Exhumation Processes: Normal Faulting, Ductile Flow and Erosion Geological Society Special Publications Series Editors A

Exhumation Processes: Normal Faulting, Ductile Flow and Erosion Geological Society Special Publications Series Editors A. J. FLEET R. E. HOLDSWORTH A. C. MORTON M. S. STOKER

It is recommended that reference to all or part of this book should be made in one of the following ways.

RING, U., BRANDON,M. T., LISTER, G. S. & WlLLETT,S. D. (eds) 1999. Exhumation Processes: Normal Faulting, Ductile Flow and Erosion. Geological Society, London, Special Publications, 154.

THOMSON, S. N., STOCKHERT,B. & BRIX, M. R. 1999. Miocene high-pressure metamorphic rocks of Crete, Greece: rapid exhumation by buoyant escape. In: RING, U., BRANDON, M. T., LISTER, G. S. & WILLETT, S. D. (eds) Exhumation Processes: Normal Faulting, Ductile Flow and Erosion. Geological Society, London, Special Publications, 154. GEOLOGICAL SOCIETY SPECIAL PUBLICATION NO. 154

Exhumation Processes: Normal Faulting, Ductile Flow and Erosion

EDITED BY UWE RING (Johannes Gutenberg-Universitfit, Mainz, Germany) MARK T. BRANDON (Yale University, New Haven, USA) GORDON S. LISTER (Monash University, Clayton, Australia) and SEAN D. WILLETT (Pennsylvania State University, USA)

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Preface vii

Acknowledgements viii

RING, g., BRANDON, M. T., WILLETE, S. D. & LISTER, G. S. Exhumation Processes 1

Subduction-related accretionary wedges (B-type subduction)

SEDLOCK, R. L. Evaluation of exhumation mechanisms for coherent blueschists in 29 western Baja California, Mexico

RING, U. & BRANDON, M. T. Ductile deformation and mass loss in the Franciscan 55 Subduction Complex: implications for exhumation processes in accretionary wedges

THOMSON, S. N., STOCKHERT, B. & BRIX, M. R. Miocene high-pressure metamorphic rocks 87 of Crete, Greece: rapid exhumation by buoyant escape

RAWLING,T. J. & LISTER, G. S. Oscillating modes of orogeny in the Southwest Pacific 109 and the tectonic evolution of New Caledonia

WINTSCH, R. P., BYRNE, T. & TORIUMI, M. Exhumation of the Sanbagawa blueschist belt, 129 SW Japan, by lateral flow and extrusion: evidence from structural kinematics and retrograde P-T-t paths

Collisional belts and intra-continental convergence (A-type subduction)

SCHLUNEGGER,E • WILLETT,S. Spatial and temporal variations in exhumation of the 157 central Swiss Alps and implications for exhumation mechanisms

VANDERHAEGHE, O., BURG, J.-P. & TEYSSIER, C. Exhumation of migmatites in two collapsed 181 orogens: Canadian Cordillera and French Variscides

CALVERT, A. W., GANS, P. B. & AMATO, J. M. Diapiric ascent and cooling of a sillimanite 205 gneiss dome revealed by 40Ar/39Ar thermochronology: the Kigluaik Mountains, Seward Peninsula, Alaska

GLAZNER, A. E Exposure of deep, dense rocks: interplay between erosion and sinking 233

MILLER, J. McL., GREGORY, R. T., GRAY, D. R. & FOSTER, D. A. Geological and 241 geochronological constraints on the exhumation of a high-pressure metamorphic terrane, Oman

BATT, G. E., KOHN, B. P., BRAUN, J., McDOUGALL, I. & IRELAND,T. R. New insight into the 261 dynamic development of the Southern Alps, New Zealand, from detailed thermochronological investigation of the Mataketake Range pegmatites

GARVER, J. I., BRANDON, M. T., RODEN-TICE, M. & KAMP, P. J. J. Exhumation history of 283 orogenic highlands determined by detrital fission-track thermochronology

Lithospberic extension: divergent plate motions (rifting)

FORSTER, M. A. & LISTER, G. S. Detachment faults in the Aegean core complex of Ios, 305 Cyclades, Greece vi CONTENTS

GOODWIN, L. B. Controls on pseudotachylyte formation during tectonic exhumation in 325 the South Mountains metamorphic core complex, Arizona

FOSTER, D. A. & JOHN, B. E. Quantifying tectonic exhumation in an extensional orogen 343 with thermochronology: examples from the southern Basin and Range Province Preface

The general idea of this book is to provide an overview of exhumation processes. The idea was conceived dur- ing a conference on the same topic. The papers were organized to provide a broad sampling of frontier research on all processes that contribute to exhumation of metamorphic rocks in ancient and modern orogens. Examples from a variety of tectonic settings, including continental rifts, oceanic subduction zones and continental collision zones are given. The papers provide innovative applications of structural geology, metamorphic petrology and thermochronology to resolve the rates and geometry of normal faulting, and the interaction between erosion and tectonics. One of the weaknesses of the volume is that the role that surface processes play in the exhuma- tion of deeply seated rocks is not well presented. The volume contains 16 papers. The opening contribution by Ring et aL is a review aimed at providing an umbrella for the more focused papers that follow. The remaining papers are arranged into three sections, divid- ed according to tectonic setting. The first section, Subduction-related accretionary wedges (B-type subduction), starts with studies of the Franciscan subduction complex by Sedlock and Ring & Brandon. Sedlock documents normal faulting as the primary exhumation mechanism for blueschists in Baja California. Ring & Brandon examine the role of deformation, primarily ductile flow in tectonically exhuming the high-grade Eastern Franciscan Belt, and show that these processes played only a minor role. The papers of Thomson et al. and Rawling & Lister are examples of dominantly normal-faulting-controlled exhumation at retreating subduction zones. The contribution of Wintsch et aL calls for margin-parallel shear as the principal exhumation process for Cretaceous high-pressure metamorphic rocks at the Japan convergent margin. The second section is Collisional belts and intra-conthzental convergence (A-type subduction). The first three papers address the exhumation of high-temperature rocks in the internides of collisional orogens. The paper of Schlunegger & Willett examines how exhumation influenced the postcollisional growth and destruction of the Alps. The paper illustrates how difficult it is to distinguish between tectonic exhumation and erosion. Vanderhaeghe et al. also highlight the interplay between various exhumation mechanisms during the destruc- tion of the migmatitic core in two collisional orogens. Calvert et al. report on an interesting example of exhuma- tion by diapirism. Glazner reviews how magmatism might influence extensional deformation. The paper focus- es on buoyancy of magmas and their level of emplacement in the crust. Miller et al. report thermochronological aspects of exhumation of eclogite beneath the Samail ophiolite in Oman. The time-temperature history of exhumation is also addressed in Batt et al. and Garver et al. Batt et al. concentrate on constraining cooling and exhumation rates and their temporal variations, whereas Garver et al. use fission-track ages preserved in detrital sediments to resolve the progressive evolution of exhumation in several orogens. The last section is called Lithospheric extension and divergent plate motions (rifling). Forster & Lister describe multiple generations of low-angle normal faults in the back-arc region of the active Hellenic subduction zone in the eastern Aegean. They also examine differences between extensional faulting in the Aegean and the Basin- and-Range province. The remaining two papers by Goodwin and Foster & John deal with the highly attenuat- ed crustal sections in the Basin-and-Range province. Goodwin concentrates on a microstructural and micro- chemical study of pseudotachylyte formation associated with the later stages of crustal extension in the South Mountains metamorphic core complex. Foster & John use thermochronological techniques to place constraints on the rate of extensional faulting, the change in thermal gradients during detachment faulting, and the original dip of the detachments surfaces in the Colorado River extensional corridor. The editors are grateful to the Geological Society of London for making the publication of this book poss- ible and to Angharad Hills, Staff Editor of the Geological Society Publishing House, and Alan Roberts as the corresponding editor for their continued support and patience.

UWE RING MARK f. BRANDON GORDON S. LISTER SEAN D. WILLETF Acknowledgements

The following colleagues and two anonymous referees kindly reviewed the articles submitted to this book:

John Aitchinson Ron Harris Ray Price Gary Axen Rod Holcomb Steve Raiser Sue Baldwin Simon Inger Steve Reddy John Bartley Rebecca Jamieson Mike Sandiford Geoff Batt Christopher Johnson Elizabeth Schermer Andy Bobyarchick Laurent Jolivet Stefan Schmid Mark Brandon Peter Koons Jane Selverstone Martin Burkhart Paul Layer Jinny Sisson Darrel Cowan Gordon Lister John Spray Allen Dennis Neff Mancktelow Bernhard St6ckhert David Dinter Dieter Mertz Stuart Thomson Mihai Ducea Nick Mortimer Janos Urai Michel Faure Roland Oberh~nsli John Wakabayashi David Foster Onno Oncken Simon Wallis Kevin Furlong Cees Passchier Dave Waters Arthur Goldstein Terry Pavlis Sean Willett