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Igneous Rocks: a Classification and Glossary of Terms This page intentionally left blank IGNEOUS ROCKS: A CLASSIFICATION AND GLOSSARY OF TERMS Decades of field and microscope studies and more recent quantitative geo- chemical analyses have resulted in a vast, and sometimes overwhelming, array of nomenclature and terminology associated with igneous rocks. Under the auspices of the International Union of Geological Sciences (IUGS), a group of petrologists from around the world has laboured for more than 30 years to collate these terms, gain international agreement on their usage, and reassess the methods by which we categorize and name igneous rocks. This book presents the results of their work and gives a complete classifi- cation of igneous rocks based on all the recommendations of the IUGS Sub- commission on the Systematics of Igneous Rocks. Revised from the 1st edition (1989), it shows how igneous rocks can be distinguished in the sequence of pyroclastic rocks, carbonatites, melilite-bearing rocks, kalsilite-bearing rocks, kimberlites, lamproites, leucite-bearing rocks, lamprophyres and charnockites. It also demonstrates how the more common plutonic and volcanic rocks that remain can then be categorized using the familiar and widely accepted modal QAPF and chemical TAS classification systems. The glossary of igneous terms has been fully updated since the 1st edition and now includes 1637 entries, of which 316 are recommended by the Subcommission, 312 are regarded as local terms, and 413 are now considered obsolete. Incorporating a comprehensive list of source references for all the terms included in the glossary, this book will be an indispensable reference guide for all geologists studying igneous rocks, either in the field or the laboratory. It presents a standardized and widely accepted naming scheme that will allow geologists to interpret terminology found in the primary literature and provide formal names for rock samples based on petrographic analyses. Work on this book started as long ago as 1958 when Albert Streckeisen was asked to collaborate in revising Paul Niggli’s well-known book Tabellen zur Petrographie und zum Gesteinbestimmen (Tables for Petrography and Rock Determination). It was at this point that Streckeisen noted significant problems with all 12 of the classification systems used to identify and name igneous rocks at that time. Rather than propose a 16th system, he chose instead to write a review article outlining the problems inherent in classifying igneous rocks and invited petrologists from around the world to send their comments. In 1970 this lead to the formation of the Subcommission of the Systematics of Igneous Rocks, under the IUGS Commission on Petrology, who published their conclusions in the 1st edition of this book in 1989. The work of this international body has continued to this day, lead by Bruno Zanettin and later by Mike Le Bas. This fully revised 2nd edition has been compiled and edited by Roger Le Maitre, with significant helpfrom a panelof co-contributors. IGNEOUS ROCKS A Classification and Glossary of Terms Recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks R.W. LE MAITRE (EDITOR), A. STRECKEISEN, B. ZANETTIN, M.J. LE BAS, B. BONIN, P. BATEMAN, G. BELLIENI, A. DUDEK, S. EFREMOVA, J. KELLER, J. LAMEYRE, P.A. SABINE, R. SCHMID, H. SØRENSEN, A.R. WOOLLEY Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo Cambridge University Press The Edinburgh Building, Cambridge , United Kingdom Published in the United States by Cambridge University Press, New York www.cambridge.org Information on this title: www.cambridge.org/9780521662154 © R.W. Le Maitre & International Union of Geological Sciences 2002 This book is in copyright. Subject to statutory exception and to the provision of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published in print format 2002 ISBN-13 978-0-511-06864-5 eBook (EBL) ISBN-10 0-511-06864-6 eBook (EBL) ISBN-13 978-0-521-66215-4 hardback ISBN-10 0-521-66215-X hardback Cambridge University Press has no responsibility for the persistence or accuracy of s for external or third-party internet websites referred to in this book, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate. v Contents Figures ...................................................................................................................................... vi Tables ....................................................................................................................................... vii Albert Streckeisen ..................................................................................................................viii Foreword to 1st edition.............................................................................................................. x Chairman’s Preface .................................................................................................................xiii Editor’s Preface ....................................................................................................................... xv 1 Introduction ........................................................................................................................... 1 1.1 Changes to the 1st edition ............................................................................................. 1 2 Classification and nomenclature............................................................................................ 3 2.1 Principles ...................................................................................................................... 3 2.1.1 Parameters used .................................................................................................... 4 2.1.2 Nomenclature ....................................................................................................... 4 2.1.3 Using the classification ........................................................................................ 6 2.2 Pyroclastic rocks and tephra ......................................................................................... 7 2.2.1 Pyroclasts ............................................................................................................. 7 2.2.2 Pyroclastic deposits .............................................................................................. 7 2.2.3 Mixed pyroclastic–epiclastic deposits .................................................................. 8 2.3 Carbonatites ................................................................................................................ 10 2.4 Melilite-bearing rocks ................................................................................................. 11 2.4.1 Melilitolites ........................................................................................................ 11 2.4.2 Melilitites ........................................................................................................... 11 2.5 Kalsilite-bearing rocks ................................................................................................ 12 2.6 Kimberlites.................................................................................................................. 13 2.6.1 Group I kimberlites ............................................................................................ 13 2.6.2 Group II kimberlites ........................................................................................... 14 2.7 Lamproites .................................................................................................................. 16 2.7.1 Mineralogical criteria ......................................................................................... 16 2.7.2 Chemical criteria ................................................................................................ 16 2.7.3 Nomenclature ..................................................................................................... 16 2.8 Leucite-bearing rocks ................................................................................................. 18 2.9 Lamprophyres ............................................................................................................. 19 2.10 Charnockitic rocks .................................................................................................... 20 2.11 Plutonic rocks............................................................................................................21 2.11.1 Plutonic QAPF classification (M < 90%) ........................................................ 21 2.11.2 Ultramafic rocks (M > 90%) ............................................................................ 28 2.11.3 Provisional “field” classification ...................................................................... 29 2.12 Volcanic rocks ........................................................................................................... 30 2.12.1 Volcanic QAPF classification (M < 90%)........................................................ 30 2.12.2 The TAS classification ..................................................................................... 33 2.12.3 Provisional “field” classification ...................................................................... 39 2.13 References ................................................................................................................
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