Geology and Geochemistry of Mafic and Felsic Volcanics of Joga (Sandur Schist Belt), Karnataka, India

Transcription

1 Indexed in Scopus Compendex and Geobase Elsevier, Chemical Abstract Services-USA, Geo-Ref Information Services-USA, List B of Scientific Journals, Poland, Directory of Research Journals ISSN , Volume 07, No. 05 October 2014, P.P Geology and Geochemistry of Mafic and Felsic Volcanics of Joga (Sandur Schist Belt), Karnataka, India Department of Studies in Geology, Karnataka University, Dharwad , India srsuresh68@gmail.com, m_basavanna@rediffmail.com Abstract: Metavolcanics found around Joga village in the Sandur Schist Belt (SANDUR SCHIST BELT) are Tholeiitic and exhibit pillow structures indicating ocean floor/submarine environment of deposition of basaltic magmas. Analysis of geochemical data indicates that Joga metabasalts are intra arc setting basalts derived near Archaean Mid Oceanic Ridge environment (AMOR). Some volcanic rocks are of Adakitic in nature. Metabasalts are indicating higher concentration of Nb (NEB). Metabasalts show sulphide mineralization associated with shear zone hosted quartz carbonate vein emplacement. Metavolcanics are of both mafic and felsic compositions (bimodal). Keywords: Sandur Schist Belt, Volcanics, Adakites, Nb Enriched Basalts (NEB), Intra Arc terrains. Introduction: The two blocks of the Dharwar Craton viz. the western and eastern, are separated by the Chitradurga Shear Zone which is represented by a 5km wide and almost 400km long, steeply dipping, mylonite belt that is situated at the eastern margin of the Chitradurga Schist Belt, not far from the western margin of Closepet Granite. This 400km long belt extends from Gadag in the north to Mysore in the south (Drury and Holt, 1980; Chadwick et al., 1996, 2000). The western block has dimensionally larger greenstone belts, or greenstone terranes, with predominant metabasalts along with Komatiites and minor bimodal volcanic rocks, whereas the eastern block has smaller greenstone terranes with prevalent bimodal volcanic rocks. The Archaean greenstone belts are surrounded by younger granitic batholiths (Moyen et al., 2003; Naqvi, 2005; Manikyamba and Khanna 2007; Naqvi and Rana Prathap, 2007). Distinct volcano sedimentary associations present in greenstone belts of the western and eastern blocks are consistent with distinct geodynamic settings, as endorsed by recent geochemical studies (Zachariah et al., 1996; Naqvi et al., 2002, 2006; Manikyamba et al., 2004a, 2005, 2008, 2009; Jayananda et al., 2008; Manikyamba and Kerrich, 2011). Geology of the Sandur Schist belt The schist belts of Western Dharwar Craton (WDC) are grouped into older (Sargur) and younger (Bababudan and Chitradurga) supracrustal belts punctuated by a major crust forming event during Ga (Naqvi and Rogers, 1987; Swami Nath and Ramakrishnan, 1981; Peucat et al., 1995). Chadwick et al., (1996) correlate Sandur Schist Belt with the Chitradurga group, though Radhakrishna (1983) had correlated it with the Bababudan group. SHRIMP zircon ages from Bababudan, Chitradurga and Sandur Schist Belts cluster around 2.7 Ga (Peucat et al., 1995; Nutman et al., 1996; Trendall et al., 1997). The acid volcanic of the eastern shelf sequences of Sandur Schist Belt have been dated by U Pb SHRIMP method that indicated an age of 2.7 Ga (Nutman et al., 1996). The high Mg basalts and ultramafic komatiitic rocks from the Sultanpura Volcanic Block (SVB) have indicated an age of 2.7 Ga by the Sm/Nd method (Naqvi et al., 2002). Sandur Schist Belt is surrounded by the Closepet Granite. It is unique in the sense that, it is a transitional belt between the Eastern and Western blocks, having the litho-assemblage affinity of Bababudan type, but geographically located towards the eastern segment. Peninsular Gneiss of younger phase having granodiorite to granite composition dating around 2600 million years encloses all these narrow greenstone belts in the Eastern block. Chadwick et al., (1996) termed the word Dharwar Batholith instead of Closepet granite based on its scale and variations in composition and structure. The volcanic rocks encountered in different parts of the Schist Belt vary from Komatiitic ultramafic Schists to Rhyolite-felsic suite of rocks. The sedimentary component consists of Banded Iron Formations (BIFs), Manganese formations, Carbonates, Stromatolites, Arenites, oligomictic polymictic Conglomerates, Breccia, greywacke, Shales, carbon Phyllite, autoclastic Conglomerates, Fuchsite Quartzite and pelagic sediments (Manikyamba and Naqvi, 1998; Manikyamba et al., 1997). Though these rock types have been divided into formations, groups and blocks, the structure and # Copyright 2014 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.

2 Geology and Geochemistry of Mafic and Felsic Volcanics of Joga (Sandur Schist Belt), Karnataka 1638 stratigraphy of these rock types are debated among the contemporary workers. Roy and Biswas (1983) provided a stratigraphic succession classifying the Sandur Schist Belt into Yashwanthnagar, Deogiri, Donimalai and Nandihalli formations. Chadwick et al.,(1996) revised this stratigraphy and coined the Sandur Group (Table 1) with six formations viz. Yashwanthnagar, Deogiri, Ramanmala, Donimalai, Taluru and Vibhutigudda formations and proposed a crustal thickness of 35 km for the Sandur Schist Belt. Manikyamba and Naqvi (1996) proposed a revised stratigraphy of the Sandur Schist Belt (Table 1). There are lithological, structural, compositional and metamorphic discontinuities from east to west and both the eastern and western margins of the belt have shelffacies sediments. BIFs are exposed at three geographically separated horizons i.e. within: (1) Western Volcanic Block (WVB); (2) Eastern Volcanic Block (EVB); and (3) Sultanpura Volcanic Block (SVB) (Table 1). A search for the evidence of: (a) repetition of strata within the different blocks; and (b) accretion of different blocks is essential for understanding the evolutionary history of the Sandur Schist Belt and proposed a simplified geological map of Sandur Schist Belt (Fig.1). The earlier studies (Manikyamba and Naqvi, 1996, 1998; Manikyamba et al., 1997) have suggested a NNW SSE striking allocthonous terrain in the north-western part of Sandur Schist Belt. Table 1: Integrated Stratigraphy of Sandur Schist Belt (After Naqvi et al., 2002) Roy and Biswas., 1983 Chadwick et al., 1996 Manikyamba et al., 1997a Nandihalli Formation Vibhutigudda Formation Eastern Acid Volcanic Block Donimalai Formation Deogiri Formation Taluru Formation Donimalai Formation Ramanmala Formation Deogiri Formation Sultanpura Volcanic Block Northern Central Acid Volcanic Block Eastern Volcanic Block Central Volcanic Block Western Volcanic Block Deogiri Block Yeshwanthnagar Formation Yeshwanthnagar Formation Yeshwanthnagar Volcanic Block The conglomerates exposed on the southern side of the Joga village and adjacent to research area, outcropped over a long distance of more than one kilometre, overlaid by thick horizon (approximately 3 to 4 km thickness) of metavolcanic. BIFs associated with carbonate bands (Dolomite/Ankeirte) occur within the metavolcanics and juvenile Granite form the youngest lithounit with vast dimension. Juvenile granite consists of Mafic Magmatic Enclaves (MME), suggesting an inclusion of undigested mafic enclaves of subducted block. A predominant coarse grained gabbroic dyke runs in NE-SW direction over a length of 8 km, bisecting all the litho units of the schist belt on the northern region. Fine grained doleritic dykes are also prominent in the area and appear to be a local phenomenon and may be contemporaneous with gabbroic dykes. Joga is a small village near Hospet town of Bellary district in Karnataka (State), which is 18kms away from Hospet and accessible through Kakubalu village by all weather metallic roads. The study area lies between longitudes of 76 31' 53 and 76 36' 22 and latitude of 15 10' 36 and 15 12' 15. Joga is located on the northern portion of Sandur Schist Belt (Fig.1). Physiography of Joga consists of hillocks and valley, BIFs and Granites occupy the hilly terrains where as metabasalt occurs on the low to medium relief mounds/hillocks. The study area is consisting of a reservoir adjacent to the sulfidic BIF. Manikyamba et al., (1996) reported that Sandur greenstone belt of Dharwar Craton is an allochthonous remnant of accreted oceanic volcanism. Pillows of eastern parts of Sandur Schist Belt are undeformed whereas the ones of western boundary of Sandur Schist Belt are deformed and show stretching. Comparison of Length/Width ratio of the elongated and normal pillows and their Poisson s ratios from the western and eastern parts indicates that 7-8 times shortening has taken place along the western margin of the belt. This shortening along the belt is interpreted due to horizontal compression, consequent of convergent margin movement and rock mass transport, implying their allochthonous character. Chadwick et al., (1996) reported that the volcano sedimentary association in the Sandur Schist Belt accumulated in manly shallow marine environments in a setting comparable with that of mixed mode basins, i.e., with variable intra- and extra-basinal uplift and

3 1639 subsidence (Chadwick et al., 1996). The chemical composition of the volcanic rocks is consistent with an intra arc setting (Hanuma Prasad et al., 1997). Fig.1: Generalised geology of Sandur Schist Belt (After Manikyamba et. al., 1997); red block indicates study area. (1.Yeshwanthnagar Volcanic Block. 2. Deogiri Block. 3. Western Volcanic Block (BIF block). 4. Central Volcanic Block. 5. Greywacke in Central Volcanic Block. 6. Eastern Volcanic Block (BIF Block). 7. North Central Acid Volcanic Block (Greywacke, Conglomerate). 8 Sultanpura Volcanic Block. 9. Metasediments of Eastern Acid Volcanic Block. 10. Acid Volcanic Rock. 11. Amphibolites. 12. Granitic Gneiss. 13. Granite. 14. Faults. 15. Location of areas in the Sandur Schist Belt studied for gold exploration.) Age of Sandur Schist Belt The Sandur Schist Belt is intruded by Closepet Granite, which is dated at Ga and has yielded an Rb-Sr isochron date of 2.4 Ga. The mafic and felsic volcanic rocks of the Sandur Schist Belt have yielded a thermal resetting Rb-Sr isochron age of 2.4 Ga (Bhaskar Rao et al., 1992). The basic volcanics of the Kudremukh belt (which is stratigraphically equated with the basic volcanic of the Sandur Schist Belt has yielded a Sm-Nd age of ~2.9 Ga (Drury et al., 1983). The gneissose basement on which, this belt is resting is dated elsewhere at 3.1 Ga (Taylor et al., 1984). In view of the available radiometric age data, the age of Sandur Schist Belt can be said to vary between 3.1 and 2.6 Ga. Field Techniques and Sampling Fig 2: Geological map of the Joga area, (adapted from Suresh et al., 2014) The study area has been marked on the survey of India toposheet No. 57A/12 and enlarged it to A3 size scale for field reference. Geological mapping of the area has been carried out with the help of GPS Garmin, Map 62S model with 3 to 4 meters accuracy and compass. All the outcrops data like, location coordinates, trends and descriptions were recorded during the geological traverses and processed with MapInfo software to prepare a generalised geological map (Fig.2). In

4 Geology and Geochemistry of Mafic and Felsic Volcanics of Joga (Sandur Schist Belt), Karnataka 1640 addition to this, Google satellite image data is also used to delineate the regional gabbroic dyke. During geological mapping, fresh outcrop samples (Fig.2, blue triangular symbols) from the representative litho units were collected. These samples were analysed by XRF/ICPMS methods for petrochemical studies. Few representative samples were also prepared as thin sections and studied for petrographic characteristics. Geology of Joga area: Joga forms a part of the northern portion of the Sandur Schist Belt (Fig.1). The region consists of Granites, Metabasalts, Gabbro and Dolerite dykes, BIFs and Phyllites. The general geomorphology of the area consists of hillocks and valleys. Hillocks are composed of BIFs associated with metabasalts. Small streams are occupying the valley portion of the area. A Gabbro dyke is emplaced all along the NE-SW trending conspicuous hill range over several kilometres as a regional General Stratigraphy of Joga area discordant body and cutting across all the litho units of the region. Banded Iron Formations are minor and discontinuous bands occurring on the central and south western regions, showing a trend of EW and dipping towards south predominantly. Metavolcanics are the predominant lithounits exposed in the study area, which exhibit pillow structure prominently, suggesting a depositional environment near to volcanic vent. Vesicles and amygdales are common in the basalts. The dolomite bands are occurring with BIF bands discontinuously along the strike direction, preferably on the footwall side of the BIF. Quartz Carbonate (QC) veins are prominent near shear zones within metabasics. These QC veins are complex in structure and exhibit brecciated nature near the sulphidic zone. The common sulphides observed are Pyrite, Pyrrhotite, and Chalcopyrite. Gabbroic dyke/doleriatic Dyke Juvenile Granites BIF with intercalations of Dolomite Conglomerates Sultanpura volcanic block (SVB)/Taluru Formations Metavolcanics Joga area exhibits the local stratigraphy by predominant lithounits as envisaged above; correlated with the standard regional stratigraphy proposed by previous workers (Table.1). 80 E followed by N80-90 W. Only a few exceptional Metabasalts trends show NE and NW directions. Metabasalts are the predominant rock types covering approximately 70% of the study area. These metabasalts are predominantly of pillowed and vesicular type with rare occurrences of massive types. Pillow structures are well preserved in the metabasalts (Fig.3). Metabasalts are also exhibiting amygdales filled with quartz carbonate materials. The metabasalts indicate pillow younging direction towards north eastern side. The metabasalts are well exposed on the road cuttings, stream beds and hillocks. The metabasalts are pale greenish to dark greenish in colour, fine to medium grained. Metabasalts are predominantly Basaltic in nature (Fig.6) with an exception of one sample which shows composition of picrobasalt. Metabasalts are tholeiitic in nature (Fig.7) and found derived in intra arc terrain (IAT) and mid Oceanic Ridge Basalt (MORB) setting (Fig.8 and 9). Joga metabasalt samples are showing abundance of Nb as high as 25ppm (Table 1), which is much higher than the tholeiitic basalts where Nb is appx. 3ppm. Hence, these basalts can be termed as high-nb Basalts (HNB). Rose diagram (Fig.4), shows trends of metavolcanics exposed in the Joga area. The predominant trend is N70- Fig. 3: Photograph showing pillow structures in metabasalts. Note that pillows show random orientation without any defined younging direction

5 1641 subducting slab during subduction of a hot and young oceanic lithosphere in Late Archaean period. Fig. 4: Rose Diagram showing trends of Metavolcanic outcrops Adakites Manikyamba et al., (2005) reported Adakites from felsic volcanics of the Eastern Felsic Volcanic Terrane (EFVT) of Sandur Schist belt. In this study, a small band of felsic volcanic rock is identified in the northern portion, was sampled and analysed for chemical composition (Table 1 and Fig. 5). It shows chemical composition similar to the adakites. Fig. 6: Binary diagram of SiO 2 versus Na 2 O+K 2 O (after LeBas et. al., 1986) indicating that metabasalt samples are of Basaltic nature. Sample no.716 is indicating composition of picrobasalt Fig. 7: Binary diagram of Zr/ (P 2 O 5 *10 4 ) versus Nb/Y (after Floyd and Winchester 1975) for the Joga metabasalts indicating their Tholeiitic composition. Sample no.705 is falling on the boundary of alkalibasalt and Tholeiitic basalt Fig.5: Binary plot after Gill 1981, K 2 O versus SiO 2 Generally, Cenozoic adakites and magnesian andesites are derived by slab melting of hot, young (<20Ma) ocean crust in intraoceanic arcs (Ko nig et. al., 2007: Richards and Kerrich, 2007). These rocks have higher Ni, Cr and Co compared with typical calc alkaline rocks. Adakites of Sandur Schist Belt have low Sr which is a characteristic feature of the adakites in different greenstone belts of Dharwar Craton, indicating plagioclase fractionation during melting. The geochemical nature of adakites from Sandur Schist Belt indicate that they were formed by melting of a Fig. 8: Binary plot of Ti/1000 versus V (after Shervais 1982) indicating that the metabasalts are of intra arc terrain (IAT) and MORB settings

6 Geology and Geochemistry of Mafic and Felsic Volcanics of Joga (Sandur Schist Belt), Karnataka 1642 Fig. 9: Binary plot of Zr versus Zr/Y (after Pearce and Norry, 1979) for the Joga metabasalts showing their origin in MORB setting and affinity towards volcanic arc setting Fig. 10: Photomicrograph of metabasalt sample from Joga Petrography of metabasalts: Mineral Assemblages: Major minerals include Plagioclase (40%), Chlorite (35%), Sericite (20%), Actinolite (9%) and the accessories are primarily opaque minerals (1%) (Fig. 10). Microscopic examination: The rock is very fine-to fine-grained and shows relict intergranular texture. Dominant minerals are plagioclase and actinolite (altering to chlorite). The plagioclase grains are anhedral to subhedral in outline, grain size ranges from 0.01mm to 0.3mm. The grains are highly sericitised with development of sericite. Some of the deformation lamellae can also be observed in the plagioclase grains. The feldspar grains also show relict intergranular texture retaining its igneous origin (Fig.10). Few subhedral grains of quartz are also observed having low grain boundary angle. Amphiboles observed are mostly actinolites, which show weak alignment, mostly they are altered to chlorite and epidote. Several opaques are also observed with anhedral to subhedral grain boundaries, mostly in the vicinity of chlorite and epidote. These opaques range in size from 0.03mm to 0.2mm. The rock is deformed and the deformation planes are defined by chlorite and elongated quartz grains. Metabasalt sample collected from the shear zone with carbonate and vein quartz, has shown enormous sulphide minerals. Polished thin sections have revealed the presence of Pyrrhotite, Pentalandite, Chalcopyrite, Millerite and some suspected PGE. Petrographic study has revealed the presence of Ilmenite, Pyrite, Chalcopyrite, Pyrrhotite, Arsenopyrite and Goethite in metabasalts. Conclusions Based on the geological and geochemical studies, the following conclusions are drawn; 1. Basaltic rocks are Tholeiitic in nature. 2. They are associated with plate margin settings and accretionary processes. 3. Origin of Ocean floor environment/marine environment of deposition of flows as indicated by well-defined pillows. 4. Predominantly basaltic in nature with one exception which is picrobasalt. 5. Shows close affinity to intra arc terrain and MORB settings. 6. Intermixing of felsic volcanic similar to Adakites within the basic metavolcanic. 7. Metabasalts indicates high concentration of Nb and can be termed as Nb Enriched Basalts (NEB). 8. Metabasalt are also associated with sulphide mineralization and indicating the presence of Pentalandite, Pyrrhotite, Arsenopyrite, Chalcopyrite and Pyrite. Presence of Pentalandite is indicating possibility of occurrence of PGE (Platinum Group of Elements), for which detailed study is essential. Acknowledgements: The authors are grateful to Chairman, Department of Studies in Geology, Karnataka University, Dharwad for his encouragement and facilities extended to prepare this paper. The authors are grateful to CESS, Trivandrum for the petrochemical analysis. The authors are also thankful to PPOD Laboratory, GSI, Bangalore for providing facility to carry out petrographic studies. The authors grateful to referees and reviewers, whose suggestions improved the quality of the paper. Authors are also thankful to Chief Editor for his kind co-ordination to achieve this publication.

7 1643 Table 2: Average chemical composition of Joga metabasalt/rhyolite and that of Archaean Basalt standard Sample AB SiO TiO Al 2 O FeO MgO CaO Na 2 O K 2 O P 2 O Rb Sr Ba Th Nb Zr Y La Ce V Cr Co Ni (AB = Archaean Basalt standard sample referred from Manikymba et al., 2006) (Joga samples numbered 400, 550, 582, 705, 710 and 716 were analysed at CESS, Trivandrum). References [6] S.A.Drury., R.N.Holt, P.C.Vanclastern, and R.D.Beckinsale Sm-Nd and Rb-Sr ages of [1] Bhaskar Rao, Y.J., Sivaraman, T.V., Pantulu, Archaean rocks in Western Karnataka, South G.V.C., Gopalan, K. and Naqvi, S.M. Rb-Sr Ages India, J.Geol.Soc.India, v24, pp,1983. of Late Archaean Metavolcanics and Granites, [7] M.Hanuma Prasad, B. Krishna Rao, V.N. Vasudev, Dharwar Craton, South India, and Evidence for R.Srinivasan, and V. Balaram., Geochemistry of Early Proterozoic Thermotectonic Event(s), Archaean Bimodal volcanic rocks of the Sandur Precamb.Res., v59, pp Supracrustal Belt, Dharwar Craton, Southern India. [2] Chadwick, B., Vasudev, V. N. and Ahmed, N, The Jour.Geol. Soc.India, 47, Sandur Schist Belt and its adjacent Plutonic Rocks: [8] N.B.W. Harris and S.Jayaram,Metamorphism of Implications for Late Archaean Crustal Evolution cordierite gneisses from the Bangalore region of the in Karnataka, J.Geol.Soc.India, vol.47, Jan 1996, Indian Archaean.Lithos.v.15,pp 89-98, pp [9] M.Jayananda,T.Kano,J.J.Peucat and [3] Brian Chadwick, V.N.Vasudev and G.V.Hegde, S.Channabasappa. 3.35Ga komatiite volcanism in The Dharwar craton, southern India, and its late the Western Dharwar Craton, Southern India: Archaean Plate tectonic setting: current Constraints from Nd isotopes and whole rock interpretations and controversies, Proc.Indian geochemistry. Precambrian Research, 162(1- Acad.Sci (Earth Planet. Sci.), 106, No.4, December, 2): pp, pp , [10] S.Ko nig.,s.schuth,c.munker, and C. Qopoto. The [4] B.Chadwick, V.N.Vasudev, G.V.Hegde. The role of slab melting in the petrogenesis of high Mg Dharwar Craton, Southern India. Interpreted as a andesites: evidence from Simbo Volcano, Solomon Result of Late Archaean Oblique Convergence. Islands. Contributions to Mineralogy and Precambrian Research, v99, pp, Petrology, 153 (1):85-103pp, [5] S.A.Drury, R.W.Holt. The tectonic framework of [11] C.Manikyamba.S.M.Naqvi., Evidence of Archean south Indian Craton: A reconnaissance involving crustal shortening from deformed pillow lavas: an LANDSAT imagery, Tectonophysics, v65, 1-5pp. example from Sandur greenstone belt, Dharwar Craton. Current Science,

8 Geology and Geochemistry of Mafic and Felsic Volcanics of Joga (Sandur Schist Belt), Karnataka 1644 [12] C.Manikyamba., S.M.Naqvi,. Later Archaean mantle fertility; constraints from metavolcanics of the Sandur Scshit belt, India. Gondawana Research, [13] C.Manikyamba., R.Kerrich, S.M.Naqvi., M.Ram Mohan., Geochemical systematics tholeiitic basalts from the 2.7Ga Ramagiri-Hungund composite greenstone belt, Dharwar Craton. Precambrian Research, v134, pp [14] C.Manikyamba, Robert Kerrich,. Neoarchaean Boninites: implications for Archaean subduction processes. Earth and Planetary Science Letters, 65-83, [15] C.Manikyamba,R. Kerrich, Geochemistry of black shales from the Neoarchaean Sandur Superterrane, India:First cycle volcanogenic sedimentary rocks in an intraoceanic arc-trench complex. Science Direct, [16] C.Manikyamba., Robert Kerrich,. Crustal growth processes as ilustrated by the Neoarchaean intraoceanic magmatism from Gadwal greenstone belt, eastern Dharwar Craton, India. Gondawana Reserach, pp,2007. [17] C.Manikyamba,Robert Kerrich, Geochemistry of adakites and rhyolitees from the Neoarchean Gadwal greenstone belt, eastern Dharwar Craton, India: implications for sources and geodynamic setting. Canadian Journal of Earth Sciences, pp, [18] C.Manikyamba,R.Kerrich,T.C.,Khanna, A.K.Krishna,M.Satyanarayana. Geochemical systematics of komatiite-tholeiite and adakite-arc basalt associations: the role of a mantle plume and convergent margin in formation of Sandur Superterrane, Dharwar Craton, India. Lithos 106, pp, [19] C.Manikyamba,R.Kerrich,T.C.Khanna,M.Satyanar ayana, A.K.Krishna.Enriched and depleted arc basalts, with high Mg andesites and adakates: a potential paired arc-backarc of the 2.7Ga Hutti greenstone terrane, India. Geochemica et Cosmochimica Acta, v73, pp, [20] C.Manikyamba., Robert Kerrich, Eastern Dharwar Craton, India: Continental lithosphere growth by accretion of diverse plume arc terranes. Geoscience Frontiers, , [21] J.F.Moyen,H.Martin,M.Jayananda., and B.Auvray. Late Archaean granites: a typology based on the Dharwar Craton (India). Precambrian Research, 127(1-3), pp, [22] S.M.Naqvi, C.Manikymba,T.Gnaneshwar Rao,D.V.Subba Rao, M.Ram Mohan, D.Srinivas Sarma. Geochmical and isotopic constraints of Neoarchean fossil plume for evolution of volcanic rocks of Sandur greenstone belt, India, J.Geol.Soc.India, v60, 27-56pp, [23] S.M.Naqvi., and J.G.Rana Prathap, Geochemistry of adakites from Neoarchean active continental margin of Shimoga schist belt, Western Dharwar Craton, India; implication for genesis of TTG. Precambrian Research,156(1-2): 32-54pp, [24] A.R.Nutman,. SHRIMP U-Pb Zircon ages of acid volcanic rocks in the Chitradurga and sandur groups and granites adjacent to the Sandur Schist belt, Karnataka. Journal Geological Society of India, pp,1996. [25] J.B.Peucat,. Age of the Holenarsipur greenstone belt, relationship with the surrounding gneisses (Karnataka, South India). Journal of Geology, pp,1995. [26] B.P.Radhakrishna. Archean granite greenstone terrain of South India.In:S.M.Naqvi and J.J.W.Rogers (Editors), Precambrian of South India. Mem.Geol.Soc.India,4:1-46pp,1983. [27] J.P.Richards., and R.Kerrich. Special paper: adakite-like rocks: their diverse origins and questionable role in metallogenesis. Economic Geology and the Bulletin of the Society of Economic Geologists, 102(4): pp [28] Robert Kerrich and C.Manikyamba, Contemporaneous eruption of Nb-enriched basalts- K-adakites-Na-adakites from the 2.7Ga Penakacherla terrane: Implications for subduction zone processes and crustal growth in the eastern Dharwar Craton, India, Can.J.Earth.Sci.49; (2012). [29] A.Roy and S.K. Biswas,. Metamorphic history of Sandur Schist belt, Karnataka. J.Geol.Soc.India, v20, pp , [30] A.Roy and S.K.Biswas. Stratigraphy and structure of Sandur Schist belt, Karnataka. J.Geol.Soc.India, v24, 19-28pp, [31] S.R.Suresh and M.Basavanna, Geology and Geochemistry of Banded Iron Formations from Joga (Sandur Schist Belt) and associated gold mineralization. International Journal of Earth Sciences and Engineering. Vol.7, No.2, pp,April 2014 [32] P.N.Taylor,S.Moorbath,B.Chadwick,M.Ramakrish nan, and M.N.Vishwanatha. Petrography, chemistry and isotopic ages of Peninsular gneiss, Dharwar Acid Volcanic rocks and the Chitradurga granite with special reference to the Late Archaean evolution of Karnataka Craton, Southern India. Precambrian Research., v23, pp [33] A.F.Trendall, de J.R.Laeter, D.R.Nelson, D.Mukhopadhyay. A precise zircon U-Pb age for base of the BIF of the Mulaingiri Formation (Bababudan Group, Dharwar Supergroup) of the Karnataka Craton. J.Geol.Soc.India,v50, pp,1997.

9 1645 [34] J.R.Zachariah,. Accretionary evolution of the Ramagiri schist belt, Eastern Dharwar Craton,. J.Geol. Soc. India, pp, [35] Miscellaneous Publications compiled by GSI, operation Karnataka & goa, Bangalore [36] S.M.Naqvi and J.J.W.Rogers. Precambrian Geology of India. Oxford Univ.Press, New York, 223pp [37] J.N.Swaminath, and M.Ramakrishnan. Present classification and correlation.in:j.swaminath and M.Ramakrishnan (Editors),Early Precambrian Supracrustals of Southern Karnataka. Mem.Geol.Surv.India, 112:23-38pp,1981.