scholarly journals A study of diamonds, diamond inclusion minerals and other mantle minerals from the Swartruggens kimberlite dyke swarm, South Africa

2019 ◽  
Keyword(s):  
South Africa ◽  
Dyke Swarm ◽  
Mantle Minerals ◽  
Diamond Inclusion

scholarly journals Baddeleyite U–Pb ages and gechemistry of the 1875–1835 Ma Black Hills Dyke Swarm across north-eastern South Africa: part of a trans-Kalahari Craton back-arc setting?

GFF ◽  
2015 ◽  
Vol 138 (1) ◽  
pp. 183-202 ◽  
Author(s):  
J.R. Olsson ◽  
M.B. Klausen ◽  
M.A. Hamilton ◽  
N. März ◽  
U. Söderlund ◽  
...  
Keyword(s):  
South Africa ◽  
Black Hills ◽  
Dyke Swarm ◽  
Kalahari Craton ◽  
North Eastern ◽  
Arc Setting ◽  
Back Arc

Characterisation of grain-size, shape and orientation of plagioclase in the Rooi Rand dyke swarm, South Africa

2013 ◽  
Vol 583 ◽  
pp. 145-157 ◽  
Author(s):  
Warwick William Hastie ◽  
Michael K. Watkeys ◽  
Charles Aubourg
Keyword(s):  
South Africa ◽  
Grain Size ◽  
Dyke Swarm

scholarly journals Evolution of ultrapotassic volcanism on the Kaapvaal craton: deepening the orangeite versus lamproite debate

2021 ◽  
pp. SP513-2021-84
Author(s):  
Sebastian Tappe ◽  
Azhar M. Shaikh ◽  
Allan H. Wilson ◽  
Andreas Stracke
Keyword(s):  
South Africa ◽  
Subduction Zones ◽  
Kaapvaal Craton ◽  
Dyke Swarm ◽  
Geochemical Data ◽  
Volatile Components ◽  
Mantle Lithosphere ◽  
Cratonic Mantle ◽  
Supplementary Material ◽  
Potassic Rocks

AbstractOrangeites are a significant source of diamonds, yet ambiguity surrounds their status among groups of mantle-derived potassic rocks. This study reports mineralogical and geochemical data for a ca. 140 Ma orangeite dyke swarm that intersects the Bushveld Complex on the Kaapvaal craton in South Africa. The dykes comprise distinctive petrographic varieties that are linked principally by olivine fractionation, with the most evolved members containing minor amounts of primary carbonate, sanidine and andradite garnet in the groundmass. Although abundant groundmass phlogopite and clinopyroxene have compositions that are similar to those of cratonic lamproites, these phases show notable Ti-depletion, which we consider a hallmark feature of type orangeites from the Kaapvaal craton. Ti-depletion is also characteristic for the bulk rock compositions and is associated with strongly depleted Th-U-Nb-Ta contents at high Cs-Rb-Ba-K concentrations. The resultant high LILE/HFSE ratios of orangeites suggest that mantle source enrichment occurred by metasomatic processes in the proximity of ancient subduction zones.The Bushveld-intersecting orangeite dykes have strongly enriched Sr-Nd-Hf isotopic compositions (initial 87Sr/86Sr = 0.70701-0.70741; εNd = −10.6 to −5.8; εHf = −14.4 to −2.5), similar to those of other orangeites from across South Africa. Combined with the strong Ti-Nb-Ta depletion, this ubiquitous isotopic feature points to the involvement of ancient metasomatized mantle lithosphere in the origin of Kaapvaal craton orangeites, where K-rich metasomes imparted a ‘fossil’ subduction geochemical signature. Previous geochronology studies identified ancient K-enrichment events within the Kaapvaal cratonic mantle lithosphere, possibly associated with collisional tectonics during the 1.2-1.1 Ga Namaqua-Natal orogeny of the Rodinia supercontinent cycle. It therefore seems permissible that the cratonic mantle root was preconditioned for ultrapotassic magma production by tectonomagmatic events that occurred along convergent plate margins during the Proterozoic. However, reactivation of the K-rich metasomes had to await establishment of an extensional tectonic regime, such as that during the Mesozoic breakup of Gondwana, which was accompanied by widespread (1000 × 750 km) small-volume orangeite volcanism between 200 and 110 Ma.Although similarities exist between orangeites and lamproites, these and other potassic rocks are sufficiently distinct in their compositions such that different magma formation processes must be considered. In addition to new investigations of the geodynamic triggers of K-rich ultramafic magmatism, future research should more stringently evaluate the relative roles of redox effects and volatile components such as H2O-CO2-F in the petrogeneses of these potentially diamondiferous alkaline rocks.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5440652

Identification of a new 485 Ma post-orogenic mafic dyke swarm east of the Pan-African Saldania-Gariep Belt of South Africa

2021 ◽  
Vol 354 ◽  
pp. 106043
Author(s):  
Cole G. Kingsbury ◽  
Martin B. Klausen ◽  
Ulf Söderlund ◽  
Wladyslaw Altermann ◽  
Richard E. Ernst
Keyword(s):  
South Africa ◽  
Dyke Swarm ◽  
Mafic Dyke ◽  
Pan African ◽  
Mafic Dyke Swarm ◽  
Gariep Belt

scholarly journals PETROGENESIS OF THE FALSE BAY DYKE SWARM, CAPE PENINSULA, SOUTH AFRICA: EVIDENCE FOR BASEMENT ASSIMILATION

2011 ◽  
Vol 114 (3-4) ◽  
pp. 335-352 ◽  
Author(s):  
N. R. BACKEBERG ◽  
D. L. REID ◽  
R. B. TRUMBULL ◽  
R. L. ROMER
Keyword(s):  
South Africa ◽  
Dyke Swarm ◽  
Cape Peninsula

In-situ assimilation of mantle minerals by kimberlitic magmas — Direct evidence from a garnet wehrlite xenolith entrained in the Bultfontein kimberlite (Kimberley, South Africa)

Lithos ◽  
2016 ◽  
Vol 256-257 ◽  
pp. 182-196 ◽  
Author(s):  
Ashton Soltys ◽  
Andrea Giuliani ◽  
David Phillips ◽  
Vadim S. Kamenetsky ◽  
Roland Maas ◽  
...  
Keyword(s):  
South Africa ◽  
Direct Evidence ◽  
Mantle Minerals
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