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Geochemistry and Tectonic Significance of Basalts in the Poya Terrane, New Caledonia

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Geochemistry and Tectonic Significance of Basalts in the Poya Terrane, New Caledonia Reprinted from I TECTONOPHYSICS INTERNATIONAL JOURNAL OF GEOTECTONICS AND THE GEOLOGY AND PHYSICS OF THE INTERIOR OF THE EARTH Tectonophysics 284 (1998) 203-219 Geochemistry and tectonic significance of basalts in the Poya Terrane, New Caledonia Jean-Philippe Eissen a,*, Anthony J. Crawford b, Joseph Cotten ', Sébastien Meffre b, Hervé Bellon ', Mireille Delaune ORSTOM UWGP 22, Centre ORSTOM de Brest, B.P. 70, 179280 Plouzané Cedex, France Department of Geology, Universiy of Tasmania, GPO Box 2517C, Hobart, Tas 7001, Australia ' Université de Bretagne Occidentale, Sciences de la Terre, UMR 6538, 6 avenue Le Gorgeu, BP 809, 29285 Brest Ceda, Fraizce ORSTOM UWGP 22, Centre ORSTOM de Bondy, 32, averzue Heiiri Varagizut, 93143 Bondy Cedex, France Received 30 October 1996; accepted 16 June 1997 TECTONOPHY SICS Editors-in-Chief J.-P. BRUN Université de Rennes, Institut de Géologie, Campus de Beaulieu, Ave. du Général Leclerc, Rennes 35042 Cedex France. Phone: +33.99.28 61 23; FAX: +33.99.28 67 80; e-mail: [email protected] T. ENGELDER Pennsylvania State University, College of Earth & Mineral Sciences, 336 Deike Building, University Park, PA 16802, USA. Phone: +I .814.865.3620/466.7208; FAX: +I B14.863.7823; e-mail: [email protected] K.P. FURLONG Pennsylvania State University, Department of Geosciences, 439 Deike Building, University Park, PA 16802, USA. Phone: +i.814.863.0567; FAX +I .814.865.3191; e-mail: kevinQgeodyn.psu.edu F. WENZEL Universität Fridericiana Karlsruhe, Geophysikalisches Institut, Hertzstraße 16, Bau 42, D-76187 Karlsruhe, Germany. Phone: +49.721.608 4431; FAX +49.721.711173; e-mail: [email protected] Honorary Editors: M. Friedman S. Uyeda Editorial Board D.L. Anderson, Pasadena, CA A. Hirn, Paris W.M. Schwerdtner, Toronto, Ont. H.G. Avé Lallemant, Houston, TX F. Horváth, Budapest C. Sengör, Istanbul E. Banda, Barcelona E.S. Husebye, Bergen T. Seno, Tokyo 2.Ben-Avraham, Tel Aviv H. Kanamori, Pasadena, CA Shi Yang-Shen, Nanjing H. Berckhemer, Koenigstein S. Karato, Minneapolis, MN N. Sleep, Stanford, CA C. Blot, Sollies-Pont R.J. Knipe, Leeds S. Sobolev, Strasbourg G.C. Bond, Palisades, NY M. Kono, Tokyo C.A. Stein, Chicago, IL G.J. Borradaile, Thunder Bay, Ont. X. Le Pichon, Paris P. Suhadolc, Trieste B.C. Burchfiel, Cambridge, MA G.S. Lister, Clayton, Vic. K. Tamaki, Tokyo K.C. Burke, Houston, TX R.I. Madariaga, Paris M. Tomé, Barcelona S. Cloetingh, Amsterdam Y. Mart, Haifa C.I. Trifu, Kingston, Ont. P.R. Cobbold, Rennes M. McNutt, Cambridge, MA J. Tullis, Providence, RI D. Denham, Canberra, ACT W.D. Means, Albany, NY D.L. Turcotte, Ithaca, NY J.F. Dewey, Oxford K. Mengel, Clausthal-Zellerfeld B.A. van der Pluijm, Ann Arbor, MI G.H. Eisbacher, Karlsruhe A. Nicolas, Montpellier R. van der Voo, Ann Arbor, MI E.R. Engdahl, Denver, CO G. Oertel, Los Angeles, CA B.C. Vendeville, Austin, TX E.R. Flüh, Kiel A. Pérez-Estaun, Oviedo R.L.M. Vissers, Utrecht K. Fujita, East Lansing, MI H.N. Pollack, Ann Arbor, MI J.S. Watkins, College Station, TX Y. Fukao, Tokyo C.McA. Powell, Nediands, W.A. H.-R. Wenk, Berkeley, CA R. Geller, Tokyo L. Ratschbacher*Würzburg R.W.C. Westaway, Durham J.-P. Gratier, Grenoble E.H. Rutter, Manchester G. Westbrook, Birmingham A.G. Green, Zürich M.P. Ryan, Reston, VA B.F. Windley, Leicester R.H. Groshong, Jr., Tuscaloosa, AL D.J. Sanderson, Southampton M.J.R. Wortel, Utrecht H.K. Gupta, Hyderabad S.M. Schmid, Basel P.A. Ziegler, Binningen T.W.C. Hilde, College Station, TX Scope of the journal Tectonophysics is an international medium for the publication of original studies and comprehensive reviews in the field of geotectonics and the geology and physics of the earth’s crust and interior. The editors will endeavour to maintain a high scientific level and it is hoped that with its international coverage the ioumal will contribufe to the sound development of this field. (TMcontinued on inside back cover) O 1998, ELSEVIER SCIENCE B.V. ALL RIGHTS RESERVED. 0040-1951/98/$19.00 This journal and the individual contributions contained in it are protected by the copyright of Elsevier Science B.V., and the following terms and conditions apply to their use: Photocopying: Single photocopies of single articles may be made for personal use as allowed by national copyright laws. Permission of the publisher and payment of a fee is required for all other photocopying, including multiple or systematic copying, copying for advertising or promotional purposes, resale, and all forms of document delivery. Special rates are available for educational institutions that wish to make photocopies for non-profit educational classroom use. In the USA, users may clear permissions and make payment through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In the UK, users may clear permissions and make payments through the Copyright Licensing Agency Rapid Clearance Service (CLARCS), 90 Tottenham Court Road, London WIP OLP, UK. In other countries where a local copyright clearance center exists, please contact it for information on required permisssions and payments. Derivative Works: Subscribers may reproduce tables of contents or prepare lists of articles including abstracts for intemal circulation withinTheir institutions. Permission of the Publisher is required for resale or distribution outside the institution. Permission of the Publisher is required for all other derivative works, including compilations and translations. Electronic Storage: Permission of the Publisher is required to store electronically any material contained in this journal, including any article or part of an article. Contact the Publisher at the address indicated. Except as outlined above, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without written permission of the Publisher. Notice: No responsibilityis assumed by the Publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. 0 The paper used in this publication meets the requirements of ANSVNISO 239.48-1992 (Permanence of Paper). PRINTED IN THE NETHERLANDS Contents Direct, the free e-mail alerting service, delivers the table of contents for this journal directly to your PC, prior to publication. The quickest way to register for Contents Direct is via the Internet at: http://www.elsevier.nUlocate/ContentsDirect.If you don’t have access to the Internet you can register for this service by sending an e-mail message to cdsubsQelsevier.co.uk -specifying the title of the publication you wish to register for. TECTONOPHYSICS ELSEVIER Tectonophysics 284 (1998) 203-219 Geochemistry and tectonic significance of basalts in the Poya Terrane, New Caledonia Jean-Philippe Eissen a,*, Anthony J. Crawford Joseph Cotten Sébastien Meffre Hervé Bellon Mireille Delaune a ORSTOM UUGP 22, Centre ORSTOM de Brest, B.P. 70, 29280 Plouzane' Cedex, France Department of Geology, University of Tasmania, GPO Box 252C, Hobart, Tas 7001, Australia Universite' de Bretagne Occidentale, Sciences de la Terre, UMR 6538, 6 avenue Le Gorgeu, BP 809, 29285 Brest Cedex, France ORSTOM UUGP 22, Centre ORSTOM de Bondy, 32, avenue Henri Varagnat, 93143 Bondy Cedex, France Received 30 October 1996; accepted 16 June 1997 Abstract The Norfolk-New Caledonia Ridge represents a continental slice which drifted away from Australia during the Late Cretaceous breakup of the eastern Gondwana margin. The presence of widespread basaltic rocks beneath the main ophiolite nappe of New Caledonia has been long known but the origin and the age of the Poya Terrane basalts (PTB herein) remained controversial. Recent palaeontologically determined ages date the PTB as Late Cretaceous (Campanian). New geochemical data show that two main discrete groups constitute the PTB: a MORB-like tholeiitic suite, and a more alkaline intra-plate basaltic suite distinguished mainly on immobile HFSE and REE elements. Furthermore, low ENd and high Th/Nb relative to MORB, and weak negative Nb anomalies, reflect limited assimilation of continental crust by these otherwise MORB-like tholeiites. Inter-PTB sedimentary rocks all have a pelagic or hemi-pelagic origin; detrital material originated from the nearby Norfolk-New Caledonia ridge basement. The PTB form a parautochthonous sheet below the main harzburgitic nappe constituting the New Caledonian ophiolite. They are genetically unrelated to the ophiolite, and are interpreted to be 70-85-Ma-old rift tholeiites formed during of the eastemmost continental part of Mesozoic Gondwana, and opening the East New Caledonia Basin. The Norfolk-New Caledonia Ridge formed the western passive margin of this new oceanic basin, but the rifted-off eastem block is less easily identified. It may form part of the basement of the Westem Belt of the New Hebrides island arc (Vanuatu). The cessation of rifting of the eastern Australian margin around 56 Ma was followed by an eastward-directed subduction which produced boninitic melts and its associated refractory harzburgitic mantle, in the forearc of the primitive Loyalty-d'Entrecasteaux arc. Following the major Pacific plate motion reorganization around 42 Ma, collision of the Norfolk-New Caledonia Ridge with the forearc region of the intra-oceanic Loyalty-d'Entrecasteaux arc around 40 Ma led first to westward thrusting of the PTB as a slice picked up from the upper crustal section of the colliding Norfolk Ridge. Subsequent collisional tectonism led to detachment of the main New Caledonian harzburgitic nappe from its forearc location in the Loyalty arc, and westward emplacement of this nappe over the PTB nearby allochthon. The presence of parautochthonous sheets of basalts unrelated to immediately overlying forearc-derived, boninite-bearing harzburgitic ophiolites is briefly discussed in the light of two other examples in arc-continent collision settings.
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