東部南海トラフにおけるガスハイドレートの生成集積過程に関する地質学的・地球化学的制約
スポンサーリンク
概要
- 論文の詳細を見る
From January to May of 2004, METI/JOGMEC-MH21 prepared the METI Exploratory Test Wells Tokai-oki to Kumanonada, including drillings, loggings, and long-term borehole temperature monitoring by DTS/FBG. A high-resolution geochemical study of interstitial water and sediments was conducted at the Dai-ichi Tenryu Knoll and the Daini-Atsumi Knoll. Cl- baselines (original in situ Cl- concentration) at both sites show contrasting and characteristic patterns. The oxygen isotope compositions of the interstitial water seem to show a symmetrical pattern mirror image similar to the Cl- concentration. The fluctuations of oxygen and the Cl- baseline can generally be explained by dilution/enrichment mechanisms caused by gas-hydrate formation and dissociation. The formation and dissociation history of gas hydrate at the two sites is summarized as follows: (1) Sea level had fallen toward the Last Glacial Maximum, and BGHS had traveled upward. Methane and heavy oxygen-enriched water traveled upward in response to gas-hydrate dissociation: (2) Released methane was again trapped above the new BGHS, and gas hydrates were concentrated within sandy sediments. The upper BSR in the Dai-ichi Tenryu Knoll area was formed at this time: (3) BGHS has migrated downward following the transgression over the last 18,000 yrs. In the Daini-Atsumi area, relic-BSR corresponding to the upper-BSR in the Dai-ichi Tenryu Knoll area would have disappeared due to rapid accumulations of gas hydrate generated by a high methane flux, whereas in the Dai-ichi Tenryu Knoll area, it would have remained long after BGHS migration due to a lower methane supply. Eustatic sea-level change has brought about a hydrostatic pressure change, and gas hydrate stability zone would also have changed. However, the amount of additional gas hydrate accumulation would have obliterated or facilitated the development of the relic BSR.
- 2009-10-25
著者
-
松本 良
東京大学大学院理学系研究科地球惑星科学専攻
-
武内 里香
東京大学大学院理学系研究科地球惑星科学専攻
-
Matsumoto Ryo
Geological Institute Faculty Of Science The University Of Tokyo
-
武内 里香
東大 大学院理学系研究科
-
松本 良
東京大学大学院理学系研究科
関連論文
- オホーツク海および日本海に胚胎する表層型ガスハイドレート鉱床における間隙水のハロゲンと放射性ヨウ素同位体(129I)の地球化学
- 石灰質微化石層序からみた沖縄本島南部,知念層の地質年代
- 上越沖,海底表層メタンハイドレート賦存域での深海底構造・微地形調査について
- 特集号「メタンハイドレート(Part II):探査と資源ポテンシャル」 : ―はじめに―
- 総説 メタンハイドレート : ―海底下に氷状巨大炭素リザバー発見のインパクト―
- 特集号「メタンハイドレート(Part I):産状,起源と環境インパクト」 : ―はじめに―
- 日本海東縁,上越海盆における計量魚群探知機を利用したメタンプルームの観測 (総特集 西太平洋のガスハイドレートとメタン湧水)
- 計量魚群探知機によるメタンプルームの観測とメタン運搬量の見積もり
- P-52 日本海上越沖におけるメタン生成菌とメタン酸化菌の分離に関する予備研究(ポスター発表)
- 日本海東縁上越仲メタンハイドレート胚胎域における海底地形の特徴 (総特集 西太平洋のガスハイドレートとメタン湧水)