Sr-Nd-Pb isotopic constraints on the nature of the mantle sources involved in the genesis of the high-Ti tholeiites from northern Parana Continental Flood Basalts (Brazil)
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Journal of South American Earth Sciences
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There has been little research on geochemistry and isotopic compositions in tholeiites of the Northern
region from the Paraná Continental Flood Basalts (PCFB), one of the largest continental provinces of the
world. In order to examine the mantle sources involved in the high-Ti (Pitanga and Paranapanema) basalt
genesis, we studied Sr, Nd, and Pb isotopic systematics, and major, minor and incompatible trace element
abundances. The REE patterns of the investigated samples (Pitanga and Paranapanema magma type) are
similar (parallel to) to those of Island Arc Basalts’ REE patterns. The high-Ti basalts investigated in this
study have initial (133 Ma) 87Sr/86Sr ratios of 0.70538e0.70642, 143Nd/144Nd of 0.51233e0.51218, 206Pb/204Pb of 17.74e18.25, 207Pb/204Pb of 15.51e15.57, and 208Pb/204Pb of 38.18e38.45. These isotopic
compositions do not display any correlation with Nb/Th, Nb/La or P2O5/K2O ratios, which also reflect that
these rocks were not significantly affected by low-pressure crustal contamination. The incompatible
trace element ratios and SreNdePb isotopic compositions of the PCFB tholeiites are different to those
found in Tristan da Cunha ocean island rocks, showing that this plume did not play a substantial role in
the PCFB genesis. This interpretation is corroborated by previously published osmium isotopic data
(initial gOs values range from þ1.0 to þ2.0 for high-Ti basalts), which also preclude basalt generation by
melting of ancient subcontinental lithospheric mantle. The geochemical composition of the northern
PCFB may be explained through the involvement of fluids and/or small volume melts related to metasomatic processes. In this context, we propose that the source of these magmas is a mixture of sublithospheric peridotite veined and/or interlayered with mafic components (e.g., pyroxenites or eclogites).
The sublithospheric mantle (dominating the osmium isotopic compositions) was very probably enriched
by fluids and/or magmas related to the Neoproterozoic subduction processes. This sublithospheric
mantle region may have been frozen and coupled to the base of the Parana basin lithospheric plate above
which the Paleozoic subsidence and subsequent Early Cretaceous magmatism occurred.
Como referenciar
ROCHA JUNIOR, EDUARDO R.V.; MARQUES, LEILA S.; BABINSKI, MARLY; NARDY, ANTONIO J.R.; FIGUEIREDO, ANA M.G.; MACHADO, FÁBIO B. Sr-Nd-Pb isotopic constraints on the nature of the mantle sources involved in the genesis of the high-Ti tholeiites from northern Parana Continental Flood Basalts (Brazil). Journal of South American Earth Sciences, v. 46, p. 9-25, 2013. DOI: 10.1016/j.jsames.2013.04.004. Disponível em: http://repositorio.ipen.br/handle/123456789/4081. Acesso em: 30 Dec 2025.
Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.