Chemical enrichment processes in Early Earth's surface environments

2016 Fiscal Year Final Research Report

• Project/Area Number: 26709069
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Partial Multi-year Fund
• Research Field: Earth system and resources engineering
• Research Institution: Hokkaido University
• Principal Investigator: Otake Tsubasa 北海道大学, 工学(系)研究科(研究院), 准教授 (80544105)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: バーバトン緑色片岩帯 / 初期地球 / 地球表層環境 / 縞状鉄鉱層 / クロムスピネル / 熱水実験 / 生命の進化

Outline of Final Research Achievements

Both geological survey in the Barberton Greenstone Belt, South Africa and laboratory experiments using a hydrothermal flow-through apparatus were conducted to investigate the origin of chromium spinel and temporal/special distributions of chromium enrichment found in a banded iron formation formed 3.2 billion years ago. The experimental results demonstrated that chromium spinel can be formed from iron and chromium hydroxides by the addition of dissolved ferrous iron under low temperature hydrothermal conditions (e.g., 150 degree Celsius). The results of geological survey showed that chromium enrichment in the banded iron formation were due to chemical processes. However, the chromium enrichments were localized in a particular geological unit and area. Important factors controlling the chemical enrichment of chromium are likely the degree of hydrothermal activity and sedimentary environments. These results suggest that a part of ocean was already oxygenated 3.2 billion years ago.

Free Research Field

地球化学