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Characteristics of Mesoproterozoic Felsic Meta-Volcanics from the Shillong Group of Rocks, Meghalaya, North East India


Affiliations
1 Geological Survey of India, North Eastern Region, Shillong 793 003, India
2 Department of Applied Geology, Dibrugarh University, Dibrugarh 786 004, India
3 Regional Training Institute, Geological Survey of India, Eastern Region, Kolkata 700 091, India
 

Shillong Group comprises a thick meta-volcano-sedimentary sequence forming a part of Shillong Plateau and Mikir Hills. The litho variants of felsic meta-volcanics are characterized in detail based on their constituent material, textural variation, depositional feature and mode of eruption. Lava flows are characterized as porphyritic, spherulitic and aphyric type whereas pyroclastic deposits are classified as tuff breccia, lapilli tuff, tuffand ignimbrite. Fractured crystal and brecciated lithic fragments in tuff; fiamme and eutaxitic texture of ignimbrite suggest for subaerial eruption. The felsic meta-volcanics are rhyolitic to dacitic in composition and interbedded with tuffaceous phyllite, phyllite and quartzite.

Keywords

Felsic Volcanics, Ignimbrite, Lava Flow, Tuff, Shillong Group, Subaerial.
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  • Khonglah, M. A., Khan, M. A., Karim, M. A., Kumar, A. and Choudhury, J., Geology and structure of the areas in and around Shillong, Meghalaya, North East India, revisited. Nagaland Univ. Res. J., Spec. Publ., 2008, 115–139.

  • Bhattacharyya, B. P. and Ray Barman, T., Precambrian geology in northeast India: a perception of contribution during pre- and post-independence era. In M. S. Krishnan Centenary Commemorative, National Seminar, Calcutta, 1998, vol. 12, pp. 11–12.

  • Ghosh, S., Chakraborty, S., Bhalla, J. K., Paul, D. K., Sarkar, A., Bishui, P. K. and Gupta, S. N., Geochronology and geochemistry of granite plutons from East Khasi Hills, Meghalaya. J. Geol. Soc. India, 1991, 37, 331–342.

  • Ghosh, S., Chakraborty, S., Paul, D. K., Bhalla, J. K., Bishui, P. K. and Gupta, S. N., New Rb–Sr isotopic ages and geochemistry of granitiods from Meghalaya and their significance in middle to late Proterozoic crustal evolution. Indian Minerals, 1994, 48, 33–44.

  • Majumdar, S. K., The Precambrian framework of part of the Khasi Hills. Meghalaya Rec. Geol. Surv. India, 1986, 117(2), 1–59.

  • Yin, A., Dubey, C. S., Webb, A. A. G., Kelty, T. K., Grove, M., Gehrels and Burgess, W. P., Geological correlation of the Himalayan orogen and Indian Craton: Part 1. Structural geology U–Pb zircon geochronology and tectonic evolution of the Shillong Plateau and its neighboring regions in NE India. Geol. Soc. Am. Bull., 2010, 122, 336–359.

  • Mitra, S. K., Structural history of the rocks of the Shillong Group around Sohiong, East Khasi Hills Meghalaya. Indian J. Geol., 1998, 70, 123–131.

  • Mero, A., Imchen, I., Sujata, S. and S. Praveen., Specialized the-matic mapping of the Shillong Group, Mylliem Granite around Laitkor, Mylliem and Lingkardem area, East Khasi Hills District, Meghalaya, 2016. GSI report published in GSI portal.

  • Venkateswaralu, M., Sarma, K. P. and Laskar, J. J., Palaeomagnetic and petrological studies of volcanic tuff from Shillong plateau, NE India. Himal. Geol., 2012, 33(2), 118–125.

  • Donaldson, C. H. and Henderson, C. M. B., A new interpretation of round embayments in quartz crystals. Mineral. Mag., 1988, 52, 27–33.

  • McPhie, J., Doyle, M. and Allen, R., Volcanic Textures – A Guide to the Interpretation of Textures in Volcanic Rocks, Tasmania Government Printing Office, Tasmania, 1993.

  • Le Bas, M. J., Lemaitre, R.W., Streckeisen, A. and Zanettin, B., A Chemical classification of volcanic–rocks based on the total alkali silica diagram. J. Petrol., 1986, 27(3), 745–750.

  • Nelson, S. T. and Montana, A., Sieve textured plagioclase in volcanic rocks produced by rapid decompression. Am. Mineral., 1992, 77, 1242–1249.

  • Lofgren, G., Effect of alkali-rich solutions on the devitrification rate of rhyolite glass (abs.).Progr. Geol. Soc. Amer. Ann. Meet., 1967, 132.


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  • Characteristics of Mesoproterozoic Felsic Meta-Volcanics from the Shillong Group of Rocks, Meghalaya, North East India

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Authors

R. R. Naik
Geological Survey of India, North Eastern Region, Shillong 793 003, India
K. Theunuo
Geological Survey of India, North Eastern Region, Shillong 793 003, India
T. K. Goswami
Department of Applied Geology, Dibrugarh University, Dibrugarh 786 004, India
M. A. Khonglah
Geological Survey of India, North Eastern Region, Shillong 793 003, India
T. Pal
Geological Survey of India, North Eastern Region, Shillong 793 003, India
S. K. Tripathy
Regional Training Institute, Geological Survey of India, Eastern Region, Kolkata 700 091, India

Abstract


Shillong Group comprises a thick meta-volcano-sedimentary sequence forming a part of Shillong Plateau and Mikir Hills. The litho variants of felsic meta-volcanics are characterized in detail based on their constituent material, textural variation, depositional feature and mode of eruption. Lava flows are characterized as porphyritic, spherulitic and aphyric type whereas pyroclastic deposits are classified as tuff breccia, lapilli tuff, tuffand ignimbrite. Fractured crystal and brecciated lithic fragments in tuff; fiamme and eutaxitic texture of ignimbrite suggest for subaerial eruption. The felsic meta-volcanics are rhyolitic to dacitic in composition and interbedded with tuffaceous phyllite, phyllite and quartzite.

Keywords


Felsic Volcanics, Ignimbrite, Lava Flow, Tuff, Shillong Group, Subaerial.

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DOI: https://doi.org/10.18520/cs%2Fv118%2Fi7%2F1123-1128