The Chogat-Chamardi subvolcanic complex, Saurashtra, northwestern Deccan Traps: Geology, petrochemistry, and petrogenetic evolution

Sheth, Hetu; Choudhary, Amol; Bhattacharyya, S.; Cucciniello, Ciro; Laishram, Ramesh; Gurav, Trupti

doi:10.1016/j.jseaes.2011.02.012

Cited by 44 publications

(31 citation statements)

References 44 publications

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“…Misra's (1999) statement that the "lava bomb"-bearing pitchstone of Bhaguda-Longdi is seemingly a vertical sheetlike body with horizontal columnar jointing (a possible magma conduit or dike in our view) is in support of this interpretation. The interpretation is also supported by the regional geological context of the Saurashtra region, which abounds in subvolcanic intrusions (e.g., Sheth et al 2011a).…”

Section: Emplacement Environment and Stylementioning

confidence: 71%

“…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%

“…CB01 Chatterjee and Bhattacharji(2001),L87 Lightfoot et al (1987),M85 Mahoney et al. (1985),SM08 Sheth and Melluso (2008), S11aSheth et al (2011a), S11bSheth et al (2011b),M96 Maithani et al (1996), andM95 Melluso et al (1995). Boundary lines between the subalkalic and alkalic fields proposed byMacdonald and Katsura (1964, short heavy line) andIrvine and Baragar (1971, curved dashed line) are also shown…”

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confidence: 99%

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

et al. 2011

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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.

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Section: Emplacement Environment and Stylementioning

confidence: 71%

Section: Silicic Magmatism In the Deccan Trapsmentioning

confidence: 99%

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confidence: 99%

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

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“…Their main outcrops are located in the Mumbai, Pavagadh, Rajpipla and Chhota Udaipur areas, as well as the Saurashtra peninsula in the northwestern Deccan Traps (Fig. 1a) (e.g., Krishnamurthy and Cox, 1980;Lightfoot et al, 1987;Gwalani et al, 1993;Bhattacharji, 2001, 2004;Sheth et al, 2011a;Kshirsagar et al, in press;Zellmer et al, in press). A small but significant rhyolitepitchstone-basaltic andesite lava flow sequence is exposed at Osham Hill in Saurashtra (Fig.…”

Section: Introductionmentioning

confidence: 99%

Geology, petrochemistry, and genesis of the bimodal lavas of Osham Hill, Saurashtra, northwestern Deccan Traps

Sheth

Choudhary

Cucciniello

et al. 2012

Journal of Asian Earth Sciences

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“…It is dominantly made up of flood lavas of basalt and basaltic andesite, though it also contains rhyolite, trachyte, basanite, nephelinite, and carbonatite magmas (e.g., Lightfoot et al 1987;Kshirsagar et al 2011;Sheth et al 2011). Some spectacular outcrops in the Mumbai area of the Deccan Traps provide insights into the mingling and mixing of mafic (basalt) and felsic (trachyte) magma.…”

Section: Introductionmentioning

confidence: 99%

Remobilization of granitoid rocks through mafic recharge: evidence from basalt-trachyte mingling and hybridization in the Manori–Gorai area, Mumbai, Deccan Traps

Zellmer

Sheth

Iizuka³

et al. 2011

Bull Volcanol

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Products of contrasting mingled magmas are widespread in volcanoes and intrusions. Subvolcanic trachyte intrusions hosting mafic enclaves crop out in the Manori-Gorai area of Mumbai in the Deccan Traps. The petrogenetic processes that produced these rocks are investigated here with field data, petrography, mineral chemistry, and whole rock major, trace, and Pb isotope chemistry. Local hybridization has occurred and has produced intermediate rocks such as a trachyandesitic dyke. Feldspar crystals have complex textures and an unusually wide range in chemical composition. Crystals from the trachytes cover the alkali feldspar compositional range and include plagioclase crystals with anorthite contents up to An 47 . Crystals from the mafic enclaves are dominated by plagioclase An 72-90 , but contain inclusions of orthoclase and other feldspars covering the entire compositional range sampled in the trachytes. Feldspars from the hybridized trachyandesitic dyke yield mineral compositions of An 80-86 , An 47-54 , Ab 94-99 , Or 45-60 , and Or 96-98 , all sampled within individual phenocrysts. We show that these compositional features are consistent with partial melting of granitoid rocks by influx of mafic magmas, followed by magma mixing and hybridization of the partial melts with the mafic melts, which broadly explains the observed bulk rock major and trace element variations. However, heterogeneities in Pb isotopic compositions of trachytes are observed on the scale of individual outcrops, likely reflecting initial variations in the isotopic compositions of the involved source rocks. The combined data point to one or more shallow-level trachytic magma chambers disturbed by multiple injections of trachytic, porphyritic alkali basaltic, and variably hybridized magmas.

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The Chogat-Chamardi subvolcanic complex, Saurashtra, northwestern Deccan Traps: Geology, petrochemistry, and petrogenetic evolution

Cited by 44 publications

References 44 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

Geology, petrochemistry, and genesis of the bimodal lavas of Osham Hill, Saurashtra, northwestern Deccan Traps

Remobilization of granitoid rocks through mafic recharge: evidence from basalt-trachyte mingling and hybridization in the Manori–Gorai area, Mumbai, Deccan Traps

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