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dc.contributor.authorCucciniello, C.
dc.contributor.authorMelluso, L.
dc.contributor.authorJourdan, Fred
dc.contributor.authorMahoney, J.
dc.contributor.authorMeisel, T.
dc.contributor.authorMorra, V.
dc.date.accessioned2017-01-30T15:16:11Z
dc.date.available2017-01-30T15:16:11Z
dc.date.created2014-02-25T20:00:40Z
dc.date.issued2013
dc.identifier.citationCucciniello, C. and Melluso, L. and Jourdan, F. and Mahoney, J.J. and Meisel, T. and Morra, V. 2013. 40Ar–39Ar ages and isotope geochemistry of Cretaceous basalts in northern Madagascar: Refining eruption ages, extent of crustal contamination and parental magmas in a flood basalt province. Geological Magazine. 150 (1): pp. 1-17.
dc.identifier.urihttp://hdl.handle.net/20.500.11937/44742
dc.identifier.doi10.1017/S0016756812000088
dc.description.abstract

The Madagascar Cretaceous igneous province exposed in the Mahajanga basin is represented by basalt and basaltic andesite lavas. New 40Ar–39Ar plateau ages (92.3 ± 2.0 Ma and 91.5 ± 1.3 Ma) indicate that the magmatism in the Mahajanga basin started about 92 Ma ago. Four geochemically distinct magma types (Groups A–D) are present. Group A and C rocks have low to moderate TiO2 (1.2–2.6 wt%), Nb (3–9 μg g−1) and Zr (82–200 μg g−1), and show large variations in ɛNdi (+0.1 to −10.8), 206Pb/204Pb (15.28 to 16.33) and γOs (+11.4 to +7378). The large isotopic variations, particularly in Os, Nd and Pb isotopic compositions, are likely due to crustal contamination. The low Pb isotope ratios observed in the Group A and C rocks suggest involvement of continental crust with low μ (238U/204Pb). Group B and D rocks have moderate to high TiO2 (2.2–4.9 wt%), Nb (8–24 μg g−1) and Zr (120–327 μg g−1). Age-corrected isotopes of Group B and D lavas show a small range in ɛNdi (+1.0 to +4.0) and a wide range in γOs (+128 to +1182). Values of 207Pb/204Pb are within the range for Groups A and C, but the Group D 206Pb/204Pb (16.52–17.08) and 208Pb/204Pb (37.51–38.01) values are higher, indicating a different crustal contaminant. Pb isotopic values of the Group B rocks seem to reflect the isotopic features of their mantle source. The magma groups of Mahajanga display a wide range of trace element and isotopic compositions that cannot be explained only by open-system crystallization processes but, rather, by distinct mantle sources.

dc.publisherCambridge University Press
dc.subjectCretaceous
dc.subjectbasalts
dc.subjectisotope geochemistry
dc.subjectMadagascar
dc.subjectages
dc.title40Ar–39Ar ages and isotope geochemistry of Cretaceous basalts in northern Madagascar: Refining eruption ages, extent of crustal contamination and parental magmas in a flood basalt province
dc.typeJournal Article
dcterms.source.volume150
dcterms.source.number1
dcterms.source.startPage1
dcterms.source.endPage17
dcterms.source.issn1469-5081
dcterms.source.titleGeology Mag
curtin.note

Copyright © 2012 Cambridge University Press 2012

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curtin.accessStatusOpen access


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