Reaction microtextures in jadeitites from the Nishisonogi metamorphic rocks, Kyushu, Japan

• SHIGENO Miki

  Graduate School of Science and Technology, Kumamoto University

• MORI Yasushi

  Kitakyushu Museum of Natural History and Human History

• NISHIYAMA Tadao

  Department of Earth Sciences, Kumamoto University

Bibliographic Information

Other Title

• Reaction microtextures of jadeitite from the Nishisonogi metamorphic rocks, Kyushu, Japan

Abstract

Jadeitite exhibiting jadeite with quartz inclusions has been newly found in the Nishisonogi metamorphic rocks, Kyushu, Japan. The jadeitites occur in boulders from a riverbed, together with boulders of albitites, clinozoisite-muscovite rocks, and serpentinites. The distribution of these boulders is confined to an area that is downstream from an outcrop of a serpentinite melange, suggesting that they were originally tectonic blocks in this serpentinite melange. The jadeitites consist mainly of jadeite with small amounts of muscovite, paragonite, phlogopite, albite, analcime, clinozoisite, and titanite. The jadeite consists of a core with abundant inclusions of quartz and omphacite, and a rim that is free from quartz inclusions. The quartz inclusions are in direct contact with the host jadeite, which has an almost pure NaAlSi₂O₆ composition (Jd₁₀₀-Jd₉₅). The volume fraction of the quartz inclusions (V_Qtz/(V_Jd + V_Qtz) = 0.20-0.28) in the jadeite core is close to the value (V_Qtz/(V_Jd + V_Qtz) = 0.27) of quartz produced by the reaction albite = jadeite + quartz. These findings suggest that the jadeite core was produced by an isochemical breakdown of albite at high-P/T conditions. In addition, the jadeite is locally replaced by albite and/or analcime at the rim and along microfractures. These microtextures provide information to deduce a retrograde P-T path during the exhumation of the jadeitite.

Journal

• Journal of Mineralogical and Petrological Sciences

  Journal of Mineralogical and Petrological Sciences 100 (6), 237-246, 2005

  Japan Association of Mineralogical Sciences

Keywords

• Jadeitite
• Microtexture
• Inclusion
• Jadeite + quartz
• Tectonic block
• Nishisonogi metamorphic rocks

Details

• CRID: 1390282681522305920
• NII Article ID: 10016725446
• NII Book ID: AA11460926
• DOI: 10.2465/jmps.100.237
• BIBCODE: 2005JMPeS.100..237S
• COI: 1:CAS:528:DC%2BD28Xms1WjtA%3D%3D
• ISSN: 13493825
• ISSN: 13456296
• Text Lang: en
• Data Source:
  • JaLC
  • Crossref
  • CiNii Articles
• Abstract License Flag: Disallowed