Regional tectonics and sulphide ore localisation in Delhi-Aravalli belt, Rajasthan, India—Use of LANDSAT imagery

Adv. Space Res. Vol.1, pp.299—302.

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0273—1177/81/0401—0299$05.00/0

1981. Printed in Great Britain.

REGIONAL TECTONICS AND SULPHIDE ORE LOCALISATION IN DELHI-ARAVALLI BELT, RAJASTHAN, INDIA—USE OF LANDSAT IMAGERY D.K. Bharktya and R.P. Gupta Department of Earth Sciences, University ofRoorkee, Roorkee-247672, India

ABSTRACT Interpretation of the LANDSAT imagery has brought to light several transverse and longitudinal tectonic dislocation zones in the Delhi—Aravalli belt. The multi— metal sulphide deposits of Khetri, Pur—Banera and Zawar belts conform to longitudinal lineaments and exhibit little affinity towards transverse features. These observations are in conformity with the prevalent ideas of syngenetic-remobilized origin of these deposits and could be helpful in planning further exploration strategy. INTRODUCTION The Deihi—Aravalli belt, comprising metamorphosed Precambrian rocks, extends over a distance of about 600 km across Rajsthan in NE—Sw direction. A number of workers have carried out structural and geological mapping on various scales in the area. However, these studies fail to give a synoptic picture of the belt. In this context, remote sensing studies have a great potential. The present investigation using LANDSAT data is aimed at (i) study and mapping of lineament— tectonic pattern of the Delhi—Aravalli belt as a whole and (ii) deciphering existing control, if any, of lineaments on sulphide ore mineralization. REGIONAL GEOLOGY AND STRUCTURE The area exhibits a complex structural pattern, as it has undergone at ]east four successive cycles of deformation (1),(2). It can be generalized that the Delhi group of rocks are characterized by two sets of major folding giving rise to NNE—SSW and WNW—ESE structural trends (1),(3) and the Aravalli group of rocks also contain two completely different structural trends in E—W and Nw—SE directions which are absent in the younger Deihis (3). METHOD OF STUDY The LANDSAT images of the area were studied using elements of photointerpretation, viz., tone, texture, shape, size and pattern. Various types of geologic features such as lineaments, faults, curvilinear features and trend—lines were mapped. Trend diagrams of lineaments were prepared by measuring lengths and bearings in units of 10 degrees of arc. The various trends of lineaments have been interpreted in terms of tectonic deformations in the area.

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O.K. Bharktya and R.P. Gupta

The above liriearnent-tectonic interpretation of the Delhi—Aravalli belt from the LANDSAT images, has been compared with field observations. As the area covered is very large, some field check has been made by the authors and in some areas, published maps and observations of earlier workers have been used as ground truth. The observations from LANDSAT images and the ground truth data show close corroboration. RE SU LTS The most dominant recti—linear features are the NNE—SSw trending ones, which correspond to the strike of the formations and can be termed as thelongitudinal features. In addition, several transverse lineament trends are found developed which truncate and displace the longitudinal linear features. Summarily, the area exhibits increasing complexity from north to south. In the northern and central parts, the dominant lineament trends are (i) NNE—SSW (longitudinal), (ii) ENE-wSW and NNW—SSE (shear) and (IN) ESE—WNW (tensional). Further in this area, the stress field giving rise to the dominant lirieament pattern could have been P 1 (maximum principal stress) = ESE-WNw, P,, (intermediate principal stress) = vertical and P (minimum principal stress) = NNE—SSW. In the southern region, the complexity greater. The predominant lineament sets are found to be NNE—SSW (to N—S), ENE—wSw, SE-Nw and NNw—ssE. A number of regional lineaments have been recognized in the area, the important ones among these being (I) a major lirteament about 20 km south of Beawar (ii) Bhim—Deogarh fault zone (ili) SabarmatiSom lineament zone. Ground check for these lineament zone is in progress. SULPHIDE ORE LOCALIZATION IN DELI-Il—ARAVALLI BELT According to prevalent theories and concepts on the origin and distribution of mineral deposits, many major ore deposits are localized by large structural features such as faults, joints, folds, bedding planes, shear zones etc., which are also manifested on the LANDSAT images. In the present investigation, relationship of photo—lineaments obtained from the LANDSAT imagery, with known ore occurrences in Khetri Cu belt, Pur—Banera Pb-Zn-Cu belt and Zawar Pb—Zn belt, was sought with a view to select potential target areas. KHETRI COPPER BELT The rock formations of Khetri Copper belt are quartzites, carbonaceous phyllites banded amphibolite-quartzite, and schists, belonging to Precambrian Delhi super group. The lineament-tectonic map of the Khetri copper belt prepared from the LANDSAT images (Fig.1) shows three sets of linear features trending NNE—SSw, NNw—sSE (shear) , ESE—wNw (shear) and ENE—wSW (tensional) To study the relationship between lineament and sulphide ore—localization, nearly twenty known significant sulphide—mineralization localities were superimposed on lineament tectonic map of the Khetri copper belt (Fig. 1). It has been found that the sulphide ore occurrences in Khetri copper belt have been largely localized along a major longitudinal NNE—SSw to NE-Sw trending lineament. Field data shows this lineament to be the manifestation of lithologic contat between quartzites and meta—pelites (Li). The transverse linear features such as faults and shear zones have no or little affinity with mineralization. It can be concluded that sulphide deposits are regionally stratigraphically controlled rather than structurally. PUR—BANERA Pb—Zn—Cu BELT The area comprises rock units mainly schists, quartzites, calc-silicates, nieta— basics and pegmatites of the pre—Aravalli age. The sulphide mineralization is

Tectonics and Ore Localization in Delhi—Aravalli Belt

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ZAWAR Pb Zn BELT

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301

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INDEX BEDDING PLANE FOLIATION

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ARAVALLI BELT}

LINEAMENT

DELHI

FAULT LINEAMENT WITH SENSE OF DISPLACEMENT

(~ CURVILINEAR FEATURE •

BASE METAL DEPOSITS

confined to banded magnetite quartzites interlayered with quartz—sericite schists along the crestal region of a synclinal fold (5). On LANDSAT imagery, the structural features of Pur—Banera lead zinc copper belt shows two types of linear features, viz. NNE—SSw (longitudinal) and ENE—wSw (transverse). It has been found that about ten major mineral localities in this belt lie on the longitudinal linearnents. The transverse features seem to have little impact on the mineral local I za t ion. ZAWAR Pb-Zn BELT The most significant lead—zinc deposit of Rajasthan is located at Zawar known as Zawar lead—zinc belt. The belt consists mainly of dolomites, phyllites, gray— wackes and conglomerates (5), (6). The mineralisation in the area, has been found along western and northern parts of a northerly plunging anticlinally folded JASR 1:10 -

302

O.K. Bharktya and R.P. Gupta

calcareous band, at a number of localities (5). On the LANDSAT images, the anti clinal structure closing northwards is well expressed (Fig.2). The mineralisation is found to be associated with longitudinal linear features, parallel to the strike of formation. Although many transverse faults are observed, mineralisation does not seem to have any affinity to these faults. Hence, the faults seem to be post-mineralisation. The above interpretation is in conformity with the prevailing ideas of syngenetic remobilized origin of these deposits. In this connection, it is worthwhile to note that the eastern limb of the fold is fairly well brought— out on the LANDSAT images, though it is covered with sands and alluvium. Since the mineralisation has been found in western limb and northern nose of the anticlinal fold, there exists a fair chance of striking similar sulphide deposits in the dolomitic band in the eastern limb of the fold as well. This could be a suitable site for further exploration. CONCLUSIONS The sulphide ore occurrences in Khetri copper belt, Pur—Banera Pb—Zn—Cu belt and Zawar Pb—Zn belt seem to be controlled by longitudinal lineaments and show little affinity towards transverse features. These observations are in comformity with the prevalent ideas of syrigenetic—remobilized origin of these deposits. The above study of controls of ore localization could be helpful in future exploration strategy. ACKNOWLEDGEMENTS One of us (RPG) wishes to acknowledge award of a research fellowship from the Alexander von Humboldt Foundation, Bonn, during which this study was initiated at the Central Laboratory for Geo—Photogramnietry and Remote Sensing, Munich. Grateful thanks are due to Prof.Dr. J. Bodechtel, Munich, for many a suggestion and critical discussions. REFERENCES

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1.

A.M. Heron, Mem. Geo. Surv. md.,

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A.K. Banerjee and S.K. Mitra, Jour. Geo. Soc.

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M.K. Roy Chowdhary and S.P. Das Gupta, Economic Geology, 60 (1965).

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6.

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