The Mount Pavagadh volcanic suite, Deccan Traps: Geochemical stratigraphy and magmatic evolution

Sheth, Hetu; Melluso, Leone

doi:10.1016/j.jseaes.2007.10.001

Cited by 66 publications

(59 citation statements)

References 67 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Most continental flood basalt provinces contain at least some silicic (rhyolite-dacite-trachyte) igneous rocks, and these are variably interpreted as derived by crystal fractionation of mafic magmas, partial melting of underplated mafic rocks or the deeper parts of the flood basalt pile, combined assimilation and fractionation processes, or anatexis of older basement crust (e.g., Lightfoot et al 1987;Sheth and Melluso 2008;Sheth et al 2011a). Silicic rocks (rhyolite, granophyre, and trachyte) are abundant in the western and northwestern parts of the Deccan province, particularly the Saurashtra peninsula and the Mumbai area, on the western Indian rifted margin (Fig.…”

Section: Silicic Magmatism In the Deccan Trapsmentioning

confidence: 99%

Spherulites and thundereggs from pitchstones of the Deccan Traps: geology, petrochemistry, and emplacement environments

et al. 2011

Self Cite

View full text Add to dashboard Cite

Spherulites and thundereggs are rounded, typically spherical, polycrystalline objects found in glassy silicic rocks. Spherulites are dominantly made up of radiating microscopic fibers of alkali feldspar and a silica mineral (commonly quartz). They form due to heterogeneous nucleation in highly supercooled rhyolitic melts or by devitrification of glass. Associated features are lithophysae ("stone bubbles"), which have an exterior (sometimes concentric shells) of fine quartz and feldspar, and internal cavities left by escaping gas; when filled by secondary silica, these are termed thundereggs. Here, we describe four distinct occurrences of spherulites and thundereggs, in pitchstones (mostly rhyolitic, some trachytic) of the Deccan Traps, India. The thundereggs at one locality were previously misidentified as rhyolitic lava bombs and products of pyroclastic extrusive activity. We have characterized the thundereggs petrographically and geochemically and have determined low contents of magmatic water (0.21-0.38 wt.%) in them using Fourier transform infrared spectroscopy. We consider that the spherulite-bearing outcrops at one of the localities are of lava flows, but the other three represent subvolcanic intrusions. Based on the structural disposition of the Deccan sheet intrusions studied here and considerations of regional geology, we suggest that they are cone sheets emplaced from a plutonic center now submerged beneath the Arabian Sea.

show abstract

Section: Silicic Magmatism In the Deccan Trapsmentioning

confidence: 99%

Spherulites and thundereggs from pitchstones of the Deccan Traps: geology, petrochemistry, and emplacement environments

et al. 2011

Self Cite

View full text Add to dashboard Cite

show abstract

“…Thus the central Kachchh plugs and the Karinga Dungar maar-diatreme form the base of the local Deccan stratigraphy. Sheth and Melluso (2008) mention "breccia deposits with outward dips" at the base of the thick Pavagadh sequence (Fig. 1a), which rests on Precambrian basement exposed nearby.…”

Section: Hydrovolcanism In the Deccan Trapsmentioning

confidence: 99%

Mafic alkalic magmatism in central Kachchh, India: a monogenetic volcanic field in the northwestern Deccan Traps

2010

Self Cite

View full text Add to dashboard Cite

Magmatism in Kachchh, in the northwestern Deccan continental flood basalt province, is represented not only by typical tholeiitic flows and dikes, but also plug-like bodies, in Mesozoic sandstone, of alkali basalt, basanite, melanephelinite and nephelinite, containing mantle nodules. They form the base of the local Deccan stratigraphy and their volcanological context was poorly understood. Based on new and published field, petrographic and geochemical data, we identify this suite as an eroded monogenetic volcanic field. The plugs are shallow-level intrusions (necks, sills, dikes, sheets, laccoliths); one of them is known to have fed a lava flow. We have found local peperites reflecting mingling between magmas and soft sediment, and the remains of a pyroclastic vent composed of non-bedded lapilli tuff breccia, injected by mafic alkalic dikes. The lapilli tuff matrix contains basaltic fragments, glass shards, and detrital quartz and microcline, with secondary zeolites, and there are abundant lithic blocks of mafic alkalic rocks. We interpret this deposit as a maar-diatreme, formed due to phreatomagmatic explosions and associated wall rock fragmentation and collapse. This is one of few known hydrovolcanic vents in the Deccan Traps. The central Kachchh monogenetic volcanic field has >30 individual structures exposed over an area of ∼1,800 km 2 and possibly many more if compositionally identical igneous intrusions in northern Kachchh are proven by future dating work to be contemporaneous. The central Kachchh monogenetic volcanic field implies low-degree mantle melting and limited, periodic magma supply. Regional directed extension was absent or at best insignificant during its formation, in contrast to the contemporaneous significant directed extension and vigorous mantle melting under the main area of the Deccan flood basalts. The central Kachchh field demonstrates regional-scale volcanological, compositional, and tectonic variability within flood basalt provinces, and adds the Deccan Traps to the list of such provinces containing monogenetic-and/or hydrovolcanism, namely the Karoo-Ferrar and Emeishan flood basalts, and plateau basalts in Saudi Arabia, Libya, and Patagonia.

show abstract

“…On the other hand, high-MgO picrites with Fo 88-92 olivine from Gujarat and especially from Saurashtra ( Fig. 1a) have been interpreted as near-primary liquids with ~16 wt% MgO (Krishnamurthy and Cox 1977;Cox 1980;Melluso et al 1995Melluso et al , 2006Krishnamurthy et al 2000;Sheth and Melluso 2008;Sen and Chandrasekharam 2011). Krishnamurthy and Cox (1977) considered these picrites as parental to the interlayered tholeiites and concluded that the tholeiites evolved through equilibrium crystallization aided by compensated crystal settling from picritic liquids.…”

Section: Introductionmentioning

confidence: 99%

Origin of the Powai ankaramite, and the composition, P–T conditions of equilibration and evolution of the primary magmas of the Deccan tholeiites

Chatterjee

Sheth

2015

Contrib Mineral Petrol

View full text Add to dashboard Cite

and Mahabaleshwar Formations show that their primary magmas (wt% SiO 2 : 48-50, last equilibrated with spinel lherzolite at ~8-13 kb (~30-49 km depths) and ~1268-1332 °C, and trace element considerations indicate ≤15 % batch melting of mantle. These tholeiitic primary magmas then underwent olivine gabbro fractionation in upper crustal magma chambers at depths ≤23 km. The minimum depth of equilibration of the primary magmas is shallower than the present-day Moho in the Mumbai area based on seismological data, indicating localized mantle upwelling and lower crustal interactions previously inferred from the Nd-Sr isotopic ratios and other geochemical characteristics of the ankaramite and associated tholeiites.

show abstract

The Mount Pavagadh volcanic suite, Deccan Traps: Geochemical stratigraphy and magmatic evolution

Cited by 66 publications

References 67 publications

Spherulites and thundereggs from pitchstones of the Deccan Traps: geology, petrochemistry, and emplacement environments

Spherulites and thundereggs from pitchstones of the Deccan Traps: geology, petrochemistry, and emplacement environments

Mafic alkalic magmatism in central Kachchh, India: a monogenetic volcanic field in the northwestern Deccan Traps

Origin of the Powai ankaramite, and the composition, P–T conditions of equilibration and evolution of the primary magmas of the Deccan tholeiites

Contact Info

Product

Resources

About