报告时间：2026年11月5日（周四），下午 14:00-16:00
报告地点：天津大学卫津路校区地科院（第16教学楼）221报告厅
特邀嘉宾：Yuji Sano 教授，日本东京大学教授、高知大学海洋岩心研究所所长 （邀请人：徐胜 教授）
报告简介：
Manganese crusts are minerals composed of metal oxides that form by covering the seafloor bedrock. As manganese and iron in seawater gradually form layers of oxides over millions of years, these crusts serve as records of long-term changes in the marine environment. In this study, a manganese crust collected from the summit of a seamount in the western equatorial Pacific was dissected into layers, and their 10Be ages, iron and helium isotope ratios, and concentrations of major and trace elements were measured. Based on temporal variations in iron isotope ratios and 3He concentrations, we detected iron of presumed extraterrestrial origin in parts that grew approximately 8.5 million and 9.5 million years ago. The carrier of this iron was likely fine particles generated by asteroid belt impacts that reached the vicinity of Earth’s orbit and subsequently fell to Earth. This iron, combined with that derived from Aeolian dust originating from land, may break the iron limitation on biological production in the open ocean, leading to the proliferation of phytoplankton. The rate of carbon fixation increased, and as organic matter sinking into the ocean underwent oxidative decomposition in the deep sea, the concentration of dissolved oxygen decreased. As a result, the formation of oxides was inhibited, which may have triggered a reduction in the growth rate of manganese crust.
