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Abstract This paper analyzes mineralogical, geochemical, and geochronological aspects, along with the effect of hydrothermal/metasomatic overprints, to identify the presence of primary phosphate as well as depositional and paleoenvironmental conditions in marble and calcsilicate sequences recrystallized under transitional amphibolite-granulite metamorphic conditions in the Tanque Novo-Ipirá Complex within the Salvador-Curaçá Orogen, northeastern São Francisco Craton, state of Bahia, Brazil. Petrographic studies have identified up to 10 vol.% disseminated apatite and whole-rock P2O5 contents up to 3.2 wt.%. Post-depositional events affected the lithofacies to varying degrees. Late hydrothermalism did not modify the rare earth element and yttrium (REEY) patterns considerably. When normalized to Post-Archean Australian Shale (PAAS), these lithofacies are marked by flat pattern REEY, true negative Ce anomalies, and positive Y and Gd. The highly variable Eu anomalies were inherited from the source composition but may have been affected by interaction with fluids. U-Pb LA-ICP-MS (laser ablation multicollector inductively coupled plasma mass spectrometry) ages indicate a maximum depositional age of 2128 Ga, as well as Paleoproterozoic and Neoarchean sources. Samples with anomalous phosphorus show Y/Ho ratios >30 and Ce/Ce* anomalies between 0.53 and 1.0 with an average of 0.70, suggesting a sub-oxic environment for phosphate precipitation.

Baseando-se em interpretações paleoambientais utilizando dados geoquímicos, os mármores e as rochas calcissilicáticas do Vale do Jacurici, centro-norte da Bahia, demonstraram estar associados a um paleoambiente de deposição marinho raso Paleoproterozoico. Essas rochas encontram-se deformadas, metassomatizadas e metamorfizadas em condições de anfibolito alto a granulito. São intruditas pelo Sienito de Itiúba e pelo Complexo Máfico-ultramáfico Vale do Jacurici, mineralizado em cromita, relação que sugere idade mínima paleoproterozoica para a sucessão. Os estudos realizados em testemunhos de sondagem permitiram a caracterização de mármores, diopsiditos e rochas calcissilicáticas granulitizadas. São identificadas assinaturas marinhas preservadas em padrões de elementos terras-raras (ETR + Y), bem como anomalias negativas de Ce, positivas de Y e Gd e relações Y/Ho próximas aos valores da água do mar (60–168) nos mármores. Foram constatados padrões de contaminação crustal que indicam componentes provenientes de input terrígeno, resultando em relações positivas Zr versus Hf, enriquecimento relativo de metais traços, ΣETR + Y e razões Pr/Yb[SN], padrões Y/Ho (< 30) e anomalias menos acentuadas, sobretudo nas rochas calcissilicáticas. A presença de magnitudes variáveis de anomalias positivas de Eu pode refletir contribuição de assinaturas das águas dos mares arqueanos residuais e influência de fluidos magmáticos tardios. A ocorrência de valores anômalos de P2O5 nos mármores (1,38 e 4,56%) e diopsiditos (2,07 e 2,3%) relacionada às razões Y/Ho (parâmetro de contaminação detrítica na bacia) sugere assinaturas de zonas limítrofes entre contribuição terrígena e marinha, bem como evidencia controle estratigráfico preservado nas concentrações de fósforo. Esses dados indicam um paleoambiente influenciado por eventos climáticos globais favoráveis à fosfogênese, envolvendo alta disponibilidade de oxigênio, cenário semelhante aos registros em bacias paleoproterozoicas mineralizadas em fosfato sedimentar,

Abstract The Precambrian basement of Northeastern Brazil is the product of Rhyacian block convergence. The main deformation and intrusion of crustal granitoids occurred between 2.15 and 1.8 Ga ago. This large area has been subjected to long-lasting and rather uniform stresses during the Cambrian period. Gold provinces in Bahia represent metallogenetic products of distinct tectonothermal events. Gold mineralization took place during the Paleoproterozoic collision and the Cambrian convergence, respectively, accompanied by heat flow, crustal deformation, and granite intrusion. The tectonic framework of the region was reconstructed at ca. 700 Ma ago, considering the hypothesis of wrench-fault tectonics. The new hypothesis provides geological evidence and metallogenic constraints that make further investigation necessary, with reference to well-established São Francisco Craton concept and its peripheral fold belts.

ABSTRACT: This report reviews and incorporates new elemental and isotope chemostratigraphic data for correlation of Neoproterozoic carbonate-dominated successions in South America (Argentina, Bolivia, Brazil, Paraguay and Uruguay). These thick mixed carbonate/siliciclastic successions were largely deposited in epicontinental basins or accumulated on passive margins on the edges of cratons (e.g. São Francisco, Amazonia, Rio Apa Block, Pampia and Río de la Plata paleocontinents) during extensional events related to the rifting of the Rodinia Supercontinent. From the stratigraphic point of view, these successions occur as three mega-sequences: glaciogenic, marine carbonate platform (above glaciomarine diamictites or rift successions), and dominantly continental to transitional siliciclastics. In the orogenic belts surrounding cratons, carbonate-dominated successions with important volcanoclastic/siliciclastic contribution have been, in most cases, strongly deformed. The precise ages of these successions remain a matter of debate, but recently new paleontological and geochronological data have considerably constrained depositional intervals. Here, we report high-resolution C, O, Sr, and S isotope trends measured in well-preserved sample sets and mainly use Sr and C isotopes in concert with lithostratigraphic/biostratigraphic observations to provide detailed correlations of these successions. The establishing of a high-level and definite chemostratigraphic correlation between Neoproterozoic basins in South America is the main goal of this work.