Atmospheric oxygen evolution in the Paleoproterozoic revealed by behavior of trace elements in weathering profiles

2015 Fiscal Year Final Research Report

• Project/Area Number: 24340132
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Petrology/Mineralogy/Science of ore deposit
• Research Institution: The University of Tokyo
• Principal Investigator: Murakami Takashi 東京大学, 理学(系)研究科(研究院), 教授 (00253295)
• Co-Investigator(Kenkyū-buntansha): UTSUNOMIYA SATOSHI 九州大学, 大学院理学系研究院, 准教授 (40452792) ; SUZUKI YOHEY 東京大学, 大学院理学系研究科, 准教授 (00359168)
• Project Period (FY): 2012-04-01 – 2016-03-31
• Keywords: 大気進化 / 風化 / 低酸素 / 微量元素 / 古土壌

Outline of Final Research Achievements

Weathering profiles retain records of atmospheric compositions at the time of weathering. We examined the behaviors of redox-sensitive trace elements in paleosols (ancient weathering profiles) formed in the Neoarchean and Paleoproterozoic. There are two distinct types in trace element behavior in the paleosols in terms of retention and loss, and the timings of the retention and loss differed between trace elements. The results suggest that continental oxidative weathering increased its intensity gradually in almost the whole Paleoproterozoic, and thus, support rather gradual oxygen increase in the same time period. The ocean chemistry could have changed with age accordingly.

Free Research Field

環境鉱物学