The Effect of Hydrothermal Alteration on the Sr and Nd Isotopic Signatures of the Barra do Itapirapuã Carbonatite, Southern Brazil

Andrade, Fábio Ramos Dias de; Möller, P.; Höhndorf, A.

doi:10.1086/314339

Cited by 12 publications

(4 citation statements)

References 40 publications

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“…REE carbonates, REE fluorocarbonates, and oxides, which are the products of hydrothermal environments, represent to some extent the individual fenitizing fluids enriched in IE rather than the primary carbonates [37]. For instance, different generations of carbonatite dykes are present in the Barra do Itapirapuã complex (Figure 3, V) [28,85,86].…”

Section: Hydrothermal Carbonatitesmentioning

confidence: 99%

“…Synchysite, parasite, and bastnäsite may occur as single crystals and/or polycrystals. Textural and chemical relationships between the REE fluorocarbonates provide insights into the mobility of REEs during fluid-rock interaction [28,31,85]. At Cerro Chiriguelo (Figure 8), calciocarbonatites are the prevailing rock types and show relatively high contents of Ba, Ta, Th, and Nb.…”

Section: Hydrothermal Carbonatitesmentioning

confidence: 99%

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Carbonatites from the Southern Brazilian platform: I

et al. 2020

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We present a comprehensive overview of the geochemical characteristics and evolution of the carbonatites from the southern Brazilian Platform (Paraná Basin). The carbonatites from different complexes display large compositional variability in terms of abundances of incompatible and rare earth elements. This is in agreement with an origin from heterogeneous lithospheric sources, as confirmed by isotopic data (see Speziale et al., this issue). The characteristic major and trace element abundances of these carbonatites present compelling evidence for invoking liquid unmixing as the main mechanism of their formation and evolution albeit few exceptions. We propose an evolutionary trend for the Brazilian carbonatites, which can be summarized as following: exsolution of the primary Ca- or Mg-carbonatitic liquids systematically takes place at the phonolite-peralkaline phonolite stage of magma differentiation; this is followed by progressive Fe-enrichment and by final emplacement of fluorocarbonatites associated with hydrothermal fluids.

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Section: Hydrothermal Carbonatitesmentioning

confidence: 99%

Section: Hydrothermal Carbonatitesmentioning

confidence: 99%

Carbonatites from the Southern Brazilian platform: I

et al. 2020

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“…However, the resultant negative correlations between Sr and Nd isotopes do not always take place in a balanced way. For example, hydrothermal alteration, contamination (Andrade et al 1999;Kalsbeek and Frei 2006), retrograde metamorphism (Luais et al 2001) or disequilibrium partial melting of a metasedimentary protolith involving certain minerals (Zeng et al 2005a, b) could generate particular Sr and Nd isotope compositions that do not necessarily overlap with those of the surrounding rocks.…”

Section: Introductionmentioning

confidence: 99%

Shear-assisted water-fluxed melting and AFC processes in the foreland of the Early Paleozoic Famatinian orogen: petrogenesis of leucogranites and pegmatites from the Sierras de Córdoba, Argentina

Demartis

Jung

Hauff

et al. 2021

Int J Earth Sci (Geol Rundsch)

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In the Comechingones pegmatitic field, central Argentina, leucogranite and pegmatite bodies crop out in a relatively narrow (25 × 10 km) belt, and were emplaced synkinematically with the main deformational event of the crustal-scale Guacha Corral shear zone during the Early Ordovician (~ 475 Ma). These leucogranites and pegmatites are geochemically evolved rocks with high silica and alkalis, low Fe 2 O 3 , MgO, TiO 2 and CaO, and high ASI values. The leucogranites display quite variable Sr and Nd isotope compositions (initial 87 Sr/ 86 Sr ratios from 0.7048 to 0.7170, and ε Nd values from + 2.0 to − 3.1), some of which do not overlap with almost any other pre-Famatinian rock from the Sierras de Córdoba. The major and trace element geochemistry and the particular Sr and Nd isotope compositions of the leucogranites are here explained by the following processes: (1) water-fluxed partial melting of amphibolites at relatively low P-T conditions generating currently unexposed granodioritic melts with unradiogenic 87 Sr/ 86 Sr ratios and radiogenic ε Nd values; (2) fractionation of mostly plagioclase and monazite leading to compositions close to the leucogranite melts; and (3) assimilation of metasedimentary rocks with crustal isotopic signatures, modelled by assimilation and fractional crystallization processes. The major, trace and isotope compositions of the pegmatites suggest a derivation from partial melting of the same metasedimentary protoliths of the Sierras de Córdoba that were assimilated by leucogranite melts. We propose a feedback relationship among deformation, anatexis, magma evolution and mass transfer in the context of such a crustal-scale shear zone in the foreland of the Famatinian orogen.

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“…The association of mantle-derived, carbonate-bearing igneous rocks with other alkaline silicate rocks, commonly nephelinites, phonolites and nepheline syenites in continental rift settings has been described worldwide (Andrade et al, 1998;Woolley, 2001). However, the origin of the association of carbonate and silicate magmas and their relationship remains controversial (Bell and Blenkinsop, 1989;Harmer, 1997;Bell, 1998;Harmer and Gittins, 1998).…”

Section: Introductionmentioning

confidence: 99%