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M. Raza ¹, S. H. Jafri ², S. H. Alvi ¹, M. Shamim Khan ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh-202002, IN
2 National Geophysical Research Institute, Uppal Road, Hyderabad - 500007, IN

Abstract

Geochemical data on Proterozoic volcanic rocks of Indian shield overwhelmingly suggest that tlhey were generated in two different tectonic settings. The mafic volcanic suites of Aravalli (Aravalli craton) and Bijawar (Rundelkhand craton) belts and those of lesser Himalayan region appear to be lift related continentat type. On the other hand Delhi volcanics (Aravalli craton), Dongargarh volcanics (Bhandara craton) and Dbanjori-Jagannathpur volcanics (Singhbhum craton) exliibit the characteristic signature of subduction zone magmatism implying the destruction of oceanic lithosphere by processes akin to those of modern plate tectonics. Geochemical and geological evidences suggest the occurrence of a nearly Proterozoic ocean in Central India located between Dharwar-Singbhum-Malwar rotocontinent in the south and Bundelkhand protocontinent in the north. During middle Proterozoic, the oceanic lithosphere subducted towards south along the northern margin of southern protocontinent. The lack of complete calc-alkaline series in the subduction - generated volcanic suites suggests that are volcanism along this margin could not acquire maturity and that the period of subduction was short lived. The collision of the two protocontinents led to the closure of ocean and induced the Satpura - Delhi orogeny at about 1500 m.y. ago-The ophiolitic seqeunce of Phulad (Delhi belt), Dalma (Singhbhum belt) and probably Tal (Bijawar belt) are the possible evidences of closure.

Keywords

Geodynamics, Indian Shield, Proterozoic Volcanism, Crustal Evolulion.

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A. H. M. Ahmad ¹, G. M. Bhat ², M. Shamim Khan ¹, S. Hilal Farooq ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh - 202 002, IN
2 PG Department of Geology, University of Jammu, Jammu, IN

Abstract

The paper embodies results of petrofacies, detrital mineralogy, texture and diagenetic aspects of glauconitic sandstones of Kheinjua Formation of Vindhyan Basin, Son valley These glauconitic sandstones consisting of various types of quartz, feldspar, rock fragments, mica and a sulte of heavy minerals, are medium to very fine grained, and well to moderately well sorted These sediments including glauconite grams are generally subangular to subroundcd with a few grams bang well rounded These sandstones are well compacted and dominated by interpenetrative contacts and are maniy cemented by iron cement with small amount of glauconite and silica cement The existing optical poroslly has developed due to dissolution of Iron cement, feldspar and rock fragments These observations suggest progressive compaction, which initiated at the sediment-water interface and continued till deep bunal diagenesis in a rapidly subsiding basin

The plots of petrofacies in Qt-F-L, Qm-F-Lt, Qp-Lvm-Lsm and Qm-P-K ternary diagrams suggest mainly basement uplift source (craton interior) In a rifted continental margin basin setting, which has also received sediment Input from recycled orogen provenance The plot of various quartz types on diamond diagrarn after Basu et a1 (1975) reflects derivation of the sediments from the plutonic and middle to high-rank metamorphic terrains Besides, Lower part of the Semri Group, the most probable provenance of these sandstones IS Bijawar metasedimentary and Bundelkhand Gneissic complexes, which bordered the basin in the north and northeast.

Keywords

Sandstones, Petrofacies, Provenance, Tectonic setting, Vindhyan, Son valley, Central India.

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Kamal Kant Sharma ¹, M. Shamim Khan ², M. Raza ², M. Safdar-E-Azam ², G. Vallinayagam ³, M. Shamim Khan ², M. Raza ², M. Safdar-E-Azam ²

Affiliations
1 Government College, Sirohi- 307 00 1 (Rajasthan), IN
2 Dept. of Geology, Aligarh Muslim University, Aligarh - 202 003, IN
3 Department of Earth Sciences, Kurukshetra University, Kurukshetra - 136 1 19, IN

Abstract

No Abstract.

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M. Shamim Khan ¹, M. Raza ¹, M. Safdar-E-Azam ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh 202 002, IN

Abstract

Neoproterozoic Bombolai volcanics of Trans - Aravalli terrain of western Rajasthan, consist of three distinct flows separated by metasediments including bedded chert, phyllite and quartzite In terms of their major oxides and trace and rare earth element abundances, all these flows are compositionall identical and evolved (Mg No 0 397-0 474, Ni - 61-92 ppm and Cr - 172-234 ppm) Major and trace element contents permi one to classify them as subalkaine basalts having enriched LREE abundances However, MORB and PM- nomalised spidergrams characterize them as within plate tholeites On the basis of their TiO₂, content (1 84-2 43), Ti/Y ratio (294-347) and Zr/Y ratio (2 9-3 7), the Bombolai volcanics are classified as low Ti-continental tholentes The general geology geochemistry and associated lithologies indicate that the Bombolai volcanics were erupted in a reactivated nit environment (Pali lineament) which probably occurred as a precursor event to a large magmatic activity ie Malani volcanism in Trans-Aravalli region.

Keywords

Geochemistry, Continental Flood Basalts, Neoproterozoic, Tans-Aravallis, Pali District Rajasthan.

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M. Raza ¹, M. Safdar-E-Azam ¹, M. Shamim Khan ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh -202002, IN

Abstract

Mesoproterozoic volcanism in Bayana basin in the northeastern part of Aravalli-Delhi fold belt consists of mafic lava flows with quartzite-conglomerate intercalations. The volcanics are tholeiites, characterized by enrichment of large ion lithophile elements (LILE) and light rare earth elements (LREE) and depletion of Nb, P and Sr. The values of TiO₂ (1.06 to 2.31 %), Zr (50 to 182 ppm), Ti/Y (286 to 521), and Zr/Y (2.63 to 5.70) are low, which illustrate their close similarity with low-Ti continental flood basalts. The Bayana volcanics may have been derived from an enriched mantle source with no significant crustal contamination. The parental magma appears to have been derived from a subcontinental lithospheric mantle source with Fe/Mg ratio exceeding that of model pyrolite. It is suggested that the mantle source of these volcanics was enriched through metasomatism by progressive transport of mantle fluids and/or melts from deeper mantle. Olivine and clinopyroxene dominated the fractional crystallization and played a major role in the evolution of magma, following its derivation from shallow mantle source(s) where clinopyroxene occurred as a residual phase.

Keywords

Geochemistry, Mafic Volcanism, Bayana Basin, Delhi Fold Belt, Proterozoic, Rajasthan.

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