Japan Geoscience Union Meeting 2018

Presentation information

[EJ] Poster

S (Solid Earth Sciences) » S-MP Mineralogy & Petrology

[S-MP37] Deformed rocks, Metamorphic rocks and Tectonics

Mon. May 21, 2018 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Yoshihiro Nakamura(Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology), Yumiko Harigane(Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST))

[SMP37-P14] Fabric development on chemically heterogeneous mantle beneath the Gakkel Ridge in Arctic ocean

*Yumiko Harigane1, Katsuyoshi Michibayashi2, Tomoaki Morishita3, Jonathan Snow4 (1.Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 2.Shizuoka Univ., 3.Kanazawa Univ., 4.Univ. Houston)

Keywords:olivine fabric, rare-earth element, mylonite, peridotite, heterogeneous mantle, Gakkel Ridge

Gakkel ridge is ultraslow-spreading ridge (6-13 mm/year in full spreading rate) which extends for 1,800 km across the Eurasian basin of the Arctic Ocean (Coakley and Cochran, 1998 and other references). Based on results from bathymetry and rock sampling, Michael et al. (2003) revealed three distinct regimes with different abundance of rock types on the Gakkel Ridge: a western volcanic zone, sparsely magmatic zone on central zone and an eastern volcanic zone. The sparsely magmatic zone is characterized by abrupt morphological changes with no volcanic ridges and large exposures of mantle peridotite. Previous geochemical study proposed that osmium isotopic results of some refractory peridotites have 2 billion years-old, implying the long-term preservation of refractory peridotites in the asthenospheric mantle (Liu et al., 2008) and the heterogeneous mantle existed beneath the Gakkel Ridge is the consequence of ancient melting, combined with subsequent melt percolation and entrapment. (D’Errico et al., 2016). However, an olivine fabric in such heterogeneous mantle has not yet been studied in detail. Here, we present the detailed rock descriptions, analyses of mineral fabrics, and geochemical analyses of the minerals in the 14 deformed peridotite samples recovered from two dredge sites (PS59-235 and PS66-238) on the sparsely magmatic zone of Gakkel Ridge.