Geochemistry of stream sediments southwards of the SW Variscan suture in Portugal (Guadiana and Chança river basins) : insights into element anomalies of variable origin and intensity

• Autor(a) principal: Luz, Filipa
• Data de Publicação: 2012
• Outros Autores: Mateus, António, Matos, João Xavier, Gonçalves, M. A.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.9/2207
• topic: Geoquímica; Sedimentos de corrente; Anomalias geoquímicas; Sutura varisca; Bacia do Rio Guadiana (Portugal); Bacia do Rio Chança (Portugal); Pulo do Lobo (Portugal); Zona Sul Portuguesa; Faixa Piritosa Ibérica

Stream sediment samples were collected in the Trindade–Chança region at 1034 sites for mineral exploration purposes during 1996–97. Concentrations of Cu, Zn, Pb, Co, Cr and Ni are high enough in most sample sites to allow data assessment by multi-element anomaly definition and threshold computation using the area concentration multifractal model technique. The regional threshold values are 20, 45, 30 and 15 ppm for Cu, Zn, Pb and Co respectively. Anomalies for Cu, Zn, Pb, Co, Cr and Ni are delimited by first order local threshold values at 40, 94, 70, 21, 37 and 42 ppm. The main anomalies are clustered to the east-southeast of the surveyed region and reflect mixed contributions from a variety of sources, namely different volcanic units with local contributions from pelite rocks, contamination from old (abandoned) mining activities and hydrothermal mineralisation controlled by different fault zones.