Presentation Information
[R7-P-08]Description of rock and mineral and analysis of fluid inclusions found in and near the metamorphic soles of the Oman Ophiolite
*Tohma Tanaka1, Tatsuhiko Kawamoto1, Takumi Wani2, Yuji Ichiyama2, Hajime Taniuchi4, Eiichi Takazawa3, Yuto Miki3 (1. Shizuoka Univ. Sci., 2. Chiba Univ. Sci., 3. Niigata Univ. Sci., 4. AIST)
Keywords:
Oman Ophiolite,metamorphic sole,carbonation,diopsidite,fluid inclusion
The Oman Ophiolite is formed in a fast-spreading environment (Nicolas, 1989). Analysis of the temperature and pressure conditions and components of the carbonate veins in the serpentinized peridotite of the Oman Ophiolite is a very important indicator of the behavior of rocks and fluids during subduction zones and impulse processes (e.g., Noël et al., 2018). In the Oman Ophiolite, outcrops of metamorphic sole, a metamorphic body that underlies the lowermost mantle peridotite, diopsidite which is thought to be due to high-temperature thermal water, and many other rocks that are important for understanding the formation of subduction zones (e.g., Akizawa et al., 2016, Python et al., 2007). In this study, we collected and examined rocks distributed near the boundary between sole and mantle in Oman.
Microstructural observations using polarized light microscopy, Raman spectroscopy, and micro-XRF analysis were used to identify the constituent minerals and to analyze the constituent elements. Fluid inclusions in the minerals are analyzed by microthermometry.
The sole is metamorphosed by contact metamorphism of a subducting oceanic plate with the mantle of the subducting plate. Carbonates were observed as veins in both rocks. The boundary between the mantle and sole also showed veins composed of calcite, Sr-thomsonite and pectolite.
Two types of diopsidite were collected and compared: dike in harzburgite and dike in the mantle wedge dunite. The results of microthermometry showed that the dikes in dunite were formed by aqueous fluid with salinity like or slightly higher than that of seawater, while those in harzburgite were related to fluid with a higher salinity. In addition, the homogenization temperature of dike in harzburgite is at least 200°C higher than that of dunite. Therefore, it can be concluded that the fluids associated with the diopsidite in the harzburgite were higher in temperature and salt content than those in the dunite.
Microstructural observations using polarized light microscopy, Raman spectroscopy, and micro-XRF analysis were used to identify the constituent minerals and to analyze the constituent elements. Fluid inclusions in the minerals are analyzed by microthermometry.
The sole is metamorphosed by contact metamorphism of a subducting oceanic plate with the mantle of the subducting plate. Carbonates were observed as veins in both rocks. The boundary between the mantle and sole also showed veins composed of calcite, Sr-thomsonite and pectolite.
Two types of diopsidite were collected and compared: dike in harzburgite and dike in the mantle wedge dunite. The results of microthermometry showed that the dikes in dunite were formed by aqueous fluid with salinity like or slightly higher than that of seawater, while those in harzburgite were related to fluid with a higher salinity. In addition, the homogenization temperature of dike in harzburgite is at least 200°C higher than that of dunite. Therefore, it can be concluded that the fluids associated with the diopsidite in the harzburgite were higher in temperature and salt content than those in the dunite.