The formation of carbonate build-ups associated with seafloor methane vents - where microbially mediated sulphate-dependent anaerobic oxidation of methane produces alkalinity - is well documented in modern marine environments and in the geologic record. However, the triggering event(s) behind the processes leading to hydrocarbon disequilibrium, seeping and consequent deposition of seep-carbonates remain poorly constrained. This contribution characterizes the salinity, geochemistry and temperature framework of a suit of fluid inclusions from hydrocarbon-derived seep-carbonate veins, collected from the Marmorito Formation in the Monferrato Hills, NW Italy. The datasets yield evidence of three different precipitation events, which comprise porous structures composed of well bladed calcites and aggregated spherules of aragonite. Fluid inclusions analysis show the presence of a heterogeneous entrapment of immiscible fluids proving the paleo-dissolution of a suite of complex hydrocarbons, which have a wide-range of closing temperature starting at c. 60° C. These physical and chemical conditions are considered to indicate seep-carbonate deposition driven by disequilibrium of hydrocarbon-bearing compounds at temperatures much warmer than the background ambient bottom waters (c. 1 to 5° C; Sibuet and Olu, 1998) due to the influence of the Late Oligocene to Early Miocene tectonic compression at the junction of the southern Alps and Apennines.
The influence of tectonic activity on clathrate destabilization: microthermometry and Raman insights from seep carbonates in the Alps‐Apennines tectonic knot
Ceriani, Andrea;Di Giulio, Andrea;Decarlis, Alessandro;Amadori, Chiara;
2022-01-01
Abstract
The formation of carbonate build-ups associated with seafloor methane vents - where microbially mediated sulphate-dependent anaerobic oxidation of methane produces alkalinity - is well documented in modern marine environments and in the geologic record. However, the triggering event(s) behind the processes leading to hydrocarbon disequilibrium, seeping and consequent deposition of seep-carbonates remain poorly constrained. This contribution characterizes the salinity, geochemistry and temperature framework of a suit of fluid inclusions from hydrocarbon-derived seep-carbonate veins, collected from the Marmorito Formation in the Monferrato Hills, NW Italy. The datasets yield evidence of three different precipitation events, which comprise porous structures composed of well bladed calcites and aggregated spherules of aragonite. Fluid inclusions analysis show the presence of a heterogeneous entrapment of immiscible fluids proving the paleo-dissolution of a suite of complex hydrocarbons, which have a wide-range of closing temperature starting at c. 60° C. These physical and chemical conditions are considered to indicate seep-carbonate deposition driven by disequilibrium of hydrocarbon-bearing compounds at temperatures much warmer than the background ambient bottom waters (c. 1 to 5° C; Sibuet and Olu, 1998) due to the influence of the Late Oligocene to Early Miocene tectonic compression at the junction of the southern Alps and Apennines.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
