Dissolution processes of alkali feldspar and plagioclase in granitic melts during partial melting of a metapelitic rock

• MORITA Hidehiko

  Graduate School of Science and Technology, Chiba University Present address: Canon Optron Inc.

• HIROI Yoshikuni

  Department of Earth Sciences, Graduate School of Science, Chiba University

• FURUKAWA Noboru

  Department of Earth Sciences, Graduate School of Science, Chiba University

Bibliographic Information

Other Title

• 泥質変成岩の部分融解におけるアルカリ長石と斜長石の花崗岩質メルトへの溶解過程
• デイシツ ヘンセイガン ノ ブブン ユウカイ ニ オケル アルカリ チョウセキ ト シャチョウセキ ノ カコウガンシツ メルト エノ ヨウカイ カテイ

Abstract

Partial melting experiments of migmatitic pelitic gneiss were performed at 850 °C and 200 MPa with varied run duration up to 1008 hrs. Granitic melts form at almost all grain boundaries between various minerals including alkali-free pairs such as sillimanite-quartz. The melts exhibit compositional heterogeneity, particularly in SiO₂ and Al₂O₃. Relatively voluminous melts form at feldspar-quartz boundaries, where the melt thickness increases with the run duration. In low-SiO₂ domains located relatively far from quartz grains, Al₂O₃ mineral grains form around and in feldspar grains. The melts surrounding feldspars are enriched in Al₂O₃. In addition to the Al₂O₃ mineral, euhedral An-rich plagioclase newly forms around alkali feldspar, typically at the alkali feldspar-plagioclase boundaries. On the other hand, pre-existing plagioclase is partially modified to form ‘reaction zones’ composed of fine-grained An-rich plagioclase and interstitial melt along twin surfaces and cracks. The An-rich plagioclase at the outermost part of these reaction zones subsequently dissolves in the melts. These results indicate that the dissolution processes of alkali feldspar and plagioclase in peraluminous granitic melts are controlled not only by diffusive supply of SiO₂ from quartz but also by the growth of Al-rich minerals and the interface reactions.

Journal

• Japanese Magazine of Mineralogical and Petrological Sciences

  Japanese Magazine of Mineralogical and Petrological Sciences 37 (4), 96-109, 2008

  Japan Association of Mineralogical Sciences

Keywords

• Alkali feldspar
• Plagioclase
• Partial melting
• Dissolution
• Granitic melt
• Metapelitic rock

Details

• CRID: 1390001206525990656
• NII Article ID: 10021369733
• NII Book ID: AA1146088X
• DOI: 10.2465/gkk.37.96
• ISSN: 13497979
• ISSN: 1345630X
• NDL BIB ID: 9646297
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I9646297
• Text Lang: ja
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed