Evidência geoquímica de solos formados pela interação de guanos com rochas vulcânicas, Ilha Rata, Fernando de Noronha (PE)

Abstract

RESUMOOs solos fosfáticos encontrados na porção norte da ilha Rata, no Arquipélago de Fernando de Noronha, foram formados pela reação do guano de aves marinhas com as rochas máfi cas intemperizadas da Formação Quixaba. Os minerais fosfáticos determinados no solo incluem a crandalita como o constituinte mais importante. A assinatura do guano preservada no solo é caracterizada por altos teores de Cu, Pb, Zn, As, U, e Sr. Por outro lado, a herança da assinatura geoquímica dos nefelina basaltos é demonstrada pelas concentrações anômalas de Ba, Nb, Ta, Cr, Hf, V e Zr nos solos e pela notável similaridade entre os padrões de ETR na rocha e nos solos.Palavras-chave: Solos fosfáticos; Guano; Fernando de Noronha; Ilha Rata; Crandalita. ABSTRACTThe phosphatic soils found in the northern part of the Rata island, in the Fernando de Noronha Archipelago, were formed by reaction of bird guano with weathered mafi c rocks of the Quixaba Formation. Phosphate minerals identifi ed include crandallite as a major constituent. The unique guano signature preserved in soil is characterized by high levels of Cu, Pb, Zn, As, U, and Sr. On the other hand, the inheritance of the geochemical signature of the nepheline-basalts is demonstrated by the anomalous concentrations of Ba, Nb, Ta, Cr, Hf, V and Zr in soils, and by the remarkable similarity between REE patterns in rock and soils.

Phosphate speleothems in caves developed in iron ores and laterites of the Carajás Mineral Province (Brazil) and a new occurrence of spheniscidite

“…The transition metals Zn and Ni, found in high concentrations in samples PS and PL (Table 2), confirm the geochemical signatures of guano in the phosphate minerals (Tatur, 1989;Tatur & Keck, 1990;Zdanowski et al, 2005;Liu et al, 2008;Oliveira et al, 2009;Wurster et al, 2015). High content Rb were also detected, which may be another guano geochemical signature, given that the LC/SJ samples are poor in this element.…”

“…High content Rb were also detected, which may be another guano geochemical signature, given that the LC/SJ samples are poor in this element. According to Oliveira et al (2009) andWurster et al (2015), metals are concentrated in bat excrements by bioaccumulation along its food chain either by insects or plants intake.…”

“…12 shows the relationship between guano production from bat colonies and phosphate mineral and, concomitantly, total or partial replace of iron hydroxides, typically amorphous. Metals such as Zn, Ni, and Rb that bioaccumulate in guano are equally assimilated into the neominerals during the phosphatization (Liu et al, 2008;Oliveira et al, 2009;Wurster et al, 2015).…”

Solos desenvolvidos sobre diferentes rochas vulcânicas da ilha de Fernando de Noronha: padrão de elementos terras raras e composição isotópica do chumbo

“…Estudos anteriores levados a efeito numa lagoa situada na mesma ilha de Fernando de Noronha (Oliveira et al, 2009a) (Oliveira et al, 2009b). Por outro lado, estudos que investigaram o comportamento de metais nos mesmos perfi s de solo da ilha de Fernando de Noronha (Oliveira et al, submetido) indicaram a provável contribuição de Hg aerotransportado nos horizontes mais superfi ciais do perfi l MQ.…”

Geochemical evolution of soils developed from pyroclastic rocks of Trindade Island, South Atlantic

“…Of the existing studies, few report the geochemical evolution of soil formation. Among them, there are the studies of Oliveira et al (2014) that showed the soil phosphatization process of Rata Island (Fernando de Noronha Archipelago) due to the interaction of bird excrement with olivine nephelinites (ankaratritic lavas), and of Oliveira et al (2009) that report high contents of Cu, Pb, Zn, As, U, and Sr in besides soils of this island due to the interaction of guano with mafic rocks, and anomalous concentrations of Ba, Nb, Ta, Cr, Hf, V and Zr due to the geochemical inheritance of local basalts. In the Fernando de Noronha Island, Oliveira et al (2011b) showed that soils developed from mafic rocks (nepheline basalts) presented higher contents of Fe, Co, Ni and Cr, and Oliveira et al (2011a) showed that soils from these rocks concentrate rare earth elements (REEs), preferably the heavy REEs (HREEs).…”