The Greater Cederberg−False Bay Large Igneous Province in South Africa : A southern node of widespread magmatism associated with South Atlantic rifting

Summary, in English

A new 130 to 140 Ma mafic dyke swarm, is identified in western South Africa. It consists of the previously undated Cederberg dyke swarm (CDS), for which we report U-Pb ID-TIMS baddeleyite ages of 131.4 ± 4.5 Ma (Knersvlake subswarm) and 133.0 ± 1.5 Ma (Doring-Tanqua subswarm).⁴⁰Ar/³⁹Ar dates on these two samples and two additional dates of the Doring – Tanqua subswarm cluster between 128.5 ± 1.4 Ma and 132.2 ± 1.5 Ma. We also report⁴⁰Ar/³⁹Ar ages of 139.3 ± 3.5 Ma for an east-west trending dyke located further north: 27 km south of Kleinsee, and 140.3 ± 1.2 Ma for an east-west dyke near Garies. Together, these eight ages robustly date the emplacement of the northern part of a Greater Cederberg-False Bay Dyke Swarm (GCFDS) at ca. 130 to 140 Ma. Trace and rare earth element data reported herein suggest these dykes are compositionally E-MORB basalts that underwent modification either via subduction-modified lithospheric mantle, or by continental crust, or a combination thereof, and are petrogenetically similar to the ca. 132 Ma False Bay dykes around Cape Town. Therefore, we propose to unify all these coeval and compositionally similar dykes into one large igneous province (LIP) termed the Greater Cederberg-False Bay Large Igneous Province (GCF-LIP).

• Author: C. G. Kingsbury; W. Altermann; J. Kramers; R. E. Ernst; U. Söderlund; M. B. Klausen
• Department/s: Lithosphere and Biosphere Science
• Publishing year: 2023-12
• Language: English
• Pages: 471-484
• Publication/Series: South African Journal of Geology
• Volume: 126
• Issue: 4
• Links: http://dx.doi.org/10.25131/sajg.126.0023
• Document type: Journal article
• Publisher: Geological Society of South Africa
• Topic: Geology
• Status: Published
• ISBN/ISSN/Other: ISSN: 1012-0750