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

M. W. Y. Khan ¹, T. K. Bhattacharyya ¹

Affiliations
1 School of Studies in Geology, Pt. Ravishankar Shukla University, Raipur - 492 010, IN

Abstract

The fine grained, massive metabasalts of Bacheli-Kirandul areas, Bastar district, M.P., characterized by a greenschist facies mineral assemblage have been studied for their major, trace and REE geochemical distribution pattern. On Jensen's AFM Plot and diagrams of relatively immobile elements; these metabasalts fall in the tholeiitic basalts to basaltic andesite field.

Large scatter in Na₂O/K₂O, K/Rb and RblSr ratios suggest to alteration effects, while high MgO content ascribes to the oxidative diagenesis. Relatively immobile and HFSE element discriminant diagrams point to an island arc/convergent plate setting. The depletion in Nb and Ta relative to Th and LREE in these samples may be relict from a previous tectonic event.

Inferences drawn from geochemical tectonic discriminant diagrams have been evaluated in the light of additional geological data, and an ensialic rift setting for these volcanics is envisaged.

Keywords

Geochemistry, Tectonics, Metabasalts, Bastar District, Madhya Pradesh.

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M. W. Y. Khan ¹, T. K. Bhattacharyya ¹

Affiliations
1 School of Studies in Geology, Pt. Ravishankar Shukla University, Raipur - 492 010, IN

Abstract

The metasedimentary sequence of Bailadila Group exposed in Bacheli area, south Bastar is studied in detail. Based on field relations, structural disposition, conglomerate ocurrence and petrographic characters, Bailadila Group is divided into three Subgroups, which in turn comprise five formations. Formal stratigraphic formationidentified are namely, Bhansi metabasalt-metapelite, Bacheti metasiliclastic, East Ridge Shale, Loa Conglomerate and shale Kailash Nagar Iron Formation. Based on the Stratigraphic continuity, the metabasalt-metapelite association (Bengpal) underlying the feldapathic quartzite (Bacheli metasiliciclastic-Bailadila) is proposed to be included as basal formation of Balladila Group.

Further, high L_aN/Y_bN(10.41-15.89(ratio and Eu/Eu* (0.56-0.64) negative anamolies suggest a sialic continental crust.

It is also proposed that metavolcania-clastic association at chandenar and Tulsi Dongar being similar in lithoassociation to the proposed Bhansi Formation should also be considered of Bailadila Group.

Keywords

Stratigraphy, Bailadila Group, Bacheli, Baster District, Madhya Pradesh.

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M. W. Y. Khan ¹, A. Mukherjee ¹

Affiliations
1 School of Studies in Geology, Ravishankar University, Raipur 492010 (M.P.), IN

Abstract

This paper documents the geochemical and mineralogical characters of the phosphorite of Charmuria Formation (Chhattisgarh Basin). X-ray diffraction studies have revealed presence of carbonate fluorapatite as the only apatite mineral in this phosphorite, along with quartz as major gangue, and kaolinite-illite, calcite and pyrite in subordinate amounts. Structural formula of this apatite closely resembles carbonate fluorapatite. Further, CaO/P₂O₅ ratio (1.37 - 1.99) suggests that this phosphorite has not been affected by weathering. Quartz dominance over clay minerals and low CIA (24.79 - 46.87) is attributed to the tuffaceous nature of siliceous clays (lithofacies-A). The depletion of Sr, and trace elements of organic association in siliceous clays, phosphorite and phosphatic siliceous clays point to a common provenance.

Keywords

Geochemistry, Phosphorite, Carbonate Fluorapatite, Chhattisgarh Basin.

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P. C. Mishra ¹, B. Mishra ², M. W. Y. Khan ³

Affiliations
1 South Zone, Berhampur - 760 010, IN
2 PG Dept of Geology, Khallikote Autonomous College, Berhampur - 760 001, IN
3 School of Studies in Geology and Water Resources, Pt R S University, Raipur - 492 010, IN

Abstract

Marine marginal zones are most susceptible to geomorphic modifications. Study of sequential datasets enables clear understanding of the changes that an area has undergone. Systematic study of the datasets of Bahuda estuary region revealed that the mouth of the river is oscillating during the past seven decades. The morphology of the estuary is also modified due to combined action of fluvial, fluviomarine, marine and aeohan action. The tidal influence together with the fluvial regime is responsible for modification of the coastal landforms and tidal swamps located inland. The channel bars and mouth bars are under constant influence of the physical processes and are adjusting to the dominant processes, which control their existence and geometry. The Bahuda estuary region can be considered as one of the most attractive sites along the coast of Orissa due to panoramic view and unique geomorphological set up in the context of tourist potential.

Keywords

Marine Marginal Zone, Bahuda Estuary, Spit, Tidal Energy, Ambaghai Nadi, Tidal Swamp, Ganju Tampara, Fluviomarine Processes, Morphological Changes, Orissa.

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D. V. Subba Rao ¹, M. W. Y. Khan ², D. N. Sridhar ¹, K. Naga Raju ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad - 560007, IN
2 Pt. Ravishankar Shukla University, Raipur (C. G)., IN

Abstract

Younger and fine-Grained unmetamorphosed dolerite dykes intrude the Raipur Group sediments in the central part of the Meso-Neoproterozoic Chhattisgarh Basin in Central India. Petrologically these dykes consist of unaltered microphenocrysts of intermediate pigeonite (X_Mg=0.40), augite (X_Mg=0.595), calcic plagioclase (X_ca=O.64), titanomagnetite and ilmenite. These rocks show high Fe₂O₃^T (14.43 to 15.19%), TiO₂ (2.75 to 2.87%) and P₂O₅(0.27 to 0.29%) contents with an unusual Continental Flood Basalt (CFB) affinity. Significantly these dykes show lower K₂O content (0.43%). The trace element abundance such as Ba, Sr, Rb, Zr, Nb and trace element ratios Sm/Nd, Ba/Nb, Zr/Nb, Y/Nb, Th/Yb, Ta/Yb and K/Ba in these rocks chemically resemble the least contaminated Deccan Basalts. Chondrite/OIB normalized REE patterns of these rocks also show striking similarities with the Deccan tholeiitic basaltic flows. The available petrological, mineralogical, major, trace and rare earth element data indicate that these within basin basaltic dykes of Raipur are intraplate basalts, which were derived from an enriched mantle source.

Keywords

Basaltic Dykes, Chhattisgarh Basin, Geochemistry, Continental Flood Basalts.

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D. Subba Rao ¹, A. Mukherjee ², M. W. Y. Khan ³, D. N. Sridhar ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
2 central Ground Water Board, Raipur (CG), IN
3 Pandit Ravi Shankar Shukla University, Raipur (CG), IN

Abstract

A new occurrence of Within-Basin pyroclastic flow rocks (welded felsic tuffs and ignimbrites) is reported for the first time from Sukda area in the NE part of the Chhattisgarh basin. The flows are characterized by the presence of microporphyritic textures, feldspars, quartz, glass shards, volcanic rock fragments and magmatic garnet. High concentrations of Na₂O (-6.61 wt%), low K₂O (0.01 to 1.0 wt%) and high Sr contents (416 ppm) are found in these rocks. REE show a Well-Fractionated trend with high LREE enrichment, sloping HREE patterns and absence of Eu anomalies. Major, trace and REE geochemistry of the Chhattisgarh welded tuffs indicate that they are Na- Rhyolites. The characteristic high Sr/Y and La/Yb_N, ratios and low HREE contents suggest that the parental magmas of these rocks were produced by extensive partial melting of a mafic source in deeper crustal levels (lower crust) where garnet and or hornblende are residual phases.

Keywords

Felsic Tuffs, Na-Rhyolites, Ignimbrites, Chhattisgarh Basin, Chhattisgarh State.

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