Study on fractionation behaviours for HFS elements in environmental samples

2016 Fiscal Year Final Research Report

• Project/Area Number: 26800278
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Geochemistry/Cosmochemistry
• Research Institution: University of Tsukuba
• Principal Investigator: SAKAGUCHI Aya 筑波大学, 数理物質系, 准教授 (00526254)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: HFS元素 / 鉄マンガンクラスト / Zr / Hf / 放射性トレーサー

Outline of Final Research Achievements

In this study, we have attempted to clarify the accumulation/fractionation mechanisms of “geochemical twin” Zr and Hf in ferromanganese crusts (FMCs) by performing sequential extraction and DFO complexed radio-Zr and radio Hf adsorption experiments, wchich includes XAFS analysis for synthesised and natural samples.The their KDs between natural FMCs and seawater were around 10^8, and their ratios were fractionated compared to that of seawater. The observed Zr chemical states in FMCs resembled that for coprecipitation with ferrihydrite, coprecipitation with d-MnO2 and a basalt-like composition, although the results of sequential extraction showed that Zr and Hf existed predominantly in the Fe fraction. In the case of the adsorption experiments for DFO-Zr and DFO-Hf to ferrihydrite and d-MnO, it was found that the Hf-DFO underwent more adsorption on both minerals than Zr-DFO. The observed bond length of Hf-O was slightly shorter than that of Zr-O in the synthesised minerals.

Free Research Field

地球化学