Abstract
The Askot crystallines form a doubly plunging synformal belt and occurs as a detached crystalline belt or klippen in the vast sedimentary terrain lying between Central crystallines towards north and the Almora crystallines to the south. It is dominated by granite gneiss and augen gneiss, and also comprise of metapelites, migmatites and basic intrusives. In this paper, the geochemical studies of the granite gneiss and augen gneiss from the Askot crystallines, Kumaun Himalaya were carried out in order to understand their origin and evolution.
The granite gneiss is generally foliated, with less foliated and porphyritic variety seen in the core part. The K-feldspar shows Carlsbad twinning, while plagioclases show complex twinning. They show euhedral zircon and apatite along with titanite as accessory minerals. The granite gneiss is moderately evolved (Mg# ∼50) and has granodiorite composition with metaluminous, calc-alkaline trends. They show higher concentration of Ti, Ca, Mg and low abundance of ∑REE (∼165 ppm) in comparison to augen gneiss. They show volcanic arc signatures and compare well with Lateorogenic granites of Proterozoic times distributed world wide. These calc-alkaline granites appear derived from a Paleoproterozoic mafic/intermediate lower-crust reservoir probably involving arc magma underplating. Granite gneiss is also peraluminous with molar A/CNK>1.1, and the heterogeneity of granite gneiss can be explained with the precursor melts, experiencing assimilation during up-rise through crust or contamination of source itself involving sediments from the subduction zone.
The augen gneiss is more evolved (Mg# ∼18) and show granite composition. They show megacrysts of perthites in a fine-to medium-grained matrix of feldspars and micas. The REE pattern of the augen gneiss shows much wide compositional variation (∑REE ∼171 ppm) than granite gneiss. It shows syn- to post-orogenic environment and derivation from the partial melting of an upper crustal source. Existing Rb-Sr isotopic data suggest that the granite gneiss defines an isochron age of ∼1700–1800 Ma with a Sri ratio of ∼0.71, while the augen gneiss defines an age of ∼1300 Ma with much evolved Sri ratio (∼1.65). The dominance of granite gneiss in the eastern Kumaun region suggests the production of heterogeneous granitic melts similar to those of Askot crystallines as an important event of crustal growth during Late Paleoproterozoic period in the region.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Auden, J.B. (1935) Traverses in the Himalaya. Rec. Geol. Surv. India, v.71, pp.407–433.
Bhanot, V.B., Pandey, B.K., Singh, V.P. and Thakur, V.C. (1977) Rb-Sr whole rock age of the granitic-gneiss from Askot area, eastern Kumaun and its implication on tectonic interpretation of the area. Himalayan Geol., v.7, pp.118–122.
Bhanot, V.B., Pandey, B.K., Singh, V.P. and Kansal, A.K. (1980). Rb-Sr ages for some granitic and gneissic rocks of Kumaun and Himachal Himalaya. In: K.S. Valdiya and S.B. Bhatia (Eds.), Stratigraphy and correlation of Lesser Himalayan Formation, Hindusthan Publishing Corp., Delhi, pp.139–142.
Bentor, Y.K. (1985) The crustal evolution of the Arabo-Nubian massif with special reference to the Sinai Peninsula. Precambrian Res., v.28, pp.1–74.
Chakraborty, S.K. and Malaviya, A.K. (1996). Geology of the Almora Group of the Kumaon Lesser Himalaya. Geol. Surv. India Spec. Publ., v.21, pp.39–45.
Davidson, J.P. (1996). Deciphering mantle and crustal signatures in subduction zone magmatism. Geophysics Monograph, v.96, pp.251–262.
de la Roche, Leterrier, J., Grandclaude, P. and Marchal, M. (1980) A classification of volcanic and plutonic rocks using R1–R2 diagrams and major element analyses its relationships with current nomenclature. Chem. Geol., v.29, pp.183–210.
Gairola, V.K. (1967) Refolding in the taconites of Kausani area, district Almora, U.P. Pub. Centre. Adv. Stud. Geol. Panjab Univ., v. 3, pp.101–106.
Ghose, A. (1972) A note on the polymetallic sulphides mineralization in Askot area, Pithoragarh district, Uttar Pradesh. Rec. Geol. Surv. India, v.107(Part-II), pp.1–11.
Harris, N.B.W., Pearce, J.A. and Tindle, A.G. (1986) Geochemical characteristics of collision-zone magmatism. In: M.P. Coward and A.C. Ries (Eds.), Collision Tectonics. Geol. Soc. London Spec. Publ., v.19, pp.67–81.
Haskin L.A., Wildeman T.R. and Haskin, M.A. (1968) An accurate procedure for the determination of the rare earths by neutron activation. Jour. Radioanal. Chem., v.1, pp.337–348.
Heim, A. and Gansser, A. (1939) Central Himalayas: geological observations of the Swiss Expedition 1936. Mem. Soc. Helv. Sci. Nat., v.73, pp.1–245.
Islam, R., Ahmad, T. and Khanna, P.P. (2005) An overview on the granitoids of the NW Himalaya. Himalayan Geol., v.26, pp.49–60.
Kent, R.W. (1995) Continental and oceanic flood basalt provinces: Current and future perspectives. In: R.K. Srivastava and R. Chandra (Eds.), Magmatism in relation to diverse tectonic settings, Oxford & IBH Publishing Co., New Delhi, pp.17–42.
Khanna, P.P., Saini, N.K., Mukherjee, P.K. and Purohit, K.K. (2009) An appraisal of ICP-MS technique for determination of REEs: long term QC assessment of Silicate Rock Analysis. Himalayan Geol., v.30(1), pp.95–99.
Kumar, S., Singh, B.N. and Joshi, M. (1995). Petrogenesis and tectonomagmatic environment of Cambro-Ordovician granitoids of Himalaya: a reappraisal. Geol. Surv. India, Spec. Publ., v.21(1), pp.205–214.
Kumar, Y. and Patel, R.C. (2004) Deformation mechanisms in the Chiplakot crystalline belt (CCB) along Kali-Gori valleys (Kumaon), NW-Himalaya. Jour. Geol. Soc. India, v.64, pp.76–91.
Maniar, P.D. and Piccoli, P.M. (1989) Tectonic discrimination of granitoids. Geol. Soc. Amer. Bull., v. 101, pp.635–643.
Mehdi, S.H., Kumar, G. and Prakash, G. (1972) Tectonic evolution of eastern Kumaun Himalaya: a new approach. Himalayan Geol., v.2, pp.481–501.
Misra, R.C. and Sharma, R.P. (1973) Geology of the Nandprayag Klippe and central crystallines, Kumaun Himalaya. Bull. Indian Geol. Assoc., v.6, pp.85–98.
Myers, J.S. (1997) Geology of Granite. Jour. Roy. Soc. Western Australia, v.80, pp.87–100.
Naqvi, S.M., Divakar Rao, V. and Harinarian, H. (1974) The protocontinental growth of the Indian shield and the antiquity of its rift valley. Precambrian Res., v.1, pp.345–398.
Pandey, B.K., Singh, V.P., Bhanot, V.B. and Mehta, P.K. (1981) Rb-Sr geochronological studies of the gneissic rocks of the Ranikhet and Masi area of Almora crystallines, Lesser Himalaya, Kumaun, U.P. Abstr. Himalayan Geology Seminar, 12th 237–244.
Pande, I.C. and Verma, P.K. (1970) A study of migmatites occurring around Dangoli, Almora district, U.P. In: W.D. West Commemmorative volume, Today & Tomorrow’s Publ., New Delhi, pp.554–568.
Paul, S.K. (1998) Geology and tectonics of the central crystallines of northeastern Kumaun Himlaya, India. Jour. Nepal Geol. Soc., v.18, pp.151–167.
Pearce, J.A., Harris, N.B.W. and Tindle, A.C. (1984) Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. Jour. Petrol., v.25, pp.956–983.
Pitcher, W.S. (1982) Granite type and Tectonic Environment. In: K.J. Hsu (Ed.), Mountain Building Processes. Academic Press, pp.19–40.
Powar, K.B. (1972) Petrology and structure of the Central Crystalline zone, northeastern Kumaun. Himalayan Geol., v.2, pp.34–46.
Powell, C., Mc A., Crawford, A.R., Armstrong, R.L., Prakash, R. and Wynne Edward, H.R. (1979) Reconnaissance Rb-Sr dates for the Himalayan Central Gneiss, Northwest India. Indian Jour. Earth Sci., v.6, pp.139–151.
Rahman, A. and Zainuddin, S.M. (1993) Bundelkhand granites: an example of collision-related Precambrian magmatism and its relevance to the evolution of the Central Indian Shield. Jour. Geol., v.101, pp.413–419.
Rashid, S.A. and Zainuddin, S.M. (1995) The Lower Palaeozoic granitic magmatism near Ranikhet, Kumaun Himlaya: major and trace element geochemistry and tectonic setting. Jour. Geol. Soc. India, v.46, pp.15–25.
Roddick, J.A. (1983) Circum-Pacific plutonic terranes: an overview. Geol. Soc. Amer. Inc., Mem., no.159, pp.1–3.
Rogers, J.W.R. and Greenberg, J.K. (1981) Trace element in continental-margin magmatism: Part III. Alkaline granites and their relationship to cratonization: summary. Geol. Soc. Am. Bull., v.92(Part-I), pp.6–9.
Rogers, J.W.R. and Greenberg, J.K. (1990) Late-orogenic, postorogenic, and anorogenic granites: distinction by major-element and trace-element chemistry and possible origins. Jour. Geol., v.98, pp.291–309.
Rogers, J.W.R., Hodges, K.V. and Ghuma, M.A. (1980) Trace element in continental-margin magmatism: Part II. Trace elements in Ben Ghnema batholith and nature of the Precambrian crust in central North Africa: summary. Geol. Soc. Amer. Bull., v.91(Part-I), pp.445–447.
Saini, N.K., Mukherjee, P.K., Rathi, M.S., Khanna, P.P. and Purohit, K.K. (1998). A new geochemical reference sample of granite (DH-G) from Dalhousie, Himachal Himalaya. Jour. Geol. Soc. India, v.52, pp.603–606.
Saxena, S.P. and Rao, P.N. (1975). Does Almora Nappe exist? Himalayan Geol., v.5, pp.169–184.
Sharma, K.K. (1998) Geologic and tectonic evolution of the Himalaya before and after the India-Asia collision. Proc. Indian Acad. Sci. (Earth Planet. Sci.), v.107, pp.265–282.
Sheraton, J.W., Ellis, D.J. and Kuehner, S.M. (1985) Rare earth element geochemistry of Archean orthogneisses and evolution of the east Antarctica shield. Bur. Miner. Resour. Jour. Aust. Geol. Geophys., v.9, pp.207–218.
Tarney, J., Saunders, A.D., Mattey, D.P., Wood, D.A. and Marsh, N.G. (1981) Geochemical aspects of back-arc spreading in the Scotia Sea and west Pacific. Phil. Trans. Roy. London, v.A300, pp.263–285.
Trevidi, J.R., Gopalan, K. and Valdiya, K.S. (1984) Rb-Sr age of granitic rocks within the Lesser Himalayan Nappes, Kumaun, India. Jour. Geol. Soc. India, v.25, pp.641–654.
Valdiya, K.S. (1962) An outline of the stratigraphy and structure of the southern part of the Pithoragarh district, U.P. Jour. Geol. Soc. India, v.3, pp.27–48.
Validya, K.S. (1980) Geology of Kumaun Lesser Himalaya. The Himachal Times Press, Dehradun, India, 291 pp.
Wilson, M.R. (1980) Granite types in Sweden. Forh. Geol. Foren. Stockholm, v.102, pp.167–176.
Wood, D.A., Joron, J.L. and Treuil M. (1979) A re-appraisal of the use of trace elements to classify and discriminate between magma series erupted in different tectonic settings. Earth Planet. Sci. Letts., v.45, pp.326–336.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Rameshwar Rao, D., Sharma, R. Petrogenesis of the granitoid rocks from Askot crystallines, Kumaun Himalaya. J Geol Soc India 74, 363–374 (2009). https://doi.org/10.1007/s12594-009-0133-6
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s12594-009-0133-6