Metamorphic Reactions: Kinetics, Textures, and Deformation PDF
Preview Metamorphic Reactions: Kinetics, Textures, and Deformation
Advances in Physical Geochemistry Volume 4 Editor-in-Chief Surendra K. Saxena Editorial Board L. Barron P. M. Bell N. D. Chatterjee R. Kretz D. H. Lindsley Y. Matsui A. Navrotsky R. C. Newton L. L. Perchuk R. Powell R. Robie A. B. Thompson B. J. Wood Advances in Physical Geochemistry Series Editor: Surendra K. Saxena Volume 1 R. C. NewtoniA. Navrotsky/B. 1. Wood (editors) Thermodynamics of Minerals and Melts 1981. xii, 304 pp. 66 illus. ISBN 0-387-90530-8 Volume 2 S. K. Saxena (editor) Advances in Physical Geochemistry, Volume 2 1982. x, 353 pp. 113 illus. ISBN 0-387-90644-4 Volume 3 S. K. Saxena (editor) Kinetics and Equilibrium in Mineral Reactions 1983. x, 273 pp. 99 illus. ISBN 0-387-90865-X Metamorphic Reactions Kinetics, Textures, and Deformation Edited by Alan Bruce Thompson and David C. Rubie With Contributions by B. Bayly K. H. Brodie M. A. Carpenter R. J. Knipe E. L. McLellan S. A. F. Murrell A. Putnis J. Ridley D. C. Rubie E. H. Rutter B. K. Smith A. B. Thompson R. J. Tracy R. P. Wintsch With 81 Illustrations Springer-Verlag New York Berlin Heidelberg Tokyo Alan Bruce Thompson David C. Rubie Departement fUr Erdwissenschaften Department of Geology ETH-Zentrum The University of Manchester CH-8092 Ziirich Manchester, M13 9PL Switzerland Great Britain Series Editor Surendra K. Saxena Department of Geology Brooklyn College City University of New York Brooklyn, New York 11210 U.S.A. Library of Congress Cataloging in Publication Data Main entry under title: Metamorphic reactions. (Advances in physical geochemistry; v. 4) Includes bibliographies and index. 1. Metamorphism (Geology) I. Thompson, Alan Bruce, 1947- II. Rubie, David C. III. Series. QE475.A2M4745 1985 552'.4 84-20307 © 1985 by Springer-Verlag New York, Inc. Softcover reprint of the hardcover 1st edition 1985 All rights reserved. No part of this book may be translated or reproduced in any form without written permission from Springer-Verlag, 175 Fifth Avenue, New York, New York 10010, U.S.A. The use of general descriptive names, trade names, trademarks, etc., in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as understood by the Trademarks and Merchandise Marks Act, may accordingly be used freely by anyone. Typeset by Bi-Comp, Incorporated, York, Pennsylvania. 9 8 7 6 543 2 ISBN-13: 978-1-4612-9548-8 e-ISBN-13: 978-1-4612-5066-1 DOl: 10.1007/978-1-4612-5066-1 Preface The fourth volume in this series consists of eleven chapters. The first five deal with more theoretical aspects of the kinetics and mechanisms of meta- morphic reactions, and the next six consider the interdependence of defor- mation and metamorphism. All papers deal with natural processes that inter- act on various time scales and with different degrees of mass and heat transfer. Consequently, many fundamental axioms of metamorphic petrol- ogy and structural geology are questioned both for their accuracy and their usefulness. In raising such questions, most contributors have pointed to ways in which the answers could be forthcoming from appropriate experi- mental studies or observations on natural materials. In their discussion of how order/disorder can influence mineral assem- blages, Carpenter and Putnis emphasize that metastable crystal growth is common in metamorphic systems and state' 'there may be some reluctance (among many earth scientists) to accept that significant departures from equilibrium could occur." On the basis of presented evidence, they question whether reactions ever occur close to an equilibrium boundary. The neces- sity for pressure or temperature overstepping is also required by nucleation- rate theory. In any case, the degree of order is severely influenced by these kinetic effects in igneous, sedimentary, and metamorphic environments. From an evaluation of available mineral kinetic data, Rubie and Thomp- son present some guidelines for quantitative approaches to experimental kinetic studies. Proposals are made as to how the common variables that can affect mineral kinetics may be controlled in experiments so that such data may be more realistically applied to natural situations. In examining the effect of reaction enthalpy on the progress of a metamor- phic reaction, Ridley has considered the relationships among kinetics, heat flow, and microstructures of metamorphic rocks. He provides insight into how the inverse problem of observation of grain size and porphyroblast vi Preface development could be used to deduce the rate-controlling step during meta- morphic reaction. In the fourth chapter, Smith illustrates how information on dislocation types and their densities, obtained mainly by transmission electron micros- copy, can be used to learn much about the mechanisms of mineral reactions. The progressive effects of deformation are especially well shown by the successive motion of dislocations in the chosen orthosilicate examples for garnet to chlorite and olivine to spinel transformations. Tracy and McLellan present kinetic interpretations of textural and com- positional phenomena in contact metamorphosed emeries. They discuss cri- teria by which diffusion-controlled and interface-controlled processes may be distinguished. Because the silica diffusion rate must have been very slow during their contact metamorphism, diffusion of Si02 through crystals or along dry grain boundaries is inferred to have occurred. Brodie and Rutter review the minerology and microstructures of meta- morphosed basaltic rocks and examine theoretically some of the interrela- tionships between metamorphism and deformation. They emphasize the value of shear zones to such studies because deformed and undeformed rocks are easily compared and conclude that in shear zones the deformabil- ity may be reaction enhanced. From their examination of polyphase mylonites, Knipe and Wintsch pro- pose an evolutionary model involving the cyclic redistribution of deforma- tion between different mineralogical domains. The flow pattern changes from a more continuous and distributed ductile deformation to a more loca- lized deformation at lower temperatures characterized by the development of mica from the syntectonic breakdown of feldspar. Murrell has used experimental observations of a sharp change in rock strength when the sample dehydrates to evaluate the geological significance of elevated pore pressure especially as regards changing styles of deforma- tion. Rutter and Brodie discuss several aspects of the permeability of medium to high-grade metamorphic rocks, especially in shear zones. They deduce apparent permeabilities of 10-26 to 10-28 m2 for metamorphic conditions, which are several orders of magnitude below any feasible measurement limit in the laboratory. Volatile permeation along shear zones is 10 to 100 times faster than across them. Wintsch has examined some possible effects of deformation in displacing mineral equilibrium boundaries. His calculations show that a significant P-T displacement of an equilibrium boundary could occur in mylonites, repeat- edly deformed rocks, and fault zones where very high dislocation densities are produced (> lOll cm-2). In the final chapter, Bayly returns to the somewhat controversial issue of the nature of chemical potential in a material under nonhydrostatic stress. The paper is presented as a series of postulates that may be capable of geological investigation. Preface vii In addition to specific details of how kinetic factors may be investigated, many contributors have pointed towards larger scale or more general geolog- ical problems and their possible solution. The observed association of high strain deformation with regional metamorphism underlines the necessity to quantify the energies of deformation and metamorphism as well as their relative timing and duration. Likewise, it has become clear that we possess very few criteria that may be used to determine if equilibrium is ever achieved on the scales assumed by many petrological studies which never consider kinetic factors and assume that fluids are ubiquitous during medium to high-grade metamorphism. Several consequences of fluid-absent meta- morphism are discussed and some suggestions given of the different reaction mechanisms compared to when fluid is present. We clearly must consider further the related problem of exactly how metamorphic reactions and defor- mation influence rock permeability. Unfortunately, most experimental studies lag behind field observations and theoretical studies. There is very little information on how the flow laws of polyphase metamorphic rocks are changed when metamorphic reactions occur. New types of experiments are indicated in several papers and would clearly be easier to apply to natural situations if the microstructures of naturally and experimentally deformed materials were understood in terms of reaction mechanisms. We realize that the subject coverage is not as broad as originally planned and items such as the influence of fluid species on defect chemistry and diffusion, or the regional scale relations between momentum transfer and heat or mass transfer, are only briefly treated. The authors have provided extensive bibliographies that hopefully will enable the reader to pursue the directions not covered in detail by the papers themselves. Thanks are due to M. Casey, N. Mancktelow, E. H. Perkins, S. Saxena, S. Schmid, J. Tullis, B. Yardley, and R. A. Yund, in addition to the contributors themselves, for their reviews of several chapters. We are grateful to K. Malmstroem for editorial assistance and to the staff at Springer-Verlag for their cooperation and patience during the preparation of the volume. ALAN BRUCE THOMPSON DAVID C. RUBIE Contents 1. Cation Order and Disorder during Crystal Growth: Some Implications for Natural Mineral Assemblages 1 M. A. CARPENTER AND A. PUTNIS 2. Kinetics of Metamorphic Reactions at Elevated Temperatures and Pressures: An Appraisal of Available Experimental Data 27 D. C. RUBIE AND A. B. THOMPSON 3. The Effect of Reaction Enthalpy on the Progress of a Metamorphic Reaction 80 J. RIDLEY 4. The Influence of Defect Crystallography on Some Properties of Orthosilicates 98 B. K. SMITH 5. A Natural Example of the Kinetic Controls of Compositional and Textural Equilibration 118 R. J. TRACY AND E. L. McLELLAN 6. On the Relationship between Deformation and Metamorphism, with Special Reference to the Behavior of Basic Rocks 138 K. H. BRODIE AND E. H. RUTTER 7. Heterogeneous Deformation, Foliation Development, and Metamorphic Processes in a Polyphase Mylonite 180 R. J. KNIPE AND R. P. WINTSCH x Contents 8. Aspects of Relationships between Deformation and Prograde Metamorphism that Causes Evolution of Water 211 S. A. F. MURRELL 9. The Permeation of Water into Hydrating Shear Zones 242 E. H. RUTTER AND K. H. BRODIE to. The Possible Effects of Deformation on Chemical Processes in Metamorphic Fault Zones 251 R. P. WINTSCH 11. Deformation with Simultaneous Chemical Change: The Thermodynamic Basis 269 B.BAYLY Index 279 Contributors BAYLY, B. Department of Geology, Rensselaer Polytechnic In- stitute, Troy, New York 12181, USA BRODIE, K. H. Geology Department, Imperial College, London, SW7 2BP, Great Britain CARPENTER, M. A. Department of Earth Sciences, University of Cam- bridge, Downing Street, Cambridge, CB2 3EQ, Great Britain KNIPE, R. J. Department of Earth Sciences, The University of Leeds, Leeds, LS2 9JT, Great Britain McLELLAN, E. L. Department of Geology and Geophysics, Yale Uni- versity, New Haven, Connecticut 06520, USA MURRELL, S. A. F. Department of Geology, University College Lon- don, Gower Street, London, WCIE 6BT, Great Britain PUTNIS, A. Department of Earth Sciences, University of Cam- bridge, Downing Street, Cambridge, CB2 3EQ, Great Britain RIDLEY, J. Departement fOr Erdwissenschaften, ETH-Zen- trum, CH-8092 Zurich, Switzerland
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