AbstractThis study is focused on mineralogical and chemical characterization of an authigenic carbonate rock (crust) collected at a recently discovered cold seep on the US North Atlantic continental margin. X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate that the carbonate rock is composed of microcrystalline aragonite cement, white acicular aragonite crystals (AcAr), equant quartz crystals, small microcrystalline aluminosilicates, and trace amounts of iron sulfide microcrystals. Element/calcium ratios were measured with laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) using a calcite standard, which was prepared by annealing USGS certified carbonate powder (MACS-3). The occurrence of microscopic, non-carbonate inclusions precluded evaluation of trace elements in the aragonite cement, but allowed for in situ analysis of AcAr crystals. Carbon and oxygen isotopes were analyzed via isotope ratio mass spectrometry (IRMS) and expressed as δ13C and δ18O. Low δ13C values suggest that aragonite grew as a result of anaerobic oxidation of methane and observed δ18O values indicate that the temperature of aragonite crystallization was 1.7–1.9 °C.
|Project Title||Biologically induced methane oxidation and precipitation of carbonate minerals: An experimental study|
|Acronym||Deep Sea Geochem CaCO3|
|Created||August 9, 2018|
|Modified||September 14, 2018|
Biologically-mediated CaCO3 precipitation widely occurs in aquatic systems and is often directly linked to the metabolic activity of microorganisms, which could significantly affect the local environment. An example is oxidation of methane and reduction of sulfate mediated by a consortium of Bacteria and Archaea. In order to investigate geochemistry of CaCO3precipitated abiotically and under microbial activity experimental work was initiated. The abiotic experiments were performed at different temperatures and pressures (nitrogen and nitrogen-methane mixture). Further geochemical analyses will allow evaluating of the effect of total pressure and methane partial pressure on the geochemistry of CaCO3. Sulfate reducing bacterial (Desulfovibrio salexigens) was successfully cultured and precipitation experiments on microbially mediated CaCO3 are in progress. This work is relevant to C-DEBI Research Theme I (Activity in the Deep Subseafloor Biosphere: function & rates of global biogeochemical processes) because carbonate growth rate is linked to microbial activity and the rate of methane oxidation.
|Rinat Gabitov||Mississippi State University (MSU)||Principal Investigator|
|Karyn L. Rogers||Rensselaer Polytechnic Institute (RPI)||Co-Principal Investigator|
|Chiara Borrelli||University of Rochester||Contact|