Paleoproterozoic metagabbro xenolith in the southeastern Dom Feliciano Belt, southern Brazil: A new piece in the West Gondwana assembly

Koester, Edinei; Porcher, Carla Cristine; Ramos, Rodrigo Chaves; Vieira, Daniel Triboli; Olmo-Barbosa, Laércio Dal; Bastos, Vivianne Andrade

doi:10.1016/j.jsames.2022.104040

Cited by 2 publications

(1 citation statement)

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“…The oldest rocks identified in the PT occur as xenoliths within the PMC rocks, shown in Figure 1b. These xenoliths are represented by the Piratini gneisses (Tonian‐Cryogenian age – Tambara et al, 2019), by the remnant of a 2.0 Ga Palaeoproterozoic crust (Koester et al, 2022) (yellow star in Figure 1b,c) and by possible remnants of the South Adamastor palaeo‐ocean (Alto Alegre amphibolites – Ramos et al, 2020).…”

Section: Geological Settingmentioning

confidence: 99%

Slab failure‐related magmatism in the Pinheiro Machado Complex, southern Dom Feliciano Belt, Brazil

Bastos,

Koester,

Lenz

et al. 2024

Geological Journal

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In the Dom Feliciano Belt, Brazil, the Pinheiro Machado Complex (PMC) includes diorites, tonalites, granodiorites, syenogranites and granites, whose evolution is related to several magmatic pulses and complex petrogenetic processes. Two magmatic stages were identified (early and late), resulting in different rock subgroups. The geochemical data showed that the early magmatism was chemically affected by partial melting. Geochemical modelling results suggest that fractional crystallization processes with assimilation of around 40% from the crustal basement and the decoupling of assimilated magma are crucial for the PMC rocks' genesis. Geochemical data also show that during the early magmatism, the subsequent process of early diorite anatexis developed by heating and continuous activity of the underlying magma chamber possibly occurred at a melting rate of 5%–10%. The hybrid rocks have contributions from the mixing process related to early terms, showing geochemical correlations in the major element curves, for the early diorite and syenogranitic melt members, at 60%–50% and 50%–40%, respectively. Slab failure tectonic context is related to the multi‐intrusive events dynamics recorded in the studied rocks. Recharge and melting events of the recently formed crust due to the constant heating of new pulses of deep slab melting would explain the magmatic interactions observed in the Complex. The results demonstrate that the studied rocks crystallized in an open system, including mixing processes to form hybrid rocks, physical disaggregation and assimilation of early intrusions, truncation, dragging and erosion of early mushes by younger pulses.

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Section: Geological Settingmentioning

confidence: 99%