Were the Deccan Flood Basalts Derived in Part from Ancient Oceanic Crust Within the Indian Continental Lithosphere?

Abstract

Deep mantle plumes supposedly incorporate deeply subducted eclogitized oceanic crust, and continental flood basalts (CFBs) are now thought by some to be derived from such eclogite-bearing peridotite plumes. Eclogite-peridotite mixtures have much lower solidi (and produce much greater melt fractions for a given temperature) than peridotite. Ferich (eclogite-or pyroxenite-bearing) sources have been inferred for many CFBs. However, plumes with considerable amounts of eclogite should have difficulty in upwelling owing to the high density of eclogite. Besides, CFBs are always located along pre-existing lithospheric structures (suture zones, edges of thick cratons) and commonly associated with lithospheric rifting and continental breakup. India's major late Mesozoic CFB, the Deccan Traps, erupted through rift zones and a new continental margin that had developed along ancient suture zones traversing the subcontinent. Many Deccan basalts are too Fe-rich to have been in equilibrium with a peridotite mantle source, and have commonly been considered to be significantly fractionated derivatives of picritic liquids. However, it is possible to view them as relatively less evolved liquids derived from a source with extra fertility (i.e., an Fe-rich source). A new non-plume, plate tectonic model for Icelandic hotspot volcanism involves melting of a shallowly recycled slab of eclogitized Iapetus oceanic crust formerly trapped along the Caledonian suture. The model explains the geochemical-petrological characteristics of Icelandic basalts, and is consistent with passive upper mantle upwelling under Iceland inferred from recent seismic tomography. Based on the petrological and geochemical features of the Deccan flood basalts of the type section, in the Western Ghats, I propose that old, eclogitized oceanic crust trapped in the ancient Indian suture zones could have produced voluminous basaltic melts during the Deccan event.

Complex rift geometries resulting from inheritance of pre-existing structures: Insights and regional implications from the Barmer Basin rift

“…The common assumption that the R eunion Mantle Plume triggered rifting throughout west India at the Cretaceous-Paleogene boundary (Morgan, 1971;Plummer and Belle, 1995;Sen and Chandrasekharam, 2011) is not consistent with the interpretation presented herein of early northwestesoutheast extension within the Barmer Basin, or the formation of a pre-Deccan Barmer-Cambay Rift System. A mantle-plume origin for the Deccan Traps has been questioned, with many aspects of the Deccan geology inconsistent with that predicted by the plume-head model (Sheth, 2005a(Sheth, , 2005b(Sheth, , 2007, and we suggest that the two non-coaxial episodes of rifting observed within early deposits of the Barmer Basin are better explained by a model of plate reorganisations that initiated long before the arrival of the R eunion Mantle Plume (e.g. Sharma, 2007;Collier et al, 2008).…”

“…Successful separation of the Seychelles microcontinent from the Greater Indian continent was followed by two further jumps of the Carlsberg Ridge at 56 Ma and 41 Ma (Torsvik et al, 2013). Extrusion of the voluminous Deccan Traps (68e60 Ma) was contemporaneous with, and closely associated to rifting of the Seychelles microcontinent from the Greater Indian continent (Cox, 1989;White and McKenzie, 1989;Sheth, 2005aSheth, , 2005bSheth, , 2007Collier et al, 2008), with volcanism commonly thought to have instigated rifting (Morgan, 1971;Plummer and Belle, 1995;Sen and Chandrasekharam, 2011). Evidence presented in support of the presence of a mantle plume beneath northwest India at the Cretaceous-Paleogene boundary ( Fig.…”

“…A postulated alternative to the plume-head model (e.g. Campbell and Griffiths, 1990) invokes the passive release of fertile lithosphere material, trapped within ancient lithosphere sutures, upon extension, to provide a significant contribution to the voluminous Deccan Trap magmatism (Sheth, 2005b). Similar models involving high mantle fertility beneath Iceland and heat accumulation beneath the Karoo Large Igneous Province (Hastie et al, 2014), provide further support for the generation of excessive volcanism during rifting in the absence of a mantle plume.…”

Comparative study of Wenner and Schlumberger electrical resistivity method for groundwater investigation: a case study from Dhule district (M.S.), India

“…The Narmada-Satpuda-Tapi dyke swarm is a liner ENE-WSW trending Giant dykes (Melluso et al 1999). The petrographic and geochemical studies of dykes in Nandurbar Dhule area have been carried out by earlier researchers (Sheth 2005;Bhattacharji et al 2004;Das Balaram Maity and Tarafdar 2007). Since the dykes are not emplaced along faults or fracture, it suggests regional horizontal compressive stress along north-south as a region for the emplacement of dyke (Sant and Karanth 1990).…”

K-T magmatism and basin tectonism in western Rajasthan, India, results from extensional tectonics and not from Réunion plume activity

“…This coincided with the separation of the Seychelles from India, large-scale Deccan volcanism, development of the Cambay rift and alkali magmatism in western Rajasthan. Crustal rifting during the K-T boundary period resulted in large-scale Deccan volcanism (Sheth, 2005a(Sheth, , 2005b) and development of the Cambay-Barmer rift system. The extensional tectonics resulted in deep fractures manifested by the development of rift basins, alkali magmatism and lamprophyre-carbonatite dykes.…”