2:30 PM - 2:45 PM
[SEM17-15] Comprehensive study of the relationship between exsolved magnetite inclusions and host plagioclase crystal in gabbroic rocks
Keywords:Magnetite inclusion, Plagioclase
Plagioclase crystals were prepared from natural mafic-plutonic rocks. A gabbroic anorthosite from the northwestern part of the Duluth complex, a layered gabbro from the southern part of the Oman ophiolite, and a medium-grained gabbro from the Murotomisaki gabbroic Intrusion were crushed into mineral grains. The plagioclase crystals were collected under a stereoscopic microscope and used for the measurements after a hydrochloric acid leaching. The main series of measurements for the single grain plagioclase crystals were as follows: (1) To estimate a content of magnetic mineral in the plagioclase crystals, magnetic hysteresis loop was measured using an Alternating Gradient Magnetometer. (2) To investigate chemical compositions of the plagioclase crystals, microscopic observation was conducted using electron microprobes. (3) To investigate the average valence state of Fe, LIII-edge X-ray absorption near edge structure (XANES) measurement was performed at BL27SU of SPring-8. In addition to these single crystal measurements, low-temperature remanence measurements (field cooling remanence, zero field cooling remanence, and room temperature saturation isothermal remanence) were conducted for plagioclase grains using a Magnetic Property Measurement System. On the basis of measurement results, we will discuss a relationship between the content of magnetite and the Fe state in plagioclase crystal.