| 研究実績の概要 |
In this study, marine sediments were analysed for magnesium and lithium isotopes to create a time-series of chemical and physical silicate weathering in the Earth’s geological past. The purpose is to elucidate the response of silicate weathering, which experts a major control on atmospheric CO2 concentration, to regional and global warming. A warmer, wetter climate should provide more energy and fluids for silicate weathering reaction at the Earth’s surface to occur, consuming atmospheric CO2 and reversing the global warming trend. However, if the products of silicate weathering remain in the surficial system for too long before being deposited in marine sediments, they are converted back to silicates (reverse weathering), remitting the consumed CO2 leading to no net change on climate.
During the past fiscal year, 200 sediment samples from several International Ocean Drilling Program (IODP) and Ocean Drilling Program (ODP) cores collected from deep ocean basins as well as the Amazon margin were ordered, dried, crushed and chemically processed to extract the carbonate, iron oxide and silicate phase. Magnesium is currently being purified from these phases with further purification Li still to be conducted. Magnesium and Li isotopes with then be measured via inductively coupled plasma mass spectrometry. This work will provide records of past weathering during periods of regional (Amazonian) and global warming over tens of thousands to millions of years to help understand the silicate weathering capacity to reverse global warming.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
Marine sediments from the Amazon margin, Pacific Ocean, Indian Ocean and Atlantic Ocean were ordered and received from IODP. The samples were dried and crushed before undergoing a leaching technique to separate the carbonate, iron oxide and silicate phases. Major, minor and Rare Earth elements of these phases have been analysed successfully. These phases are now being purified with respect to magnesium and lithium which will then be measured for Mg and Li isotopes which is progressing smoothly.
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| 今後の研究の推進方策 |
Currently, 50 samples have been dried, crushed, leached, analysed for element concentration and been purified for magnesium and lithium. Magnesium and Li isotopes will be measured by inductively coupled plasma isotope mass spectrometry at Kochi Core Center within the next few months. Following that, a further 150 samples will undergo the same workflow.
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