Geologia e geoquimica do Tonalito-diorito Itareru, borda ocidental do Greenstone Belt do Rio Itapicuru, Bahia-Brasil

AUTOR(ES)
DATA DE PUBLICAÇÃO

2001

RESUMO

Elongated tonalitic bodies, like peridotite belts and large-scale shear zones, are significant geological features that help identify tectonie discontinuities in orogenie OOlts. The Rio Itapicuru Greenstone Belt, located on the northeastern edge of the Palaeoproterozoic ltabuna-Salvador-Curaçá orogen, is an important gold-producing geological unit. It is made up mostly of metamorphosed mafie and felsie volcanics, and sediments, intruded by tonalite to granodiorite domes. Although a back-are tectonic setting has been suggested, the location of the are and of any 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 tonalite to granodiorite intrusions were recognized on the southern portion of the greenstone belt. New field work also helped to recognize a NW-SE to N-S-trending body that may mark the western boundary between the greenstone belt and an Arehaean block within the ltabuna-Salvador-Curaçá Orogen. It is a sheet-like body (up to 7.5 km wide and over 80 km long) composed of enc1ave-rich, porphyritic diorite to tonalite. lsotope studies indicated an age of2,1O9:t 5 Ma (U-Pb SHRIMP on zircons) and slightly negative &Nd values. To the east of the ltareru Tonalite-diorite supracrustaI rocks of the greenstone belt and foliated granitoid intrusions dominate, whereas Archaean banded gneisses and isotropic granitoids are the main rock-types to the west. It is suggested that the ltareru Tonalite defines a tectonic discontinuity between two terranes, and that for its syn-tectonie eharateristies it marks the timing of continent-continent collision

ASSUNTO(S)

geoquimica mapeamento geologico

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