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

K. S. Balasubramaniam ¹, A. L. Paropkari ², R. Nagarajan ¹

Affiliations
1 Geology Section, Indian Institute of Technology, Bombay 400076, IN
2 National Institute of Oceanography, Goa, IN

Abstract

Laboratory studies of three bauxitic profiles from Maharashtra and Tamil Nadu suggest that plagioclase feldspar alters to gibbsite via halloysite and not from kaolinite. The alteration characteristics of feldspars and the morphological aspects of clays leading to the genesis of bauxites were studied under electron microscope.

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A. L. Paropkari ¹, Ch. M. Rao ¹, P. S. N. Murty ¹

Affiliations
1 National Institute of Oceanography, Dona Paula 403004, Goa, IN

Abstract

Total phosphate in the sediments ranges from 0.15 to 0.29% in the bulk samples and from 0.09 to 0.23% in the acid soluble fractions of the samples. There was no appreciable variation in the phosphate within the Gulf and no significant relation was observed between phosphate content and texture of the sediments. Invariably higher concentrations of phosphate were associated with the acid soluble fractions as compared to the acid insoluble fractions. The contributions made by the acid insoluble fractions to the phosphate concentration in the bulk samples was probably through the detrital minerals with which it might be associated, while the contributions made by the acid soluble fraction was probably in the form of adsorbed phosphate than in association with the carbonate phase.

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Ch M. Rao ¹, A. L. Paropkari ¹, A. Mascarenhas ¹, P. S. N. Murty ¹

Affiliations
1 National Institute of Oceanography, Dona Paula, Goa 40300, IN

Abstract

Phosphate content in the bulk sediments range from 0.02 to 2.17% and on carbonate free basis it varies from 0.03 to 6.57%. The partition studies indicate that contribution from the acid resistant detrital minerals (HCl insolubles) is negligible. In the inner shelf, the phosphorus is mainly associated with iron (as ferric-phosphate?) and organic carbon. In the outer shelf/slope its association with carbonate suggests its authigenic/diagenetic origin. This is also supported by X-ray diffraction studies wherein the apatite peak is revealed in some samples. In general, sympathetic relationship of phosphorus with organic carbon in the study region indicates genetic relationship between these two elements, which is an important condition for phosphatogenesis. Further, these studies suggest that the outershelf/slope region between Bombay and Quilon is the promising area for detailed exploration for phosphorite deposits.

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J. N. Pattan ¹, G. Pratibhan ², C. Prakesh Babu ², N. H. Khadge ¹, A. L. Paropkari ², V. N. Kodagali ¹

Affiliations
1 National Institute of Oceanography, Dona Paula-403004, Goa, IN
2 National Institute of Oceanography, Dona Paula -403004, Goa, IN

Abstract

A closely spaced 75 surface sediments drawn from "Gas Hydrate" Project taken up by National Institute of Oceanography on a regional scale from the Krishna- Godavari Basin (Latitude 15°35' to 16°20' N; Longitude 81° 40' to 82°30E) are analysed for texture, major, and some trace and rare earth elements to understand their source and provenance. Water depth in the study area varies between 300 to 2000 m and there is a WNW-ESE trending sedimentary ridge in the southwestern part of basin. Sediments are mosdy silty clay in nature. Ti - bearing minerals such as titanite and pyrophanite are evident by the strong positive correlation between Ti and Ca (r = 0.89) and Ti and Mn (r =0.67) respectively. An independent behaviour of Zr suggests occurrence of zircon mineral. The strong positive correlation among Al, Fe, Mg and K (r = 0.68 to 0.90) suggests their association with clay. The average total REE (Σ2REE 176±13 ppm) abundance is similar to that of average shale with a flat shale- normalized REE pattern suggest a terrigenous source. High concentration of Fe (6.45±0.43% ), Ti (0.82+0.07%), V (192±23 ppm), Cr (128±13 ppm) and Zr (159±19 ppm) and presence of smectite as a major clay mineral suggest that Peninsular Godavari River has sediment influx from source rocks of Eastern India mainly Deccan Trap, Precambrian and Dharwar formation. Further, it confirms that the role of Ganges-Brahmaputra River sediments to the basin appears to be small compared to the Peninsular rivers.

Keywords

Surface sediments, Geochemistry, Silty clay, Smectite, Titanite, Pyrophanite, Zircon, Bathymetry, Krishna-Godavari Basin, East Coast of India.

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