Busca avançada
Ano de início
Entree
(Referência obtida automaticamente do Web of Science, por meio da informação sobre o financiamento pela FAPESP e o número do processo correspondente, incluída na publicação pelos autores.)

Columnar joints in the Patino Formation sandstones, Eastern Paraguay: a dynamic interaction between dyke intrusion, quartz dissolution and cooling-induced fractures

Texto completo
Autor(es):
Velazquez, Victor Fernandez [1] ; Giannini, Paulo Cesar Fonseca [2] ; Riccomini, Claudio [2] ; Sallun, Alethea Ernandes Martins [3] ; Hachiro, Jorge [2] ; Gomes, Celso de Barros [2]
Número total de Autores: 6
Afiliação do(s) autor(es):
[1] Univ Sao Paulo, Escola Artes Ciencias & Humanidades, BR-03828080 Sao Paulo - Brazil
[2] Univ Sao Paulo, Inst Geociencias, BR-05508080 Sao Paulo - Brazil
[3] Inst Geol, Secretaria Meio Ambiente, BR-04301903 Sao Paulo - Brazil
Número total de Afiliações: 3
Tipo de documento: Artigo Científico
Fonte: EPISODES; v. 31, n. 3, p. 302-308, SEP 2008.
Citações Web of Science: 6
Resumo

The Patino Formation sandstones, which crop out in Aregua neighborhood in Eastern Paraguay and show columnar joints near the contact zone with a nephelinite dyke, have as their main characteristics the high proportion of syntaxial quartz overgrowth and a porosity originated from different processes, initially by dissolution and later by partial filling and fracturing. Features like the presence of floating grains in the syntaxial cement, the transitional interpenetrative contact between the silica-rich cement and grains as well as the intense fracture porosity are strong indications that the cement has been formed by dissolution and reprecipitation of quartz from the framework under the effect of thermal expansion followed by rapid contraction. The increase of the silica-rich cement towards the dyke in association with the orthogonal disposition of the columns relative to dyke walls are indicative that the igneous body may represent the main heat source for the interstitial aqueous solutions previously existing in the sediments. At macroscopic scale, the increasing of internal tensions in the sandstones is responsible for the nucleation of polygons, leading to the individualization of prisms, which are interconnected by a system of joints, formed firstly on isotherm surfaces of low temperature and later on successive adjacent planes towards the dyke heat source. (AU)

Processo FAPESP: 01/10714-3 - A evolução do magmatismo alcalino na Plataforma Sul-Americana: implicações petrogenéticas e geodinâmicas
Beneficiário:Celso de Barros Gomes
Linha de fomento: Auxílio à Pesquisa - Temático
Processo FAPESP: 97/01210-4 - Petrologia e geoquímica de rochas alcalinas
Beneficiário:Celso de Barros Gomes
Linha de fomento: Auxílio à Pesquisa - Temático