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

Mohd Ismail Bhat ¹, Syed M. Zainuddin ¹

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

Abstract

Chemical analysis of 62 rock samples representing 24 flows of the Panjal Traps on Mount Kayol in Lidder Valley area do not show any systematic variation of the various oxides from the base to the top. The plots on MgO-Al/Si diagram of Murata, and Fe₂O₃/FeO ratio indicate that the rocks are of tholeiitic lineage. However, the points fall within the fields of alkali-olivine basalt and high-alumina basalt on the alkali-silica diagram of Kuno. This is interpreted to be due to alkali metasomatism. The addition of alkali is probably responsible for the shift of the points to the alkali-olivine basalt field on the alkali-silica diagram.

The Solidification Index (MgO × 100/MgO+Fe₂O₃+FeO+Na₂O+K₂O) lies within the range of basalt and basaltic andesite of 'pigeonite rock series'.

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Abdul Rahman ¹, Syed M. Zainuddin ¹

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

Abstract

The granite is fine-to coarse-grained and constitutes mainly of quartz; K-feldspar and plagioclase. Among accessories, muscovite, biotite, chlorite, zircon, apatite and sphene are common. K-feldspar is generally microcline with perthitic intergrowth. The albite grains have similar optical orientation as that of the microcline; they are inferred to have formed by the ionic exchange of K by Na. The rock ranges in composition from granodiorite to granite. Variation trends of the plots of major and trace elements on Harker's diagram indicate that the granite is not formed by a simple fractional crystallization or partial melting of common homogeneous source. Plots on Rb, Ba and Sr ternary diagram reveal that it is a least differentiated normal granite type. Molar concentration of Al/(Na+K+Ca) > 1.1 and Rb/Sr ratio of 0.53 indicate a peraluminous source of the granitic magma. High silica content, and the mineral assemblages of the granite correspond to S-type granite.

Keywords

Ahar Granite, Geochemistry, Petrography (Igneous), Rajasthan.

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M. E. A. Mondal ¹, Syed M. Zainuddin ¹

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

Abstract

The Bundelkhand massif comprises various types of granites. On the basis of field relations, three compositionally distinct granitic phases have been delineated. These are hornblende granite, biotite granite and leuco granite in stratigraphic sequence. The major elements variations against SiO₂, display smooth trends which should be expected for a composite massif evolved by fractionai crystallization. The variations of incompatible elements compared to the compatible elements suggest a partial melting process for the evolution of the massif.

Keywords

Petrogenesis, Geochemistry, Bundelkhand, Granites, Central India.

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Shamim Alam ¹, Syed M. Zainuddin ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh 202001, IN

Abstract

Three genetically different types of granites: coarse-grained biotite granite, spotted granite and fine grained granite are recognised. The presence of xenoliths and a significantly high proportion of C-twins, and the presence of oscillatory and normal zoning in plagioclase crystals suggest a magmatic origin. The plots of the three rock types on quartz-albite-orthoclase ternary diagram and the high proportion of albite in K-feldspar indicate a high temperature of crystallization.

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