Paleomagnetism of Mafic Dikes in the Northern Pilbara Craton, Western Australia
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چکیده
Two well preserved Archean cratons, Kaapvaal and Pilbara, have remarkably similar geological successions during the Archean and Paleoproterozoic. This has led some to propose that the two may have been connected during that interval, thus experiencing similar tectonic events. We sampled Archean and Proterozoic rocks from the Pilbara craton in order to test the Vaalbara hypothesis, especially the reconstruction of de Kock et. al (2009). Unfortunately, many of the samples did not yield interpretable results. We did identify the primary magnetization direction of two dikes from the Round Hummock swarm. The ages of these dikes are poorly constrained and they are in need of a geochronological study. However, by investigating some plausible ages due to our limited constraints, we can identify two possible interpretations. If we assume that the dikes are correlative with the similarly-striking Tom Price swarm to the south (dated at 2008 ± 16 Ma. by Müller et. al. (2005)), then we can test the Vaalbara hypothesis at ca. 2.0 Ga. With the VGPs given by the Round Hummock dikes we are not able to rule out Vaalbara at 2.0 Ga. Alternatively, we can compare the VGPs with existing Proterozoic paleomagnetic poles for Australia. We find that they plot very near to the 1067 Ma Bagemall Basin Sills pole raising the possibility that the Round Hummock swarm might instead be correlated with the Bangemall Basin Sills.
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تاریخ انتشار 2009