- Email: [email protected]
Precambrian Central India and its role in the Gondwanaland-Rodinia Context
208
by low-grade schists. Relationships of the high-grade rocks with the surrounding greenschist facies rocks are marred by late- to post-kinematic granitoid intrusions. Geochemical analysis of the rocks shows that they are enriched in large ion lithophile elements and depleted in high field strength elements, typical for an island arc tectonic setting. The area defines a structural domain showing three phases of deformation (D,-DJ. D, structures have only been found in the hornblende gneiss, while D, deformation features are prevalent in both the hornblende gneiss and mica gneiss. All rock units in the region, including the weakly deformed granite, bear signatures of the third phase of deformation, D,. The most common foliation (gneissosity) in t h e rocks, D,, dips nearly uniformly at about 75" towards NNW (and rarely to SSE). Relicts of an early thrust tectonics in the region are manifested by imbricate structures showing an eastdirected shearing. The thrusts are later superimposed by a widespread extensional tectonics. Prevalent niesoscopic shear zones characteristically showing normal sense of slip support this. Shear foliation related to these high strain zones bear stretching lineations that plunge moderately to the NW. Several shear sense indicators suggest that shearing has been top-to-NW. Some of the most common
Gondwana Research, I/: 4, No. 2, pp. 208-21 I . 02001 International Association for Gondwana Research, Japan ISSN: 1342-937X
types of shear criteria are S-type asymmetrically folded quartz/pegmatite veins, rotated, pre-shearing foliation, and tailed (o-type) porphyroblasts of K-feldspar. In addition to the ductile shear zones, brittle and brittleductile shear zones also consistently show a normal, dipslip faulting. The extensional deformation affects preexisting planar fabric in all rock units and hence postdates metamorphic events. Not withstanding the metamorphic and structural complexity of the Anseba region, earlier workers have attributed the whole of central Eritrea to belong to the same group of rocks, the Nakfa terrane. The lack of uniformity in both t h e structural style and t h e metamorphic grade in this small region as seen in the present work casts doubt on earlier terrane classification in the Precambrian of Eritrea. This study shows that late, extensional tectonics is prevalent in a region previously affected by large-scale thrust tectonics. The sequence of events leads to the likely conclusion that the window of high-grade rocks in the Anseba region is the result of the interplay of exhumation process and extensional tectonics. If this interpretation is accepted, it follows that post-thrusting exhumation processes and extensional tectonics were important in the late stages of the ANS terrane amalgamation during the Neoproterozoic.
GR
Gondwana Research
Precambrian Central India and its role in the GondwanalandRodinia Context M. Yoshidal, R.S. Divi2and M. Santosh3 * J
Department of Geosciences, Osaka City University, Osaka 558-8585, Japan, E mail:[email protected] Department of Earth and Envivonmentaf Sciences, Kuwait University, Kuwait Department of Natuval Envivonmental Science, Kochi University, Kochi 780-8072, Japan
The Precambrian of Central India The Precambrian of Central India is centered by the Proterozoic Central Indian Tectonic Zone (CITZ) (Radhakrishna and Naqvi, 1986) which is juxtaposed with the Bundelkhand craton to the north and the Bastar Craton
to the south (Fig. 1).The western extension of CITZ is regarded, by several researchers, to continue to the Aravalli-Delhi Fold Belt, which runs along the western fringe of the Bundelkhand block. The eastern margin of the CITZ is covered by the Cenozoic Ganges sediment. To the further east, the Precambrian Shillong and Dispur
209
L
L/A P r e r m i I I i.n/Prs=
cratonic terrain
Fig. 1. Amalgamation of East Gondwana during the Grenvillian period. CITZ : Central Indian Tectonic Zone. IM: India-Madagascar paleocontinent including the Bastar craton. B: Bundelkhand craton. KH: Kalahari craton. E: Eastern Ghats Belt. CP: Capricorn orogen. PJ: Pinjarra orogen. AF: Albany Fraser orogen. CG: Congo craton. N AM: North American craton. NA: North Australian craton. SA: South Australian craton. (The original figure is modified from Yoshida and Santosh, 1996; data source is given in it)
blocks of Meghalaya and Assam show some similarity with the eastern part of the CITZ. In the East Gondwana reconstruction during Late Mesoproterozoic, the CITZ is generally regarded to continue to the Albany-Flaser Mobile Belt of southwestern Australia through the Shillong block (e.g. Harris, 1993). To the southeast, the Eastern Ghats Granulite Belt of Orissa also bears similar characteristics with the CITZ, and several researchers delineate a continuous Grenvillian Belt from the CITZ to both southwestern Australia and the Eastern Ghats Granulite Belt to the Grenvillian Belt proper of North America through the Circum East Antarctic Mobile Belt (Fig. 1, Yoshida, 1995; Unrug, 1996). The CITZ is generally regarded to have acted principally as the suture during the Paleoproterozoic period (ca. 22002100 Ma) between the northern and the southern Indian shields (e.g. Yedekar et al., 1990). It is pointed out, however, that a widespread and strong tectonothermal event took place during 1700-1500 Ma as well (Sarkar et al., 1998).Weak thermal events of ca. 1100-600 Ma have also been known. Thus, it is principally a pre-Rodinia suture, and hence is important for considering the global crustal processes before the East Gondwana-Rodinia. Gondwana Research, V. 4, No. 2,2001
The Central Area of the CITZ On the northern margin of the central domain of the CITZ, which has about 250 km in width (Acharrya and Roy, 2000; Geological Survey of India, 19981, occurs the Paleoproterozoic Mahakoshal Group mainly composed of shelf to slope facies marine assemblage with subordinate meta-volcanic rocks of basaltic composition. This group shows vertical structures reflecting horizontal compressional stress normal to the major trend of the Mahakoshal basin and CITZ (Bandyopadhyay et al., 1995). The possible Paleoproterozoic Sausar Group composed of the metasupracrustal package of stable continental margin sediments with minor acid volcanic rocks occupies the southern margin of the CITZ. Isoclinal folds and possible nappe structures developed (Bandyopadhyay et al., 1995; Kano et al., 2001) and high-pressure granulite metamorphism preceding the major tectonothermal events including the ITD path of metamorphism (Bhowmik et al., 1999) is identified, which may indicate a continent-continent collisional event in earlier tectonic history.
210
The possible Paleoproterozoic Sakoli Group is distributed at the northern margin of the southern Indian Shield. This group is composed predominantly of metapelitic rocks with minor bimodal volcanics showing low-K island arc tholeiite to calc alkaline trend. The metasediment package is characterized by continental margin conditions. In the Bundelkhand craton to the north of the CITZ, are developed the platform sediments of the lower Mesoproterozoic Bijawar Group and the middle to upper Mesoproterozoic Vindhyan Supergroup. In the Bastar craton to the south of the CITZ, Paleoproterozoic greenstone belt of the Dongargarh Supergroup occurs, which is composed of the lower volcanigenic Nandgaon Group and the upper volcanoclastic Khairagarh Group separated by an unconformity. Basement granite/gneisses are called the Bundelkhand Granite and Bundelkhand Gneiss in the north, the Tirodi gneiss in the central zone of the CITZ, the Amgaon Gneiss in the southern zone of CITZ, and the Bastar Gneiss in the Bastar craton. Reliable radiometric ages from this area are quite insufficient (refer, Kano et al., 2001) and therefore, age constraints of most of the above geologic units are quite poor. This gives us a difficulty in drawing a model of tectonic evolution of this area. A possible event stratigraphy of the central area of the CITZ is tentatively summarized in Fig. 2.
Albany Flaser
Capricorn
CITZ
,'.' ,' ".'
Eastern Extension of the CITZ Proterozoic mobile belts in western Australia include the Capricorn, Albany-Flaserand Pinjarra orogens (Myers, 1993; Myers et al., 1996). The Pinjarra orogen is poorly known, but is regarded to be a recyclic orogen of the Grenvillian and Pan-African (e.g. Myers, 1993). A schematic event stratigraphy of the Albany Flaser and the Capricorn belts summarized from existing literatures (e.g. Powell and Horwitz, 1994; Clarke et al., 1995) are shown in figure 2, to compare with that of the CITZ. The Singhbhum Fold Belt and the Chotanagpur Gneiss Complex occurring to the east of the central domain of the CITZ show also the principal signature of Paleoproteroiwk to early Mesoproterozoic tectonothermal events and geoteetonic settings which are comparable with the central domain of the CITZ (Mazumder, 1996; Yedekar et al., 1990). Both the CITZ and the Capricorn Belt experienced a principal orogenic event during the Paleoproterozoic, suturing the northern and southern Archaean cratons which are characterized with greenstone belts and Neoarchaean granite-migmatite activity, However, it is found that there is poor similarity in ages and geological
Fig. 2. Event stratigraphic columns of the CITZ, Capricorn and AlbanyFraser belts. Thick stripe: Supracrustals with definite dates. Dashed stripe: Supracrustals with indefinite dates. Dots: Cover sediments over the major orogenic sediments. Open circle: Acid plutonites. Solid circle: Mafic plutonites. Open triangle: Acid volcanics. Solid triangle: Mafic volcanics, dikes and sills. Wave: Regional metamorphism and deformation. Star: Strong rejuvenation. Cross: Weak rejuvenation. MB: Mount Bruce Formation. Sv: Savory Group. Bg: Bangemal Group. Vj: Vindhyan Supergroup. Chg: Chhattisgarh Supergroup. Ss: Sausar Group. Sk: Sakoli Group. Kg: Khairagarh Group. Ng: Nandgaon Group. Am: Amgaon Gneiss. (Data source is given in references in text and references therein).
signatures between the CITZ and the Capricorn orogen. The cratonic blocks of both sides of the two belts have also clearly different geohistories. With regard to the younger events, the CITZ has a better similarity with the Gondwana Research, V. 4, No. 2,2002
21 I
Albany-Flaser Belt than the Capricorn Belt, as well as the Eastern Ghats Granulite Belt. However, lack of evidence of the suturing events during the Grenvillian period in the CITZ precludes the possibility of its direct continuation with the Albany Flaser Belt at that period.
Western Extension of the CITZ The Paleoproterozoic Aravalli Supergroup and the Mesoproterozoic Delhi Supergroup in the western margin of the Bundelkhand craton of NW India is geologically comparable with the central area of the CITZ, in their geological signatures. In eastern Gujarat of western India, which is the topographic westward continuation of the CITZ, occurs Proterozoic metasupracrustal Champaner Group geologically comparable to both the Aravalli-Delhi Belt and the Central area of the CITZ. Thus the continuation of the CITZ and the Aravalli-Delhi Belt is considered appropriate. The Arabian-Nubian Shield of NE Africa, which is juxtaposed with NW India in a general Gondwana reconstruction has principally the Neoproterozoic geohistory (e.g., Johnson et al., 19871, and shows poor evidence of juxtaposition with the CITZ area.
Concluding Remarks Candidates of juxtaposition of the CITZ are found, in some extent, in western Australia and southeast India, but not in the Arabian Nubian Shield. Major tectonothermal events in the CITZ is considered to be during the Paleoproterozoic (ca. 2200-2100 Ma) and early Mesoproterozoic (1700-1500 Ma), overprinted by minor ca. 1100-600 Ma events. It is suggested that the configuration of cratonic blocks surrounding Central India, i.e., continuation of the mobile belts, changed from time to time among those of the Paleoproterozoic to Mesoproterozoic. It is possible that the Pinjarra orogen of western margin of western Australia played a fundamental role in the assembly of cratonic blocks of this part of East Gondwana during the Circum East Antarctic/Grenvillian orogeny (Yoshida, 2000).
References Acharyya, S.K. and Roy, A. (2000) Tectonothermal history of the Central Indian Tectonic Zone and reactivation of major fault/shear zones. J. Geol. SOC.India, v. 55, pp. 239-256. Bandyopadhyay, B.K., Roy, A. and Huin, A.K. (1995) Structure and tectonics of a part of the Central India Shield. Geol. Soc. India, Mem. No. 31, pp. 433-467.
Gorrdzoana Rrieauch, V 4, No 2,2001
Bhowmik, S.K., Pal, T., Roy, A. and Pant, N.C. (1 999) Evidencc for Pre-Grenvillian high-pressure granulite metamorphism from the northern margin of the Sausar Mobile Belt in Central India. J. Geol. Soc. India, v. 53, pp. 385-399. Clarke, G.L., Sun, S.S. and White, R.W. (1995) Grenville-age belts and associated older terranes in Australia and Antarctica. AGSO J. Australian Geol. Geophys., v. 16, pp. 25-39. Geological Survey of India (1998) Geological Map of India, Scale 1:2,000,000 (7"' Ed.), Geol. Surv. India, Calcutta. Harris, L.B. (1993) Correlations of tectonothermal events between the central Indian tectonic zone and the Albany mobile belt of western Australia. In: Unrug, R. et al. (Eds.), Gondwana Eight. Balkema, pp. 165.180. Johnson, P.R., Scheibner, E. and Smith, A.E. (1987) Basement fragments, accreted tectonostratigraphic terranes, and overlap sequences: elements in the tectonic evolution of the Arabian Shield. In: Kroner, A. (Ed.), Proterozoic lithospheric evolution. Amer. Geophys. Union, Geodyn. Series, v. 17, pp. 323-343. Kano, T., Yoshida, M., Satish-Kumar, Wada, H., Bandyopadhyay, Roy, A,, Khan, A.S., Huin, A.K., Chattopadhyay, A., Bhowmilt, S.K. and Pal, T.K. (2001) Field studies in the Sakoli and Sausar belts of central India, 1999-2000. J. Geosci., Osaka City Univ., v. 44, (in press). Mazumder, S.K. (1996) Precambrian geology of Peninsular eastern India -a perspective review. Indian Mineral., v. 50, pp. 139-174. Myers, J.S. (1993) Precambrian history of the west Australian craton and adjacent orogens. Ann. Rev. Earth Planet. Sci., v. 21, pp. 453-485. Myers, J.S., Shaw, R.D. and Tyler, M. (1996) Tectonic evolution of Proterozoic Australia. Tectonics, v. 15, pp. 1431.1446. Powell, C. McA and Horwitz, R.C. (1994) Late Archaean and early Proterozoic tectonics and basin formation of the Hammersley Ranges. Geol. Soc. Australia (WA Division) Excursion Guidebook No. 4, 53p. Radhakrishna, B.P. and Naqvi, S.M. (1986) Precambrian continental crust of India and its evolution. J. Geol., v. 94, pp. 145-166. Sarkar, A., Bodas, M.S., Kundu, H.K., Mamgain, V.V. and Ravishanltar (1998) Geochronology and geochemistry of Mesoproterozoic intrusive plutonites from the eastern segment of the Mahakoshal Greenstone Belt, Central India (Ext. Abstract). GRG Miscl. Pub., No. 8, Field Sci. Pub., Osaka, pp. 82-85. Unrug, R. (1996) The assembly of Gondwanaland. Episodes, V. 19, pp. 11-20. Yedekar, D.B., Jain, S.C., Nair, K.K.K. and Dutta, K.K. (1990) The central Indian collision suture. GSI Spl. Pub. No. 28, pp. 1-43. Yoshida, M. (1995) Assembly of East Gondwanaland during the Mesoproterozoic and its rejuvenation during the Pan-African period. Geol. SOC.India, Mem. No. 34, pp. 25-45. Yoshida, M. (2000) Central Indian Tectonic Zone: implications to the Gondwanaland tectonics. Abstracts, AGU Western Pacific Geodynamics Meeting, 26-30 June 2000, Tokyo. Yoshida, M. and Santosh, M. (1996) Southernmost Indian Peninsula and the Gondwanaland. Gond. Res. Group, Mem. No. 3 , Field Sci. Pub., Osaka, pp. 15-24.
by low-grade schists. Relationships of the high-grade rocks with the surrounding greenschist facies rocks are marred by late- to post-kinematic granitoid intrusions. Geochemical analysis of the rocks shows that they are enriched in large ion lithophile elements and depleted in high field strength elements, typical for an island arc tectonic setting. The area defines a structural domain showing three phases of deformation (D,-DJ. D, structures have only been found in the hornblende gneiss, while D, deformation features are prevalent in both the hornblende gneiss and mica gneiss. All rock units in the region, including the weakly deformed granite, bear signatures of the third phase of deformation, D,. The most common foliation (gneissosity) in t h e rocks, D,, dips nearly uniformly at about 75" towards NNW (and rarely to SSE). Relicts of an early thrust tectonics in the region are manifested by imbricate structures showing an eastdirected shearing. The thrusts are later superimposed by a widespread extensional tectonics. Prevalent niesoscopic shear zones characteristically showing normal sense of slip support this. Shear foliation related to these high strain zones bear stretching lineations that plunge moderately to the NW. Several shear sense indicators suggest that shearing has been top-to-NW. Some of the most common
Gondwana Research, I/: 4, No. 2, pp. 208-21 I . 02001 International Association for Gondwana Research, Japan ISSN: 1342-937X
types of shear criteria are S-type asymmetrically folded quartz/pegmatite veins, rotated, pre-shearing foliation, and tailed (o-type) porphyroblasts of K-feldspar. In addition to the ductile shear zones, brittle and brittleductile shear zones also consistently show a normal, dipslip faulting. The extensional deformation affects preexisting planar fabric in all rock units and hence postdates metamorphic events. Not withstanding the metamorphic and structural complexity of the Anseba region, earlier workers have attributed the whole of central Eritrea to belong to the same group of rocks, the Nakfa terrane. The lack of uniformity in both t h e structural style and t h e metamorphic grade in this small region as seen in the present work casts doubt on earlier terrane classification in the Precambrian of Eritrea. This study shows that late, extensional tectonics is prevalent in a region previously affected by large-scale thrust tectonics. The sequence of events leads to the likely conclusion that the window of high-grade rocks in the Anseba region is the result of the interplay of exhumation process and extensional tectonics. If this interpretation is accepted, it follows that post-thrusting exhumation processes and extensional tectonics were important in the late stages of the ANS terrane amalgamation during the Neoproterozoic.
GR
Gondwana Research
Precambrian Central India and its role in the GondwanalandRodinia Context M. Yoshidal, R.S. Divi2and M. Santosh3 * J
Department of Geosciences, Osaka City University, Osaka 558-8585, Japan, E mail:[email protected] Department of Earth and Envivonmentaf Sciences, Kuwait University, Kuwait Department of Natuval Envivonmental Science, Kochi University, Kochi 780-8072, Japan
The Precambrian of Central India The Precambrian of Central India is centered by the Proterozoic Central Indian Tectonic Zone (CITZ) (Radhakrishna and Naqvi, 1986) which is juxtaposed with the Bundelkhand craton to the north and the Bastar Craton
to the south (Fig. 1).The western extension of CITZ is regarded, by several researchers, to continue to the Aravalli-Delhi Fold Belt, which runs along the western fringe of the Bundelkhand block. The eastern margin of the CITZ is covered by the Cenozoic Ganges sediment. To the further east, the Precambrian Shillong and Dispur
209
L
L/A P r e r m i I I i.n/Prs=
cratonic terrain
Fig. 1. Amalgamation of East Gondwana during the Grenvillian period. CITZ : Central Indian Tectonic Zone. IM: India-Madagascar paleocontinent including the Bastar craton. B: Bundelkhand craton. KH: Kalahari craton. E: Eastern Ghats Belt. CP: Capricorn orogen. PJ: Pinjarra orogen. AF: Albany Fraser orogen. CG: Congo craton. N AM: North American craton. NA: North Australian craton. SA: South Australian craton. (The original figure is modified from Yoshida and Santosh, 1996; data source is given in it)
blocks of Meghalaya and Assam show some similarity with the eastern part of the CITZ. In the East Gondwana reconstruction during Late Mesoproterozoic, the CITZ is generally regarded to continue to the Albany-Flaser Mobile Belt of southwestern Australia through the Shillong block (e.g. Harris, 1993). To the southeast, the Eastern Ghats Granulite Belt of Orissa also bears similar characteristics with the CITZ, and several researchers delineate a continuous Grenvillian Belt from the CITZ to both southwestern Australia and the Eastern Ghats Granulite Belt to the Grenvillian Belt proper of North America through the Circum East Antarctic Mobile Belt (Fig. 1, Yoshida, 1995; Unrug, 1996). The CITZ is generally regarded to have acted principally as the suture during the Paleoproterozoic period (ca. 22002100 Ma) between the northern and the southern Indian shields (e.g. Yedekar et al., 1990). It is pointed out, however, that a widespread and strong tectonothermal event took place during 1700-1500 Ma as well (Sarkar et al., 1998).Weak thermal events of ca. 1100-600 Ma have also been known. Thus, it is principally a pre-Rodinia suture, and hence is important for considering the global crustal processes before the East Gondwana-Rodinia. Gondwana Research, V. 4, No. 2,2001
The Central Area of the CITZ On the northern margin of the central domain of the CITZ, which has about 250 km in width (Acharrya and Roy, 2000; Geological Survey of India, 19981, occurs the Paleoproterozoic Mahakoshal Group mainly composed of shelf to slope facies marine assemblage with subordinate meta-volcanic rocks of basaltic composition. This group shows vertical structures reflecting horizontal compressional stress normal to the major trend of the Mahakoshal basin and CITZ (Bandyopadhyay et al., 1995). The possible Paleoproterozoic Sausar Group composed of the metasupracrustal package of stable continental margin sediments with minor acid volcanic rocks occupies the southern margin of the CITZ. Isoclinal folds and possible nappe structures developed (Bandyopadhyay et al., 1995; Kano et al., 2001) and high-pressure granulite metamorphism preceding the major tectonothermal events including the ITD path of metamorphism (Bhowmik et al., 1999) is identified, which may indicate a continent-continent collisional event in earlier tectonic history.
210
The possible Paleoproterozoic Sakoli Group is distributed at the northern margin of the southern Indian Shield. This group is composed predominantly of metapelitic rocks with minor bimodal volcanics showing low-K island arc tholeiite to calc alkaline trend. The metasediment package is characterized by continental margin conditions. In the Bundelkhand craton to the north of the CITZ, are developed the platform sediments of the lower Mesoproterozoic Bijawar Group and the middle to upper Mesoproterozoic Vindhyan Supergroup. In the Bastar craton to the south of the CITZ, Paleoproterozoic greenstone belt of the Dongargarh Supergroup occurs, which is composed of the lower volcanigenic Nandgaon Group and the upper volcanoclastic Khairagarh Group separated by an unconformity. Basement granite/gneisses are called the Bundelkhand Granite and Bundelkhand Gneiss in the north, the Tirodi gneiss in the central zone of the CITZ, the Amgaon Gneiss in the southern zone of CITZ, and the Bastar Gneiss in the Bastar craton. Reliable radiometric ages from this area are quite insufficient (refer, Kano et al., 2001) and therefore, age constraints of most of the above geologic units are quite poor. This gives us a difficulty in drawing a model of tectonic evolution of this area. A possible event stratigraphy of the central area of the CITZ is tentatively summarized in Fig. 2.
Albany Flaser
Capricorn
CITZ
,'.' ,' ".'
Eastern Extension of the CITZ Proterozoic mobile belts in western Australia include the Capricorn, Albany-Flaserand Pinjarra orogens (Myers, 1993; Myers et al., 1996). The Pinjarra orogen is poorly known, but is regarded to be a recyclic orogen of the Grenvillian and Pan-African (e.g. Myers, 1993). A schematic event stratigraphy of the Albany Flaser and the Capricorn belts summarized from existing literatures (e.g. Powell and Horwitz, 1994; Clarke et al., 1995) are shown in figure 2, to compare with that of the CITZ. The Singhbhum Fold Belt and the Chotanagpur Gneiss Complex occurring to the east of the central domain of the CITZ show also the principal signature of Paleoproteroiwk to early Mesoproterozoic tectonothermal events and geoteetonic settings which are comparable with the central domain of the CITZ (Mazumder, 1996; Yedekar et al., 1990). Both the CITZ and the Capricorn Belt experienced a principal orogenic event during the Paleoproterozoic, suturing the northern and southern Archaean cratons which are characterized with greenstone belts and Neoarchaean granite-migmatite activity, However, it is found that there is poor similarity in ages and geological
Fig. 2. Event stratigraphic columns of the CITZ, Capricorn and AlbanyFraser belts. Thick stripe: Supracrustals with definite dates. Dashed stripe: Supracrustals with indefinite dates. Dots: Cover sediments over the major orogenic sediments. Open circle: Acid plutonites. Solid circle: Mafic plutonites. Open triangle: Acid volcanics. Solid triangle: Mafic volcanics, dikes and sills. Wave: Regional metamorphism and deformation. Star: Strong rejuvenation. Cross: Weak rejuvenation. MB: Mount Bruce Formation. Sv: Savory Group. Bg: Bangemal Group. Vj: Vindhyan Supergroup. Chg: Chhattisgarh Supergroup. Ss: Sausar Group. Sk: Sakoli Group. Kg: Khairagarh Group. Ng: Nandgaon Group. Am: Amgaon Gneiss. (Data source is given in references in text and references therein).
signatures between the CITZ and the Capricorn orogen. The cratonic blocks of both sides of the two belts have also clearly different geohistories. With regard to the younger events, the CITZ has a better similarity with the Gondwana Research, V. 4, No. 2,2002
21 I
Albany-Flaser Belt than the Capricorn Belt, as well as the Eastern Ghats Granulite Belt. However, lack of evidence of the suturing events during the Grenvillian period in the CITZ precludes the possibility of its direct continuation with the Albany Flaser Belt at that period.
Western Extension of the CITZ The Paleoproterozoic Aravalli Supergroup and the Mesoproterozoic Delhi Supergroup in the western margin of the Bundelkhand craton of NW India is geologically comparable with the central area of the CITZ, in their geological signatures. In eastern Gujarat of western India, which is the topographic westward continuation of the CITZ, occurs Proterozoic metasupracrustal Champaner Group geologically comparable to both the Aravalli-Delhi Belt and the Central area of the CITZ. Thus the continuation of the CITZ and the Aravalli-Delhi Belt is considered appropriate. The Arabian-Nubian Shield of NE Africa, which is juxtaposed with NW India in a general Gondwana reconstruction has principally the Neoproterozoic geohistory (e.g., Johnson et al., 19871, and shows poor evidence of juxtaposition with the CITZ area.
Concluding Remarks Candidates of juxtaposition of the CITZ are found, in some extent, in western Australia and southeast India, but not in the Arabian Nubian Shield. Major tectonothermal events in the CITZ is considered to be during the Paleoproterozoic (ca. 2200-2100 Ma) and early Mesoproterozoic (1700-1500 Ma), overprinted by minor ca. 1100-600 Ma events. It is suggested that the configuration of cratonic blocks surrounding Central India, i.e., continuation of the mobile belts, changed from time to time among those of the Paleoproterozoic to Mesoproterozoic. It is possible that the Pinjarra orogen of western margin of western Australia played a fundamental role in the assembly of cratonic blocks of this part of East Gondwana during the Circum East Antarctic/Grenvillian orogeny (Yoshida, 2000).
References Acharyya, S.K. and Roy, A. (2000) Tectonothermal history of the Central Indian Tectonic Zone and reactivation of major fault/shear zones. J. Geol. SOC.India, v. 55, pp. 239-256. Bandyopadhyay, B.K., Roy, A. and Huin, A.K. (1995) Structure and tectonics of a part of the Central India Shield. Geol. Soc. India, Mem. No. 31, pp. 433-467.
Gorrdzoana Rrieauch, V 4, No 2,2001
Bhowmik, S.K., Pal, T., Roy, A. and Pant, N.C. (1 999) Evidencc for Pre-Grenvillian high-pressure granulite metamorphism from the northern margin of the Sausar Mobile Belt in Central India. J. Geol. Soc. India, v. 53, pp. 385-399. Clarke, G.L., Sun, S.S. and White, R.W. (1995) Grenville-age belts and associated older terranes in Australia and Antarctica. AGSO J. Australian Geol. Geophys., v. 16, pp. 25-39. Geological Survey of India (1998) Geological Map of India, Scale 1:2,000,000 (7"' Ed.), Geol. Surv. India, Calcutta. Harris, L.B. (1993) Correlations of tectonothermal events between the central Indian tectonic zone and the Albany mobile belt of western Australia. In: Unrug, R. et al. (Eds.), Gondwana Eight. Balkema, pp. 165.180. Johnson, P.R., Scheibner, E. and Smith, A.E. (1987) Basement fragments, accreted tectonostratigraphic terranes, and overlap sequences: elements in the tectonic evolution of the Arabian Shield. In: Kroner, A. (Ed.), Proterozoic lithospheric evolution. Amer. Geophys. Union, Geodyn. Series, v. 17, pp. 323-343. Kano, T., Yoshida, M., Satish-Kumar, Wada, H., Bandyopadhyay, Roy, A,, Khan, A.S., Huin, A.K., Chattopadhyay, A., Bhowmilt, S.K. and Pal, T.K. (2001) Field studies in the Sakoli and Sausar belts of central India, 1999-2000. J. Geosci., Osaka City Univ., v. 44, (in press). Mazumder, S.K. (1996) Precambrian geology of Peninsular eastern India -a perspective review. Indian Mineral., v. 50, pp. 139-174. Myers, J.S. (1993) Precambrian history of the west Australian craton and adjacent orogens. Ann. Rev. Earth Planet. Sci., v. 21, pp. 453-485. Myers, J.S., Shaw, R.D. and Tyler, M. (1996) Tectonic evolution of Proterozoic Australia. Tectonics, v. 15, pp. 1431.1446. Powell, C. McA and Horwitz, R.C. (1994) Late Archaean and early Proterozoic tectonics and basin formation of the Hammersley Ranges. Geol. Soc. Australia (WA Division) Excursion Guidebook No. 4, 53p. Radhakrishna, B.P. and Naqvi, S.M. (1986) Precambrian continental crust of India and its evolution. J. Geol., v. 94, pp. 145-166. Sarkar, A., Bodas, M.S., Kundu, H.K., Mamgain, V.V. and Ravishanltar (1998) Geochronology and geochemistry of Mesoproterozoic intrusive plutonites from the eastern segment of the Mahakoshal Greenstone Belt, Central India (Ext. Abstract). GRG Miscl. Pub., No. 8, Field Sci. Pub., Osaka, pp. 82-85. Unrug, R. (1996) The assembly of Gondwanaland. Episodes, V. 19, pp. 11-20. Yedekar, D.B., Jain, S.C., Nair, K.K.K. and Dutta, K.K. (1990) The central Indian collision suture. GSI Spl. Pub. No. 28, pp. 1-43. Yoshida, M. (1995) Assembly of East Gondwanaland during the Mesoproterozoic and its rejuvenation during the Pan-African period. Geol. SOC.India, Mem. No. 34, pp. 25-45. Yoshida, M. (2000) Central Indian Tectonic Zone: implications to the Gondwanaland tectonics. Abstracts, AGU Western Pacific Geodynamics Meeting, 26-30 June 2000, Tokyo. Yoshida, M. and Santosh, M. (1996) Southernmost Indian Peninsula and the Gondwanaland. Gond. Res. Group, Mem. No. 3 , Field Sci. Pub., Osaka, pp. 15-24.