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The reaction antigorite → olivine + talc + H2O in the Bergell aureole, N. Italy

Published online by Cambridge University Press:  05 July 2018

R. H. Worden ,
G. T. R. Droop  and
P. E. Champness
R. H. Worden
Affiliation:
Department of Geology, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
G. T. R. Droop
Affiliation:
Department of Geology, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
P. E. Champness
Affiliation:
Department of Geology, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
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Abstract

The low-grade contact metamorphic decomposition of antigorite serpentine to olivine and talc has been studied using TEM. The reaction was more complex than has been assumed by previous workers in that (i) FeO played a significant role in controlling the temperature of reaction, and (ii) minor amounts of an aluminous phase (chlorite) were probably produced. The reaction occurred over a range of temperatures within which the assemblage antigorite + talc + olivine was stable and the antigorite became progressively more Mg-rich as the reaction proceeded. Oriented nucleation of talc occurred within the antigorite. However, the olivine breakdown product did not require nucleation; rather it appears to have grown on pre-existing olivine grains. Communication between the sites of reaction was probably facilitated by an ubiquitous grain-boundary fluid.

Keywords

antigoriteolivinetalcTEMcontact metamorphismBergell aureole
Type
Research Article
Information
Mineralogical Magazine , Volume 55 , Issue 380 , September 1991 , pp. 367 - 377
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1991

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Footnotes

*

Present address: BP International Limited, Sunbury Research Centre, Chertsey Road, Sunbury-on-Thames, Middlesex TW16 7LN, U.K.

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