Tracking the slab-derived fluid in spring water

2015 Fiscal Year Final Research Report

• Project/Area Number: 25400524
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Geochemistry/Cosmochemistry
• Research Institution: Japan Agency for Marine-Earth Science and Technology (2014-2015); Tokyo Institute of Technology (2013)
• Principal Investigator: NAKAMURA Hitomi 国立研究開発法人海洋研究開発機構, 地球内部物質循環研究分野, 研究員 (60572659)
• Co-Investigator(Kenkyū-buntansha): NAKAI Shunichi 東京大学, 地震研究所, 教授 (50188869) ; IWAMORI Hikaru 国立研究開発法人海洋研究開発機構, 地球内部物質循環研究分野, 分野長 (80221795)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: 温泉水 / スラブ起源 / 塩水 / 深部流体 / 沈み込み帯 / 構造線 / 同位体 / REE

Outline of Final Research Achievements

Possibility of upwelling of slab-derived fluid in the non-volcanic fore-arc region has been examined, by using heavy elements that are known as a powerful tracer for slab-derived materials. We have developed the analytical methods for condensing and extracting low-abundance heavy elements from a brine, and then applied them to the natural samples for quantitative analyses.
As a result, we have successfully determined the Sr-Nd-Pb isotopic composition of the Arima spring waters by the co-precipitation method with iron hydroxide, which indicates that the brine is originated from the Philippine Sea slab (Nakamura et al., 2014).We have also established the effective method for rare earth element analysis in spring water, based on which we found that (i) the slab-derived fluid has ascended along the tectonic lines without much interaction with crustal materials, then (ii) the fluid was mixed with meteoric water at a shallow depth, to produce the wide compositional variation.

Free Research Field

地球化学