Characterization of Carbonate Crust from a Recently Discovered Methane Seep on the North Atlantic Continental Margin of the USA

• Published in: Minerals
• Main Authors: Rinat Gabitov, Chiara Borrelli, Jacob Buettner, Brenda Kirkland, Adam Skarke, Dustin Trail, Brittany Garner, Maurice Testa, Mahnaz Wahidi, Christopher Hoff, Salavat Khasanov, Giuliana Panieri, Roobanvenkatesh Thirumalai, Jay Thomas, Jeremy Weremeichik, Irina Zverkova
• Format: Text
• Language: English
• Published: Multidisciplinary Digital Publishing Institute 2019
• Subjects: authigenic carbonates; aragonite; methane seep; magnesium; sulfur; strontium; barium; carbon isotopes; North Atlantic
• Online Access: https://doi.org/10.3390/min9030138

This 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.