Portal de Periódicos da CAPES

GEOLOGIA DO TONALITO ITARERU, BLOCO SERRINHA, BAHIA: UMA INTRUSÃO SIN-TECTÔNICA DO INÍCIO DA COLISÃO CONTINENTAL NO SEGMENTO NORTE DO ORÓGENO ITABUNA-SALVADOR-CURAÇÁ

2003; Sociedade Brasileira de Geologia; Volume: 33; Issue: 1 Linguagem: Inglês

10.5327/rbg.v33i1.1028

2317-4889

Marcelo Juliano de Carvalho, Elson P. Oliveira,

Geological and Geochemical Analysis

Elongated tonalitic bodies, associated with peridotite belts and large-scale shear zones, are important geological features for identifying sutures in orogenic belts. The Rio Itapicuru Greenstone Belt, located on the northeastern edge of the Palaeoproterozoic Itabuna-Salvador-Curaca orogen, is made up mostly of metamorphosed mafic and felsic volcanics, and sediments, intruded by tonalite to granodiorite domes. Although a back-arc tectonic setting has been suggested, the location of the arc and of the suture zone, or even the relations with the basement have been hampered by deformation and paucity of high-quality isotope data. Recently, on the basis of Nd isotope data juvenile, arc-related tonalitic to granodioritic intrusions were recognized on the southern portion of the greenstone belt. New field studies also helped to recognize a NW-SE to N-S-trending tonalitic body that may mark the western boundary between the greenstone belt and the Archaean Retirolândia block within the Itabuna-Salvador-Curaca Orogen. The Itareru Tonalite is a sheet-like body (up to 7.5 km wide and over 80 km long) composed of enclave-rich, porphyritic diorite to tonalite. Isotope studies indicated an age of 2,109 ± 5 Ma (U-Pb SHRIMP on zircons) and slightly negative e Nd values (-0,79 a 0,00). To the east of the Itareru Tonalite supracrustal rocks of the greenstone belt and foliated granitoids dominate, whereas Archaean banded gneisses, TTG and isotropic granitoids are the main rock-types to the west . It is suggested that the Itareru Tonalite defines a tectonic discontinuity between two terranes, and because of its syn-tectonic emplacement it possibly defines the timing of the Paleoproterozoic continentcontinent collision.