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Title: An exotic Cretaceous kimberlite linked to metasomatized lithospheric mantle beneath the southwestern margin of the São Francisco Craton, Brazil.
Authors: Carvalho, Luisa Diniz Vilela de
Jalowitzki, Tiago Luis Rei
Cipriano, Ricardo Augusto Scholz
Gonçalves, Guilherme de Oliveira
Rocha, Marcelo Peres
Pereira, Rogério Silvestre
Lana, Cristiano de Carvalho
Castro, Marco Paulo de
Queiroga, Gláucia Nascimento
Fuck, Reinhardt Adolfo
Keywords: Osvaldo França 1 kimberlite
Alto Paranaíba Igneous Province
Metasomatized cratonic lithosphere
Zircon U-Pb geochronology
Issue Date: 2022
Citation: CARVALHO, L. D. V. de. et al. An exotic Cretaceous kimberlite linked to metasomatized lithospheric mantle beneath the southwestern margin of the São Francisco Craton, Brazil. Geoscience Frontiers ,v. 13, 2022. Disponível em: <>. Acesso em: 29 abr. 2022.
Abstract: We present major and trace element compositions of mineral concentrates comprising garnet xenocrysts, ilmenite, phlogopite, spinel, zircon, and uncommon minerals (titanite, calzirtite, anatase, baddeleyite and pyrochlore) of a newly discovered Late Cretaceous kimberlite (U-Pb zircon age 90.0 ± 1.3 Ma; 2r) named Osvaldo França 1, located in the Alto Paranaíba Igneous Province (APIP), southeastern Brazil. Pyrope grains are lherzolitic (Lherz-1, Lherz-2 and Lherz-3), harzburgitic (Harz-3) and wehrlitic (Wehr-2). The pyrope xenocrysts cover a wide mantle column in the subcratonic lithosphere (66–143 km; 20–43 kbar) at relatively low temperatures (811–875 C). The shallowest part of this mantle is represented by Lherz-1 pyropes (20–32 kbar), which have low-Cr (Cr2O3 = 1.74–6.89 wt.%) and fractionated middle to heavy rare earth elements (MREE-HREE) pattern. The deepest samples are represented by Lherz-2, Lherz-3, Harz-3, and Wehr-2 pyropes (36–43 kbar). They contain high-Cr contents (Cr2O3 = 7.36–11.19 wt.%) and are char- acterized by sinusoidal (Lherz-2 and Wehr-2) and spoon-like (Lherz-3 and Harz-3) REE patterns. According to their REE and trace elements, pyrope xenocrysts have enriched nature (e.g., Ce and Yb vs. Cr2O3), indicating that the cratonic lithosphere has been affected by a silicate melt with subalkaline/ tholeiite composition due to their low Zr, Ti and Y concentrations. Besides minerals with typical kimber- litic signatures, such as ilmenite and zircon, the exotic compositions of phlogopite and ulvöspinel suggest an enriched component in the magma source. The formation of rare mineral phases with strong enrich- ment of light-REE (LREE) and high field strength elements (HFSE) is attributed to the late-stage kimber- litic melt. We propose a tectonic model where a thermal anomaly, represented by the low-velocity seismic anomaly observed in P-wave seismic tomography images, supplied heat to activate the alkaline magmatism from a metasomatized cratonic mantle source during the late-stages of Gondwana fragmen- tation and consequent South Atlantic Ocean opening. The metasomatism recorded by mineral phases is a product of long-lived recycling of subducted oceanic plates since the Neoproterozoic (Brasiliano Orogeny) or even older collisional events, contributing to the exotic character of the Osvaldo França 1 kimberlite, as well as to the cratonic lithospheric mantle.
ISSN: 1674-9871
metadata.dc.rights.license: This is an open access article under the CC BY-NC-ND license ( licenses/by-nc-nd/4.0/). Fonte: o PDF do artigo.
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