search for




 

Ammonium Behavior and Nitrogen Isotope Characteristics of 2:1 Clay Minerals from Submarine Hydrothermal System in the Wakamiko Crater of Kagoshima Bay, Southwestern Japan
일본 서남부 가고시마 와카미코 해저 열수환경에서 형성된 2:1 점토 광물 내 암모늄 거동 및 질소동위원소 특성
Econ. Environ. Geol. 2021 Feb;54(1):151-60
Published online February 28, 2021;  https://doi.org/10.9719/EEG.2021.54.1.151
Copyright © 2021 the Korean society of economic and environmental gelology.

Jaeguk Jo1,3, Toshiro Yamanaka2,3, Dongbok Shin1,*
조재국1,3 · 토시로 야마나카2,3 · 신동복1,*

1Department of Geoenvironmental Sciences, Kongju National University, Gongju 32588, Korea.
2Department of Ocean and Environmental Sciences, Tokyo University of Marine Science and Technology, Tokyo 108-8477, Japan
3Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
1공주대학교 지질환경과학과 2동경해양대학 해양환경과학부 3오카야마대학 자연과학기술대학원
Received December 1, 2020; Revised February 3, 2021; Accepted February 6, 2021.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
 Abstract
2:1 clay minerals such as smectite incorporating ammonium were extracted to investigate the ammonium behavior and nitrogen isotope characteristics for two different sediment cores which were collected from shimmering sites on seafloor of the Wakamiko crater, southwestern Japan. Inorganic nitrogen contents in clay fraction were estimated by calibration curve based on consistently decreasing carbon and nitrogen ratio during the treatment to decompose organic materials, after removing inorganic carbon. The results show that the proportions of inorganic nitrogen for total nitrogen in clay fraction of SWS site(Core#1094MR: av. 18.2%) are higher than those in SES site(Core#1093MG: av. 11.5%). Relatively good crystallinity of the former suggests that exchangeable ammonium was transformed to non-exchangeable ammonium during more evolving diagenetic process. Nitrogen isotope variance of clay fraction(SES site: Core#1093MG: -4.4 ~ +0.2 ‰, av. -2.4 ‰; SWS site: Core#1094MR: -0.7 ~ +3.0 ‰, av. +1.5 ‰) during sequential decomposition of exchangeable ammonium suggests that heat flow derived from deep magma led to nitrogen isotope fractionation between dissolved ammonium and ammonia in the fluids involved in the formation of 2:1 clay mineral incorporating ammonium with local temperature variation.
Keywords : southwestern Japan, Wakamiko seafloor Crater, 2:1 clay mineral, ammonium behavior, nitrogen isotope

 

February 2021, 54 (1)