Hydrocarbon-derived ferromanganese nodules in carbonate-mud mounds from the Gulf of Cadiz: Mud-breccia sediments and clasts as nucleation sites

Ferromanganese nodules and micro-hardgrounds associated with the Cadiz Contourite Channel (NE Atlantic): Palaeoenvironmental records of fluid venting and bottom currents

“…).ln addition, thermogenic hydrocarbons (n-alkanes and phenanthrene) were discovered in the samples analysed (Fig. 8c), in accordance with fluid venting from deep-seated reservoirs towards the sea-bottom through mud diapirs, mud volcanoes and fault systems (González et al, 2009;Medialdea et al, 2009). Hydrocarbons contained in the nodules were also detected in host sediments and carbonate chimneys and crusts in the area.…”

“…The African-Eurasian convergence has promoted fault reactivatio n and widespread mud-salt diapirism and hydrocarbon-rich fluid venting structures (mud volcanoes, diapiric ridges, carbonate mud mounds, pockmarks and hydrocarbon-derived authigenic carbonates (HDACs)) (e.g. Somoza et al, 2003;León et al, 2006;Fernández-Puga et al, 2007;González et al, 2009;León et al, 2012;Magalhaes et al, 2012).…”

Mechanisms of trace metal enrichment in submarine, methane-derived carbonate chimneys from the Gulf of Cadiz

“…Thus, we infer that this oxidation process also affected some trace metals, promoting their removal, at least partly, from pyrite. Consequently, Locations of the mud-volcanoes and mud-mounds are from León et al (2006) and González et al (2009). Allochthonous Unit outline is from Medialdea et al (2009). we assume that the trace metal concentrations that we observed in carbonate chimneys are minimum values and probably lower than the concentrations at the time of iron sulphide precipitation.…”

“…Methane-enriched fluid venting is a widespread process in the continental slope of the Gulf of Cadiz. Evidence of this phenomenon is the abundance of methanerelated seafloor structures in this area, including pockmarks (Baraza and Ercilla, 1996;Casas et al, 2003); mud volcanoes, some of which contain gas hydrates (Niemann et al, 2006;Pinheiro et al, 2003;Van Rensbergen et al, 2005); Fe-Mn nodules (González et al, 2009(González et al, , 2010; and carbonate-mud mounds featuring carbonate chimneys, crusts and slabs (León et al, 2006). In addition, biomarkers of methanotrophic archaea have been identified on carbonate crusts and pavements collected from mud-volcanoes in the Gulf of Cadiz (Niemann et al, 2006;Stadnitskaia et al, 2008).…”

Tracing the composition, fluid source and formation conditions of the methane-derived authigenic carbonates in the Gulf of Cadiz with rare earth elements and stable isotopes

“…These methane-derived authigenic carbonates occur from the upper continental slope to~4500 m water depth on the lower continental rise. The carbonate distribution in the Gulf of Cadiz is much more extensive and widespread than previously reported in other cold seepage regions Gonzalez et al, 2009;Le on et al, 2010;Magalhães et al, 2012). They are associated with mud volcanoes, mud diapirs, diapiric ridges or deep routed faults represent evidence of fluid migration and can be used to understand the circulation of methane-rich fluids in the Gulf of Cadiz .…”