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A. Ramaswamy ¹, M. S. Murty ¹

Affiliations
1 Department of Geology, S. V. University, Tirupati, IN

Abstract

A detailed description of myrmekite is furnished and its origin discussed in the light of the existing theories. Myrmekite is believed to be formed by exsolution, deriving both the components - quartz and plagioclase, which are held in solid solution in the form of albite and CaAl₂, Si₆O₁₆ in po:ash felspar. Myrmekite in norite is presumed to be formed due to the breakdown of anorthite molecule of the plagioclase releasing the required silica, thus making the plagioclase less basic than its parent. The granulite facies (charnockite environmental) conditions seem to be ideal for the formation of myrmekite by exsolution process.

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A. Sriramadas ¹, M. S. Murty ¹

Affiliations
1 Department of Geology, Andhra University, Waltair, IN

Abstract

An area of about four hundred and eighty square kilometres in Visakhapatnam, consisting of khondalites, charnockites and granites, was geologically mapped. The trend of the formations varies from NE-SW through E-W to NW-SE. This trend neither conforms with NE-SW trend of the Eastern Ghats nor with the NW-SE trend of the hinterland of the Eastern Ghats between the Godavari and Mahanadi rivers. The change in the trend pattern is inferred to be due to the area being located in an intensely folded and faulted region in the eastern margin of the Eastern Ghats.

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M. S. Murty ¹

Affiliations
1 Department of Geology, S. V. University, Tirupati, Andhra Pradesh, IN

Abstract

The present paper reports the occurrence of sodalite-cancrinite-fiuorite syenite from Podili. This felspathoidal syenite is inferred to be formed by the crystallisation of alkaline felsic magma, derived by the partial melting of deep-crustal rocks, enriched in volatiles.

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