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consolidation of Gondwanaland. Ann. Rev. Earth Planet. Sci.,

Tembo, F., Kampunzu, A.B. and Musonda, B.M. (2000) Geochemical characteristics of Neoproterozoic A-type granites in the Lufilian belt, Zambia. J. Ah: Earth Sci., 18th Colloquium of African Geology, Spl. Abstr. Issue, v. 30, p. 85.

’hcker, R.D., Ashwal L.D., Handtke M.J., Hamilton, M.A., Le Grange, M. and Rambeloson, R.A. (1999) U-Pb geochronology and isotope geochemistry of the Archean granite-greenstone belts of Madagascar. J. Geol., v. 107, pp. 135-153.

Van Schmus, W.R. (2000) Mesopmterozoic orogenesis in USA. Intl. Geol. Congress, Rio de Janeiro, Brazil, Ext. Abstr. Vol., 4p.

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Yibas, B., Reimold, W.U., Armstrong, R.A., Phillips, D. and Koeberl, C. (2000) The geology of the Precambrian of southern Ethiopia: 11. U- Pb single zircon SHRIMP and laser 4nAr/39Ar dating of granitoids. Inform. Circul. No 345, Econ. Geol. Res. Inst., University of the Witwatersrand, South Africa, 30p.

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Evidence of Structural Reworking in the Eastern Ghats Granulite Belt, India: Implication for a Contiguous Supercontinent in the Proterozoic Rajib Kar Department of Geology, J. K. College, Purulia - 723 101, West Bengal, India

The Eastern Ghats granulite belt, skirting the east coast of India records complex deformation. Study area around Jenapore, Orissa, situated near the northern boundary of the belt, primarily exposes khondalite and massif-type charnockite. Three phases of folding is recorded from the area. Minor quartzite bands in the khondalite host and hornblende rich mafic granulite bands in the charnockite host define rootless, isoclinal and reclined F, folds; these bands are designated as So. The pervasive gneissosity of the khondalite and streaky gneissic foliation of the charnockite are axial planar to these folds and are designated as S,. Intersection of So and S, generates striping lineation, L,. F, folds, generally developed on S,, are characterised by the development of axial planar leptynitic foliation, S,. A stretching lineation is developed on S, plane and is designated as L,. F, folds are broad warps.

Poles of S, in charnockite plot on a great circle with a point maximum and the mean cluster of poles to So plane also plot close to this point maximum. This indicates that the regional F, fold is highly asymmetrical and the northerly dipping short limb is much less represented. Pole to the great circle lies well within the cluster of the L, lineation. The deviation of S, poles from the great circle as also L, lineation from the pole of the great circle may be the effect of late F, warp. The L, lineation is highly variable, although distributed on mean S, and their clustering near L, maximum, can only be explained as the effect of shearing along S, in the direction of mean L,. In the khondalite, most of the S, gneissosity is steep, and the mean So plane is also parallel to it. Minor F, and F, fold axes and L,, L, are steep and variably oriented unlike that in the charnockite. Shear component is differently manifested here; stretching along L, might have resulted in F,-F, coaxial relationship.

Combined structural analyses can be interpreted with the help of a schematic diagram. Regional F, folds are steep and asymmetric with reclined geometry and regional F, folds are also asymmetric, upright and have gentle plunge. The hinge

region of F, folds, here represented by khondalite, produces F,-F, coaxial relation, while the limb region of regional F, folds, represented by charnockite, produces F,-F, non-coaxial relation. Such geometry can be interpreted as a result of break in the deformation history. Also, the progressive rotation of earlier material line (L,) during late simple shear confirms this break. This is in sharp contrast to the proposal of continuous progressive deformation (Dobmeier and Raith, 2000).

Recent studies on metamorphism and geochronology of the Eastern Ghats belt emphasizes the hypothesis of tectonic reworking in the Proterozoic (Dasgupta and Sengupta, 1998; Sarkar and Paul, 1998). Also, from palaeomagnetic studies it is clear that east coast of India was juxtaposed with Antarctica before Rodonia breakup in the Mesoproterozoic time (Yoshida et al., 1992; Yoshida, 1995). Notably, evidence of structural reworking during Mesoproterozoic in the east Antarctica was also proposed (Clarke, 1988).

References Clarke, G.L. (1988) Structural constraints on the Proterozoic reworking

of Archaean crust in the Rayner complex, MacRobertson and Kemp land coast, East Antarctica. Precamb. Res., v. 40/41, pp. 137-156.

Dasgupta, S. and Sengupta, €? (1998) Reworlung of an isobarically cooled deep continental crust: evidence of decompressive P-T trajectory from the Eastern Ghats belt, India. Ind. J . Geol., v. 70, pp. 133-144.

Dobmeier, C. and Raith, M. (2000) On the origin of ‘arrested’ charnockitization in the Chilka Lake area, Eastern Ghats Belt, India: a reappraisal. Geol. Mag., v. 137, pp. 27-37.

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NO. 44, pp. 51-86.

Gondwana Research, v14, No. 4,2001