Morphology and stratigraphy of Serra Geral silicic lava flows in the northern segment of the Torres Trough, Paraná Igneous Province

Autor(es)

Marcell Leonard Besser ^[1] ; Eleonora Maria Gouvea Vasconcellos ^[2] ; Antonio José Ranalli Nardy ^[3]

Afiliação do(s) autor(es)

^[1] Universidade Federal do Paraná. Setor de Ciências da Terra - Brasil

^[2] Universidade Federal do Paraná. Departamento de Geologia. Laboratório de Análise de Minerais e Rochas - Brasil

^[3] Universidade Estadual Paulista “Júlio de Mesquita Filho”. Petrologia e Metalogenia - Brasil

• Tipo de documento: Artigo Científico
• Fonte: BRAZILIAN JOURNAL OF GEOLOGY; v. 48, n. 2, p. 201-219, 2018-06-00.

Resumo

ABSTRACT: The impetus for this research was the enigma regarding the origin of the extensive silicic volcanic units in the Paraná-Etendeka Igneous Province. Are they rheoignimbrites, lava flows, or a combination of both? The São Joaquim silicic eruptive sequence is comprised of Palmas-Type aphyric dacites and is located in the northern segment of Torres Trough, a dissected mountainous region in southern Brazil. These dacite outcrops form plateaus and remnant hills that are scattered above a basaltic andesitic landscape. The original morphology of the silicic volcanic flows was constrained based on the internal architecture, geometry, and cyclicity of the lithofacies, in conjunction with petrographic and geochemical information. The data suggests the presence of ancient large tabular and lobate silicic lava flows (~100 m thick and ~10-40 km extents). No pyroclastic features were found. Eight interdigitating units were mapped. These large aspect ratios are similar to ones for basaltic flows and those of Snake River-type rhyolites, and they suggest high effusion rates and high temperatures as well as the presence of well-insulated cooled crusts. Lavas would have overflowed from long fissure vents that had created an extensive volcanic silicic surface body composed of conjugated and interdigitated flows above the north segment of the Torres Trough region. (AU)

• Processo FAPESP: 11/10508-6 - Petrologia e quimioestratigrafia do vulcanismo Mesozóico ácido da Província Magmática do Paraná
• Beneficiário: Antonio José Ranalli Nardy
• Modalidade de apoio: Auxílio à Pesquisa - Regular