New SHRIMP U-Pb zircon ages for the Portalegre and Alcáçovas orthogneisses document a complex pre- Variscan history for the Iberian basement in Portugal. The available geochemical and geochronological data for the Alcáçovas orthogneiss (ca. 540 Ma) tend to favor its involvement in a Cadomian orogenic event. This is consistent with the development of an active continental margin setting at the e...

Abstract Based on natural gas compositions, carbon isotope ratios, and geological analysis, the genesis origin of gases in Lower Paleozoic Ordos basin are discussed. Due to differences distribution genesis, were divided into five types, namely western margin gas, weathered crust pre-salt Ordovician deep Cambrian gas. The results show that δ 13 C 1 2 range from −35.6 −38.9‰ −27.2 −35.9‰, respect...

Kullingia is considered a key taxon in demonstrating the presence of terminal Proterozoic–early Cambrian chondrophorine hydrozoans. However, Kullingia concentrica from the Lower Cambrian of northern Sweden possesses several features that show that it is not a body fossil but that it was formed by current or wave-induced rotation of an anchored tubular organism, possibly a sabelliditid. A scratc...

reservas, similares procesos metalogenéticos habrian actuado en el Paleozoico Inferior del Brea. La deformación y el metamorfisme regional hercinicos no han actuado en este sector como un importante reconcentrador de menas, y la mayor parte de indicios epigenéticos Many mineralizations, showings and geochemical anomalies de edad tardihercinicaestán relacionados alas células hidrotermales have b...