Geocronology, isotopic geochemistry and geochemical of the dioritic-granitic plutonism between Lavras and Conselheiro Lafaiete: implicatins to paleoproterozoic evolution of Mineiro Belt central part / Geocronologia, geoquímica isotópica e litoquímica do plutonismo diorítico-granítico entre Lavras e Conselheiro Lafaiete: implicações para a evolução paleoproterozóica da parte central do Cinturão Mineiro

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The study area is located in the southern border of the São Francisco Craton, Mineiro Belt. This portion comprises part of the Sul Mineira Province. In this context occurs medium to high metamorfic grade Archean and Paleoproterozoic terrains mosaic and granite-greenstone associations. The plutonic bodies, studied in this work, make part of volumous paleoproterozoic plutonism intrusive in to Nazareno greenstone belt (Archean) and Rio das Mortes greenstone belt (Proterozoic). The Lenheiro shear zone (LSZ delimits these greenstone belts: Nazareno (in the south) and Rio das Mortes (in the north); as well as the Paleoproterozoic plutons. The plutons chose for this work are: Fé Granitic Gneiss, Mama Rosa Granite, Cassiterita Tonalite/Trondhjemite, Ritápolis Granite, Brumado Diorite e Glória Quartz-Monzodiorite, located in the north LSZ; and: Lajedo Granitoid, Gentio Granitoid, Dores do Campo Quartz-Diorite, Brito Quartz-Diorite, Brumado de Baixo Granodiorite and Brumado de Cima Granodiorite, located in the south LSZ. Their petrographic characteristics are was follow: Fé Granitic Gneiss (monzogranite to sienogranite), Mama Rosa Granite (monzogranite), Cassiterita Tonalite/Trondhjemite (tonalite to granodiorite), Ritápolis Granite (tonalite, granodiorite, monzogranite and syenogranite), Brumado Diorite (diorite, quartz-diorite and tonalite), Glória Quartz-Monzodiorite (quartzdiorite, quartz-monzodiorite and tonalite), Lajedo Granitoid (granodiorite), Gentio Granitoid (kfeldspar granite), Dores do Campo Quartz-Diorite (quartz-diorite), Brito Quartz-Diorite (quartzdiorite), Brumado de Baixo Granodiorite (granodiorite to monzogranite) and Brumado de Cima Granodiorite (granodiorite to monzogranite). The Fé, Mama Rosa and Lajedo plutons have peraluminous/metaluminous composition, the Dores do Campo Quartz-Diorite is metaluminous and the Gentio Granitoid is peraluminous. The Fé Granitic Gneiss, Mama Rosa Granite and Gentio Granitoid alternate calc-alcaline trend to shoshonitic trends, in terms of K2O contents. The Lajedo Granitoid is calcic-alkaline and Dores do Campo Quartz-Diorite alternate toleiitic and calcic-alkaline caracteristics. We have obtained U-Pb ages (zircon) for the following rocks: Fé Granitic Gneiss (2191 ± 9 Ma), Lajedo Granitoid (2208 ± 26 Ma), Gentio Granitoid (2066± 10 Ma - minimum age) and Dores do Campo Quartz-Diorite (2198 ± 6 Ma). The geochemistry, geocronology and isotope information consent define the existence of two groups of plutons, in the north and south of LSZ. The plutons: Brito, Brumado de Cima, Nazareno, Itutinga, Brumado de Baixo, Lajedo and Quartzo Diorito Dores do Campo, located in south of LSZ, have Paleoproterozoic magma contribution with reducted contamination of short crustal life materials. These plutons belong to the first evolutive stage of the Mineiro Belt, between 2220 Ma and 2198 Ma. The plutons Cassiterita, Brumado, Fé and Glória located in north of LSZ, considered of the "Arc Stage" have significant Paleoproterozoic magma interation with Archean components compared to the other isotopic group; and a late cristalization time, between the north and the south group. The Ritápolis (2121 ± 7 Ma) and Mama Rosa plutons (north of the Lenheiros fault) display strong intersection with Archean components, and are tecnically related to the syn- to late- collision stage of the Mineiro belt evolution. The Gentio pluton shows similar isotopic characteristics, but it belongs to the pos-tectonic stage. Finaly, the U-Pb and ; TDM ages of the Mineiro belt plutons, compared with the Paleoproterozoic plutons that occursin the northen São Francisco craton, reveal that significant time differences took place during the Transamazonian orogeny. In addition, the auxilable isotopic characteristics of these plutons suggest the important role of mixing of Paleoproterozoic magmas and Archean protholits during magma genesis.

ASSUNTO(S)

geochronology geocronologia mineiro belt cinturão mineiro isotopic geochemistry geoquímica isotópica

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