Trace element and isotopic features of carbonates from the mud volcanic ejecta from the Kura depression (Azerbaijan)

Abstract

A collection of veins and dispersed Ca carbonates from the mud volcanic ejecta from Azerbaijan has been studied. The appearance of calcite veins healing cracks are divers. Isotopic characteristics of the majority of Ca carbonates are the follows: δ13С (from -4 to +2‰) and δ18О (from +20 to +26‰) and are typical of marine carbonate sediments. The fragments of vein calcite enriched in 12C (δ13С from -49.2 to -6‰) were found in the mud masses of a few mud volcanoes and might be connected with the dormant methane seeps, occurring at the high level of Caspian Sea. The dispersed Ca carbonates from mud masses have δ13С from -6.1 to +11.9‰, and δ18О from +23.8 to +32.7‰. Studied carbonates have no geochemical links with the mud volcanic waters of current emission. The aqueous fluids are characterized by high НСО3- contents (up to 8 g/l) and average δ13С(TDIC) and δ18О(Н2О) values as high as δ13С = +20.0‰ and δ18О = +4.0‰. Both isotopic and REE signatures of vein calcites allows one to connect them with post-depositional interaction between formational waters and carbonate sedimentary matter. On the base of these data mud volcanic feeder channels have been considered as isolated hydrodynamical systems, avoiding the connection with the aquafers of host sedimentary strata.