Hf-Pb isotope and trace element constraints on the origin of the Jacupiranga Complex (Brazil): Insights into carbonatite genesis and multi-stage metasomatism of the lithospheric mantle |
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| Institution: | 1. Programa de Pós-graduação em Geologia, Universidade Federal do Paraná, Av. Coronel Francisco Heráclito dos Santos 210, 81531-970 Curitiba, Brazil;2. Géosciences Montpellier, CNRS and Université de Montpellier, Place Eugène Bataillon, 34090 Montpellier, France;3. Instituto de Geociências, Universidade de São Paulo, Rua do Lago 562, 05508-080 São Paulo, Brazil;1. Geology Department, Faculty of Science, Beni-Suef University, Beni-Suef 62521, Egypt;2. Geology Department, Faculty of Science, Helwan University, 11790 Cairo, Egypt;3. Geology Department, Faculty of Science, Cairo University, Giza 12613, Egypt;4. Economic Geology Research Unit (EGRU), Department of Earth and Oceans, James Cook University, Townsville, 4011, QLD, Australia;5. Department of Economic Geology and Petrology, Institute of Mineralogy, Technische University Bergakademie, Freiberg, Brennhausgasse 14, 09596 Freiberg/Sachsen, Germany;1. Hebei GEO University, Shijiazhuang, Hebei 050031, China;2. Tianjin Institute of Geology and Mineral Resources, Tianjin 300170, China;3. School of Earth Sciences and Resources, China University of Geosciences Beijing, Beijing 100083, China;4. Department of Earth Science, University of Adelaide, Adelaide 5005, Australia;1. Departamento de Geología Regional, Instituto de Geología, Universidad Nacional Autónoma de México, 04510 México, DF, Mexico;2. National Taiwan Normal University, Department of Earth Sciences, 88 Tingzhou Road Section 4, Taipei 11677, Taiwan;3. Department of Geology, St. Mary''s University, Halifax, Nova Scotia, Canada B3H 3C3;4. Department of Energy, Halifax, Nova Scotia B3J 3J9, Canada;1. GNS Science, PO Box 30-368, Lower Hutt, New Zealand;2. GEOMAR, Helmholtz Center for Ocean Research Kiel, Wischhofstrasse 1-3, 24148 Kiel, Germany;3. Institut für Geowissenschaften, Christian-Albrechts-Universität zu Kiel, Ludewig-Meyn-Strasse 10, 24118 Kiel, Germany;4. Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S5B6, Canada;5. National Institute of Water and Atmospheric Research, PO Box 14-901, Wellington, New Zealand;6. School of Geography, Environment and Earth Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand |
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| Abstract: | The Lower Cretaceous Jacupiranga complex, in the central-southeastern portion of the South American Platform, includes carbonatites in close association with silicate rocks (i.e. strongly and mildly silica-undersaturated series). Here we document the first hafnium isotope data on the Jacupiranga complex, together with new trace element and Pb isotope compositions. Even though liquid immiscibility from a carbonated silicate melt has been proposed for the genesis of several Brazilian carbonatites, isotopic and geochemical (e.g., Ba/La ratios, lack of pronounced Zr-Hf and Nb-Ta decoupling) information argues against a petrogenetic relationship between Jacupiranga carbonatites and their associated silicate rocks. Thus, an origin by direct partial melting of the mantle is considered. The isotopic compositions of the investigated silicate samples are coherent with a heterogeneously enriched subcontinental lithospheric mantle (SCLM) source of rather complex evolution. At least two metasomatic processes are constrained: (1) a first enrichment event, presumably derived from slab-related fluids introduced into the SCLM during Neoproterozoic times, as indicated by consistently old TDM ages and lamprophyre trace signatures, and (2) a Mesozoic carbonatite metasomatism episode of sub-lithospheric origin, as suggested by εNd-εHf values inside the width of the terrestrial array. The Jacupiranga parental magmas might thus derive by partial melting of distinct generations of metasomatic vein assemblages that were hybridized with garnet peridotite wall-rocks. |
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