Rapid growth of garnet within a metamorphic vein inferred from misorientation angle distribution of garnet porphyroblasts

Atsushi Okamoto, Katsuyoshi Michibayashi

研究成果: Conference contribution

抄録

The microstructure of garnet aggregates within a metamorphic vein are investigated to constrain the duration of vein formation. Garnet-bearing veins occur subparallel to the foliation of a host mafic schist in the Sanbagawa metamorphic belt, Japan. Microstructural observations using SEM, EPMA and EBSD reveal that numerous small garnets (10-100 μm diameter) coalesced to form large porphyroblasts within the vein. EBSD analysis of the porphyroblasts reveals that misorientation angles of neighbor-pair garnet grains within the vein have a random distribution. This contrasts with previous studies that found coalescence of garnets in mica schist leads to an increased frequency of low angle misorientation boundaries by misorientation-driven rotation. The random misorientation angle distribution indicates that (1) garnets within the vein grew so fast that they could not rotate within the vein, and thus (2) random orientations of garnets at the nucleation stage were preserved. On the basis of a simple kinetic model that assumes rotation of garnet is rate-limited by diffusion creep of matrix quartz, the time taken for a small garnet grain to rotate 1° is estimated to be 10 3 - 10 4 years. This duration may indicate the upper limit of the duration of garnet growth, and of vein formation.

本文言語English
ホスト出版物のタイトルWATER DYNAMICS
ホスト出版物のサブタイトル3rd International Workshop on Water Dynamics
ページ167-170
ページ数4
DOI
出版ステータスPublished - 2006 5 15
イベントWATER DYANMICS: 3rd International Workshop on Water Dynamics - Sendai, Japan
継続期間: 2005 11 162005 11 17

出版物シリーズ

名前AIP Conference Proceedings
833
ISSN(印刷版)0094-243X
ISSN(電子版)1551-7616

Other

OtherWATER DYANMICS: 3rd International Workshop on Water Dynamics
国/地域Japan
CitySendai
Period05/11/1605/11/17

ASJC Scopus subject areas

  • 物理学および天文学(全般)

フィンガープリント

「Rapid growth of garnet within a metamorphic vein inferred from misorientation angle distribution of garnet porphyroblasts」の研究トピックを掘り下げます。これらがまとまってユニークなフィンガープリントを構成します。

引用スタイル