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

P. K. Ramam ¹

Affiliations
1 Geological Survey of India, Hyderabad, IN

Abstract

Bauxite forms cappings at altitudes varying from 1090 to 1445 m above mean sea level, over the garnet-sillimanite gneisses near Anantagiri in Visakhapatnam district, Andhra Pradesh. Major cappings occur on Galikonda, Raktakonda, Katuki and Chittamgondi hills while those near Kottavalasa are relatively small. Bauxite is either light to dark brown or pink in colour and moderately hard with crystalline gibbsite occuring in varying proportions. The average thickness of bauxite in the various cappings may range between 3 and 15 m, while the maximum thickness encountered is about 50 m on Galikonda. A typical profile of the bauxite residuum in the area consists of a lateritic bauxite underlain by partially lateritised khondalitic gneiss or lithomarge followed by kaolinised and unaltered khondalitic gneiss. These bauxites are low in silica and titania and relatively high in iron oxide when compared to those derived from the Deccan basalts. The development of bauxite over the sillimanite rich gneisses, relict foliation, pseudomorphs of gibbsite after sillimanite, garnet and felspar, and the unaltered partings of the bed rock within the bauxite residuum, reveal that these bauxites' are formed from tbe in situ transformation of the subjacent garnet-sillimanite gneiss (khondalite). While the lithology and physical properties of these gneisses are congenial for lateritisation/bauxitisation on a regional scale, the preservation of some of the cappings with remarkable thickness may be attributed to a favourable structural setting. It is surmised that these bauxites are of post Mio-Pliocene age.

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P. K. Ramam ¹, T. V. Viswanathan ¹

Affiliations
1 Geological Survey of India, Southern Region, Hyderabad, IN

Abstract

The carbonate rocks near Borra, hitherto considered as crystalline limestones forming part of the khondalite group of metasediments of the Eastern Ghats mobile belt, have been identified as carbonatites. Genetically associated rocks include pyroxenite and syenite, characteristic of alkalic carbonatite complexes. Phlogopitization, local domingup and other features characterstic of forceful intrusion of carbonatites have been noticed. Characteristic rare-earths include Ce and La. The rare earth mineral identified is bastnaesite. The typical zirconium mineral is badleyite. Relative rarity of magnetite and pyrochlore makes the complex' atypical'. The Borra carbonatite is the oldest known occurrence in the country; the K-Ar dating of the phlogopite has given an age of 1490± 50 million years. It is surmised that the apatite-magnetite veins associated with a possible carbonatite at Kasipatnam and the Borra carbonatite are localised along a deep seated NW-SE fault system in the Eastern Ghats mobile belt.

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P. K. Ramam ¹

Affiliations
1 33/4 RT, Barkatpura, Hyderabad 500027, IN

Abstract

The bauxite deposits occurring amidst the Eastern Ghats overlie either the Khondalite or Charnockite group of rocks. Their frequency, however, is more on the khondalitic rocks. Gibbsite constitutes the main aluminous mineral in both the cases. Goethite is ubiquitous in the residuum derived from charnockitic rocks while hematite occurs in larger proportions in the others. Salient contrasts in the residuum derived from either of the two major rock types of the Eastern Ghats are described and their possible implications surmised.

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P. K. Ramam ¹, P. Prakash ², P. F. Augustine ²

Affiliations
1 33/4 RT, Barkatpura, Hyderabad 500027, IN
2 Hyderabad 500027, IN

Abstract

Vestiges of khondalite (garnet-sillimanite gneiss) occur sporadically in some bauxite profiles of Visakhapatnam district, Andhra Pradesh. Based on their mode of occurrence, the vestiges may be classified into (i) outcrop island, and (ii) sub-crop intercalation types. Neither of them has lateral nor downward persistence. Their occurrence within the residuum is by no means anomalous; instead, they are in conformity with the natural laws governing the processes of residual chemical weathering (RCW). Either the litho-textural and structural fabric of the vestige itself is resistant to RCW or the vestige may be circumscribed by a zone of impeded drainage that prevents thorough leaching locally. These vestiges are comparable to the kaolinised nepheline syenite pockets, within the bauxite residuum, of the well known Arkansas deposits in U.S.A., and the boulders of parent basic rock in the bauxite deposits of Sarawak.

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P. K. Ramam ¹, G. V. Ananta Iyer ², T. R. Narayanan Kutty ², M. V. N. Murthy ³

Affiliations
1 33/4 RT, Barkatpura, Hyderabad-500027, IN
2 Dept. of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore - 560012, IN
3 A/3, Himanshu Bhawan, Sawai Jai Singh Highway, Jaipur-302006, IN

Abstract

The field observation that chrysotile asbestos near Pulivendla is localised along stylolites in the Proterozoic carbonate sediments of the Vempalli Formation (Cuddapah Supergroup) proved crucial and paved the way for a re-thinking on the origin of Pulivendla asbestos. The length of the fibre, nowhere, transgresses the amplitude of the stylolite. Further, the lateral termination of the chrysotile seams invariably coincides with that of the enclosing stylolite. The stylolite development and fibre growth appear to be a sequel to directional pressure. X-ray and infra-red studies of the massive serpentinous zones revealed dioctahedral dewelyite to be the main serpentine mineral. It is suggested that the chemical pre-requisites (e.g. magnesia, silica and hydroxyl molecules) necessary for serpentinisation and pari passu chrysotilisation, were present in the carbonate sediment itself at the loci of stylolitisation and that the intrusive dolerite merely provided the desired thermal energy. The emplacement took place, possibly, when the carbonate sediment was in a semi-consolidated stage. Stylolitisation and chrysotilisation appear to have ceased with the complete consolidation of the enclosing sediment.

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P. K. Ramam

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P. K. Ramam ¹

Affiliations
1 Hyderabad, IN

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P. K. Ramam ¹

Affiliations
1 Hyderabad, IN

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P. K. Ramam ¹

Affiliations
1 Hyderabad, IN

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P. K. Ramam ¹

Affiliations
1 Hyderabad, IN

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P. K. Ramam ¹

Affiliations
1 H.I.G. Block-3, Flat-10, Bagh Lingampalli, Hyderabad 500044, IN

Abstract

The formation of lateritic bauxite deposits is, by and large, governed by the cumulative effect of several controls. Salient amongst them are: (i) favourable source rock, (ii) effective porosity, (iii) high rainfall, (iv) good drainage, (v) tropical climate, (vi) low to moderate topographic relief, (vi i) prolonged stability, and (viii) presence of vegetation. Despite a general consensus on these causative factors to promote bauxitisation, the decisive controls, still remain to be discerned. A synthesis attempted from this angle in respect of the East Coast Bauxite (EeB) deposits of India has brought to focus the effective permeability of the source rock and a congenial geomorphic base, preferably unidirectional, of low to moderate slope angles (3° to 15°) as the decisive controls in their formation. These, in turn, are dependent on the structural history of the terrain.

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P. K. Ramam

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P. K. Ramam ¹

Affiliations
1 Hyderabad, IN

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P. K. Ramam ¹

Affiliations
1 Hyderabad, IN

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P. K. Ramam ¹

Affiliations
1 Hyderabad, IN

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No Abstract.

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P. K. Ramam ¹

Affiliations
1 Hyderabad, IN

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P. K. Ramam ¹

Affiliations
1 Hyderabad, IN

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P. K. Ramam ¹

Affiliations
1 Flat 10. HIG Block 3, Bagt Lingampalle Hyderabad - 500 044, IN

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P. K. Ramam ¹

Affiliations
1 Hyderabad, IN

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P. k. Ramam ¹, Dev Dutt Sharma ²

Affiliations
1 #202, Plot No.22, H.No.8-3-1022 (Naimisam), Srinagar Colony, Hyderabad - 500 073, Andhra Pradesh, IN
2 Essar Oil Limited, E&P Division, Essar House, Mahalaxmi, Mumbai - 400 034, IN

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P. K. Ramam ¹, K. S. Rao

Affiliations
1 Plot-22, Flat #202, Naimisain Srinagar Colony P. O. Hyderabad - 500 073, IN

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No Abstract.

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P. K. Ramam ¹

Affiliations
1 Director, Impact Environs (P) Ltd., HIG Block-3, Flat-10,Bagh, Lingampalli, Hyderabad - 500044, IN

Abstract

The East Coast Bauxite (ECB) Province of India, extending into the neighbouring States of Andhra Pradesh and Orissa, has contributed to a substantial rise in the total bauxite resource of the Indian sub-continent. Bauxite is gibbsitic and in situ. Thickness of the bauxite profiles varies from 3 to 54 m and bauxite is confined to select geomorphic expressions viz., sloping, landforms, and are amenable to open cast mechanised mining.

There are chances of accelerated recharge of the groundwater table, through coursed run-off, of the meteoric precipitation in the mining areas. In fact, tiny reservoirs of surface water can be created in the mined out areas. There is no possibility of toxicity due to Al as it is insoluble. Other toxic elements like Cr, Mn, V etc. are in negligible amounts to impart toxicity to the water regime. Human settlements in the area are sparsely populated and widely scattered. It is logical to expect employment opportunities to some of the inhabitants. Infrastructural facilities created to facilitate mining and movement of are, would contribute to improved socia-economic conditions and a rise in the per capita income.

Extensive green belt development and other mitigative measures, being practiced as a part of Environmental Management at Panchpatmali bauxite mine in Orissa is a case study to demonstrate that it is possible to maintain the eco-system of the terrain even during the mining phase. The bauxite deposits in Andhra Pradesh can be mined without causing any adverse impact on the prevailing environment.

Keywords

Environment, Bauxite, Open Cast Mining, Andhra Pradesh.

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P. K. Ramam ¹

Affiliations
1 Hyderabad, IN

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P. K. Ramam ¹

Affiliations
1 Geological Survey of India, 5.5.449, Mukharamjahi Road, Hyderabad 500001, IN

Abstract

The East Coast Bauxite deposits top either the Khondalite or Charnockite Group of Archaean rocks that constitute the bulk of the Eastern Ghat physiographic province. Subsequent to the Eastern Ghat orogeny (1400-1600 m.y.), faulting in Mesozoic was the major tectonic event recorded in the Indian Peninsula.

The Eastern Ghat terrain was subjected to uninterrupted planation in the intervening period. The attainment of a clear macro-relief instead of a featureless plain (peneplain) is visualised as a consequence. This macro-relief, possibly modified to some extent due to Mesozoic faulting, after attaining stability and with the onset of monsoonal climate in upper Cretaceous promoted the process of residual chemical weathering. Chemical leaching was accentuated and optimised during Upper Tertiary-Quaternary period when there was copious rainfall with less of evapo-transpiration, resulting in thick bauxitic duricrusts. This view is at variance with the concept of an once extensive residuum formed at lower levels and what are now seen at high altitudes are their erosional relics, owing their elevation and discontinuous nature to post-residuum uplift followed by denudation. As the gibbsitic duricrusts formed insitu have not been disturbed later, an in-depth study of their geomorphic characteristics, especially the slope morphology, assumes added relevance as it aids geological prognosis of the behaviour of the pay zone in terms of grade and thickness fluctuations. Once the geomorphic evolution of the duricrusts has been logically reconstructed, a conceptual approach instead of a regular grid for exploration planning is considered more pragmatic not only for acquiring a geologic grip but also in minimising exploration costs.

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