The Characteristic Of Authigenic Carbonates In Jiulong Methane Reef Of Northern South China Sea

The researching materials were provided by the international corporation project, which named SiGer, was cooperated between Gongzhou Marine geological survey and Marine Research Institute of Kirel University.Authigenic carbonates in Jiulong Methane Reef occur in the form of crusts and chimneys. X-ray studies show that carbonate minerals are aragonite, calcite, and lesser pyrite. Aragonite is acicular, elongate and fills voids of the carbonates. High-Mg calcite is granular. The δ¹³C values of carbonates range from -52.7‰PDB to -37.9‰PDB, most less than - 40‰PDB, suggesting a microbial methane-associated carbon reservoir. The δ¹⁸O values of carbonates range from 2.2‰PDB to 5.5‰PDB, giving a heavy value of O isotope ratios and indicating a ¹⁸O enriched water resource. Studies of the mineralogy and oxygen and carbon stable isotopic compositions provide clues that the carbonates from Jiulong Methane Reef of South China Sea were probably precipitated from the cold seeps, which originated from gas hydrate dissociation.