Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

S. C. Khosla ¹, P. C. Pant ¹

Affiliations
1 University of Rajasthan, Department of Geology, Udaipur 313001, IN

Abstract

The paper records the occurrence of 76 species of ostracodes from the Lower Miocene beds of Saurashtra. 41 species have been assigned to the previously established species from India and elsewhere. 35 species are hitherto not described and many of these are probably new.

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P. C. Pant ¹, S. C. Khosla ²

Affiliations
1 Wadia Institute of Himalayan Geology, 159, Vasant Vihar, Dehradun, IN
2 Department of Geology, University of Rajasthan, Udaipur, IN

Abstract

Fifty-seven species of ostracodes are recorded from the Eocene beds of Kutch, Gujarat. Forty-six species have been assigned to the previously established species from the Indian subcontinent. Eleven species are left under open nomenclature and are possibly new.

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M. K. Khandelwal ¹, P. B. Maithani ², P. C. Pant ², P. K. Hansda ², S. Ramachandran ²

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy Jaipur - 302 004, IN
2 Atomic Minerals Division, Department of Atomic Energy Vadodara - 390 001, IN

Abstract

In the region covering some 400 km² immediately to the north of Narmada lineament between Dharmrai, Dhar district, Madhya Pradesh, in the east and Nakhal and Panwad, Vadodara district, Gujarat, in the west, numerous E-W to ENE-WSW trending linear fault zones (c.l km to 5 km long X 20 m to over 100 m wide) occur within the Deccan basalts and infratrappean rocks. Brownish, brecciated, calcareous rocks, often with pockets and veins of calcite (carbonatites ?) are found within such fracture zones, and many of them show intrusive-like features. These faults apparently have developed sympathetic to the major Narmada rift to the south which provided structural avenues for the emplacement of carbonatites and associated basic alkaline rocks as found at Ambadongar. Panwad, Kawant and Saidiwasan, as part of the Deccan volcanic episode. Comparison of major and selected trace element data on these carbonatitic (?) rocks with Woolley and Kempe's average trace elements in carbonatite indicates that they are significantly impoverised in Zr, Nb, Y, La and U compared to the carbonatites and phonolites and phonolitic nephelinites of Panwad, Saidiwasan and Nakhal which are enriched in these elements. Carbonate-rich rocks of Bakhatgarh and Katarkheda in the east are rich in CaO and P²O³ compared to those of Panwad and Kawant. Based on available data it is suggested that the carbonatitic (?) types found in the east may represent an early phase of carbonatite (?) impoverished in Zr, Nb, Y, La, U and Th compared to the late residual (?) phase found in the Panwad-Saidiwasan-Nakal area which records significant radioactivity (upto 0.04% eUPR) and higher abundances of Zr (0.06%) and Nb (upto 0.1 %).

Keywords

Petrology, Geochemistry, Carbonatite, Lower Narmada Valley, Madhya Pradesh, Gujarat.

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P. C. Pant ¹, K. Chakrabarti ¹, Neeru Rawal ², P. K. Hansda ²

Affiliations
1 Eastern Region, AMD Complex, Khasmahal, Jamshedpur - 831 002, IN
2 Northern Region, West Block VIT, R.K.Puram, New Delhi - 110 066, IN

Abstract

The Cretaceous infratrappean sedimentary rocks in Temriya area, Dhar district, Madhya Pradesh are intruded by Deccan Trap dykes and sills. Petrochemistry reveals that the dyke rocks are basaltic in composition, have tholciitic affinity (01 and/or Qz normative), continental-within plate characters showing moderate iron-enrichment with Mg. No. ranging from 0.28 to 0.42. The dyke shows variable major and trace element concentration and ratios; TiO₂:2.05-2.91%, K₂O: 0.71-0.95%, Ba: 183-346ppm, Nb: <5-19ppm, Sr: 195-285ppm, Zr : 39- 124ppn1, Y 20-32ppm and Rb: 28-38ppm with MgO varying from 3.01 to 5.68% indicating that the magma was subsequently contaminated by selective addition processes from the crust. The rocks show a moderate range in REE abundances and LaIYb ratios with a conspicuous LREE enrichment and HREE depletion. The dyke is genetically related to the Deccan Trap volcanism and was derived from a single source emplaced along tensional fractures probably due to the reactivation of basement lineaments.

Keywords

Petrography, Geochemistry, Basaltic Dyke, Infratrappeans, Temriya, Madhya Pradesh.

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Navin Goyal ¹, P. C. Pant ², P. K. Hansda ³, B. K. Pandey ⁴

Affiliations
1 Atomic Minerals Directorate For Exploration and Research, Jamshedpur-831 002, IN
2 Atomic Minerals Directorate For Exploration and Research, Jamshedpur-831 002
3 Atomic Minerals Directorate For Exploration and Research, New-Delhi-110 066, IN
4 Atomic Minerals Directorate For Exploration and Research, Hyderabad-500 016, IN

Abstract

The Precambrian Godhra Granite occurring in parts of central Gujarat, intrudes the metasediments of Lunavada and Champaner Groups. RbSr isochron based on 14 whole rock samples of the Godhra Granite gives an age of 965±40 Ma, with an initial ⁸⁷Sr/⁸⁷Sr ratio of 0.7109±0.0015. Geochemical data indicate its origin by partial melting of crustal rocks in post-orogenic environment.

Keywords

Godhra Granite, Peraluminous Granite, Rb-Sr Isochron, Crustal Source, Gujarat.

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