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

N. W. Gokhale ¹, V. C. Chavadi ¹

Affiliations
1 Department of Geology, Karnatak University, Dharwar, IN

Abstract

The paper deals with the plagiodases occurring in the gabbro pluton of Vajrat. 133 twinned plagioclase grains from 26 rock samples of these gabbros are studied on the 4-axes universal stage. The anorthite content and the twin laws of these plagiodases have been determined on the lines of Reinhard. Areal variation map is prepared for the anorthite content of the plagioclases, on the lines of Dawson and Whitten. Petrographic studies of the gabbros indicate that the gabbros of the more central parts of the pluton are distinctly fine grained ru. compared to the grain size of those forming the peripheral portion. The areal variation pattern of the anorthite content together with the petrographic characters of the gabbros suggest more than one period of igneous activity in the formation of the Vajrat gabbro pluton.

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N. W. Gokhale ¹, N. N. Gothe ¹, V. B. Koppad ¹

Affiliations
1 Department of Geology, Karnatak University, Dharwar, IN

Abstract

The Bagewadi and the Bannikoppa conglomerates occupy a significant position in the Gadag belt. A detailed investigation of these conglomerates has revealed many important features regarding their origin and structure. The earlier workers reported the occurrence of a band of greywacke to the east of Bagewadi conglomerate. The present investigation bas shown that this is a micro-breccia and not a greywacke, and was formed due to the intensive brecciation of the eastern portion of the Bagewadi conglomerate. This brecciation was caused by a thrust fault. The Bannikoppa conglomerate constitutes the 'Klippe' structure.

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N. W. Gokhale ¹, S. C. Puranik ¹

Affiliations
1 Department of Geology, Karnatak University, Dharwar 580003, IN

Abstract

Presence of pyrite inappreciable quantity from the northwestern part of the Gadag Schist belt is described. On an average the volume percentage of pyrite in the rock is 41. Spectroscopic analysis of pyrite confirms presence of copper.

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N. W. Gokhale ¹, N. N. Gothe ¹

Affiliations
1 Department of Geology, Karnatak University, Dharwar, IN

Abstract

Applying geostatistical methods, it is shown that chemical composition canbe used in distinguishing ortho amphibolites from the para variety. This distinction is due to major oxides SiO₂, Fe₂O₃ and FeO.

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N. W. Gokhale ¹, B. P. Waghamare ¹

Affiliations
1 Department of Studies in Geology, Karnataka University, Dharwad 580003, IN

Abstract

About 200 basic dykes traverse the northern part of the Gadag Schist Belt. Out of these, three dykes show distinct cross cutting relations with each other. K-Ar geochronological studies indicate ages of 1535±61 m.y. for the oldest dyke, 1082±54 m.y. for the intermediate dyke, and l018±50 m.y. for the youngest dyke.

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