Reactions in amphibolite, greenschist and blueschist

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Authors:Thompson, James B., Jr.; Laird, Jo; Thompson, Alan B.
Author Affiliations:Primary:
Harvard Univ., Dep. Geol. Sci., Cambridge, MA, United States
Eidg. Tech. Hochsch., Switzerland
Volume Title:Journal of Petrology
Source:Journal of Petrology, 23(1), p.1-27. Publisher: Clarendon Press, Oxford, United Kingdom. ISSN: 0022-3530
Publication Date:1982
Note:In English. 40 refs.; illus. incl. 4 tables
Summary:The possible heterogeneous reactions in chlorite-epidote-plagioclase-amphibole-quartz low-grade mafic schists may be separated into two types, exchange reactions and net-transfer reactions; only the latter significantly alter the modal proportions of the minerals. A set of linearly-independent reactions defines a reaction space of as many dimensions as there are independent reactions. The space defined by the net-transfer reactions alone is a sub-space that can be portrayed in three dimensions for the above low-grade assemblage. A procedure is described which gives a set of independent reactions that may be taken as a basis for defining such a reaction space; all other reactions that can be written for this assemblage, as well as observed whole-rock reactions, can be portrayed as vectors in these reaction spaces. These vectors connect the region (mineral facies) accessible to the above assemblage. The whole-rock reactions of Laird relating greenschist, blueschist and various low-grade amphibolites from Vermont, and the whole-rock experiments of Liou et al., provide examples. Although reaction spaces apply to both equilibrium and disequilibrium assemblages, the reactions selected as basis vectors correspond one-for-one with the chemical conditions for equilibrium that must hold in any full equilibrated assemblage. The set selected is one that provides maximum sensitivity for estimating T, P and mu H2O. [R.A.H.]
Subjects:Amphibolite facies; Blueschist facies; Equations; Facies; Greenschist facies; Heterogeneity; Mathematical models; Metamorphic rocks; Mineral assemblages; Numerical analysis; Phase equilibria; Three-dimensional models
Abstract Numbers:82M/2706
Record ID:1987032612
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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