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Vincenza Guarinoa, Fu-Yuan Wub, Michele Lustrinocd, Leone MellusoaCorresponding author contact informationE-mail the corresponding author, Pietro Brotzua, Celso de Barros Gomese, Excelso Rubertie, Colombo Celso Gaeta Tassinarie, Darcy Pedro Sviseroe

 

U–Pb ages, Sr–Nd- isotope geochemistry, and petrogenesis of kimberlites, kamafugites and phlogopite-picrites of the Alto Paranaíba Igneous Province, Brazil

a Dipartimento di Scienze della Terra, Università degli Studi di Napoli Federico II, via Mezzocannone 8, 80134 Napoli, Italyb State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijng 100029, Chinac Dipartimento di Scienze della Terra, Università degli Studi di Roma La Sapienza, P.le A. Moro, 5, 00185 Roma, Italyd Istituto di Geologia Ambientale e Geoingegneria (IGAG), CNR, c/o Dipartimento di Scienze della Terra, Università degli Studi di Roma La Sapienza, P.le A. Moro, 5, 00185, Roma, Italye Instituto de Geociências, Universidade de São Paulo, Rua do Lago 562, Cidade Universitária, 05508 São Paulo, Brazil
Chemical Geology
Volume 353, 30 August 2013, Pages 65–82

Abstract

figura mellusoThe kimberlites, kamafugites and phlogopite-picrites of Alto Paranaíba Igneous Province (APIP), southern Brazil, span a range between ~ 91 and 78 Ma with new in-situ, more tightly constrained U–Pb ages. The kimberlites show porphyritic texture with olivine xeno- and phenocrysts plus phlogopite, Fe-Ti-Cr oxides and perovskite microcrysts set in a carbonate-rich matrix. The kamafugites are feldspar-free rocks represented by ugandites and mafurites. Ugandites and mafurites are porphyritic and contain olivine and clinopyroxene phenocrysts in a fine-grained groundmass composed by clinopyroxene, perovskite, apatite, magnetite, phlogopite, leucite and/or analcime in ugandites, and by olivine, clinopyroxene, amphibole, phlogopite, perovskite, magnetite, kalsilite and Ba-zeolites in mafurites. Phlogopite-picrites have a pseudo-fluidal porphyritic texture with olivine phenocrysts and abundant phlogopite microcrysts in a groundmass composed by olivine, spinel, apatite, perovskite, calcite and rare garnet. New in‐situ Sr and Nd isotopic data on perovskites (87Sr/86Sri = 0.70467–0.70565 and 143Nd/144Ndi = 0.51222–0.51233) fall within the known ranges of APIP rocks (87Sr/86Sri = 0.70431–0.70686; 143Nd/144Ndi = 0.51205–0.51280).

The APIP magmas derived from a source assemblage made up of an old metasomatized mica-carbonate garnet lherzolite, that did not suffer interaction with convective mantle, nor with any hypothetical melts derived from a Trindade mantle plume. Geochemical modelling show that low degree melting (f = 0.5–2%) of such a source can produce compositions resembling the APIP rocks. The geochemical and isotopic composition of the magmas, the calculated degrees of partial melting, the composition of the calculated source and the absence of a hot spot track from Goias to Alto Paranaíba igneous provinces can be explained with the presence of chemically and mineralogically heterogeneous mantle sources that melted at different pressures.