VLF EM, MAGNETIC AND RADIOMETRIC INVESTIGATIONS IN PARTS OF PEDDAVURA GREENSTONE BELT AND RAMADUGU AREA, NALGONDA DISTRICT, TELANGANA STATE, INDIA

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 7, Issue 5, September-October 2016, pp , Article ID: IJCIET_07_05_022 Available online at ISSN Print: and ISSN Online: IAEME Publication VLF EM, MAGNETIC AND RADIOMETRIC INVESTIGATIONS IN PARTS OF PEDDAVURA GREENSTONE BELT AND RAMADUGU AREA, NALGONDA DISTRICT, TELANGANA STATE, INDIA G. Sriramulu, G. Ramadass, Dubba Vijay Kumar and S.V. Jagadish Centre of Exploration Geophysics, Osmania University, Hyderabad, Telangana, India. ABSTRACT The Archaean Proterozoic Cuddapah basin, in parts of Eastern Dharwar craton of south India peninsular shield comprising supra crustal (Schist belts, mafic dyke swarms, and younger granites) within the gneissic basement is significant in terms of geological, geophysical and economic interest. The schist belts and the gneissic terrain of Peninsular India are important in determine the structural configuration of the regions as the geological nature and the interrelationship of the volcano-sedimentary supra-crustal rocks help in understanding the tectonic sedimentary environments of deposition. Accordingly, the Peddavura schist belt, the only gold bearing schist belt and Ramadugu Lamproite field occurring in Nalgonda District, Telangana State were identified for integrated geophysical investigations include VLF-EM, magnetic and radiometric methods carried out along six detailed traverses. The VLF filtered real and imaginary component anomalies identify major geological interfaces suspected to be faults/fractured zones, which may reflect that VLF anomalies are due to shear zones or alteration zones located along the contact between different rock types. The VLF EM results of the Fraser model filtered data plots, as well as Karous-Hjelt filter 2-D inversion current density (Pseudo sections) plots for traverse (PS, V-I,V-II, R-I, R-II and SG ), are presented in Figures (2 to 7). The data analysis revealed the presence of positive and negative amplitude of filtered real and imaginary for possible identification of conductive and resistive formations. The interpreted results of VLF-EM agree with magnetic and radiometric anomalies qualitatively. In particular, the disposition and extent of the Peddavura schist belt and mafic dykes swarms in Ramadugu Lamproites field are discontinuous at places was traced and its relation with the other geological members of the region examined in terms of Lamproite locations. Key words: Archaean Proterozoic Cuddapah basin, Peddavura schist belt, Lamproites, VLF EM, Mafic dykes, Current density, Pseudo section. Cite this Article: G. Sriramulu, G. Ramadass, Dubba Vijay Kumar and S.V. Jagadish, VLF EM, Magnetic and Radiometric Investigations in Parts of Peddavura Greenstone Belt and Ramadugu Area, Nalgonda District, Telangana State, India. International Journal of Civil Engineering and Technology, 7(5), 2016, pp

2 G. Sriramulu, G. Ramadass, Dubba Vijay Kumar and S.V. Jagadish 1. INTRODUCTION The Eastern Dharwar craton is significant from both the geological and geophysical points of view characterized as it is by a complex evolutionary history and a vast storehouse of valuable minerals. The broad geological configuration of the Achaean to Proterozoic craton comprises a suite of greenstone belts, volcanic, granitic rocks, Paleo to Mesoproterozoic plat formal sedimentary basins, mafic dyke swarms and Mesoproterozoic kimberlitic and Lamproites (Ramakrishnan and Vaidyanadhan, 2008). The Dharwar craton has a unique combination of special carbonic features in the form greenstone (schist) belts. The distribution of these diverse supra crustal belts in three basic regimes of metamorphism resulted in the division of cratonic region, into three blocks consist of three types of greenstone belts in Dharwar craton viz, older greenstone of Sargur type (Western Dharwar), Chitradurga (intervening block), Ramadass et al 2006 and younger greenstones of Kolar type green stones or Eastern green stones (Eastern Dharwar craton) belts. The economic significance of greenstone belts of the Easter Dharwar Craton stems from the fact that many of them are auriferous (gold- bearing ) eastern schist belts of the Dharwar craton (Kustagi, Hutti, Raichur, Sandur, Gadwal and Peddavura) two schist belts only occurring in Telangana State are the Gadwal and Peddavura schist belts. The Peninsular India with several Achaean-Proterozoic nuclei is crisscrossed by many deep-seated fractures/faults. These nuclei, underlain by thick lithosphere mantle roots, have witnessed different events of kimberlitic, Lamproites intrusions within cratons usually are localized (Ramesh Chandra Phani, 2015) in zones of high magmatic permeability, as defined by the repeated intrusion of various types of igneous rocks. While kimberlitic /Lamproites are generated in the mantle, often reactivated fault/fracture systems ( Sykes, 1978, Haggerty,1994) their intrusion into the crust, these intrusive tend to occur in cluster or fields, within the large-scale distribution possibly controlled by shallow zones of weakness such as faults ( linear lows) or the margins of databases dykes (Power and Hildes 2007). They are associated with large-scale structural features like regional and local lineaments, the intersection of major lineaments, dome structures, fracture corridors, disjunctive zones radial features and resultant structural features formed due to emplacement of diaper granites (Rao 1996) opines that the regional trend of kimberlites/lamproites rocks in the Dharwar craton is possibly related to crustal warping and closely related deeply penetrating faults. The Peddavura schist belt was not reported any detailed geophysical studies, keeping this in mind, the present work is aimed at the need to obtain a clearer perception of structural configuration along chosen profiles across the Peddavura schist belt and in parts of Ramadugu, Vattikod and Somavarigudem lamproite fields, in the Northwestern part of Dharwar craton of Nalgonda district Telangana, India, by carrying integrated geophysical studies by Total magnetic and VLF-EM and radiometric techniques. 2. GEOLOGICAL SETTING The study area is located NW margin of the Cuddapah basin bounded by Longitudes 79 5 to and Latitudes to (Figure. 1). Geologically the area forms a part of the Eastern Dharwar Craton (EDC) which is recognized for its emplacement of numerous lamproite bodies. The geological formations in the area (GSI, 1999) include unclassified granites and gneisses of Achaean age, Cumbum shales, phyllites, Srisailam quartzites of the Cuddapah super group, and shales of the younger Kurnool group of rocks. The hornblende schist and amphibolites (Older Metamorphic) which are oldest rocks occur, as rafts, enclaves and discontinuous linear bands, within the Peninsular Gneissic Complex. The district comprises migmatites, granites granodiorite, tonalitic-trondhjemite suite of rocks and hornblende-biotite schist, metabasalts, meta-rhyolite and banded hematite quartzite and Dharwar super group are exposed as linear belts near Peddavura on the Hyderabad-Nagarjuna Sagar road. Figure.1shows the disposition of the Peddavura schist belt lies in the Eastern Dharwar craton. The NW-SE trending Peddavura greenstone belt extends over 25 km with a variable width of km (Srinivasan 1991) and is flanked on both sides by granitoid rocks whose ages /- 19 Ma trending in the Nalgonda and Guntur districts of Telangana and Andhra Pradesh state with a hooked shape (Jayananda et al 2013). The belt is well exposed Vijayapuri north all along the Krishna River, downstream of Nagarjuna Sagar Dam and consists of dark- colored basalts, fine editor@iaeme.com

3 VLF EM, Magnetic and Radiometric Investigations in Parts of Peddavura Greenstone Belt and Ramadugu Area, Nalgonda District, Telangana State, India grained buff coloured felsic volcanic rocks and tuffs, and BIF that are interlayer with each other. Peddavura schist belt lies 150 km south of Hyderabad near Nagarjuna Sagar dam. North of Jugudem, in the north-west, the belt tapers down and vanishes in the gneisses. At the southeastern end, west of Tummurukota, the belt takes a spectacular U-turn and younger Cuddapaha s cover. The Northwestern half of the narrow belt is flanked on either side by younger granite intrusive. The western arm of the schist belt on the west is bounded by an NE-SE trending fault lineament. In the study area, sulphide and oxide ore minerals are concentrated within the quartz veins that are traversing the Amphibolites metavolcanic are associated gangue minerals are Pyrite, Pyrrhotite, Arsenopyrite, Chalcopyrite, Sphalerite Magnetite, Quartz, Native Gold etc. Gold mineralization is structurally controlled and is confined in association with sulphides. A number of dolerite dykes and quartz reefs traverse these rocks trending N-S.E-W, NE-SW and NW-SE direction, Lamproites occurs as dykes and trend essentially NW-SE as discontinuous isolated outcrops associated with intrusive contact with the basement granitoid. 3. GEOPHYSICAL INVESTIGATIONS The Ramadugu study area lies in between latitude to N and longitude E to E. Very low frequency (EM), Total magnetic and radiometric investigations carried out in detail using ABEM WADI VLF equipment, Model 600 Proton precession magnetometer and ECIL- Scintillometer type SM141 instrument, along six detailed traverses with 10 m station to station distance were conducted at the Peddavura schist belt (PS), Vattikod (V), Ramadugu (R) and Somavarigudem (SG) Lamproites field (Figure.1). The length of these traverses varied between 160m 450 m were taken perpendicular to the geological formations. The frequency use in the present investigation is 18 KHz (VLF), Global Position System (GPS) was used to locate the observation points and elevation to ensure reliability and accuracy of the radiometric and GPS elevation, location of geographic coordinates several observations (20 %) are repeated. The overall effective accuracy obtained for elevation, the magnetic data, radiometric data and VLF data is 1m, +/- 1nT, 2µR/hr and 2% respectively. The N-S and E-W extend of this area that falls under Survey of India (SOI) Topo sheet No. E44T1, E44T2 and E44T5, in Nalgonda district of Telangana state, India. Figure 1 Geological map of the study area along with the VLF traverses. Interpretation of VLF (EM) data is complicated by the relatively high transmitter frequency which results in secondary fields from many geological features (Philips and Richards 1975). Further, the threedimensional nature of real geologic structures may complicate, the two-dimensional inversion of real data modeling is useful for interpretation of VLF-EM data and routinely done. VLF (EM) data are useful for obtaining a qualitative view of the structure, particularly after filtering the data and analyzing the apparent current density pseudo section. The Fraser and Karous Hjelt (1977, 1983) linear filtering techniques allow editor@iaeme.com

4 G. Sriramulu, G. Ramadass, Dubba Vijay Kumar and S.V. Jagadish geophysicist to filter the real (in phase) and generate an apparent current density pseudo section, therefore, image the geological subsurface structure. The VLF method generally yields considering the EM anomalies, even over poor conductors such as sheared contacts, fracture zones and faults. Hence this method has been the most popular tool for the rapid mapping of near- surface geological structures (Parker 1980, Philips and Richards 1975, Sayadam 1975). The peaks of the real component can be interpreted as conductors (Sunderarajan et al, 2006, Ogilvi and Lee., 1991). The VLF-EM real and imaginary components are presented in the form of a profile, the crossover in real and imaginary filtered components are inferred to be the conductor (Ramesh Babu et al 2007, Wright, 1988) where positive amplitudes of filtered real crossover the inflection points of the raw real reflects fault or fractures. Further, the symmetry in the real and imaginary components is caused to the dipping nature of conductors, wherein the larger anomaly peak identities the down-dip side (Coney, 1977). The real part component will always show peak above a conductors (Sundararajan et al 2007 ) while the imaginary part can show as well as a positive or negative peak depending on the conditions of the overburden or soil type of VLF data associated with fault/ fractures. The symmetry of these conductive anomalies suggests that the conductive structures are dipping. Also, the anomaly patterns exhibit varying amplitudes, which are controlled by the depth of the body to the surface, its geometry and attitude mapped as on the profiles. Fraser filtered from various lengths of the filter is the better the response of the deeper sources. The current density pseudo section provides good visualization of targets such as mineralized veins, fractures (Fischer et al, 1983) zones. The real and imaginary components of all traverses are subjected to both Fraser and Karous-Hjelt filter processed using RAMAG (VLF) software. The corresponding pseudo sections of station intervals versus depth are shown in Figures 2 to 7. The inferred depth from the pseudo section ranges from 20 to 100 m using a skin depth of 100m. The set of the pseudo section for real and imaginary components and graph for same were presented Red colour indicates the high current density and black colour indicated low current density reflects the non-conductors or resistive formation. 4. TRAVERSE - PS (PEDDAVURA SCHIST BELT) The VLF-EM Radiometric Investigation and magnetic measurements were made along traverse the Peddavura Schist belt ( to and longitude to ) total length 440 m trending NE-SW direction. The filtered real and imaginary components along the traverse-ps are shown in Figure 2d. The traverse-ps reveal high and low amplitudes along traverse indicate one main conductor in real components, whereas imaginary is reciprocal of this, the crossover points of inflection noted as faults or fractures, the distance between them are identified as shear zones. The Peddavura schist belt is dipping vertically Figure 2(e) VLF is the apparent current density pseudo section of traverse-ps revives the presence of anomaly between station No 1 to 5, 35 to 55 Stations. The inversion of traverse-ps demonstrates the presence of one conductor and resistivity body and three Faults Zone, Fr2 and Fr3 at station 40 m, 50 m and 90 m respectively are in vertical dipping. Peddavura Schist is characterized by high resistivity is in vertically dipping in long distance. The width of the schist belt (dyke like body dominated) is characterize by moderated current density distribution and one small is conductive body possibly indicating a lead, zinc and copper association within the schist belt, as a fault-related depression zones are sometimes recognized as shear zone (Bormann et al 1986), the VLF data are useful obtain a qualitative view of the structure. The radiometric measurements obtained (Figure.2a) over the conductive body is higher values over Peddavura Schist belt but there is no Lamproite indication. The Peddavura Schist belt within the belt one fault identified. The distinct features along the traverse marked to Fr3 representing geological contact, faults, shear zones etc. The broad high of 10 to 55 µr/hr corresponds to the NW SE trending schist belt (10-30 µr/hr) within which quartz & pegmatite veins are clearly demarcated. Western and eastern margins of this belt are sheared and faulted and are reflected by sharp peaks. The highs flanking the low over the schist belt can attribute to younger granites and peninsular gneisses with the former registering higher radio activities ( µr/hr) as compared to the later ( µr/hr). Pegmatite s found in fair editor@iaeme.com

5 VLF EM, Magnetic and Radiometric Investigations in Parts of Peddavura Greenstone Belt and Ramadugu Area, Nalgonda District, Telangana State, India concentrations in the region are also reflected by relatively high radio activities. These features correspond to quartz veins and local litho variations and are less apparent from traverse to which set a limit to the NW- SE extent of the inferred causatives. The Total magnetic intensity along the traverse-ps map shows (Figure.2b) an acute variation in the magnetic intensity indicating variations in the magnetic intensity. These variations are possibly related to the zones of structural variations based on the geological investigations. While the comparison of the magnetic signatures with the geology of the region not many inferences are made because the various forms of granites (migmatites, gneisses, pink / grey granites and / or Biotite granites) are magnetically not much distinctive. The magnetic highs and lows are in conjunction of subsurface faults in the granitic terrain. Not with the composition of the granites, the study area covers various forms of granites along with little Peddavura schist. A few basic / ultra- basic dykes are available as intrusive rocks, and NW-SE trend to NE-SW (Srinivasan, 1991) trends fault axis is evident in highs and lows in Figure.2b. Two other trends of magnetic high responses are also running in the same direction. There are only two schist belts only occurring in Telangana State are the Gadwal and Peddavura schist belts are auriferous (Anand Murthy and Bhattacharji 1997, Ramadass et al 2007) reported gold mineralization from bedrock pegmatites and soil samples (0.035 to 0.25 ppm), and in a shear zone (0.035 to 4.25 ppm), and also the gold specks are in the form of disseminated specks are reported from Peddavura schist samples. Effect of shearing is well evident by the presence of mylonite. Morphologically the size of native gold is variable and ranges from 3-10 microns. (a) µr/hr (b) Fr2 nt (c) WEST EAST Fr2 (%) C-Conductor Fr-Fracture (d) DYKE (e) 1 Unit = 1.6 m Figure 3 (a) Radiometric, (b) Total Magnetic Intensity, (c) Fraser filter Real and Imaginary Components (VLF) and (d, e) Karous Hjelt current density pseudo section along the profile: 1, from west side of the Vattikod village editor@iaeme.com

6 G. Sriramulu, G. Ramadass, Dubba Vijay Kumar and S.V. Jagadish 5. TRAVERSE- V 1 (VATTIKOD) Traverse-V 1 (Figure-3) across the East- West direction running away from the Vattikod Village (latitude to , longitude to ) at a total length of 410m and (Figure.3c) shows the linearly Filter Real and Imaginary Component, of the VLF data along with the Vertical Magnetic and Radiometric data. The current density Pseudo Section (Figure.3d) shows one, conductors at distance 60 m, two faults and Fr2 faults/fractures (Fr) at 80m and 280m are indicated on the real positive amplitude and crossover of the real and imaginary components., the positive response to the real components value indicates the presence of conductive subsurface structures,while low are negative values are Indicate of all resistive formation. One dyke with a 100 m is responding with a high resistive body extending vertically. There are no Indication of Lamproites along the traverse, however magnetic (Figure.3b) responses low recorded at the station no 75 and 100 stations at the contacts at two faults remaining part the radiometric (Figure.3a) no appreciable variation is observed. Figure.e is the current density Pseudo section of imaginary components is the inversion of real component. 6. TRAVERSE-V 2 (VATTIKOD) This traverse V 2 runs 1.5km away from Vattikod Village towards Pochampally (latitude to , longitude to ) village a total length of 440 m, the VLF, magnetic and radiometric observations obtained at every 10meters. Figure (4d) shows current density Pseudo section has been constructed distinct to traverse to show the vertical variation of a current density, and consequently to derive the change of conductivity with depth qualitatively. It is possible to differentiate between conductive and resistivity formations using apparent current density pseudo section and plots of real and imaginary components (Figure 4c) locates the three dipping conductors (, C2 and C3) identified along the traverse at 110m, 220m and 330m and three dipping fault/fractures (, Fr2 and Fr3) at 130m, 230 m and 350m, two mafic dykes are traced in between m and m. Based on the moderate current density distributions occur in between gneisses and dykes contact Figure (4d) might be a possibility of the location of Lamproites. The bedrock photography is varying traverse 30m to 80m at station 200 deeper basement is traced. The magnetic behavior (Figure.4b) over this traverse lows and high evaluates are recorded at 50-80m and m respectively. The Radiometric (Figure.4a) response over this location also corroborated with survey response. 7. TRAVERSE- RM 1 (RAMADUGU) Traverse RM 1 lies under the bridge of Ramadugu trending NE-SW extending (latitude to to and longitude to ) east of Ramadugu village, the total length of 370m station interval is 10m at near Ramadugu bridge (Halia river). From (5d) VLF on real and imaginary component of the VLF-EM pseudo section (Figure 5e) revived the across the major conductive zone identified, is varying from 48m to 250m, further east only one dyke with low conductivity zone is identified fracture-zone at distance 100 and 250m at a depth of 60m to 100m there are only conductor best of 100 station and broad conductors 50 to 250m identified a resistivity body at station 275 to 320m with curves 50m width body only limited depth exclusive body. The magnetic evidence is the small conductive absent at contact of the dyke. 8. TRAVERSE- RM 2 (RAMADUGU) This traverse (Figure.6) lies in (latitude to and longitude to ) located along the road side of at a distance of 1.7km west of Ramadugu village trends NE-SW across a narrow mafic dykes. The VLF real and imaginary components (Figure.6d) a cross-over at approximately 240m along the traverse. The imaginary response, on the other hand, shows an inverse relationship with the real component. There are two conductors are identified and C 2 at 50m and 200m extending deeply at only one fracture/conductor. The total magnetic intensity is oscillatory and a editor@iaeme.com

7 VLF EM, Magnetic and Radiometric Investigations in Parts of Peddavura Greenstone Belt and Ramadugu Area, Nalgonda District, Telangana State, India radiometric response is uniform intensity observed along this traverse, two shallow mafic dykes are traced along the traverse station and in shallow station. (a) µr/hr (b) C2 C3 Fr2 Fr3 nt (c) WEST C2 Fr2 C3 Fr3 EAST (%) C-Conductor Fr-Fracture (d) BEDROCK DYKE DYKE Shear zone BEDROCK (e) 1 Unit = 1.6 m Figure 4 (a) Radiometric, (b) Total Magnetic Intensity, (c) Fraser filter Real and Imaginary Components (VLF) and (d,e) Karous Hjelt current density pseudo section along the profile:2, 1.5km away from profile:1 (Vattikod village) editor@iaeme.com

8 G. Sriramulu, G. Ramadass, Dubba Vijay Kumar and S.V. Jagadish 9. TRAVERSE- SG (SOMVARIGUDAM) This Traverse ( Figure.7) is a total length of 480 m running from ( to and longitude to ) the Figure-7 difference shows the VLF-EM section over flatted and shows the Pseudo sections of Figure.9d relative current density radiation with depth. The Fraser and KH Filter-aided in the identification of conductive and resistive structure there are three positive amplitude real component and four negative amplitude negative representative conductive resistivity bodies. (a) µr/hr Fr3 (b) Fr2 nt (c) Fr2 Fr3 (%) C-Conductor Fr-Fracture (d) Shear zone Shear zone SCHIST BELT (e) 1 Unit = 5m Figure 2 (a) Radiometric, (b) Total Magnetic Intensity, (c) Fraser filter Real and Imaginary Components (VLF) and (d, e) Karous Hjelt current density pseudo section along the profile: 3, Peddavura Schist Belt. The conductive bodies red colour resistivity is in black colour (Figure.7d). The cross over the point is the positive amplitude of real and imaginary component indicates one fracture at 220m and three editor@iaeme.com

9 VLF EM, Magnetic and Radiometric Investigations in Parts of Peddavura Greenstone Belt and Ramadugu Area, Nalgonda District, Telangana State, India conductors, C2 and C3 identified stations 20, 200m and 300m along the traverse, the subsurface bedrock thickness are varying from 60 to 100m. Two Lamproite dykes are traced at , and with a subsurface fault which is a possible indicator of Lamproites. The magnetic and radiometric responses are corroborative with VLF results. (a) µr/hr C2 C3 (b) nt (c) C2 C3 (%) C-Conductor Fr-Fracture (d) BEDROCK DYKE F DYKE F BEDROCK F Fault F (e) 1 Unit = 1.25 m Figure 5 (a) Radiometric, (b) Total Magnetic Intensity, (c) Fraser filter Real and Imaginary Components (VLF) and (d, e) Karous Hjelt current density pseudo section along the profile: 4, Nearby Somvarigudam editor@iaeme.com

10 G. Sriramulu, G. Ramadass, Dubba Vijay Kumar and S.V. Jagadish (a) µr/hr (b) nt (c) (%) C-Conductor (d) BEDROCK BEDROCK (e) 1 Unit = 1.6 m Figure 6 (a) Radiometric, (b) Total Magnetic Intensity, (c) Fraser filter Real and Imaginary Components (VLF) and (d, e) Karous Hjelt current density pseudo section along the profile: 5, under the bridge at Ramadugu Village editor@iaeme.com

11 VLF EM, Magnetic and Radiometric Investigations in Parts of Peddavura Greenstone Belt and Ramadugu Area, Nalgonda District, Telangana State, India (a) µr/hr (b) C2 nt C2 (c) (%) C-Conductor Fr-Fracture (d) (e) 1 Unit = 1.6 m Figure 7 (a) Radiometric, (b) Total Magnetic Intensity, (c) Fraser filter Real and Imaginary Components (VLF) and (d, e) Karous Hjelt current density pseudo section along the profile: 6, 1.7km away from Ramadugu Village editor@iaeme.com

12 G. Sriramulu, G. Ramadass, Dubba Vijay Kumar and S.V. Jagadish 10. CONCLUSION The interpretation of VLF, Total magnetic and radiometric data has clearly brought out the subsurface fractures associated with the conducting auriferous mineralization. Crossover of the real and imaginary components demarcate the conductors, from the current density Pseudo section of the six traverses PS,V 1, V 2 RM 1, RM 2 and SG helps in determining the conductors dip attitude and nature of the conductors the fractures inferred from VLF-EM are conductive in peddavura due to sulfide and oxide ore minerals are concentrated within the quartz veins that are traversing the Amphibolites metavolcanic are associated gangue minerals are Pyrite, Pyrrhotite, Arsenopyrite, Chalcopyrite, Sphalerite Magnetite, Quartz, Native Gold etc. This approach clearly demarcated boundaries in between peninsular gneisses and mafic dyke swarms/fractures associated with Lamproites in Ramadugu, Vattikod and Somavarigudem Lamproites clusters. ACKNOWLEDGEMENT The authors gratefully acknowledge the financial support extended by the UGC, New Delhi for granting Emeritus Professor. REFERENCE [1] Alok Kumar, Suhel Ahmed, R, Priya and M.Sridhar, Discovery of Lamproites near Vattikod Area, NW margin of the Cuddapah Basin, Eastern Dharwar craton, Southern India, Jour Gol.Soc.of India, vol.82, pp [2] Anand Murthy,S and Bhattacharjee,S Occurrence of gold in Guntipalli-Atkur area, Gadwal schist belt, Mahboobnager district, AP. Jour. Soc. India. Bangalore Vol49, pp [3] Bormann,P.,Bankwitz,P.,Bankwitz,E.,Damm,V.,Hurtig,E.,Kampf,H,Menning,M.,Paech,H.J,Schafer,V, Stackebrandt,W.,1986.Structure and development of the passive continental margin across the Princes Astrid Coast, East Antarctica,J.Geodyn [4] Chalapathi Rao.,Alok kumar,samarendra Sahoo,A.N., Dongre,Debojit Talukdar,2014.Petrology and petrogenesis Mesoproterozoic Lamproites from the Ramadugu field,nw margin of the Cuddapah basin, Eastern Dharwar craton, southern India,Lithos, (2014) pp [5] Coney, D.P, Model studies of the VLF-EM method geophysical prospecting Geoexploration, 15, p19-35 [6] Fisher, G., B, V.Le Quang and Muller, VLF ground surveys, a powerful tool for the study of shallow two-dimensional structures Geophysical Prospecting [7] GSI, District resource map of Nalgonda district, Andhra Pradesh, 1:250,000 [8] Haggerty, S.E Super kimberlites: a geodynamic window to the Earth s core. Earth Planet.Sci.Lett. Vol.122, pp [9] Jayanada,M, Peucat,J.J, Chardon,D. Rao.B.K, Fanning, C.M, Corfu,F,2013. Nearchean greenstone volcanism and continental growth, Dharwar craton, Sothern India. constraints from SIMS u-pb Zircon geochronology and Nd isotopes, Precambrian Resarch,227,55-76 [10] Karous, M., Hjelt, S.E Determination of apparent current density from VLF measurements Report. Department of Geophysics, University of Oulu, Finland, Contribution No.89.p10 [11] Karous, M., Hjelt, S.E.1983.Linear filtering of VLF dip-angle measurements, Geophysics.Prosp.31.No editor@iaeme.com

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