dilational structural sites. The kinematics of this shear zone are consistent with slumping of material off the southeastern limb of the rising Schwerin pericline. The syndeformational timing of leucosome emplacement supports a syn-intrusive, density-driven origin for the Schwerin Fold. Modelling of the cooling of the Rustenburg Layered Suite and heating of the floor rocks using a multiple intrusion model indicates that temperatures above the solidus were maintained for >600,000 years up to 300 m from the contact, in agreement with rheological modelling of floor-rock diapirs that indicate growth rates on the order of 8 mm/year for the Schwerin Fold.

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GSA Special Papers

Sixth Hutton Symposium on The Origin of Granites and Related Rocks: Proceedings of a Symposium held in Stellenbosch, South Africa, 2- 6 July 2007

John D. Clemens
John D. Clemens
Department of Earth Sciences, University of Stellenbosch, South Africa
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Colin Donaldson
Colin Donaldson
EESTRSE Editor:
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Carol D. Frost
Carol D. Frost
Guest Editors:
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Alexander F.M. Kisters
Alexander F.M. Kisters
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Jean-François Moyen
Jean-François Moyen
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Tracy Rushmer
Tracy Rushmer
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Gary Stevens
Gary Stevens
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Geological Society of America
Volume
472
ISBN print:
9780813724720
Publication date:
October 01, 2010

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