Petrology and geochemistry of mafic dykes of Sylhet traps, Northeastern India, and their Kerguelen plume linkage

Sen, Bibhas; Pal, T. K.; Theunuo, Kevilhoutuo

doi:10.1007/s00710-019-00686-8

Cited by 4 publications

(8 citation statements)

References 66 publications

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“…The REEs were analysed by Inductively Coupled Plasma Mass Spectrometer in the Chemical Laboratory, GSI Headquarters at Hyderabad and Kolkata. The details of techniques, procedure, precision, and accuracy of these analyses are described in SOP (http://www.portal.gsi.gov.in, GSI, 2009) and identical analytical methodology, techniques, instruments, and the calibration used by Sadiq et al (2017), and Sen et al (2019), was adopted.…”

Section: Methodsmentioning

confidence: 99%

“…The details of techniques, procedure, precision, and accuracy of these analyses are described in SOP (http://www.portal.gsi. gov.in, GSI, 2009) and identical analytical methodology, techniques, instruments, and the calibration used by Sadiq et al (2017), andSen et al (2019), was adopted.…”

Section: Methodsmentioning

confidence: 99%

“…Charnockitization took place around the noritic and porphyritic granitoids of West Khasi Hills (Khonglah et al, 2010, 2018). Ultramafic‐alkaline‐carbonatite complexes of Sung, Mawpyut, Jasra, Samchampi‐Sameteran, Barpung; lamprophyre dyke swarm of Nongchram (Nandy, 2001; Srivastava & Sinha, 2004), picrite‐basalt‐alkali‐basalt‐alkaline dyke swarm (Khonglah, Sougrakpam, Imchen, & Baskaran, 2016) and the Sylhet Flood Basalt flows along the southern part of SP, in the Meghalaya‐Bangladesh border of Khasi Hills (Nandy, 2001; Sen et al, 2019) characterized the Cretaceous igneous activity. The magmatism is largely controlled along the N–S trending faults (Nongchram, Umngot amongst others), E–W faults (e.g., Raibah), and the intersection points of the different faults/lineaments also became important centers for plutonism and dyke activities.…”

Section: Geological Framework Of the Shillong Plateaumentioning

confidence: 99%

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Geochemistry of meta‐mafic and meta‐tonalite‐trondhjemite intrusives from Jaintia and Karbi Anglong hills of Shillong Plateau, North East India: Implications on the evolution of the Proterozoic Shillong Basin

et al. 2022

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We present the whole‐rock and mineral chemical data of the Khasi meta‐mafic/basic‐trondhjemite intrusives (KMI) and meta‐tonalite‐trondhjemite (MTT) that coevally emplaced the Proterozoic Shillong Group (SG) of Shillong Plateau, northeast (NE) India and discuss their petrogenetic‐tectonic origin. The calc‐alkaline to tholeiite KMI are compositionally transitional between hornblende‐gabbro; hornblende‐diorite and minor‐hornblendite. They show Ta–Nb troughs and strong decoupling large‐ion lithophile/high field strength elements (HFSE) signature consistent with subduction zone‐related basic magmas. The calcic to calc‐alkaline, low‐Al2O3, and I‐type metaluminous Fe‐hedenbergite‐trondhjemite (KMT) exhibits similar trace and rare earth elements (REE) distribution to the KMI. The MTT on the other hand are depleted in trace elements and REE, and correspond with the I‐type granitoids, and are comparable to Proterozoic to Phanerozoic tonalite‐trondhjemite‐granodiorites. Gentle negative sloping of REE in KMI ([La/Lu]CN = 4.04 to 6.35) with moderate LREE, suggests partial melting or, fractional crystallization from a transitional source between garnet and spinel lherzolite. Although almost a flat pattern ([La/Lu]CN = 3.70 to 4.05) for MTT entails a high degree of partial melting from sources similar to Archaean Mafic Composite or Archaean Tholeiite. Trace elemental modellings ([Sr/Y] vs. Y and [La/Yb]N vs. YbN) for MTT infer low pressure (<15 kbar) and high degree partial melting of >50% in equilibrium with 10% garnet +90% amphibole residue. A relatively flat REE pattern with some elevated HREE of MTT compared to KMI suggests for depleted source. Bimodal plutonism and the prevalence of meta‐dacite‐rhyolite in SG invokes for tonalite‐trondhjemite‐dacite setting of a continental arc or, active continental margin tectonic setting. Emplacement of KMI initiated in a temporary relax‐extensional phase and MTT in a compressional regime. This is possibly caused by an over‐thickened crust later subjected to orogenic collapse, exhumation‐metamorphism, and decompressional melting. This event might have taken place between 1.0 to 0.5 Ga during the Pan‐African Orogenic crustal growth, linked to the amalgamation of Gondwana.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Geological Framework Of the Shillong Plateaumentioning

confidence: 99%

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Geochemistry of meta‐mafic and meta‐tonalite‐trondhjemite intrusives from Jaintia and Karbi Anglong hills of Shillong Plateau, North East India: Implications on the evolution of the Proterozoic Shillong Basin

et al. 2022

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“…The interaction between the lithosphere of the north‐eastern margin of Greater India and the Kerguelen hotspot during the Lower Cretaceous period may represent the initial stage of the split of Greater India from southwestern Australia (Mallikharjuna Rao, 2002; Mamilla et al, 2012; Sarma et al, 2014). As mentioned by earlier authors, there is a paucity of geochemical and petrological data (Sen et al, 2019). The main objective of this study is to determine the geochemical and mineralogical characteristics of the Sylhet Trap's extrusive and rarely encountered dolerite dyke, mafic rocks in order to provide an explanation for their petrogenesis, tectonic setting and petrological studies.…”

Section: Introductionmentioning

confidence: 97%

“…These basaltic tholeiitic dykes are the product of single magma injection predominant phenocrystic phases set in a ground‐mass of bytownite/labradorite, relatively Ca‐poor augite, titano‐magnetite and glass. (Sen et al, 2019). The disposition of volcanic tuff and its association indicates that it is formed by the Gondwana break‐up caused by the Kerguelen hotspot (Mamilla et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

The Kerguelen mantle plume activity in Sylhet Trap mafic rocks of Southern Shillong Plateau,NEIndia: Implications for its role in magmatism of eastern India

Kumar,

Singh,

Bikramaditya

et al. 2024

Geological Journal

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Mantle plumes related to Large Igneous Provinces have been linked to continental break‐up and validated by the outpouring of mafic‐ultramafic magmas that range from continental flood basalt magmatism to submarine plateau volcanism. This study presents a new set of geochemical and mineralogical data on mafic magmatic rocks from the Sylhet Trap of the Shillong Plateau, northeast India. The investigated mafic rocks (basalt and dolerite) are predominantly sub‐alkaline‐tholeiitic, composed of bytownite+labradorite and diopside+augite, with ophitic to sub‐ophitic and glomeroporphyritic textures, the dark interstitial region of much finer grains consisting of opaque minerals and devitrified glass. The mafic rocks of Sylhet Trap show light rare earth elements enrichment with (La/Yb)N ratio (1.92–2.86) and (La/Sm)N ratio (1.11–1.40), an almost flat pattern of heavy rare earth elements along with mild europium anomalies (Eu/Eu*= 0.94–1.11). Trace element characteristics suggest their affinity towards enriched mid‐oceanic ridge basalt and generated from low degree of partial melting of spinel source with minor involvement of crustal contamination. The similarity in geochemical characteristics of the investigated mafic rocks with the magmatism of Rajmahal Traps, eastern Peninsular India, Abor Volcanics, eastern Himalaya, along with Bunbury Basalt of western Australia and Cona Mafic exposed in southeastern Tibet, suggests their genetic linkage with mantle plume activities. Thus, we argue that the magmatic event of the Sylhet Trap is related to the Kerguelen mantle plume activity that played a significant role in the fragmentation of eastern Gondwana during the Lower Cretaceous period, giving rise to Greater India, Antarctica and northwest Australia.

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Morphology, Textures and Thicknesses of Rubbly Pahoehoe Lavas from the ~117 Ma Sylhet Traps, India

Duraiswami

Sanklecha

Monteiro

et al. 2022

Journal of the Geological Society of India

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The Sylhet Traps and the larger outcrops of the Rajmahal Traps in India constitute an important remnant of a large Continental Flood Basalt (CFB) province related to the Kerguelen hotspot. A composite log of lava flows across the southern margin of the Meghalaya plateau is presented where the Sylhet Traps are best exposed. Lavas in the lower part of stratigraphic sequence (~480 to 700 m above mean sea level) are compound and contain pahoehoe sheet lobes intruded by thin basaltic dykes constituting a swarm. These lavas record variable degrees of inflation at low effusive rates. In the upper parts, several rubbly pahoehoe lavas are interspersed with sheet lobes. These represent transitional lava types (between pahoehoe and aa) and occur due to steep gradients and/or increased effusive rates. The vesicles from within these lavas impinge and coalesce, indicating that they had time to form and grow in an insulated environment. The vesicle deformation index (VDI) ranges from 0.2 to 0.53, indicating moderate but variable shear strain on the lavas during emplacement. The coexistence of pahoehoe-rubbly pahoehoe lavas is also recorded in the surface outcrops of Rajmahal Traps and the IODP drill cores along the Kerguelen Plateau. It is postulated that the Sylhet lavas represent the distal edge of a lava-shield evolving into a flood basalt setting, dominated by pahoehoe in the lower stratigraphy with few lavas transitioning to rubbly pahoehoe towards the top. Such an architecture is in keeping with other CFB provinces worldwide.

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Petrology and geochemistry of mafic dykes of Sylhet traps, Northeastern India, and their Kerguelen plume linkage

Cited by 4 publications

References 66 publications

Geochemistry of meta‐mafic and meta‐tonalite‐trondhjemite intrusives from Jaintia and Karbi Anglong hills of Shillong Plateau, North East India: Implications on the evolution of the Proterozoic Shillong Basin

Geochemistry of meta‐mafic and meta‐tonalite‐trondhjemite intrusives from Jaintia and Karbi Anglong hills of Shillong Plateau, North East India: Implications on the evolution of the Proterozoic Shillong Basin

The Kerguelen mantle plume activity in Sylhet Trap mafic rocks of Southern Shillong Plateau,NEIndia: Implications for its role in magmatism of eastern India

Morphology, Textures and Thicknesses of Rubbly Pahoehoe Lavas from the ~117 Ma Sylhet Traps, India

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