Crustal Assembly of the Antananarivo and Masora Domains, Central
Journal of Mineralogical and Petrological Sciences, Volume 110, page 111–125, 2015 Crustal assembly of the Antananarivo and Masora domains, central–eastern Madagascar: constraints from U–Pb zircon geochronology and whole–rock geochemistry of meta–granitoids Takashi ICHIKI*, Masahiro ISHIKAWA*, Jun–Ichi KIMURA**, Ryoko SENDA** and Raymond RAKOTONDRAZAFY*** *Graduate School of Environment and Information Sciences, Yokohama National University, 79–7 Tokiwadai, Hodogaya–ku Yokohama 240–8501, Japan **Department of Solid Earth Geochemistry (D–SEG), Japan Agency for Marine–Earth Science and Technology (JAMSTEC), 2–15 Natsushima–cho, Yokosuka 237–0061, Japan ***Department of Earth Sciences, Faculty of Science, University of Antananarivo, PB 906 Antananarivo 101, Madagascar In reconstructions of the Gondwana supercontinent, correlations of Archean domains between Madagascar and India remain debated. In this paper, we aim to establish correlations among these Archean domains using whole–rock geochemistry and U–Pb zircon geochronology of meta–granitoids from the Masora and the Anta- nanarivo domains, central–eastern Madagascar. A meta–granitoid from the central part of Masora domain is dated at 3277 Ma and shows a typical Archean tonalite–trondhjemite–granodiorite composition, whereas a tonalitic gneiss from the southeastern part of the Antananarivo domain gives an age of 2744 Ma. The geo- chemical signature of this tonalitic gneiss differs from that of the ~ 2500 Ma granitoids of the northwestern part of Antananarivo domain. In addition, the geochemical composition of the ~ 760 Ma granitic gneisses is con- sistent with a volcanic–arc origin for the protolith. Based on the geochemical and geochronological results, along with existing data, we identified three episodes of granitic magmatism in central–eastern Madagascar at ~ 3300, 2700, and 2500 Ma.
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