Crustal Structure beneath the Precambrian Cratons of Gondwanaland and Its Evolution Using Teleseismic Receiver Function

Abstract

The Gondwana supercontinent was an accretion of several cratons from different landmasses, namely South America, Antarctica, Africa, Madagascar, Australia, and the Indian subcontinent. The splitting of Gondwanaland during the Mesozoic led to the gradual rifting of these different cratons over geologic time. In this study, crustal structures are imaged by modeling receiver functions to understand the differences in the nature of the crust that was once part of Precambrian Gondwanaland. On comparing the overall crustal thickness with the age of the cratons, it was found that average bounds of crustal thickness varied from ~33 to 45 km in the Precambrian cratons of different ages, and composition varied from felsic to intermediate (Vp/Vs≈1.65−1.78). Observations of gradational Moho beneath few stations could indicate the possibility of mafic underplating at some point in their history of formation, growth, or evolution. Even if plate tectonics were dominant in the middle to late Archean, difference in spreading, drifting velocity, and distance travelled by the continents after Gondwana separation possibly led to crustal delamination, and destruction of thick crustal roots of cratons. Other than delamination, the role of episodic cycles of crustal growth is also observed in the pattern of crustal thickness across each division of the Precambrian. This could be due to alternative high and low crustal regeneration process, repeated episodic recycling, and reworking of early crust, supported by previous geodynamical models.