Informatics Publishing Limited

Brindaban Das ¹, D. K. Paul ¹, A. K. Chaudhary ², Arijit Ray ¹, S. K. Patil ³, S. K. Biswas ⁴

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

Abstract

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 D_m = 338°, I_m=-47° and reverse polarity direction at D_m=14l° and I_m=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.

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