Geochemical characterization of marine sediments in the mud diapir province of the Paola Basin (Southern Tyrrenian Sea)

The study area is located along the Paola Ridge, a NNW–SSE 60-km-long anticline that confines the Paola Basin westward (north-western Calabrian margin), in the south-eastern Tyrrhenian Sea. The Paola Ridge has recently been interpreted as due to a mobile mud belt (comprised of D1, D2, D3 diapirs and MMV, RMV mud volcanoes) connected with a set of extensional NW-SE to NNW-SSE trending faults (Gamberi &Rovere, 2010). In August-September 2011 the MVP11 oceanographic cruise was carried on board the R/V CNR Urania. During the cruise, multi-beam bathymetric data, Chirp profiles, gravity coring and box cores, were acquired to define the sedimentological, petrographical, mineralogical and geochemical features of the marine sediments. In this work a detailed mineralogical and geochemical investigation of sediments collected from cores and box cores along the specific structures of the Paola Ridge is reported. The studied samples include: limestone crusts, carbonates of tubular form, iron oxy-hydroxide crusts, pyrite and sulfur crusts and cohesive muds. Each sample was characterized and analyzed by means of optical petrography, XRD, SEM-EDS, XRF, ICP-AES and ICP-MS. Selected samples were chosen for carbon, oxygen and sulfur isotopic analyses.The petrographical, mineralogical, chemical and isotopic data, obtained from the cored sediments and the rock samples, allowed to define the depths of the biogeochemical zones and the geochemical processes affecting the depositional environment into which the marine sediments were deposited (Rovere et al., 2015). Organogenic carbonate crusts consist of calcite, aragonite and dolomite, few phyllosilicates, feldspars and pyroxenes, and associated with macro fauna bivalves that are symbionts of sulfur oxidizing bacteria and usually live in extreme environments, as cold seeps (Rovere et al., 2015). Stable isotopes (C and O) on the organogenic carbonates are depleted in δ13C and slightly enriched in δ18O. Tubular authigenic carbonates contain siderite, quartz and few phyllosilicates. Stable isotopes (C and O) on the siderite are enriched in both heavy carbon and oxygen isotopes. Iron oxy- hydroxide crusts are comprised of goethite. Pyrite and sulfur crusts have pyrite and /or sphalerite, quartz and few feldspars. Cohesive muds showed a quartz, halite, feldspars, muscovite and clay minerals (illite, vermiculite, chlorite, kaolinite) and in some sample calcite or dolomite, siderite, hematite and pyrite.