Formation of amphibole after clinopyroxene by dehydration reactions: Implications for pseudomorphic replacement and mass fluxes

Timothy J. Fagan*, Howard W. Day

*この研究の対応する著者

研究成果: Article査読

15 被引用数 (Scopus)

抄録

The replacement of anhydrous by hydrous minerals is commonly used to infer infiltration of a rock by H2O. However, our work indicates that the formation of pseudomorphic amphibole after clinopyroxene (uralitization) in low-grade metavolcanic rocks is a net dehydration process. In the ophiolitic Slate Creek complex, northern California, clinopyroxene exhibits four textural stages of alteration: (1) clinopyroxene, (2) clinopyroxene + chlorite ± amphibole, (3) amphibole + chlorite, and (4) amphibole. This transformation occurs in subgreenschist to greenschist facies rocks with a common matrix assemblage: quartz, albite, chlorite, epidote, titanite, ± amphibole, ± white mica, ± rare pumpellyite. A simple reaction space model based on these observations indicates that consumption of chlorite in the rock matrix releases more water than required to produce amphibole pseudomorphs of clinopyroxene. Thus, the net flux of H2O during uralitization of greenschist facies metavolcanic rocks is outward. These results imply that uralitization in metavolcanic rocks results from heating rather than whole-rock hydration, and that natural mass fluxes may be counter to fluxes inferred from textural evidence alone.

本文言語English
ページ(範囲)395-398
ページ数4
ジャーナルGeology
25
5
DOI
出版ステータスPublished - 1997
外部発表はい

ASJC Scopus subject areas

  • 地質学

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