Algoma-type Neoproterozoic BIFs and related marbles in the Serido Belt (NE Brazil): REE, C, O, Cr and Sr isotope evidence

摘要

The Jucurutu Formation in the Serido Belt, northeastern Brazil, encompasses fine-to coarse-grained amphibolite-facies marbles, locally with cross-bedding and stromatolites. Banded iron formations (BIF) at three localities in this belt comprise itabirites (actinolite- or cummingtonite-itabirite and quartz-hematite itabirite) and iron ores, which are overlain by marbles of the Jucurutu Formation. Diamictites of uncertain stratigraphic position in the Serido Belt exhibit gneiss and quartzite clasts up to 0.6 m long and a fine-grained metapelitic matrix.