Principal component analysis (PCA) and mineral associations of litoraneous facies of continental shelf carbonates from northeastern Brazil

• Autor(a) principal: Marques, Wanessa Sousa
• Data de Publicação: 2008
• Outros Autores: Sial, Alcides Nobrega, Menor, Eldemar de Albuquerque, Ferreira, Valderez Pinto, Freire, George Satander Sá, Lima, Enjolras de Albuquerque Medeiros, Manso, Valdir do Amaral Vaz
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da Universidade Federal do Ceará (UFC)
• Texto Completo: http://www.repositorio.ufc.br/handle/riufc/64768
• topic: Carbonates; Relict sediments; Geochemical composition; Continental shelf; Northeastern Brazil; Principal component analysis (PCA)

The distribution of mineral phases according to the provenance of carbonate and terrigenous facies of carbonate sediments from a large area of the continental shelf of northeast Brazil was investigated using a major element multivariate analysis approach. Heavy minerals such as ilmenite are restricted to the litoraneous facies of the continental shelf of the states of Paraı´ba and Pernambuco, and clay minerals are found in distal facies of the continental shelf of the State of Ceara´. In the carbonate fraction, composed essentially by Mg-calcite and aragonite, there is co-variation between CaO/MgO and bathimetry in part of the studied continental shelf from depths between 15 and 20 m, apparently due to influence of the seawater temperature, degree of oxygenation and luminosity. The terrigenous facies are mainly composed of quartz, clay minerals, K-feldspars and micro-micaceous minerals, having Fe and Ti oxide and hydroxide minerals as major accessory phases. Major element behavior attests to the presence of arenaceous quartz-rich relict sediments in the 35, 60 and 80 m isobaths of the continental shelf of the state of Ceara´ which is here interpreted as a proxy of ancient coast lines during the Flandrian transgression.