Re-Os isotope and highly siderophile element systematics of the Parana continental flood basalts (Brazil)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Sr-Nd-Pb isotopic constraints on the nature of the mantle sources involved in the genesis of the high-Ti tholeiites from northern Paraná Continental Flood Basalts (Brazil)

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 (133Ma) 87Sr/86Sr ratios of 0.70538-0.70642, 143Nd/144Nd of 0.51233-0.51218, 206Pb/204Pb of 17.74-18.25, 207Pb/204Pb of 15.51-15.57, and 208Pb/204Pb of 38.18-38.45. 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 Sr-Nd-Pb 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 γOs values range from+1.0 to+2.0 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. © 2013 Elsevier Ltd.

Systematics and phylogeny of the Neotropical Pachymenes de Saussure and Santamenes Giordani Soika (Hymenoptera, Vespidae, Eumeninae)

The genera Pachymenes de Saussure and Santamenes Giordani Soika arerevised and the phylogenetic relationships among their species, based on external mor-phology and male genitalia, are presented. The cladistics analysis, using 22 terminalspecies (19 ingroup and 3 outgroup species) and 44 characters, produced a single clado-gram under implied weighting. Both genera were recovered as paraphyletic, althoughttwo major clades were formed and were well supported by the re-sampling analysis.We propose the synonymy of Pachymenes with Santamenes, and the description of twonew species: P. saussurei Grandinete n.sp. and P. riograndensis Grandinete n.sp..Newcombinations are: Pachymenes novarae (de Saussure) n.comb., P. olympicus (Zavattari)n.comb., P. peregrinus (Zavattari) n.comb. and P. santanna (de Saussure) revised combi-nation. We state the synonymy of P. obscurus orellanoides under P. obscurus consuetus,reviewing the status of the latter and raising P. consuetus to species level. Pachymenesorellanae vardyi is synonymized under P. orellanae; P. ghilianii olivaceus, P. ghilianiiavissimus and P. peruanus are proposed as synonyms of P. ghilianii; P. picturatusobscuratus is synonymized under P. laeviventris; P. picturatus nigromaculatus andP. picturatus var . intermedia are synonymized under P. picturatus and P. a t ra var . ornatis-sima get its lectotype designated and proposed as synonym of P. ater.

Reinstatement of the genus Colopalpus Pritchard and Baker (1958) and re-description of Colopalpus matthyssei Pritchard and Baker (1958), the type species of the genus (Acari, Tenuipalpidae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)