Geologia e geoquímica da soleira de Reserva, estado do Paraná

Abstract

Studies carried on the Reserva Sill, one of the most important intrusive basic bodies of the Parana State, reveal the general geologic and geochemistry framework, toward to the elaboration of magmatic evolution models and the relation with hosted rocks. The Reserva Sill is formed by basalt, microgabbro and gabbro, marked by strong textural variation due to magmatic differentiation mechanism. Other field features include metamorphism, contact aureoles and fast cooling zones. The rocks are composed by labradorite, augite, magnetite, ilmenita and quartz and accessory minerals: titanite, apatite and pyrite. The host rocks are classified as shale, siltstone and sandstone and composed predominantly by quartz, feldspar, epidote, biotite, muscovite, clay and opaque minerals. X-ray difratometry analisys in sedimentary rocks reveal quartz as main phase. In addiction occur albite, ilite, vermiculite, sanidine, muscovite and clay minerals. Geochemistry data of major and trace elements in igneous rocks allow to classify Reserva Sill rocks as andesi-basalt, lati-andesite and andesite; tholeiit basalt, lati-basalt and quartz-latite. These rocks show high concentrations of TiO 2 (>2%) and are classified as Pitanga and Paranapanema types. Variation diagrams reveal the fractional crystallization as important mechanism in the genetic evolution of these rocks. Distribution models built (differentiation index, #mg, Ca/(Ca+Na) indicate the presence of a less differentiated part in the eastern portion of the intrusive body, suggesting that the magmatic evolution occurred from east to west.