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Interactions between Acid and Intermediate Magmas in a 2.15-2.10 Ga Rhyacian Continental Arc: Insights from Petrographic, Geochemical and Isotopic Data of the Macuco De Minas Metagranitoid, Mineiro Belt, Brazil

2022; RELX Group (Netherlands); Linguagem: Inglês

10.2139/ssrn.4157477

1556-5068

Charlys Vaz de Sant’Anna Neves, Ciro Alexandre Ávila, Everton M. Bongiolo, Reiner Neumann, Wilson Teixeira, Fabiano Richard Leite Faulstich, Mônica Heilbron, Mauro César Geraldes, Cláudio de Morrison Valeriano,

earthquake and tectonic studies

The Mineiro Belt originated by Siderian to Rhyacian arcs amalgamated to the Neoarchean foreland of the southern margin of the São Francisco Craton, Brazil. The Macuco de Minas metagranitoid is one of the most important bodies related to the Rhyacian Ritápolis arc that developed close to the Siderian crust akin to the previous Cassiterita and Resende Costa arcs. We integrate new U-Pb ages, coupled geochemistry and Sr-Nd-Hf isotopes, and thermobarometry data with compiled information to unravel the petrogenesis of the Macuco de Minas metagranitoid toward its role in the formation of the Mineiro belt. This pluton is essentially represented by porphyritic granodiorites to monzogranites which exhibit centimetric microcline phenocrysts immersed in a medium-grained matrix mainly composed of quartz, oligoclase/andesine, biotite, and titanite. These rocks exhibit well-preserved mingling (mafic clots, magmatic enclaves, diorite injections with cuspate-lobate shape, and back-veining) and mixing (hybrid rocks) textures suggesting interaction with a dioritic/tonalitic magma, similar with the coeval Rio Grande metadiorite that occurs nearby. The Macuco de Minas (and hybrid) rocks are magnesian, medium-to-high-K calc-alkaline, metaluminous to slightly peraluminous, and display a high Ba-Sr signature. These exhibit enrichment in LILE and LREE compared to HFSE and HREE, as well as low Sr 87 /Sr 86 (2.1 Ga) (0.7027 to 0.7037), εNd (2.1 Ga) values from -2 to -7, and εHf (2.1 Ga) values from +3 to -7. The Nd-T DM model ages vary from 2.3 to 2.7 Ga and the zircon Hf ones from 2.38 to 2.77 Ga. The Macuco de Minas sample yielded a LA-ICP-MS zircon U-Pb crystallisation age of 2144 ± 16 Ma, and metamorphic age of 2071 ± 42 Ma in titanite. The crystallisation age is similar to the 2140 ± 17 Ma Rio Grande metadiorite. However, the latter contains inherited grains as old as 2200 ± 19 Ma and 2263 ± 21 Ma, not observed in the Macuco de Minas pluton. The bulk geochemical and isotopic signature of the studied granitoids point to a mantle source with a subordinated contribution of juvenile Siderian rocks of the Cassiterita and Resende Costa arcs and subducted sediments from the Archean rocks of the São Francisco Craton. From a tectonic point of view, the Macuco de Minas and Rio Grande plutons are compatible with the second stage of the Ritápolis arc development, the youngest episode of arc generation in the Mineiro belt.