Petrogenetic evolution of the felsic and mafic volcanic suite in the Siang window of Eastern Himalaya, Northeast India

Abstract

The Abor volcanics outcroping in the core of the Siang window in the Eastern Himalaya comprise voluminous mafic volcanics (47%e56% w(SiO 2 )), with subordinate felsic volcanics (67%e75% w(SiO 2 )). The felsic volcanics are dacitic to rhyolitic in composition and are typically enriched in LREE (La/Sm N Z 3.09e3.90) with high REE contents (256e588 ppm), moderately fractionated REE patterns (Ce N /Yb N Z 6.54e9.52) and pronounced negative Eu anomalies (Eu/Eu* Z 0.55e 0.72). Wide variations in Rb/Zr, K/Rb and La/Sm ratios suggest that they were derived from magmas which were randomly contaminated with crustal material. Chemical characteristics and petrogenetic modelling indicate that the dacites were generated by w15% partial melting of a mafic source leaving a residue with 55% plagioclase, 14% orthoclase, 18% clinopyroxene, 5% orthopyroxene, 8% hornblende. The silica-rich rhyodacites and rhyolites were derived from a dacite magma source by a higher degree (>45%) fractional crystallization of an assemblage consisting of 70% plagioclase, 12% clinopyroxene, 7% amphibole and 11% magnetite. The associated LREE-LILE enrichment and pronounced negative GEOSCIENCE FRONTIERS journal homepage: www.elsevier.com/locate/gsf GEOSCIENCE FRONTIERS 3(5) (2012) 613e634 anomalies for HFSE (Nb, P, and Ti) exhibited by these felsic volcanics are characteristic of continental rift volcanism, implying that they were emplaced during lithospheric extension. ª 2012, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.

Late Paleozoic Woniusi basaltic province from Sibumasu terrane: Implications for the breakup of eastern Gondwana’s northern margin

“…For instance, they are dominated by basaltic rocks and volumetrically minor coeval ultramafi c or felsic rocks. Geochemically, all basaltic rocks from these provinces exhibit high-sodium and low-potassium contents (Bhat, 1984;Garzanti et al, 1999;Chauvet et al, 2008;Shellnutt et al, 2011Shellnutt et al, , 2014Ali et al, 2012;Singh and Bikramaditya Singh, 2012;Zhai et al, 2013;Wang et al, 2014), similar to typical continental fl ood basalts (Farmer, 2003). Most of them, except a few from the Panjal Traps, are enriched in LREEs and LILEs, which imply an enriched mantle source region.…”

“…It is believed that there was a massive pulse of magmatism from the latest Carboniferous to Early Permian around northern Gondwana, represented by the basaltic rocks from the Panjal Trap, Tethyan Himalaya, and southern Qiangtang (Bhat, 1984;Garzanti et al, 1999;Chauvet et al, 2008;Zhu et al, 2010;Singh and Bikramaditya Singh, 2012;Shellnutt et al, 2011Shellnutt et al, , 2014Ali et al, 2012;Zhai et al, 2013;Wang et al, 2014). They have close spatial and temporal relationships and are comparable in petrology and geochemistry (Table 1).…”

Zircon U–Pb geochronology, Hf isotopic compositions, and petrogenetic study of Abor volcanic rocks of Eastern Himalayan Syntaxis, Northeast India: Implications for eruption during breakup of Eastern Gondwana

“…Geological map of the Eastern Syntaxial Belt (modified after Choudhuri, Gururajan, & Bikramaditya Singh, ); (b). Geological map of the southern part of the Siang window in the Eastern Syntaxis Belt, Arunachal Himalaya (modified after Singh, ; Singh & Bikramaditya, ) [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…And it was also ensured that the selected samples were least Choudhuri, Gururajan, & Bikramaditya Singh, 2009);. Geological map of the southern part of the Siang window in the Eastern Syntaxis Belt, Arunachal Himalaya (modified after Singh, 1993;Singh & Bikramaditya, 2012) [Colour figure can be viewed at wileyonlinelibrary.com] product, followed by epidote, quartz, amphibole, zeolite, titanite, and sericite. In a few thin sections, volcanic glass occur randomly and sometimes converted into fibrous aggregate of pale green chlorite.…”

Investigation of spatial and temporal variability of site response in the Arunachal Himalaya using ambient seismic noise and earthquake waveforms

“…Although several researchers explored the geology of Arunachal Pradesh (e.g. Gansser 1964;Nandy 1973;Acharya et al 1975;Bhattacharyya and Nandy 2008;Singh and Singh 2012;Saha 2013), the eastern part is relatively less studied than the western and central parts due to poor accessibility. The western part of Arunachal Himalaya comprises gneisses of the Sela group intruded by metasediments of Luma, Tertiary leucogranite and Dirang formations, granite gneisses and Paleoproterozoic rocks of the Bomdila group.…”