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Detailed Reference Information |
Nédélec, A., Ralison, B., Bouchez, J. and Grégoire, V. (2000). Structure and metamorphism of the granitic basement around Antananarivo: A key to the Pan-African history of central Madagascar and its Gondwana connections. Tectonics 19: doi: 10.1029/2000TC900001. issn: 0278-7407. |
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The Precambrian basement of Madagascar acquired a polyphase imprint during the Pan-African orogeny. In northern central Madagascar, emplacement of stratoid alkaline granites at midcrustal depth (4--5 kbars) led to formation of a layered crust in a postcollisional extensional regime at 630 Ma (D1). Subsequently, the structures of the stratoid granites were rotated by the sinistral and transpressive E-W Antananarivo flexure (or virgation) zone (D2). East of Antananarivo the structures of the D1 layered crust and the D2 virgation are crosscut by the steeply dipping N-S foliations of the Angavo belt. Lineations gently plunging to the north attest that the Angavo belt is a major strike-slip shear zone that formed under low-pressure granulitic conditions (3 kbars, 790 ¿C). The nearby porphyritic Carion granite was emplaced at the end of this period of N-S shearing (D3), which can thus be no younger than 530 Ma. Late-Pan-African (580--550 Ma) strike-slip motion along broadly N-S shear zones has been recognized elsewhere in Madagascar and in its Gondwana connections. Continuation of the Angavo belt as one of the high strain belts of the Arabian-Nubian Shield is discussed in the general framework of Gondwana assembly. ¿ 2000 American Geophysical Union |
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Abstract |
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Keywords
Mineralogy and Petrology, Metamorphic petrology, Tectonophysics, Continental contractional orogenic belts, Information Related to Geographic Region, Africa, Information Related to Geologic Time, Precambrian |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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