Constraints on the source and petrogenesis of early Ediacaran shoshonitic mafic magmatism and high-K calc-alkaline granitoids in the Sergipano Orogenic System, Borborema Province, Brazil
•Emplacement of the Capela pluton at 630 Ma during the early Brasiliano Orogeny.•Shoshonitic mafic rocks were derived from a metasomatized lithospheric mantle.•Evolved Sr-Nd-Pb-Hf isotope compositions reflect sediment recycling.•Lower crust melting generated contemporary high-K calc-alkaline granito...
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Veröffentlicht in: | Precambrian research 2024-05, Vol.404, p.107312, Article 107312 |
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Zusammenfassung: | •Emplacement of the Capela pluton at 630 Ma during the early Brasiliano Orogeny.•Shoshonitic mafic rocks were derived from a metasomatized lithospheric mantle.•Evolved Sr-Nd-Pb-Hf isotope compositions reflect sediment recycling.•Lower crust melting generated contemporary high-K calc-alkaline granitoids.
The early Ediacaran Capela pluton (ca. 630 Ma) is intruded into the metasedimentary succession of the Sergipano Orogenic System along the oriental segment of the Macururé Domain, southeastern Borborema Province, NE Brazil. This body is an uncommon example of mantle-derived shoshonitic mafic rocks associated with high-K calc-alkaline granitoids emplaced in a pre- to early-collisional context. Here, we aim to unravel the petrogenesis of this plutonic association to determine the role of crustal contribution to magmatism and its geodynamical significance during the early stages of the Brasiliano/Pan-African Orogeny. The Capela pluton comprises cumulate hornblendites, gabbronorites, gabbros, diorites, granodiorites, quartz monzonites, and granites. Shoshonitic mafic rocks and high-K calc-alkaline granitoids show significant enrichments in LILE and LREE compared to HREE and HFSE. Ultramafic and mafic rocks display a conspicuous crustal signature, yielding subchondritic εNd(t) and zircon εHf(t) values, along with variable radiogenic Sr–Pb isotopic compositions. The dominant factors controlling the geochemical features of the mafic magmas were the enriched signature of the lithospheric mantle source and the degree of partial melting. Mantle source metasomatism is thought to have occurred by incorporating subducted sediments into the mantle wedge before the onset of the Brasiliano Orogeny. Geochemical modeling demonstrated that low partial melting degrees (5–10%) of phlogopite-bearing lithospheric mantle in the spinel stability field metasomatized by 5–10% subducted sediments may account for the main characteristics of the mafic rocks. Introducing sedimentary material into the mantle caused a decrease in Sm/Nd and Lu/Hf ratios while increasing the Rb/Sr, U/Pb, and Th/Pb ratios, which led to the time-integrated evolved isotopic signature observed in the mafic rocks. The coeval granitoids are metaluminous to slightly peraluminous and display Nd–Pb isotopic compositions similar to those of mafic–ultramafic rocks. The petrological and isotopic features of the granitoids are consistent with derivation from an ancient mafic lower crustal source. We argue that the ascent |
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ISSN: | 0301-9268 1872-7433 |
DOI: | 10.1016/j.precamres.2024.107312 |