Provenance history of detrital diamond deposits, West Coast of Namaqualand, South Africa

Provenance history of detrital diamond deposits, West Coast of Namaqualand, South Africa The West Coast of Namaqualand in South Africa hosts extensive detrital diamond deposits, but considerable debate exists as to the provenance of these diamonds. Some researchers have suggested derivation of the diamonds from Cretaceous-Jurassic kimberlites (also termed Group I kimberlites) and orangeites (also termed Group II kimberlites) located on the Kaapvaal Craton. However, others favour erosion of diamonds from the ca.300 Ma Dwyka Group sediments, with older, pre-Karoo kimberlites being the original 40 39 source(s). Previous work has demonstrated that Ar/ Ar analyses of clinopyroxene inclusions, extracted from diamonds, yield ages approaching the time(s) of source kimberlite emplacement, which can be used to constrain the provenance of placer diamond 40 39 deposits. In the current study, Ar/ Ar analyses were conducted on clinopyroxene inclusions from two similar batches of Namaqualand detrital diamonds, yielding (maximum) ages ranging from 117.5 ± 43.6 Ma to 3684 ± 191 Ma (2σ) and 120.6 ± 15.4Ma to688.8±4.9Ma(2σ), respectively. The vast majority of inclusions (88%) produced ages younger than 500 Ma, indicating that most Namaqualand diamonds originated from Cretaceous-Jurassic kimberlites/orangeites, with few, if any, derived from the Dwyka tillites. The provenance of the Namaqualand diamonds from ca.115–200 Ma orangeites is consistent with Late Cretaceous paleo-drainage http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Mineralogy and Petrology Springer Journals

Provenance history of detrital diamond deposits, West Coast of Namaqualand, South Africa

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Publisher
Springer Journals
Copyright
Copyright © 2018 by Springer-Verlag GmbH Austria, part of Springer Nature
Subject
Earth Sciences; Mineralogy; Inorganic Chemistry; Geochemistry
ISSN
0930-0708
eISSN
1438-1168
D.O.I.
10.1007/s00710-018-0568-9
Publisher site
See Article on Publisher Site

Abstract

The West Coast of Namaqualand in South Africa hosts extensive detrital diamond deposits, but considerable debate exists as to the provenance of these diamonds. Some researchers have suggested derivation of the diamonds from Cretaceous-Jurassic kimberlites (also termed Group I kimberlites) and orangeites (also termed Group II kimberlites) located on the Kaapvaal Craton. However, others favour erosion of diamonds from the ca.300 Ma Dwyka Group sediments, with older, pre-Karoo kimberlites being the original 40 39 source(s). Previous work has demonstrated that Ar/ Ar analyses of clinopyroxene inclusions, extracted from diamonds, yield ages approaching the time(s) of source kimberlite emplacement, which can be used to constrain the provenance of placer diamond 40 39 deposits. In the current study, Ar/ Ar analyses were conducted on clinopyroxene inclusions from two similar batches of Namaqualand detrital diamonds, yielding (maximum) ages ranging from 117.5 ± 43.6 Ma to 3684 ± 191 Ma (2σ) and 120.6 ± 15.4Ma to688.8±4.9Ma(2σ), respectively. The vast majority of inclusions (88%) produced ages younger than 500 Ma, indicating that most Namaqualand diamonds originated from Cretaceous-Jurassic kimberlites/orangeites, with few, if any, derived from the Dwyka tillites. The provenance of the Namaqualand diamonds from ca.115–200 Ma orangeites is consistent with Late Cretaceous paleo-drainage

Journal

Mineralogy and PetrologySpringer Journals

Published: May 28, 2018

References

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