日本地球惑星科学連合2018年大会

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[EE] Eveningポスター発表

セッション記号 S (固体地球科学) » S-CG 固体地球科学複合領域・一般

[S-CG54] ハードロック掘削 オマーンから海洋リソスフェア,島弧形成+

2018年5月21日(月) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:高澤 栄一(新潟大学理学部地質科学科)、道林 克禎(名古屋大学大学院環境学研究科地球環境科学専攻地質・地球生物学講座岩石鉱物学研究室)、Peter B Kelemen (共同)、Damon A H Teagle (Ocean & Earth Science, National Oceanography Centre Southampton, University of Southampton, SO14-3ZH, Southampton, UK)

[SCG54-P05] Lithological and petrophysical variation of the lower crustal section from the ICDP Oman drilling project Holes GT1A and GT2A

*草野 有紀1海野 進2星出 隆志3高澤 栄一4Teagle Damon5Kelemen Peter6Coggon Judith5Phase I Science Party The Oman Drilling Project7 (1.産業技術総合研究所 地質調査総合センター、2.金沢大学、3.秋田大学、4.新潟大学、5.University of Southampton、6.Lamont-Doherty Earth Observatory、7.D/V CHIKYU)

キーワード:Oman Ophiolite、layered gabbro、foliated gabbro、Magnetic susceptibility

Oman Ophiolite is one of the best-preserved ophiolite in the world and the type locality of oceanic lithosphere. ICDP Oman Drilling Project (OmDP) drilled ~100% core recovery of continual lower crustal section in Hole GT1A (22° 53.535'N, 58° 30.904'E; 403.7 m depth) and GT2A (22° 51.793'N, 58° 31.198'E; 406.77 m depth). These cores were cut in half and conducted on-board description on D/V CHIKYU during July-August 2017. Igneous and alteration petrologists, structural geologists, geochemists, physical property specialists and paleomagnetists got a series of core description.

Both GT1A and GT2A cores consist of ~65% of olivine gabbro, ~25% of olivine-bearing gabbro and olivine melagabbro. Minor rock types are anorthositic gabbro, troctolitic gabbro, orthopyroxene-bearing gabbro, gabbronorite, dunite, gabbro, gabbronorite, varitextured gabbro, troctolite, and troctolitic gabbro. Intercalation of minor rock types into major rock types exhibits “layering” structure, but also major rock types show layering and foliation consist of mineral size, mode and structure.

Variable layering and foliation intensity is common feature of the lower crust, but it is difficult to describe it standardize due to the thickness changes from < mm to meter order. We tried to use magnetic susceptibility (MS), luminance value (L*, a*, b*) of the archive half cores measured by Multi-Sensor Core Logger with 2 cm step interval. Generally, MS and luminance are sensitive in olivine mode and alteration, respectively.