Brazilian shield

BRAZILIAN SHIELD (RU: Бразильский щит) is the most large protrusion of the pre-Cambrian basement of the South American tectonic plate. It extends itself from the valley of the Amazon river and from the syneclise with the same name at the north to the Paraná river at the south.

It is subdivided by the zone of the Baikalian folding into the Western Brazilian (Central Brazilian) and Eastern Brazilian massifs, which are often described as the independent shields. The Western Brazilian massif is formed by the rocks of the early pre-Cambrian. Within the significant places of the Eastern Brazilian massif, there also protrude the rocks of the early pre-Cambrian, which have been re-processed during the end of the pre-Cambrian - start of the Paleozoic, and which are alternating with the geosynclinal metamorphosed strata of the late pre-Cambrian (the Atlantic folded geosynclinal belt). Within the certain places on the surface of the shield, there are preserved the outliers of the continental cratonic cover from the Late pre-Cambrian (Proterozoic) and from the Phanerozoic, mainly from the Cretaceous. Within the rocks of the early pre-Cambrian, there are the large depositions of the iron ores (the Minas Gerais, and Brasília states). Within the limits of the massif, there exist also the ring-shaped alkaline intrusions of the Late Mesozoic and Paleogene ages, with which there are associated the deposits of the ores of the rare elements (niobium, tantalum, zirconium, and others).