Archean granitoids of the Bastar Craton, Central India
Published:December 14, 2020
M. E. A. Mondal, M. Faruque Hussain, Talat Ahmad, 2020. "Archean granitoids of the Bastar Craton, Central India", Archean Granitoids of India: Windows into Early Earth Tectonics, S. Dey, J.-F. Moyen
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Archean granitoids of the Bastar Craton mainly occur as gneisses (3.56, 3.50 Ga) and undeformed granitoids (c. 2.5–2.48 Ga). Based on detailed geochemical characteristics two compositional types of gneisses: tonalite–trondhjemite–granodiorite (TTG) and transitional TTG (t-TTG) have been identified. The TTG rocks are further classified into low-HREE (heavy rare earth element) type and high-HREE type. It is proposed that melting of a thick enriched oceanic plateau basalt at deeper level may have generated the low-HREE TTG, whereas melting at shallower depth of the thick plateau can explain the geochemical signatures of the high-HREE TTG. The t-TTG was formed as a result of reworking of the older TTG crust. These two gneisses were probably formed at different time at 3.56 and 3.50 Ga as manifested from the age of the gneisses. The granitoids were formed at a later stage (c. 2.5–2.48 Ga) by reworking of the pre-existing gneissic crust consisting of TTG and t-TTG. Presence of a small 3.58 Ga undeformed K-rich granitoid from the northern part of the craton might indicate yet another earlier crustal reworking event.
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Archean Granitoids of India: Windows into Early Earth Tectonics
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Granitoids form the bulk of the Archean continental crust and preserve key information on early Earth evolution. India hosts five main Archean cratonic blocks (Aravalli, Bundelkhand, Singhbhum, Bastar and Dharwar). This book summarizes the available information on Archean granitoids of Indian cratons. The chapters cover a broad spectrum of themes related to granitoid typology, emplacement mechanism, petrogenesis, phase-equilibria modelling, temporal distribution, tectonic setting, and their roles in fluid evolution, metal delivery and mineralizations. The book presents a broader picture incorporating regional- to cratons-scale comparisons, implications for Archean geodynamic processes, and temporal changes thereof. This synthesis work, integrating modern concepts on granite petrology and crustal evolution, offers an irreplaceable body of reference information for any geologist interested in Archean Indian granitoids.