Research Journal of Recent Sciences _________________________________________________ ISSN 2277-2502 Vol. 4(1), 99-108, January (2015) Res.J.Recent Sci. International Science Congress Association 99 Structural and Remote Sensing Studies of Achankovil suture of South India Besheliya J. and Manimaran G. School of Tectonics, Department of Geology, V.O. Chidambaram College, Tuticorin-628008, Tamil Nadu, INDIAAvailable online at: www.isca.in,www.isca.me Received 8th January 2014, revised 24th March 2014, accepted 24th July 2014Abstract Remote sensing studies based on Landsat imageries and relief map followed by field studies have been carried out along the Kayathar-Tirunelveli-Valliyur transect of Achankovil suture zone. Five patterns of lineaments, two sets of conjugate shear system of dextral Tenmalai shear of D and sinistral Achankovil shear of D3 were delineated. F isoclinal rootless fold, E-W upright folds of F of D; reorientation of F upright folds during D deformation, F doubly plunging fold due to interference of F and F folds were identified. The major isoclinal ‘S’ type Vallanadu quartzite fold is a shear fold and its eatern limb displaced sinistrally for 11 km are highlighted from field and remote sensing studies. The F, F and F co-axial folding suggest continued subduction of Madurai block sediments under Kerala Khondalite block through Achankovil suture zone during periods from D-D deformations of Neoproterozoic to Cambrian time. F cross folding of F and F folds were formed during late D deformation. Keywords: Achankovil suture, South India, lineaments, folding episodes, Remote sensing. Introduction Finding the suture signatures are important in fitting of the Gondwana supercontinent. South India is a key area which existed as a centre of Gondwana land. The Palghat-Cauvery shear zone (PCSZ), located in South India is widely assigned a major tectonic boundary and it may be a continuation of one of the Madagascar shear zones, either the Betsimisaraka suture of Madagascar2-4 or the Bongolava Ranotsara shear zone (BRSZ)5,6. The Southern Granulite Terrain comprise of the Kerala Khondalite Block (KKB) in the south and Madurai Granulite Block (MGB) in the north separated by Achankovil shear zone (ASZ)7,8. The MGB, the largest crustal block in South India occurs immediate south of PSCZ. This block comprises dominantly of charnockite massifs with enclaves of metasedimentary rocks including pelites, iron formations, metamorphosed calc-silicate rocks and quartzites. The southern boundary of Madurai block is marked by the late Proterozoic ASZ. This zone strike NW-SE to WNW-ESE and extends laterally to about 210 km and with a width of 20-50 km at places, and is considered as a shear zone that seperates the unique rock units to the north and the south10,11. The ASZ mainly consists of garnet-biotite gneisses, charnockites, cordierite gneisses, calc silicates and basic granulites, intruded by a number of late Neoproterozoic-Cambrian granites and also pyroxenites and hornblendites. To the south of KKB is the Nagercoil Block, consists of igneous charnockites with migmatitic metapelites and metacarbonates. Several research workers have correlated the ASZ with the Ranotsara shear zone (RSZ) in southern part of Madagascar2,3,12,13. Rajesh and Chetty14 have explained the crustal-scale structures represented by the en-echelon pattern of lineaments in the ASZ10 as the features suggesting the sinistral transpressional tectonics, assumed to be of Neoproterozoic time. Folding episodes and different sets of lineaments were delineated from remote sensing studies of southern Betsimisaraka suture of Madagascar. Different geodynamic settings can be identified through remote sensing studies15. From digital elevation model (DEM) studies of western Crete, Greece, the potential faults and lineaments were identified16. The change of landuse landcover detection using remote sensing and GIS techniques were attempted for Tuticorin coast17 and for Golaghat district of Assam18. Manimaran et al.,19 have identified four types of major shear-lineaments from Ambasumudram-Tenkasi transect of ASZ as follows: i. ENE-WSW dextral shear lineament of Ddeformation. ii. NNW-SSE to NW-SE dextral shear lineament (Tenmalai shear) of D2. iii. NW-SE to WNW-ESE sinistral shear lineament (Achankovil shear) of D and iv. N-S sinistral shear lineament (Toranamalai shear) of D. The present study is aimed at understanding of structural features like folds and shears in the Kayathar-Tirunelveli-Valliyur transect of the ASZ and tectonics of continental collision events along the tectonic boundary between Madurai Granulite block and Kerala Khondalite block. Shaded releif map prepared from shuttle Radar Topography Misssion (SRTM USGS)14 and Google Landsat imageries are used to delineate various lineaments, shears and folds from the study area falling across the ASZ (Achankovil suture zone) and the confirmations are made through field checks during ground traverses. Mid-crustal section of ASZ: Recently, a tectonic model using pacific-type orogeny to explain the evolution of Neoproterozoics from the southern part of South India and its final amalgamation within the Gondwana Assembly was proposed. The occurrance of arc magmatic rocks together with high P/T lithotypes denotes the deeply eroded zones of a subduction system. Suture zones Research Journal of Recent Sciences _____________________________________________________________ ISSN 2277-2502Vol. 4(1), 99-108, January (2015) Res.J.Recent Sci. International Science Congress Association 100 are rarely, well-defined or easily recognizable simple lineaments20. Suture mark the zones along which total subduction of oceanic lithosphere has been resulted and along which two previously seperated continental masses have joined. Coward et al.,21 define suture zones as ductile shear zones produced by thrusting along convergent plate boundaries and they range from few hundred meters to tens of kilometers wide, suture zones become less distinctive at great crustal depth (i.e., a criptic suture), where they may be represented by a shear zone with similar metamorphic rocks on both sides22. There is an increasing evidence to infer that Pacific-type orogen must have prevailed in the past in various parts of the phanerozoic age. The tectonic evolution of southern India can be related to a dominant Pacific-type in the orogeny which was started as Andean-type in the Neoproterozoic and ended as Himalayan-type in the Cambrian. The pattern of orogen is difficult to reconstruct because of the lack of tectonic data. In previous studies, the two major crustal scale zones in southern India-the Palghat-Cauvery shear zone and Achankovil shear zone have been loosely defined as shear zones based on petrology, geochemistry, geochronology and available structural features the above two zones could be critical boundary markers (i.e. suture zones). Dhanunjaya Naidu et al.,23 studied two parallel magnetotelluric (MT) traverses across the Achankovil shear zone (ASZ) in southern India using a wide band data acquisition system and their derived model shows distinct high electrical resistivity (�1000 ) for the upper crust below the Madurai Granulite block (MGB) with a gentle dip towards south and a northerly dip below the Kerala Khondalite Block (KKB). The lower crust of MGB and KKB is resistive below while it is moderately conductive (500 ) below ASZ. The ASZ is a tectonic divide between the MGB to the north and KKB to the south. The seismic, gravity and heat flow data suggest a high dense and moderately conductive mantle material brought upto the mid-lower crust and a thermally eroded crust with a flower structure at depth are pointing out the collisional suture nature of ASZ. Hence the identification of structural features of the study area through remote sensing and field traverses are very vital to clarify the suture status of ASZ where the old mid-crustal section is currently exposed. Remote sensing studies Google landsat imageries and the shaded relief map (modified after Rajesh and Chetty14) prepared from Shuttle Radar Topography mission (SRTM-USGS) are used to delineate various lineaments, shears and folds from the study area. The figure 1 shows the lineaments, shears, folds and displaced lithological units of the Tirunelveli area of ASZ. Figure-1 A, B A shaded relief map from Shuttle Radar Topogrphy Mission (SRTM USGS) modified after Guru Rajesh and Chetty, 2006 showing the study area (figure 1 A). The lineament map showing lineaments, shears and folds of the Kayathar-Valliyur transect of ASZ, South India Research Journal of Recent Sciences _____________________________________________________________ ISSN 2277-2502Vol. 4(1), 99-108, January (2015) Res.J.Recent Sci. International Science Congress Association 101 Five set of lineaments namely i) E-W; ii) N-S; iii) NE-SW; iv) NW-SE to NWW-SSE and v) WNW-ESE to NW-SE are recognised from remote sensing studies. From the field studies, it is known that the area is mainly suffered with two sets of conjugate shearing. 1. A ductile natured, NNW-SSE to NW-SE main dextral shears (Y-shear of Tenmalai shear) conjugating with ductile NE-SW striking subordinate sinistral shears and 2. A brittle-ductile natured NW-SE to WNW-ESE striking sinistral shear (Achankovil shear) conjugating with N-S striking dextral, brittle-ductile shears are commonly observed in the field and shear sense are assigned to the lineaments. The geological map of the study area is given in the figure 2. On examination of lineament map (figure 1) and geological map (figure 2), the Tenmalai conjugate shear system are seen in association with the genesis of grey granites, cordierite gneisses and F folds of D. Whereas the Achankovil conjugate shear system are formed genetically related to bands of typical antiperthitic pink granites and veins and dykes of ultrabasic rocks of hornblendites and pyroxenites are unique features of the shear zone. F folds are developed during Achankovil sinistral shearing event of D. The eastern limb of the ‘S’ type major quartzite fold sinistrally displaced for a length of 11 km are observed in the field. The careful examination of the grey granite linear band at Vallanadu also sinistrally displaced for a length of approximately 11 km and seperated by a band of cordierite gneisses are also traced in the field survey. The above feature suggests that the Achankovil shear systems of Dare of brittle-ductile nature. The ductile deformation of Dsuggests that they are formed at deep seated conditions. Whereas the brittle-ductile deformation of D3 suggests that it was happened during exhumation at higher-middle crustal level in the ASZ crustal section. Figure-2 The geological map of Kayathar-Valliyur transect of Achankovil Shear Zone, South India Research Journal of Recent Sciences _____________________________________________________________ ISSN 2277-2502Vol. 4(1), 99-108, January (2015) Res.J.Recent Sci. International Science Congress Association 102 Folding episodesFolding episodes are well preserved in the calc-silicate rocks and khondalites and they are also delineated from granites and charnockites also. The F isoclinal, tight fold with N-S axial planes with very steep dipping towards SE are observed in pelitic gneisses of Ervadi and calc-silicate rocks of Thalaiyuthu and are formed during D deformation which resulted in the development of gneissic foliation. When it is associated with other folds F and F it shows different attitudes due to the rotation of F folds. The east of Kayathar a quartzite showing isoclinal tight F folds striking N-S dipping 60°W are traced in the field (figure 1). North of Palayamkottai at Keelapattam the quartzite fold again folded during D dextral deformation. The axial plane of F is along N-S and dipping steep towards E (70°) is observed in the field. The F isoclinal sheath fold with axial plane striking N45°W 50°N; and a co-axial F plunging fold with axial plane striking N40°W dipping 55°SW and a doubly plunging co-axial folds with fold axes plunging 55° N45°W and 35° S42°E are traced from the northwestern corner of the study area. The above folds are observed in charnockite and calc-silicate rocks. The co-axial F isoclinal fold with axial plane N35°W 70°SW and F3 co-axial plunging fold with axial plane striking N55°W are also observed in the field. The grey granite of Maruvathalai shows elongate upright Ffolds which is showing F open folding formed during D due to ENE-WSW compression. The F2 of D is formed during N-S compression. Both Tenmalai dextral shearing of D and Achankovil sinistral shearing of D are observed in the grey granites of Maruvathalai. The earliest ENE-WSW dextral shear terminating against the grey granite and dextrally displacing the quartzites are also seen in middle of the imagery (figure 3).Figure-3 The F upright fold of D in grey granite at Maruvathalai. It is a sinistrally reactivated F fold during D resulted in a Fopen fold, (courtesy-Google image) At Samiyarpottai, F upright fold (Lingamalai) formed in cordierite gneiss exposed near Ervadi and a westerly moderately plunging calc-silicate F fold with axial plane striking NW-SE and with steep dip towards NE is also visible at the southeastern side of Samiyarpottai F upright fold (figure 4). Courtesy-Google image Figure-4 upright fold of cordierite gneiss at Samiyarpottai near Ervadi. Also seen a westerly plunging F2 fold in calc-silicate rock Research Journal of Recent Sciences _____________________________________________________________ ISSN 2277-2502Vol. 4(1), 99-108, January (2015) Res.J.Recent Sci. International Science Congress Association 103 The E-W running elongated Rettiyarpatti hill (figure 5) is examined at highway road cutting and was identified as upright train fold with axial plane vertical and with subhorizontal fold axis plunging 10-15° towards west. It is an upright box like train fold running for a length of 7 km and amplitude of the fold is 50 to 70 metres above the ground surface. At places across the length of the fold NW-SE striking dextral Tenmalai shearing (D) are mainly observed. At places also NW-SE Achankovil sinistral shears (D) resulted in F3 open fold with N-S axial plane are also observed. Repetition of quartzite and khondalites are seen in the upright antiform and synform folds. Both core and limbs of the fold were intruded by later formed hornblendites and pyroxenites. The style of the F upright train fold suggest that it was formed due to a strong N-S subhorizontal compression during the subduction of N-S striking sedimentary units and buckling of N-S striking pile of sediments might be resulted in F upright train folds and upright dome type and lingam like F2 folds. South of Ervadi, double upright folds called Erettamalai are observed (figure 6). The above upright folds and plunging folds of F suggest that the area was subjected to N-S subhorizontal compression of D. Cordierite gneiss exposure at Muthuswamigal Sidhirakoodam near Valliyur (figure 7) shows a N-S striking F isoclinal folds. The NW-SE striking right over-stepping sinistral shear lineaments indicate sinistral transpression during D. It also shows coaxial F and F folds. An excellent major S type F fold is exposed in quartzites at Vallandu hills (figure 8). It is an isoclinal, steeply NE dipping (65-75°) fold with axial plane also dipping NE and fold axis plunging 30° towards NW.Courtesy-Google image Figure-5The E-W running F upright train fold at Rettiyarpatti near Palayamkottai. F3 open fold developed due to later formed sinistral Achankovil shearing of D are also highlighted Research Journal of Recent Sciences _____________________________________________________________ ISSN 2277-2502Vol. 4(1), 99-108, January (2015) Res.J.Recent Sci. International Science Congress Association 104 Courtesy-Google image Figure-6 Double upright folds aligned along E-W called Erattamalai observed at south of Ervadi are seen Courtesy-Google imageFigure-7 A hillock at Muthuswamigal Sidhirakoodam near Valliyur showing N-S striking F isoclinal folds and N-W striking F and co-axial folds. NW-SE right over stepping sinistral shear lineaments indicates sinistral Transpression Research Journal of Recent Sciences _____________________________________________________________ ISSN 2277-2502Vol. 4(1), 99-108, January (2015) Res.J.Recent Sci. International Science Congress Association 105 The eastern limb of this isoclinal synform fold shows sinistral displacement of quartzite for a length of 11 km was found during field mapping (figure 1,8). Based on the orientation of NW-SE sinistral shear lineaments and ‘S’ type F3 isoclinal plunging folds with NW-SE striking and NE steep dipping suggest that the D3 deformation was of sinistral transpression nature and formed under a ENE-WSW subhorizontal compression. The NW-SE striking doubly plunging F3 fold at north of Valliyur was folded openly as F4 fold are observed near Samiyarpottai (figure 9) suggest that the F4 folding was formed from NW-SE compression of D4. The F4 folds are not well developed in the present study area. Courtesy-Google image Figure-8 A sinistrally displaced ‘S’ type quartzite fold at Vallanadu Courtesy-Google image Figure-9 The F cross folding observed in doubly plunging F fold at north of Valliyur Research Journal of Recent Sciences _____________________________________________________________ ISSN 2277-2502Vol. 4(1), 99-108, January (2015) Res.J.Recent Sci. International Science Congress Association 106 Results and Discussion The formation of ductile shear zones remains an enigma of geology24. A shear zone is a planar zone of high deformation/strain compared to the adjacent domain25. In coaxial strain (pure shear) the deformation is termed as compression or shortening/flattening and in non-coaxial strain (simple shear) it is termed as shearing26. The combination of both pure shear and simple shear is common in transpression tectonics (general shear27). Flattening co-axial strain features were identified by Ghosh et al.,28 and Radhakrishna et al.,29; and intensely transposed fabrics, shallow plunging to sub-horizontal stretching lineations and asymmetric structural features were identified from ASZ by Rajesh and Chetty14 are non-coaxizl feature. Fossen and Tickoff30, Dewey et al., 27and Rajesh and Chetty14 envisage the importance of steep to subvertical foliations as a supportive evidence of transpressional regime. As highlighted from the present study area of ASZ both subhorizontal and subvertical stretching lineations, Tenmalai dextral ductile shearing of D followed by Achankovil sinistral brittle-ductile shearing of D and common observation of steepto subvertical foliations suggest the general shear zone pattern (transgression regimes) to the ASZ. From the field evidence it is known that both shearing and folding of ASZ are genetically related. Based on seismic, gravity and deep electrical sounding and petrological studies suture status is now assigned to ASZ2,3,31. The ubiquitous interaction of veins and brands of hornblendites and pyroxenites in ASZ suggest mantle derived ultrabasic intrusive of mid-crustal level during a subduction of Madurai block sediments through Achankovil suture/shear zone (ASZ) under kerala khondalite block. The identified isoclinal, tight recumbent to reclined F fold with differently oriented axial plane striking N-S to NW-SE suggests that a layer parallel subduction (compression) (N-S to NNE-SSW striking Splanes) was inferred for F of D deformation. The F upright folds and F plunging folds with axial plane striking NW-SE and associated with NW-SE striking dextral shear planes dipping steeply NE were formed due to N-S subhorizontal compression during D episode. The doubly plunging F3 folds (NW and SE or NNW-SSE) and NW-SE striking F3 co-axial plunging folds, ‘S’ type plunging co-axial folds and F3 co-axial upright folds are identified from remote sensing studies and field observations. The above structures are related to NW-SE striking sinistral shear planes dipping steep SW were resulted due to ENE and WSW compression during a continued subduction of sediments under ASZ. The cross folding (F) of earlier folds due to NW-SE compression related to N-S striking Toranamalai shearing19 are seldom observed in the present study area of ASZ. During D, D and D the formation of F, and F co-axial plunging folds were identified and these folds might be resulted due to a continued subduction of sediments during D to D3 deformation i.e. multiphase co-axial folds represents fingerprints of subduction signatures?, which warrants further studies or supportive evidence studies from other suture zones of the world. Conclusion The N-S Tirunelveli sector of Achankovil shear zone is mainly sheared with two sets conjugate shear system of D (dextral Tenmalai shear) and of D (sinistral Achankovil shear). From the field evidence, it is observed that shearing was followed by folding events. The F rootless isoclinal folds of different orientation are due to rotation of F folds during subsequent deformations. E-W oriented upright folds of F and NNW-SSE oriented rotated F folds during later shearing events of D; Northwesterly and southwesterly doubly plunging folds are formed due to interference of F and F folds. The isoclinal ‘S’ fold observed in quartzite hillock Vallanadu was formed during sinistral Achankovil shearing followed by a shear folding along Achankovil shear and also displacements of quartzite and associated grey granite for a distance of 11 km were happened. The observed F, F and F co-axial folds with NW-SE to NNW-SSE striking axial planes, suggest a continued subduction from F1 of D1 through F of D to F of Ddeformation episodes. A continued subduction of Madurai block under Kerala Khondalite block along Achankovil suture envisaged for the period of 670 to 550 Ma. The late D4 deformation openup the folds F and F resulted in open type cross folds with E-W or N-S oriented axial planes. Acknowledgement The first author thanks the Department of Science and Technology, Government of India, New Delhi for awarding DST INSPIRE Fellowship (IF130233-2013). The second author also thanks Department of Science and Technology, Government of India, New Delhi for DST Pilot Project No.SR/S4/ES-498/2010). References1.Chetty T.R.K. and Bhaskar Rao Y.J., The Cauvery shear zone, Southern Granulite Terrain, Southern India: Evidence for Neoproterozoic Transpressional Tectonics, centenary publication, Geological survey and Mines Bureau, SriLanka, 33-36 (2003)2.Santosh M., Maruyama S. and Keisato, Anatomy of a Cambrian suture in Gondwana: Pacific-type orogeny in southern India?, Gondwana Research, 16, 321-341 (2009)3.Chetty T.R.K. and Santosh M., Proterozoic orogens in Southern peninsular India: contiguities and complexities, Jou Asian EarthSciences(2003)http://dx.dol.org/10.1016/jseaes.2013.02.021 (in press) Research Journal of Recent Sciences _____________________________________________________________ ISSN 2277-2502Vol. 4(1), 99-108, January (2015) Res.J.Recent Sci. International Science Congress Association 107 4.Raharimahefa T. and Kusky M.T., Structural and remote sensing studies of the southern Betsimisaraka suture, Madagascar, Gongwana Research, 10, 186-197 (2006)5.de Wit M.J., Bowring S., Ashwal L.D., Randrianasolo L.G., Morel V.P.L. and Rambeloson R.A., Age and tectonic evolution of eoproterozoic ductile shear zones insouthwestern Madagascar with implication for Gondwana studies, Tectonics20, 1-45 (2001) 6.Collins A.S. and Windley B.F., The tectonic evolution of central and northern Madagascar and its place in the final assembly of Gondwana, Journal of Geology, 110, 325-340 (2002) 7.Drury S.A., Harris N.B.W., Reeves Smith G.J and Wightman R.T., Precambrian tectonics of crustal evolution in South India, Jour Geology, 92, 3-20 (1984)8.Chetty T.R.K., Proterozoic shear zones in southern granulite terrain, India, Gondwana Research, Gr Mem, , 77-89 (1996)9.Santosh M., Maruyama S. and Omori S., A fluid factory insolid Earth, Lithosphere (Geological Society of America) , 29-33 (2009 b) 10.Manimaran G., Petrological and structural studies of the Northwestern part of the Tambraparni shear zone, South India, Unpubl, Ph.D Thesis Univ of Kerala, Trivandrum, India, 289 (1995) 11.Rajesh H.M., Santosh M. And Yoshida M., Dextral Pan African shear along the southwestern edge of the Achankovil shear Belt, South India, constraints on Gondwana reconstruction: A discussion, J Geol, 106, 105-109 (1998)12.Manimaran G., Deepak Bagai and Roy Chacko P.T., Chrysoberyl from southern TamilNadu of South India, with implication for Gondwana studies, Mineral Exploration: Recent strategies, Eds Rajendran S. et al., NIPA, NewDelhi 63-76 (2007)13.Collins A.S., Santosh M., Braun I. and Clark C., Age and Sedimentery provenance of thesouthern granulites, South India, U-Th-Pb SHRIMP secondary ion mass spectometry, precambrian Research, 155, 125-138 (2007) 14.Guru Rajesh K. and Chetty T.R.K., Structure and tectonics of the Achankovil Shear Zone, Southern India, Gondwana research, 10, 86- 98 (2006)15.Macro Rinaldi., Remote sensing capability in structural geology analysis of different geodynamic setting: the example of Al Qarqaf Arch (Libya), scientifica Acta, , 43-46 (2007) 16.Papadaki E.S., Mertikas S.P. and Apostolos Sarris., Identification of lineaments with possible structural arigin using Aster images and DEM derived products in western crete, Greece, EARSeL e proceedings, 10, 9-26 (2011) 17.Selvam S., Use of Remote sensing and GIS Techniques for Landuse and Land cover Mapping of Tuticorin coast, Tamilnadu, Universal Jour Environ Research and Technology, 2(4), 233-241 (2012) 18.Phukan P., Thakuriah G. and Saikia R., Landuse Landcover change detection using remote sensing and GIS Techniques – A case study of Golaghat district of Assam, India, International Research Journal of Earth Sciences, 1(1), 11-15 (2013) 19.Manimaran G., Roy Chacko P.T., Manimaran D., Selvam S., Antony Ravindran A., Besheliya J. and Sugan M., Shear-Lineaments Analysis of Ambasamudram-Tenkasi Transect of Achankovil-Tambraparni Shear Zone, South India, IRJ Earth sciences, 1(3), 1-10 (2013) 20.Gansser A., The Geology of the Himalayas, Interscience, Newyork, 298 (1964) 21.Coward M.P., Jan M.Q., Rex D., Tarney J., Thirlwall M.F. and Windley B.F., Geotectonic framework of the Himalaya of N pakistan, Jour of the Geol Soc (London), 139, 299-308 (1982)22.Burke K. and Dewey J.F., An outline of Precambrian Plate Development, Academic Press, London, 1035-1045 (1973) 23.Dhanunjaya Naidu G., Manoj C., Patro P.K., Sreedhar S.V. and Harinarayana T., Deep electrical signatures across the Achankovil shear zone, Southern Granulite Terrain inferred from magnetotelluries, Gondwana Research, 20, 405-426 (2011) 24.Montesi L.G.J., fabric development as the key for forming ductile shear zones and anabling plate tectonics, Jour Structural Geology, (2013) http://dx.dol.org/10.1016/j.jsg 2012.12.011 (in press) 25.Ramsay J.G. and Huber M.I., Ductile and brittle shear zones, The Techniques of Modern Structurl Geology, Academic Press, London, 595-640 (1987)26.Williams P.F., Goodwin L.B. and Ralser S., Ductile deformation processes, In: Hancock, P.L. (Ed.), Continental Deformation, Pergamon Press, 1-27 (1994) 27.Dewey J.F., Holdsworth R.E. and Strachan R.A., Transpression and Transtension zones, In: Holdsworth R.E., Strachan R.A., Dewey J.F (Eds.), Continental Transpressional and Transtensional Tectonics, Geological Society of London, Special Publications, 135, 1-14 (1998) 28.Ghosh J.G., de Wit M.J. and Zartman R.E., Age and tectonic evolution of Neoproterozoic ductile shear zones in the Southern Granulite Terrain of India, with Research Journal of Recent Sciences _____________________________________________________________ ISSN 2277-2502Vol. 4(1), 99-108, January (2015) Res.J.Recent Sci. International Science Congress Association 108 implications for Gondwana studies, Tectonics, 23,(2004) 29.Radhakrishna T., Joseph M. and Mathai J., Southern Granulite Terrain of India and constraints for the Precambrian continental Assemblies, Joint AOGS 1stAnnual Meeting and APHW conference, Singapore, 55-56 (2004) 30.Fossen N. and Tickoff B., Extended models of transpression and transtension and application to tectonic settings, In: Holdsworth R.E., Strachan R.A., Dewey J.F (Eds.), Continental Transpressional and Transtensional Tectonics, Geological Society of London, Special Publications,135, 15-33 (1998) 31.Tomson J.K., Bhaskar Rao Y.J., Vijayakumar T. and Choudhary A.K., Geochemistry and neodymium model ages of Precambrian charnockites, Southern Granulite Terrain, India: consraints on terrain assembly, Precambrian Research, 227, 295-315 (2013)