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

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. © 2013 Elsevier B.V.