17:15 〜 18:45
[SCG42-P02] オマーンオフィオライトマントルセクションの構造要素の鉛直変化
キーワード：マントル流動、オマーンオフィオライト、カンラン岩、面構造、結晶方位定向配列、剪断センス
The Oman ophiolite is the largest ophiolite and preserves oceanic fragments composed of volcanic rocks, sheeted dikes, gabbros, and serpentinized peridotite. The Oman ophiolite can preserve some signs of asthenospheric mantle in the peridotite, and has therefore been a good subject for mantle flow studies [1]. For instance, structural analyses in the mantle sections of the Oman ophiolite have suggested a model of forceful horizontal flow in the uppermost mantle at the edge of a diapir (an active mantle uprise) below an oceanic spreading center [2] [3]. However, although the scale of mapping in a mantle section may be sufficient to support the model, the structural consistencies between outcrops remain ambiguous.
In the Oman drilling project, 300-400m cores were continuously drilled at various sites of the Oman ophiolite [4]. We studied BA3A ultramafic cores that correspond to the uppermost mantle section and analyzed structural elements such as peridotite foliations and olivine crystal preferred orientations (CPOs). Because the BA3A cores were not oriented as correctly as their original occurrences at depth, we developed a MATLAB script to rotate both the foliations and CPO data horizontally in a certain direction. We then interpreted the shear senses obtained by the oblique relationships between the foliation and CPO data and discussed the uppermost mantle structure in the vicinity of the mantle diapir.
References
[1] Nicolas, 1989, The Netherlands: Kluwer Academic Publishers.
[2] Nicolas et al, 1988, Marine Geophysical Researches, 9(4), 293–310.
[3] Michibayashi et al, 2000, Marine Geophysical Researches, 21(3-4), 259–268.
[4] Kelemen et al., 2020, Proceedings of the Oman Drilling Project.
In the Oman drilling project, 300-400m cores were continuously drilled at various sites of the Oman ophiolite [4]. We studied BA3A ultramafic cores that correspond to the uppermost mantle section and analyzed structural elements such as peridotite foliations and olivine crystal preferred orientations (CPOs). Because the BA3A cores were not oriented as correctly as their original occurrences at depth, we developed a MATLAB script to rotate both the foliations and CPO data horizontally in a certain direction. We then interpreted the shear senses obtained by the oblique relationships between the foliation and CPO data and discussed the uppermost mantle structure in the vicinity of the mantle diapir.
References
[1] Nicolas, 1989, The Netherlands: Kluwer Academic Publishers.
[2] Nicolas et al, 1988, Marine Geophysical Researches, 9(4), 293–310.
[3] Michibayashi et al, 2000, Marine Geophysical Researches, 21(3-4), 259–268.
[4] Kelemen et al., 2020, Proceedings of the Oman Drilling Project.