Progressive sequence of reactions of the Ryoke metamorphism in the Yanai district, southwest Japan

The formation of cordierite

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

The compositions of biotite and muscovite were examined in terms of the paragenesis and the metamorphic grade in low- to medium-grade pelitic rocks of the Ryoke metamorphism in the Yanai district, southwest Japan. The biotite and muscovite that coexist with K-feldspar have a higher K component in an A'KF diagram than those in rocks lacking K-feldspar. This fact reflects an increase in the K2O content in muscovite, but in biotite it reflects an increase of not only the K2O content but also of the octahedral vacancy. At higher metamorphic grade beyond the cordierite isograd, where cordierite coexists with neither chlorite nor K-feldspar, the biotite shows an increase in illile, K Alivxii-1 Si-1, and Tschermak components, Alvi Aliv R2+-1 Si-1, where □xii and R2+ denote the interlayer vacancy and (Fe+Mg+Mn), respectively. A reaction to define the cordicrite isograd is proposed by treating this chemical change as being responsible for the first appearance of cordierite, i.e. K,Al-poor biotite+phengitic muscovite=K,Al-rich biotite+cordierite+quartz+water. By treating this as a key reaction in medium-grade metamorphism, a set of reaction in a progressive metamorphism is established for the Ryoke metamorphism, a typical low-pressure type metamorphism. Some textures in one of the high-grade areas, the K-feldspar-cordierite zone, suggest that a further two prograde reactions have taken place, i.e. andalusite+biotite+quartz=cordierite+K-feldspar+water and andalusite=sillimanite. This implies that this zone probably has a P-T path involving isobaric heating.

Original languageEnglish
Pages (from-to)39-52
Number of pages14
JournalJournal of Metamorphic Geology
Volume16
Issue number1
DOIs
Publication statusPublished - Jan 1 1998

Fingerprint

cordierite
biotite
metamorphism
feldspar
muscovite
Quartz
andalusite
Vacancies
Rocks
quartz
Water
sillimanite
paragenesis
rock
chlorite
low pressure
Textures
texture
diagram
heating

All Science Journal Classification (ASJC) codes

  • Geology
  • Geochemistry and Petrology

Cite this

@article{d50b6d88d1744a9ab4e067bb5398140c,
title = "Progressive sequence of reactions of the Ryoke metamorphism in the Yanai district, southwest Japan: The formation of cordierite",
abstract = "The compositions of biotite and muscovite were examined in terms of the paragenesis and the metamorphic grade in low- to medium-grade pelitic rocks of the Ryoke metamorphism in the Yanai district, southwest Japan. The biotite and muscovite that coexist with K-feldspar have a higher K component in an A'KF diagram than those in rocks lacking K-feldspar. This fact reflects an increase in the K2O content in muscovite, but in biotite it reflects an increase of not only the K2O content but also of the octahedral vacancy. At higher metamorphic grade beyond the cordierite isograd, where cordierite coexists with neither chlorite nor K-feldspar, the biotite shows an increase in illile, K Aliv □xii-1 Si-1, and Tschermak components, Alvi Aliv R2+-1 Si-1, where □xii and R2+ denote the interlayer vacancy and (Fe+Mg+Mn), respectively. A reaction to define the cordicrite isograd is proposed by treating this chemical change as being responsible for the first appearance of cordierite, i.e. K,Al-poor biotite+phengitic muscovite=K,Al-rich biotite+cordierite+quartz+water. By treating this as a key reaction in medium-grade metamorphism, a set of reaction in a progressive metamorphism is established for the Ryoke metamorphism, a typical low-pressure type metamorphism. Some textures in one of the high-grade areas, the K-feldspar-cordierite zone, suggest that a further two prograde reactions have taken place, i.e. andalusite+biotite+quartz=cordierite+K-feldspar+water and andalusite=sillimanite. This implies that this zone probably has a P-T path involving isobaric heating.",
author = "Takeshi Ikeda",
year = "1998",
month = "1",
day = "1",
doi = "10.1111/j.1525-1314.1998.00060.x",
language = "English",
volume = "16",
pages = "39--52",
journal = "Journal of Metamorphic Geology",
issn = "0263-4929",
publisher = "Wiley-Blackwell",
number = "1",

}

TY - JOUR

T1 - Progressive sequence of reactions of the Ryoke metamorphism in the Yanai district, southwest Japan

T2 - The formation of cordierite

AU - Ikeda, Takeshi

PY - 1998/1/1

Y1 - 1998/1/1

N2 - The compositions of biotite and muscovite were examined in terms of the paragenesis and the metamorphic grade in low- to medium-grade pelitic rocks of the Ryoke metamorphism in the Yanai district, southwest Japan. The biotite and muscovite that coexist with K-feldspar have a higher K component in an A'KF diagram than those in rocks lacking K-feldspar. This fact reflects an increase in the K2O content in muscovite, but in biotite it reflects an increase of not only the K2O content but also of the octahedral vacancy. At higher metamorphic grade beyond the cordierite isograd, where cordierite coexists with neither chlorite nor K-feldspar, the biotite shows an increase in illile, K Aliv □xii-1 Si-1, and Tschermak components, Alvi Aliv R2+-1 Si-1, where □xii and R2+ denote the interlayer vacancy and (Fe+Mg+Mn), respectively. A reaction to define the cordicrite isograd is proposed by treating this chemical change as being responsible for the first appearance of cordierite, i.e. K,Al-poor biotite+phengitic muscovite=K,Al-rich biotite+cordierite+quartz+water. By treating this as a key reaction in medium-grade metamorphism, a set of reaction in a progressive metamorphism is established for the Ryoke metamorphism, a typical low-pressure type metamorphism. Some textures in one of the high-grade areas, the K-feldspar-cordierite zone, suggest that a further two prograde reactions have taken place, i.e. andalusite+biotite+quartz=cordierite+K-feldspar+water and andalusite=sillimanite. This implies that this zone probably has a P-T path involving isobaric heating.

AB - The compositions of biotite and muscovite were examined in terms of the paragenesis and the metamorphic grade in low- to medium-grade pelitic rocks of the Ryoke metamorphism in the Yanai district, southwest Japan. The biotite and muscovite that coexist with K-feldspar have a higher K component in an A'KF diagram than those in rocks lacking K-feldspar. This fact reflects an increase in the K2O content in muscovite, but in biotite it reflects an increase of not only the K2O content but also of the octahedral vacancy. At higher metamorphic grade beyond the cordierite isograd, where cordierite coexists with neither chlorite nor K-feldspar, the biotite shows an increase in illile, K Aliv □xii-1 Si-1, and Tschermak components, Alvi Aliv R2+-1 Si-1, where □xii and R2+ denote the interlayer vacancy and (Fe+Mg+Mn), respectively. A reaction to define the cordicrite isograd is proposed by treating this chemical change as being responsible for the first appearance of cordierite, i.e. K,Al-poor biotite+phengitic muscovite=K,Al-rich biotite+cordierite+quartz+water. By treating this as a key reaction in medium-grade metamorphism, a set of reaction in a progressive metamorphism is established for the Ryoke metamorphism, a typical low-pressure type metamorphism. Some textures in one of the high-grade areas, the K-feldspar-cordierite zone, suggest that a further two prograde reactions have taken place, i.e. andalusite+biotite+quartz=cordierite+K-feldspar+water and andalusite=sillimanite. This implies that this zone probably has a P-T path involving isobaric heating.

UR - http://www.scopus.com/inward/record.url?scp=0031919137&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0031919137&partnerID=8YFLogxK

U2 - 10.1111/j.1525-1314.1998.00060.x

DO - 10.1111/j.1525-1314.1998.00060.x

M3 - Article

VL - 16

SP - 39

EP - 52

JO - Journal of Metamorphic Geology

JF - Journal of Metamorphic Geology

SN - 0263-4929

IS - 1

ER -