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

Y. Janardan Rao ¹, Ch. Sudarsana Raju ¹

Affiliations
1 Geology Department, Osmania University, Hyderabad, IN

Abstract

East of Khammam town in Andhra Pradesh, the Precambrian rocks are classified into three distinct lithological groups as (a) Peninsular Granites (b) Pakhals and (c) Gncissic Complex. Detailed structural studies on foliation, lineation, joints, folds, trends of dykes, basic enclaves, pegmatite and quartz veins of these groups show that the Peninsular Granite area with its NNW trend is structurally quite distinct from the remaining area which shows NW as well as NE trends. Mineralogical variation diagrams drawn for acid granulites, as a part of the quantitative petrological studies, show that the emplacement of these granulites has been structurally controlled by NE trend. Petrological studies in the Gneissic Complex show increasing grade of metamorphism roughly from northwest to southeast. It is concluded that the area in general is affected by two phases of disturbance, one, Dharwarian and another, late' Eastern Ghat' orogeny. It is also suggested that the demarcation line between 'charnockitic region' and 'non-charnockitic region' of Fermor should pass through the contact between Peninsular Granites and Pakhals.

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Y. Janardan Rao ¹, K. Satyanarayana ¹

Affiliations
1 Department of Geology, Osmania University, Hyderabad, IN

Abstract

Sedimentological studies of the Pakhal sediments in the Pakhallake area have been made with a view to understand the environmental conditions of deposition of these rocks which belong to the Precambrian age. Textural properties like grain size, roundness and sphericity have been determined from thin section studies of clastic rocks like quartzose sandstones and orthoquartzites.

The statistical parameters calculated from the formulae suggested by Folk and Ward and their possible geological significance have been discussed. From the basic C. M. patterns of Passega, it has been found that the clastic sediments were deposited in a beach environment acted upon by tractive currents. The Pakhal sediments in this region had their provenance from the granitic rocks and the quartz-magnetite rocks which lie to the west of the Pakhal basin, and were deposited on the beaches and were shifted to the neritic zone of environment.

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Y. Janardan Rao ¹, I. S. N. Murthy ¹

Affiliations
1 Department of Geology, Osmania University, Hyderabad, IN

Abstract

No Abstract.

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Y. Janardan Rao ¹, K. Satyanarayana ¹

Affiliations
1 Geology Department, Osmania University, Hyderabad 7, IN

Abstract

Homblendes and their host rock amphibolites from amphibolite facies and hornblende-granulite sub-facies were analysed for major elements. The hornblendes show small changes in chemistry which are related to host rock compositional changes rather than the pressure and temperatures condition of formation.

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