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Ray, Arijit
- Petrology and Geochemistry of Basanite Dykes and Gabbro from Northern Kutch, Western India: Implications on Source Rock Characteristics
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Authors
Affiliations
1 Department of Geology, Presidency College, 86/1 ,College Street, Kolkata - 700 073, IN
2 Indian Institute of Technology, Roorkee - 247 667, IN
3 Indian Institute of Geomagnetism ,Magnetic Observatory, Alibag - 402 20 1, IN
4 Flat 201, C-Wing, ISM House, 818A Thakur Village, Kandivali(E), Mumbai- 400 101, IN
1 Department of Geology, Presidency College, 86/1 ,College Street, Kolkata - 700 073, IN
2 Indian Institute of Technology, Roorkee - 247 667, IN
3 Indian Institute of Geomagnetism ,Magnetic Observatory, Alibag - 402 20 1, IN
4 Flat 201, C-Wing, ISM House, 818A Thakur Village, Kandivali(E), Mumbai- 400 101, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 70, No 5 (2007), Pagination: 771-779Abstract
Major and trace (including rare earth)element abundances, mineral compositions and Nd and Sr isotopic compositions have been determined for the mafic dykes (classified as basanite) and gabbro of the northern Island belt of Kutch rift basin. These are petrographically and geochemically distinct but have similar mantle normalized trace element patterns Measured87Sr/86Sr ratios in the mafic dykes vary from 0 70428 to 0 70593 &Nd(i) varies from 0 27 to - 6 5. The isotopic compositions are broadly similar to that of Mahabaleshwar flows of western Deccan volcanic province. The geochemical character suggests the influence of fractional crystallisation in the evolution of the basanite dykes. The parent magma was enriched in K, Ti, Na and P suggesting derivations from an enriched source during the early phase of lifting Palaeomagnetic data on the dykes show the presence of both normal polarity direction at Dm = 338°, Im=-47° and reverse polarity direction at Dm=14l° and Im=34° indicating multiple intrusion Virtual Geomagnetic Pole(VGP) for the basanite dykes differs from Deccan Super pole suggesting a magmatic event older than the main Deccan eruption.Keywords
Petrology, Geochemistry, Dykes, Gabbro, Kutch, Gujarat.
- Petrology of Mafic-Ultramafic Rocks along North Puruliya Shear Zone, West Bengal
Abstract Views :177 |
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Authors
Aditi Mandal
1,
Arijit Ray
1
Affiliations
1 Department of Geology, Presidency College, Kolkata - 700 073, IN
1 Department of Geology, Presidency College, Kolkata - 700 073, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 74, No 1 (2009), Pagination: 108-118Abstract
The North Puruliya Shear zone (NPSZ) is characterized by occurrence of mafic-ultramafic rocks aligned parallel to the shear zone, intruding the high grade Proterozoic rocks of Chhotanagpur Gneissic Complex. The ultramafic rocks occur as small lenses, pockets, veins, thin dykes and are intimately associated with mafic (gabbro, norite) rocks. Pyroxenites (viz. olivine websterite, websterite, plagioclase websterite) and hornblendite are the two important members of the ultramafic rocks containing clinopyroxene, orthopyroxene, olivine, plagioclase, amphibole, phlogopite and ilmenite. The mafic-ultramafic rocks show evidence of shearing and retrogressive metamorphism. Linear correlation of chemical attributes suggests fractionation-controlled magmatic differentiation. Enrichment of LILE and LREE in the maficultramafic suite suggests an enriched mantle source and pronounced negative Eu-anomalies in all the rock types except hornblendite suggest fractionation of plagioclase under low fO2 condition. Progressive iron enrichment trend in rocks of the mafic-ultramafic suite also indicate magmatic differentiation under low fO2 condition. Early fractionation and accumulation of clinopyroxene and plagioclase from a basaltic magma may have given rise to the ultramafic rocks of the area. Little change in the Nb/Zr and Ce/Zr ratios of ultramafic and mafic rocks (except alkali norite) strongly support low crustal contamination. A few samples of norite and gabbro-norites appeared to be variably contaminated by a crustal component or affected by late granitic intrusion resulting in enrichment of alkali in the former.Keywords
Ultramafic and Mafic Suite, Eu Anomaly, Assimilation, Fractional Crystallization, North Puruliya Shear Zone, West Bengal.References
- BAIDYA, T.K., CHAKRAVARTY, P.S., DRUBETSKOY, E. and KHILTOVA, V.J. (1987) New geochronological data on some granitic phases of the Chhotanagpur granite gneiss complex in the northwestern Puruliya district, West Bengal. Indian Jour. Earth Sci., v.14(2), pp.136-141.
- BAIDYA, T.K., MAITY, N. and BISWAS, P. (1989) Tectonic phases and crustal evolution in a part of the Eastern Chhotanagpur Gneissic Complex. Jour. Geol. Soc. India, v.34(3), pp.318-324.
- Brown, G.C. (1982) Calc-alkaline intrusive rocks: their diversity, evolution and relation to volcanic arcs. In: R.S. Thrope (Ed.), Andesites: Orogenic andesites and related rocks, John Willey, pp.437-461.
- CHATTERJEE, N., CROWLEY, J.L. and GHOSE, N.C. (2008) Geochronology of the 1.55 Ga Bengal anorthosite and Grenvillian metamorphism in the Chotanagpur gneissic complex, eastern India. Precambrian Res., v.161, pp.303-316.
- DASGUPTA, S. and 14 OTHERS (2000) Seismotectonic Atlas of India and its environs. In: P L Narula et al. (Eds.), Geol. Surv. India, 86 p.
- GHOSE, N. C. (1970) On the occurrence of peridotite dyke from Richughuta, Palamau district, and its bearing on the composition of upper mantle. Second Upper Mantle Symposium, National Geophysical Res. Inst., Hyderabad, pp.349-359.
- GHOSE, N.C. (1983) Geology, tectonics and evolution of the Chhotanagpur granite gneiss complex, Eastern India. In: Recent Researches Geol., v.10, pp.211-247.
- GHOSE, N.C. (1992) Chhotanagpur gneiss-granulite complex, Eastern India: Present status and future prospect. Indian Jour. Geol., v.64 (1), pp.100-121.
- GHOSE, N.C. and CHATTERJEE, N. (2008) Petrology, tectonic setting and source of dykes and related magmatic bodies in the Chhotanagpur Gneissic Complex, Eastern India. In: Rajesh K. Srivastava, Ch. Shivaji and N.V. Chalapati Rao (Eds.), Indian Dykes. Narosa Publ. House, New Delhi, pp.471-493.
- GSI (1977) Role of minerals in the development of Purulia district, West Bengal. Jour. Mines Metals Fuels, Purulia Seminar, Special number, v.73, pp.25-44.
- MAHADEVAN, T. M. (1992) Geological evolution of the Chhotanagpur gneissic complex in parts of Purulia district. Indian Jour. Geol., v.64(1), pp.1-22.
- MAZUMDER, S.K. (1988) Crustal evolution of Chhotanagpur gneissic complex and the mica belt of Bihar. In: D. Mukhopadhyay (Ed.), Precambrian of the Eastern Indian Shield. Mem. Geol. Soc. India, no.8, pp.49-83.
- RAY BARMAN, T., BISHUI, P.K., MUKHOPADHYAY, K. and RAY, J.N. (1994) Rb-Sr geochronology of the high grade rocks from Puruliya, West Bengal and Jamua-Dumka sector, Bihar. Indian Minerals, v.48(1-2), pp.45-60.
- SARKAR, A.N. (1988) Tectonic evolution of the Chhotanagpur plateau and Gondwana basins in Eastern India: An interpretation based on supra-subduction geological processes. In: D. Mukhopadhyay (Ed.), Precambrian of the Eastern Indian Shield. Mem. Geol. Soc. India, no.8, pp.127-146.
- SENGUPTA, D.K. and SARKAR, S.N. (1964) Structure of the granitic rock and associated metamorphites of the area around Muri- Silli-Jhalida, Ranchi and Purulia districts, India. 22nd Int. Geol. Cong., v.4, pp.374-389.
- STRECKEISEN, A. (1976) To each plutonic rocks its proper name. Earth Sci. Rev., v.12(1), pp.1-33.
- SUN, S.-S and MCDONOUGH, W.F. (1989) Chemical and isotopic systematics of oceanic basalts: implication for mantle composition and processes. In: A.D. Saunders and M.J. Norry (Eds.), Magmatism in the ocean basins. Blackwell Sci. Publ., v.42, pp.313- 345.