title: Late Jurassic ocean anoxic event: evidence from voluminous sulphide deposition and preservation in the Panthalassa.
abstract: The historically productive copper-bearing Besshi-type sulphide deposits in the Japanese accretionary complex were formed as volcanogenic massive sulphide deposits on the deep-sea floor of the Panthalassa Ocean. Here we report that eleven typical Besshi-type deposits yielded Re-Os isochron ages around 150 Ma (148.4 ± 1.4 Ma from the composite isochron) in Late Jurassic time. This date coincides with the lowest marine (87)Sr/(86)Sr ratio and highest atmospheric CO2 concentration of the past 300 million years. We infer that intense mid-ocean ridge hydrothermal and volcanic activity in the Late Jurassic produced huge sulphide deposits and large emissions of CO2 gas, leading to global warming and a stratified Panthalassa Ocean with anoxic deep seas that favored preservation of sulphides in the pelagic environment. The emergence of ocean anoxia triggered by seafloor volcanism is also consistent with a positive δ(13)C excursion and widespread deposition of petroleum source rocks and black shales.
authors.affiliation: Department of Systems Innovation, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Nozaki
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kato
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Suzuki
mesh_terms: D005075:Biological Evolution; D002245:Carbon Dioxide / Q000737:chemistry; D019015:Geologic Sediments / Q000737:chemistry*; D055593:Geological Phenomena; D006801:Humans; D000860:Hypoxia; D009792:Oceans and Seas; D012211:Rhenium / Q000737:chemistry; D012623:Seawater / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*; D018707:Volcanic Eruptions
chemical_list: D013440:Sulfides; D002245:Carbon Dioxide; D012211:Rhenium