Paleoproterozoic mafic dyke swarms from the Dharwar craton; paleomagnetic poles for India from 2.37 to 1.88Ga and rethinking the Columbia supercontinent
Here we report new paleomagnetic and geochronologic results from the Dharwar craton (south India) from 2.37 to 1.88Ga. The presence of a ~85,000km2 radiating dyke swarm with a fanning angle of 65° is confirmed within Peninsular India at 1.88Ga. North of the Cuddapah basin the dykes are oriented NW-SE and progress to an E-W orientation further south, converging at a focal point southeast of the basin. The Grand Mean dual polarity paleomagnetic pole falls at 36.5°N and 333.5°E (D=129.1°, I=4.2°, α95=4.5°, λ=2.1°) for 29 sites from the present study combined with previously published sites. Our continental reconstruction for India at ~1.9Ga conflicts with the archetypal Columbia model, suggesting that the exact configuration needs modification. We also report two separate paleomagnetic directions from NW-SE (D=3.2°, I=56.4°, α95=17.9°, λ=37°) and N-S (D=240.1°, I=-65.5°, α95=10.9°, λ=47.7°) trending ~2.2Ga dykes. We attribute this difference in directions to the separate magmatic pulses at 2.18 and 2.21Ga identified by French and Heaman (2010). Our results place India at intermediate latitudes from 2.21 to 2.18Ga and are supported by a positive baked contact test. New paleomagnetic results from E-W and NW-SE trending 2.37Ga dykes, combined with previous work in the Dharwar craton, yields a Grand Mean dual polarity paleomagnetic pole at 15.1°N and 62.2°E (A95=4.0°), placing India at polar latitudes (D=88.7°, I=-81.7°, α95=4.8°, λ=73.7°). Here we also report a shallow NE direction (D=52.2°, I=-1.5°, α95=6.3°) previously classified as a secondary magnetization from three dykes near the Cuddapah basin. A baked contact test and petrophysical analysis of two cross-cutting dykes supports a primary remanence. Finally we present a Paleoproterozoic Apparent Polar Wander Path (APWP) for the Dharwar craton, and examine paleogeographic relationships between India and other cratonic blocks for the 2.37-1.88Ga time interval. © 2013 Elsevier B.V.
Paleoproterozoic mafic dyke swarms from the Dharwar craton; paleomagnetic poles for India from 2.37 to 1.88Ga and rethinking the Columbia supercontinent.
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