Revisiting the age and paleomagnetism of the Modipe Gabbro of South Africa

S. W. Denyszyn, J. M. Feinberg, P. R. Renne, G. R. Scott

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19 Scopus citations

Abstract

The Modipe Gabbro is a Precambrian intrusive unit hosted by the Kaapvaal craton of South Africa and provides one of the oldest records of geomagnetic field behavior in the late Archean. Earlier paleomagnetic research into the Modipe Gabbro provided valuable insight into its magnetic properties and mineralogy, but predate the development of paleomagnetic tools that are important in unraveling potentially complex histories of Precambrian rocks. Further, a lack of information about the precise age of the intrusion prevented this earlier paleomagnetic study from being used to evaluate the tectonic history of the Kaapvaal craton. Here we present a comprehensive paleomagnetic and geochronologic study of the Modipe Gabbro that complements and builds upon the existing work. The emplacement age of the gabbro (2784.0. ±. 1.0. Ma), established using the U-Pb ID-TIMS method on baddeleyite, links the intrusion to nearby igneous bodies in the Kaapvaal craton, establishing one of the oldest fully differentiated magmatic events in the geologic record. The precise age of the Modipe Gabbro and field observations about its strike allow us to perform a tilt correction using the both the attitude and paleomagnetism of the nearby Derdepoort basalts. The tilt-corrected data allow a comparison of Kaapvaal craton's paleolatitude with that of the Pilbara craton at 2.78. Ga, with implications for the existence of the supercraton Vaalbara.

Original languageEnglish (US)
Pages (from-to)176-185
Number of pages10
JournalPrecambrian Research
Volume238
DOIs
StatePublished - Nov 2013

Bibliographical note

Funding Information:
The authors are grateful to M.E. Evans for discussions about the Modipe Gabbro at the beginning of this project and to Stephen Dell of the Madikwe Game Reserve for allowing unrestricted access to the Modipe Complex. Rudy Wenk and Roland Merkle are thanked for field and logistical support, respectively. Lisa Smeenk helped measure paleomagnetic samples at the BGC. Travis Drake measured rock magnetic properties as part of the NSF-Research Experience for Undergraduate program at the University of Minnesota. The manuscript was substantially improved by suggestions from Nicholas Swanson-Hysell and Andrew Biggin. This research was funded by NSF grants to JMF ( EAR-0911683 ) and to PRR and GRS ( EAR-0309686 ). The Institute for Rock Magnetism is supported by NSF grant EAR-1028690 . This is IRM contribution 1112. Anonymous reviewers and editor R. Parrish are thanked for their patience and insight.

Keywords

  • Geochronology
  • Modipe
  • Paleomagnetism
  • Vaalbara

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