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

M. V. Ramanamurthy ¹

Affiliations
1 Geological Survey of India, AMSE Wing, 2, Church Street, Bangalore-560001, IN

Abstract

Various chemical extraction techniques are being employed in exploration geochemistry to identify true and false nature of soil anomalies. The efficacy of hydroxylamine hydrochloride, sodium dithonite and ammonium acetate selective extractions have been evaluated through model experiments on a series of Pb, Zn, Mn and Fe near pure mineral forms. The results obtained suggest that these extractions are not as specific as claimed in literature. Due to its complexing tendency, ammonium acetate extractant cannot be employed to extract ion-exchangeable trace metals either in the selective or sequential extractions. Selective and differential chemical quantities arc useful in designing an interpretative methodology for recognising true and false anomalies. Selective chemical quantities of Zn have provided greater insight into the distribution characteristics. Computation of background, anomalous and highly anomalous components has been accomplished from the Zn selective quantities, which are usable directly in exploration. Evaluation of this nature can assist in taking a decision. whether to carry out detailed exploration or not. Hence practicing of such an approach is strongly recommended.

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M. V. Ramanamurthy ¹

Affiliations
1 Geological Saney of India, (AMSE Wing) Bangalore - 560 001, IN

Abstract

No Abstract.

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M. V. Ramanamurthy ¹, U. S. N. Reddy ¹

Affiliations
1 Photogeology and Remote Sensing Division, AMSE Wing, Geological Survey of India, 2, Church Street, Bangalore 560001, IN

Abstract

Ground spectral reflectances have been collected over various lithounits in Cuddapah basin and adjoining crystallines, employing the portable spectre-radiometer, designed by the I.S.R.O. Satellite Centre. With the help of the spectral signatures it is found feasible to discriminate the argillaceous, arenaceous and calcareous components, post-kinematic intrusives and gneisses, thus facilitating the intra- and inter-group separabilities

In general, the arenaceous component is characterised by electron transition bands, perhaps indicating relatively low degree of weathering than the calcareous and argillaceous components. Siliceous, nonsiliceous, ferro-dolomites and gossan zones have been identified by their spectral differences. The photon absorption bands in the visible region and lattice absorption bands in the Infra-red region are due to Fe or Mn charge transfer and the formation of secondary minerals during weathering respectively. The molecular absorption bands in the case of quartzites is attributed to the inherent compositional impurity in the rock itself. A carbonate absorption band is identified tentatively around 0.85 to 1.0 micron. The reflectance peak in the green region is attributed to the presence of chlorite/sericite. The field characteristics and spectral reflectance data evaluation for the phosphoritic horizons of Cuddapah basin have not indicated the feasibility of aerial multispectral scanner survey. Differential derivative reflectance quantities have been computed for each lithounit for obtaining optimum enhanced ratioed data products in the computer processing of LANDSAT digital data. This type of ground truth studies are of paramount importance for the purpose of classification of cover types as a basic input in digital processing of remote sensing data.

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M. V. Ramanamurthy ¹, U. S. N. Reddy ¹

Affiliations
1 AMSE Wing, GSI, Photo-geology and Remote Sensing Division 2, Church Street, Bangalore 560001, IN

Abstract

Precious and semi-precious stones are found associated with colluvial/gravel landforms and in schistose rocks associated with vein quartz/pegmatites. Utilising the LANDSAT-4 digital data, computerised classification has been adopted using known gem-bearing locations as training sets with the principal objective of delineating possible target areas for gemstone prospecting in Bangalore, Tumkur, Mandya and Mysore districts of southern Karnataka, India.

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M. V. Ramanamurthy ¹

Affiliations
1 68-1 -3/1, Netaji Street Ashok Nagar, Kakinada -533003, IN

Abstract

No Abstract.

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M. V. Ramanamurthy ¹, B. P. B.P. Radhakrishna

Affiliations
1 68-1-3/1, Netaji Street, Ashok Nagar, Kakinada - 533003, IN

Abstract

No Abstract.

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M. V. Ramanamurthy ¹

Affiliations
1 68-I-3/1, Netaji Street ,Ashok Nagar Kakinada - 533 003,Dist. East Gudavari, Andhra Pradesh, IN

Abstract

No Abstract.

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M. V. Ramanamurthy ¹

Affiliations
1 R.B. Towers, I-C, K. Agraharam, Amalapuram - 533 201, Andhra Pradesh, IN

Abstract

No Abstract.

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M. V. Ramanamurthy ¹, U. S. N. Reddy ¹

Affiliations
1 Airborne Mineral Surveys and Exploration Wing, Geological Survey of India, No.2, Church Street, Bangalore 560001, IN

Abstract

Based on total intensity aeromagnetic profile data across the Cuddapah Basin, it is possible to distinguish the Cumbum and Bairenkonda Formations of Nallamalai Group. Further subdivision within individual intercalated dolomites and quartzites of Cumbum Formation is also found feasible. This discriminatory criterion can be used to guide mineral exploration, especially in the dolomites of Cumbum Formation. The magnetic variations along the strike of the Cumbum Formation is considered to be due to minor undulations in basin geometry, ref1ecting palaeogeography of pre-Cumbum period. The high magnetic response in Tadpatri and Vempalli Formations is mostly due to their association with basic volcanism.

All along the eastern margin of the basin, there is an ascending magnetic trend which coincides with a thrust. The geometry of Iswarakuppam dome is inferred to be asymmetric and with a tilt towards cast and/or controlled by a crustal fracture. The relative high magnetic response and discordant trend over Kurnool Group of rocks in the western part of the Kunderu Basin is attributed to the occurrence of the basement at shallow levels locally. Regional and areal trend surfaces have been estimated and causative magnetic responses due to basement and overlying metasediments are evaluated. For trend surface analysis, window sizes have been determined and computerization is suggested. From the LANDSAT imagery interpretation, a three stage basin evolutionary trend has been inferred.

A northwest-southeast tectonic break near Cumbum town is proposed, along which the basin oscillated, causing shallowing of the basin to the north and deepening to the south. Further, it is postulated that the northern and southern blocks tilted to east and west respectively moving on a northeast-southwest axis, resulting in the basement rise in the northwest and southeastern parts and gentle slope in the northeastern and southwestern parts in the area of study.

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M. V. Ramanamurthy

Abstract

No Abstract.

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M. V. Ramanamurthy ¹

Affiliations
1 68- 1 -3/1, Netaji Street, Ashok Nagar; Kakinada - 533 003 Andhra Pradesh, IN

Abstract

No Abstract.

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