Paleomagnetism and geochronology of mafic dykes from the Southern Granulite Terrane, India: Expanding the Dharwar craton southward

摘要

The Southern Granulite Terrane (SGT) of India is a collage of Archean to Neoproterozoic crustal blocks hosting several generations of mafic dykes. We report new paleomagnetic and geochronologic results from mafic dykes in the Salem Block of the SGT. The 2370 Ma Bangalore dyke swarm is confirmed in this area with a U-Pb zircon age of 2363 +/- 6.6 Ma on dykes with steep dual-polarity paleomagnetic directions yielding a pole at 2 degrees N and 73 degrees E (A95 = 14 degrees). These results precisely place the Dharwar Craton and northern SGT at high latitudes in the early Paleoproterozoic. The episodic Paleoproterozoic magmatic record of India is also recovered from the SGT. Several groupings of SGT paleomagnetic directions compare favorably with the 2.21 Ga, 2.18 Ga, and 1.88 Ga Dharwar craton dykes. We also report a grand mean pole of 81 degrees N and 259 degrees E (A95 = 11 degrees) that we attribute to a widespread Ediacaran-age remagnetization associated with the final stages of Gondwana assembly. These paleomagnetic and geochronologic data permit a better resolved reconstruction of Indian crustal elements from the Paleoproterozoic onward.