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Insights into the petrogenesis of low- and high-Ti basalts: Stratigraphy and geochemistry of four lava sequences from the central Paraná basin

De Min, Angelo
Callegaro, Sara
Nardy, Antonio J.
Marques, Leila S.
Gabbarrini, Ilaria
Published in Journal of Volcanology and Geothermal Research. 2018, vol. 355, p. 232-252
Abstract Lava flow sequences were sampled in the central part of the Paraná basin aiming to verify the time-related evo- lution of the Paraná basaltic magmatism. It is shown that low- and high-Ti basalts were erupted synchronously. In particular, Esmeralda and Pitanga flows are interlayered, with the former prevailing in the upper part of the se- quence. Evidence for synchronously active magma plumbing systems is also supported by mineralogical data, showing signs of mixing between the two groups. Geochemical data, including Sr-Nd-Pb isotopic compositions are furthermore used to define the mantle source of various low- (Esmeralda and Gramado) and high-Ti (Pitanga and Urubici) magma types. Involvement of a carbonatitic component is proposed for the genesis of the basalts (particularly for the Urubici ones) as suggested by trace element enrichments unrelated to significant isotopic variations. This carbonatitic signature of the man- tle source may be conveyed by CO2-rich metasomatic fluids or melts percolating upwards within the sub-conti- nental lithospheric mantle (SCLM) leading to rapid and selective enrichment of incompatible trace elements. Metasomatism was probably localized at the outskirts of the basin, were Urubici tholeiites and contemporaneous carbonatites were erupted. Geochemical data also suggest the occurrence of significant amounts of crustal con- tamination in the LTi magmas (mainly in the Gramado and in the late Esmeralda lavas) while crustal assimilation seems negligible in the HTi samples. Globally, a very complex picture arises for the genesis of the Paraná tholei- ites, with near-synchronous and geographically coincident flows undergoing significantly different extents of in- teraction with the crust and tapping different mantle sources.
Keywords Parana' flood basaltsLava stratigraphyCarbonatitic metasomatismGeochemistryPetrogenesis
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Research groups Isotope Geochemistry, Geochronology and Thermochronology
Mineral Resources and Geofluids
(ISO format)
DE MIN, Angelo et al. Insights into the petrogenesis of low- and high-Ti basalts: Stratigraphy and geochemistry of four lava sequences from the central Paraná basin. In: Journal of Volcanology and Geothermal Research, 2018, vol. 355, p. 232-252. https://archive-ouverte.unige.ch/unige:104621

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Deposited on : 2018-05-23

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