岡山大学 地球科学研究報告
Published by Okayama University Earth Science Reports Editorial Committee

Phlogopite and Hornblende in the Contact Metamorphosed Ultramafic Complex at Yanomine, Sangun Metamorphic Zone, Japan

Inoue, Yoshinori
Kase, Katsuo
Thumnail ESR_6_1.pdf 762 KB
Abstract
Phlogopite and hornblende were found in amall amounts in the contact-metamorphosed dunite-harzburgite complex at Yanomine. Phlogopite occurs in interstices of silicate minerals in dunite and harzburgite located near the contact with granite. Some phlogopite grains also occur as inclusions in chromian spinel of chromitite bands. Hornblende is present associated with such metamorphic minerals as talc, olivine and orthopyroxene. Interstitial phlogopite is characterized by lower TiO2 and higher K/(K+Na) atomic ratio compared to that included in chromian spined. Hornblende in dunite chages its composition from edenite associated with olivine-talc through edenitic hornblende to Si-poorer magnesio-hastingsitic hornblende and magnesio-hastingsite with olivine or olivine-orhtopyroxene. The interstitial phlogopite is suggested to have been formed intimately connected with fluids generated in ralation to the intrusion of granite. On the other hand, included phlogopite is considered to have crystallized from the incompatible elements-enriched hydrous melt resulted from mantle-melt interaction. Hornblende should be a metamorphic mineral formed under high temperature conditions.
Keywords
Phlogopite
Hornblende
Ultramafic complex
Dunite
Harzburgite
Chromitite
Contact metamor-phism
Yanomine
ISSN
1340-7414
NCID
AN10506284