DOCSLIB.ORG

Ophiolites and Their Modern Oceanic Analogues

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Ophiolites and Their Modern Oceanic Analogues Downloaded from http://sp.lyellcollection.org/ by guest on October 1, 2021 Ophiolites and their modern oceanic analogues L. M. PARSON & B. J. MURTON Institute of Oceanographic Sciences, Deacon Laboratory, Brook Road, Worrnley, Godalming, Surrey GU8 SUB, UK Conventional studies of oceanic structure and spective on ridge geometry and processes of evolution are inevitably hampered by the diffi- axial reconfiguration. Two papers, the inter- culties with sampling the crust in the third pretations in which have largely been derived dimension. Remote sensing of surficial struc- from these remotely sensed techniques, follow. ture, topography and morphotectonics has be- Searle provides a general assessment of the come easier and of higher resolution with the style of crustal formation at mid-ocean ridges as advent of more sophisticated techniques such as recognised on sidescan and swath bathymetric GLORIA long range sidescan sonar and TOBI data, while Rusby presents a more in-depth deeptow sidescan sonar, as well as multibeam analysis of the tectonics of a complex section of swath bathymetric mapping systems. Subsurface the Easter micro-plate. Finally, Karson reviews studies, however, have enjoyed less of this prog- in some detail the types of extensional fault ress, and although deep drilling, electro- fabrics which are recognized on mid-ocean magnetic surveys and deep seismic techniques ridges, and assesses their variations along strike still provide some measure of understanding as well as across strike. below the seafloor, these data are few and relatively widely spaced. The integration of studies of ophiolites, therefore, can offer the Geochemistry and petrology marine community the benefits of a vast body of A number of regional geochemical papers fol- knowledge with regard to deeper structure and low, each providing a direct comparison of a crustal compositions, which is unattainable in present oceanic setting with studies of ophiolites the deep sea. In turn, many of the regional and of a range of ages. Taylor, Murton& Nesbitt detailed structures which have been recently collectively present data from deep sea drilling identified in active mid-ocean spreading sys- in the Western Pacific, in particular the geo- tems, such as ridge segmentation patterns and chemical variations in oceanic crust formed be- ridge axis discontinuities, now form a significant tween the arc and the trench. These data they contribution to recent studies of ophiolite com- compare with similar geochemical and geo- plexes. The complementary work of the two graphical variations of boninite sequence vol- schools is clear and ripe for development. canics described from the Troodos ophiolite, Cyprus. Kostopoulos & Murton further expand Tectonics these studies of boninite petrogenesis and en- vironments of formation, focusing in particular The first two contributions to this volume on the OIB-like component and suggesting its demonstrate the appropriate choice of theme. origin lies in the melt extraction process beneath Alexander & Harper's detailed review of the oceanic spreading centres. Ballantyne describes Josephine Ophiolite discusses the architecture the dismembered ophiolitic rocks of eastern of mid-ocean ridge magma chambers, quantifies Indonesia, notes the relatively limited MORB- the extensional tectonics, and provides a study like component of the ophiolite complex, and of the range of fault structures, both transfer discusses the mantle sequence of depleted harz- and normal, associated with slow spreading. burgites and subordinate lherzolites. Whilst They also document the alteration of the host sharing many of the petrological characteristics rock by hydrothermalism, and the relative with plutonic rocks of the Papuan and Marum chronology of deformation. MacLeod & Rothery ophiolites of the island of New Guinea, these reinforce this type of assessment of ophiolitic rocks appear to have strong affinities to others complexes with their analysis of ridge axis dis- occurring in suprasubduction environments. continuities in the 500 km long exposed section This contrasts with the likely forearc basement of the Oman ophiolite. Outcrop interpretations overthrust emplacement for the PNG com- of these types of structures, which are at present plexes. Roberts, along with Vaisami & Cann, studied only by marine structural geophysicists Girardeau & Mercier, present more detailed and geologists using remotely sensed methods, analyses of particular lithological associations offer an exciting, new and high resolution per- within Mediterranean ophiolites. Roberts con- Downloaded from http://sp.lyellcollection.org/ by guest on October 1, 2021 2 L.M. PARSON & B.J. MURTON tributes a study of the setting of chromite de- interpretation. Borgia & Treves, along with posits in cumulate sequences, and Valsami & Harris conclude the volume with regional Cann use the epidositic reaction zones as means studies of emplacement of oceanic crusts, with of assessing the mobility of rare earth elements. two papers describing two contrasting scales for Laurent describes intrusive peridote diapirs cut- the formation of emplacement of ophiolites. ting the ultramafic cumulates and gabbroic rocks The first uses the volcanic edifice building pro- of the Troodos ophiolite and ascribes an origin cesses associated with the Hawaiian shield vol- of formation in terms of melt percolation at the canoes as an analogue for both spreading and top of upwelling mantle columns beneath mid- overthrust (emplacement) mechanisms. This ocean spreading axes, He goes on to offer them paper is particularly thought provoking, es- as analogues of the recently drilled seamounts pecially with its controversial use of oceanic occurring in the Mariana forearc. Girardeau & dynamic terms to describe the behaviour of the Mercier conclude this section with a review of large shield volcanic systems. The second dis- plagioclase wehrlites sampled by deep drilling cusses the importance of synorogenic forearc in the eastern Pacific Ocean, by submersible extension for the formation and immediate em- and in the field in Oman and Troodos. placement suprasubduction zone ophiolites, by examining the tectonic evolution of current com- plex collision dynamics in the Banda-arc- Analogous settings Australian collision zone. The final four papers have a varied content, but We hope to have compiled in this volume a have been grouped to demonstrate the similarity suitable cross-section of current research in of methods and concepts which apply to both ophiolite geology and its bearing on studied of oceanic and ophiolitic studies. Allerton & Vine present mid-ocean ridge processes. It is our describe their paleomagnetic surveys of crustal hope that progress in the two fields of interest, rocks in the Troodos ophiolite, and report their marine and land-based, will be made together; findings of block rotation, on axes with both and that symposia such as this provide a mutual horizontal and vertical components adjacent to benefit to geologists and geophysicists alike. major fault structures. They also include details of ridge transform intersection tectonics and We would like to acknowledge the hard work and efforts of all those individuals whose names do not ridge jumps in a study which is of direct and appear as authors in this volume. They include the immense relevance to marine oceanic research referees for the manuscripts, a list of whom appear on mid-ocean ridges. Brewer, Pelling, Lovell & below, staff at Burlington House -- particularly Siam Harvey present new data from deep drilling Roblings, and at the Geological Society Publishing work in the eastern Pacific in the form of geo- House, particularly Angharad Hills. Finally thanks go chemical wireline logs. These type of data have to Yvonne Baker and Annie Williams at IOSDL for been interpreted by some geochemical petro- the endless secretarial support. physicists to provide approximate modal analy- ses of some downhole lithologies unsampled by S. Agar, J. Andrews, P. Browning, J. Cann, P. Floyd, I. Gass, A. Griffiths, J. Hall, C. Jacobs, L. coring. The methods by which some of these Johnson, J. Karson, M. Kleinrock, D. Kostopoulos, wireline log data are analysed and interpret- R. Laurent, P. Lonsdale, K. Macdonald, C. Mac- ations derived are the subject of some contro- Leod, C. Neary, R. Nesbitt, J. Pearce, H. Prichard, versy amongst 'purist' petrologists, but the D. Rickard, S. Roberts, A. Robertson, N. Rogers, authors argue convincingly for the validity of R. Searle, M. Sinha, R. Stem, P. Styles, R. Taylor, their methods, while still urging caution in the M. Wilson. .
Load more

Recommended publications
  • Ophiolite in Southeast Asia
    Ophiolite in Southeast Asia CHARLES S. HUTCHISON Department of Geology, University of Malaya, Kuala Lumpur, Malaysia ABSTRACT semblages are classified into definite ophiolite, tentatively identified ophiolite, and associations that have previously been named No fewer than 20 belts of mafic-ultramafic assemblages have ophiolite but that are not. Each of the ophiolite or other been named "ophiolite" in the complex Southeast Asia region of mafic-ultramafic associations is listed in Table 1, with brief reasons Sundaland. Fewer than half of these can be confidently classified as for its classification, particularly in regard to the petrography of the ophiolite. The only well-documented complete ophiolite, with con- rock suite and the nature of its sedimentary envelope. The basis for tinuous conformable sections from mantle harzburgite through identification (or rejection) of these rock associations as ophiolite is gabbro to spilite, occurs in northeast Borneo and the neighboring discussed in the following section. Philippine Islands. It contains a record of oceanic lithospheric his- tory from Jurassic to Tertiary and has a Miocene emplacement age. OPHIOLITE FORMATION All other ophiolite belts of the region are either incomplete or dis- membered. The Sundaland region probably has examples of several The oceanic lithosphere, with its thin oceanic crust formed along types of emplacement mechanism and emplacement ages ranging the spreading axes of divergent plate junctures, is thought to be from early Paleozoic to Cenozoic. Key words: Sundaland, plate consumed at arc-trench systems of convergent plate junctures (Fig. tectonics. 2). Minor subtractions of crustal and mantle material from de- scending slabs of oceanic lithosphere are thought to be added to INTRODUCTION belts of mélange, and imbricate slices are caught in crustal subduc- tion zones at the trenches (Dickinson, 1972).
    [Show full text]
  • Hydrothermal Alteration of a Supra-Subduction Zone Ophiolite Analog, Tonga
    AN ABSTRACT OF THE THESIS OF Melanie C. Kelman for the degree of Master of Science in Geology presented on May 29, 1998. Title: Hydrothermal Alteration of a Supra-Subduction Zone Ophiolite Analog, Tonga. Southwest Pacific. Abstract approved: Redacted for Privacy Sherman Bloomer The basement of the Tonga intraoceanic forearc comprises Eocene arc volcanic crust formed during the earliest phases of subduction. Volcanic rocks recovered from the forearc include boninites and arc tholeiites, apparently erupted into and upon older mid- oceanic ridge tholeiites. Rock assemblages suggest that the forearc basement is a likely analog for large supra-subduction zone (SSZ) ophiolites not only in structure and Ethology, but also in the style of hydrothermal alteration. Dredged volcanic samples from the central Tonga forearc (20-24° S) exhibit the effects of seafloor weathering, low (<200°C, principally <100°C) alteration, and high temperature (>200°C) alteration. Tholeiites and arc tholeiites are significantly more altered than boninites. Seafloor weathering is due to extensive interaction with cold oxidizing seawater, and is characterized by red-brown staining and the presence of Fe- oxyhydroxides. Low temperature alteration is due to circulation of evolving seawater- derived fluids through the volcanic section until fluid pathways were closed by secondary mineral precipitation. Low temperature alteration is characterized by smectites, celadonite, phillipsite, mixed-layer smectite/chlorite, carbonates, and silica. All phases fill veins and cavities; clay minerals and silica also replace the mesostasis and groundmass phases. Low temperature alteration enriches the bulk rock in K, Ba, and Na, and mobilizes other elements to varying extents. The few high temperature samples are characterized by mobilizes other elements to varying extents.
    [Show full text]
  • New Perspectives on Tasmanian Geology
    TASMANIA - ANISLANDOFPOmNIIAL New perspectives on Tasmanian geology C. MeA. POWELL Geology Departrrumt, The University ofWe stem Australia. ABSTRACT New infonnation about the structure and sedimentary basin cotljiguration in the southern TastnIJII Fold Bell cotljirms thiltthe eastern TasmLlllia terrane is the on-strike COlllinuation o/the Melbourne Zone o/VictoriIL It represents a passive-margin to back-arc basin which was deformed and amalgamated with the western TasmLlllia terrane in the late Middle Devonian. The western TastnlJlliaterrane hils chilracteristics 0/ both the western lAchlan Fold Bell and the Kanmantao Fold Bell, and could be a largely exotic block lying across the jutlCtion between the tw%ld bells. The Precambrian "basemelll" o/TQStnIJ1Iia, regarded/or so long asfirmly rooted to its mafIlle lithosphere, could be composed o/thrust-bounded slices accreted to the TQStnIJ1I Fold Bell initially in the Middle Cambrian during westward thrusting o/the KanmafIloo Fold Belt over the platform margin in the Adelaide region. Renewed contraction in the Middle Devonian/ormed tnIJIIy o/the preselllthrust contacts. These new ideas make it imperative that existing esploration philosophies and nwdels are re-exmnined 10 take ill/o accoulllthe thrust-/aull geometry and the possible allochthonous nature o/much o/TasmLlllia. INTRODUCTION local areas of contractional deformation (powell, 1983, 1984a). The whole eastern Lachlan Fold Belt appears to have been a zone of transcurrence with local areas of transtension Tasmania occupies an imponant place in the geological and transpression. Theeasternand western] acblanFoldBelt framework of AuslIalia, lying at the southern extension of were reunited in the Middle Devonian when contractional the 1000-km wide Tasman Fold Belt, which occupies the deformation affected both parts, and the region rose above eastern third of the continent (fig.
    [Show full text]
  • Thermo-Mechanical Modeling of the Obduction Process Based on The
    Thermo-mechanical modeling of the obduction process based on the Oman ophiolite case Thibault Duretz, Philippe Agard, Philippe Yamato, Céline Ducassou, Evgenii Burov, T. V. Gerya To cite this version: Thibault Duretz, Philippe Agard, Philippe Yamato, Céline Ducassou, Evgenii Burov, et al.. Thermo- mechanical modeling of the obduction process based on the Oman ophiolite case. Gondwana Research, Elsevier, 2016, 32, pp.1-10. 10.1016/j.gr.2015.02.002. insu-01120232 HAL Id: insu-01120232 https://hal-insu.archives-ouvertes.fr/insu-01120232 Submitted on 9 Mar 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. ACCEPTED MANUSCRIPT Thermo-mechanical modeling of the obduction process based on the Oman ophiolite case Thibault Duretz1,2, Philippe Agard2, Philippe Yamato3, Céline Ducassou4, Evguenii B. Burov2, Taras V. Gerya5 1Institut des sciences de la Terre, University of Lausanne, 1015 Lausanne, Switzerland 2ISTEP, UMR CNRS 7193, UPMC Sorbonne Universités, 75252 Cedex 05, Paris, France 3Geosciences Rennes, UMR CNRS 6118, Université de Rennes 1, 35042 Rennes Cedex, France 4Applied Geosciences, GUtech, PO Box 1816, Athaibah, PC 130, Sultanate of Oman 5Institute of Geophysics, ETH Zürich, Sonneggstrasse 5, 8092 Zürich, Switzerland submission to – Gondwana Research Keywords: Obduction; Oman; numerical modeling ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT Abstract Obduction emplaces regional-scale fragments of oceanic lithosphere (ophiolites) over continental lithosphere margins of much lower density.
    [Show full text]
  • The Callovian Unconformity and the Ophiolite Obduction Onto the Pelagonian Carbonate Platform of the Internal Hellenides
    Δελτίο της Ελληνικής Γεωλογικής Εταιρίας, τόμος L, σελ. 144-152 Bulletin of the Geological Society of Greece, vol. L, p. 144-152 Πρακτικά 14ου Διεθνούς Συνεδρίου, Θεσσαλονίκη, Μάιος 2016 Proceedings of the 14th International Congress, Thessaloniki, May 2016 THE CALLOVIAN UNCONFORMITY AND THE OPHIOLITE OBDUCTION ONTO THE PELAGONIAN CARBONATE PLATFORM OF THE INTERNAL HELLENIDES Scherreiks R.1, Meléndez G.2, Bouldagher-Fadel M.3, Fermeli G.4 and Bosence D.5 1Bayerische Staaatssammlung, Department of Geology, University of Munich, Luisenstr. 33, 80333 Munich, Germany, [email protected] 2Departamento de Geologia (Paleontologia), Universidad de Zaragoza, 50009 Saragossa, Spain, [email protected] 3Earth Sciences, University College London, Gower Street, London WC1E6BT, UK, [email protected] 4Department of Historical Geology and Paleontology, University of Athens, Panepistimioupolis, Zographou, 15784 Athens, Greece, [email protected] 5Department of Earth Sciences, Royal Holloway University of London, Egham TW20 0EX, UK, [email protected] Abstract The carbonate-platform-complex and the oceanic formations of the central Pelagonian zone of the Hellenides evolved in response to a sequence of plate-tectonic episodes of ocean spreading, plate convergence and ophiolite obduction. The bio- stratigraphies of the carbonate platform and the oceanic successions, show that the Triassic-Early Jurassic platform was coeval with an ocean where pillow basalts and radiolarian cherts were being deposited. After convergence began during late Early- Jurassic - Middle Jurassic time, the oceanic leading edge of the Pelagonian plate was subducted beneath the leading edge of the oceanic, overriding plate. The platform subsided while a supra-subduction, volcanic-island-arc evolved.
    [Show full text]
  • Zeolites in Tasmania
    Mineral Resources Tasmania Tasmanian Geological Survey Record 1997/07 Tasmania Zeolites in Tasmania by R. S. Bottrill and J. L. Everard CONTENTS INTRODUCTION ……………………………………………………………………… 2 USES …………………………………………………………………………………… 2 ECONOMIC SIGNIFICANCE …………………………………………………………… 2 GEOLOGICAL OCCURRENCES ………………………………………………………… 2 TASMANIAN OCCURRENCES ………………………………………………………… 4 Devonian ………………………………………………………………………… 4 Permo-Triassic …………………………………………………………………… 4 Jurassic …………………………………………………………………………… 4 Cretaceous ………………………………………………………………………… 5 Tertiary …………………………………………………………………………… 5 EXPLORATION FOR ZEOLITES IN TASMANIA ………………………………………… 6 RESOURCE POTENTIAL ……………………………………………………………… 6 MINERAL OCCURRENCES …………………………………………………………… 7 Analcime (Analcite) NaAlSi2O6.H2O ……………………………………………… 7 Chabazite (Ca,Na2,K2)Al2Si4O12.6H2O …………………………………………… 7 Clinoptilolite (Ca,Na2,K2)2-3Al5Si13O36.12H2O ……………………………………… 7 Gismondine Ca2Al4Si4O16.9H2O …………………………………………………… 7 Gmelinite (Na2Ca)Al2Si4O12.6H2O7 ……………………………………………… 7 Gonnardite Na2CaAl5Si5O20.6H2O ………………………………………………… 10 Herschelite (Na,Ca,K)Al2Si4O12.6H2O……………………………………………… 10 Heulandite (Ca,Na2,K2)2-3Al5Si13O36.12H2O ……………………………………… 10 Laumontite CaAl2Si4O12.4H2O …………………………………………………… 10 Levyne (Ca2.5,Na)Al6Si12O36.6H2O ………………………………………………… 10 Mesolite Na2Ca2(Al6Si9O30).8H2O ………………………………………………… 10 Mordenite K2.8Na1.5Ca2(Al9Si39O96).29H2O ………………………………………… 10 Natrolite Na2(Al2Si3O10).2H2O …………………………………………………… 10 Phillipsite (Ca,Na,K)3Al3Si5O16.6H2O ……………………………………………… 11 Scolecite CaAl2Si3O10.3H20 ………………………………………………………
    [Show full text]
  • Synchronous Formation of the Metamorphic
    Earth and Planetary Science Letters 451 (2016) 185–195 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl Synchronous formation of the metamorphic sole and igneous crust of the Semail ophiolite: New constraints on the tectonic evolution during ophiolite formation from high-precision U–Pb zircon geochronology ∗ Matthew Rioux a, , Joshua Garber a,b, Ann Bauer c, Samuel Bowring c, Michael Searle d, Peter Kelemen e, Bradley Hacker a,b a Earth Research Institute, University of California, Santa Barbara, CA 93106, USA b Department of Earth Science, University of California, Santa Barbara, CA 93106, USA c Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA d Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, UK e Department of Earth and Environmental Studies, Columbia University, Lamont Doherty Earth Observatory, Palisades, NY 10964, USA a r t i c l e i n f o a b s t r a c t Article history: The Semail (Oman–United Arab Emirates) and other Tethyan-type ophiolites are underlain by a Received 11 April 2016 sole consisting of greenschist- to granulite-facies metamorphic rocks. As preserved remnants of the Received in revised form 2 June 2016 underthrust plate, sole exposures can be used to better understand the formation and obduction Accepted 25 June 2016 of ophiolites. Early models envisioned that the metamorphic sole of the Semail ophiolite formed Available online 29 July 2016 as a result of thrusting of the hot ophiolite lithosphere over adjacent oceanic crust during initial Editor: M.
    [Show full text]
  • RESEARCH a Non–Plate Tectonic
    RESEARCH A non–plate tectonic model for the Eoarchean Isua supracrustal belt A. Alexander G. Webb1,*, Thomas Müller2, Jiawei Zuo1, Peter J. Haproff3, and Anthony Ramírez-Salazar2 1DEPARTMENT OF EARTH SCIENCES AND LABORATORY FOR SPACE RESEARCH, UNIVERSITY OF HONG KONG, POKFULAM ROAD, HONG KONG, CHINA 2SCHOOL OF EARTH AND ENVIRONMENT, UNIVERSITY OF LEEDS, MATHS/EARTH AND ENVIRONMENT BUILDING, LEEDS LS2 9JT, UK 3DEPARTMENT OF EARTH AND OCEAN SCIENCES, UNIVERSITY OF NORTH CAROLINA, WILMINGTON, NORTH CAROLINA 28403, USA ABSTRACT The ca. 3.8–3.6-b.y.-old Isua supracrustal belt of SW Greenland is Earth’s only site older than 3.2 Ga that is exclusively interpreted via plate- tectonic theory. The belt is divided into ca. 3.8 Ga and ca. 3.7 Ga halves, and these are interpreted as plate fragments that collided by ca. 3.6 Ga. However, such models are based on idiosyncratic interpretations of field observations and U-Pb zircon data, resulting in intricate, conflicting stratigraphic and structural interpretations. We reanalyzed published geochronological work and associated field constraints previously interpreted to show multiple plate-tectonic events and conducted field-based exploration of metamorphic and structural gra- dients previously interpreted to show heterogeneities recording plate-tectonic processes. Simpler interpretations are viable, i.e., the belt may have experienced nearly homogeneous metamorphic conditions and strain during a single deformation event prior to intrusion of ca. 3.5 Ga mafic dikes. Curtain and sheath folds occur at multiple scales throughout the belt, with the entire belt potentially representing Earth’s largest a-type fold. Integrating these findings, we present a new model in which two cycles of volcanic burial and resultant melt- ing and tonalite-trondhjemite-granodiorite (TTG) intrusion produced first the ca.
    [Show full text]
  • Geodynamic Patterns of Ophiolites and Marginal Basins in the Indonesian and New Guinea Regions
    Geodynamic patterns of ophiolites and marginal basins in the Indonesian and New Guinea regions RON HARRIS Department ofGeology, Brigham Young University, Provo, UT 84602-4606, USA (e-mail: [email protected]) Abstract: Analysis of spatial, temporal, geological and geochemical patterns of ophiolites in the Indonesian and New Guinea region indicates a strong correlation with marginal basin development and closure. The spatial distribution of ophiolites is mostly linked with marginal basin producing zones of oblique convergence and collision. Strain partitioning in these zones creates a series of ephemeral plate boundaries between several independently moving lithospheric blocks. Repeated disruption of the diffuse boundaries between the blocks by changes in plate motion and collision-induced mantle extrusion creates space that is rapidly filled by new ocean basins in the upper plate of subduction zones. Suprasubduction zone (SSZ) spreading of these basins is enhanced by episodic extrusion of asthenosphere escaping collisional suture zones. Various closure events and global plate motion changes are reflected in the temporal distribution of marginal basin and ophiolite ages. Most ophiolite slabs in the Indonesian and New Guinea region represent fragments of oceanic lithosphere with a subduction zone component, as indicated by the common refractory petrochemistry of the mantle sequence and occurrence ofboninite. .Age and compositional heterogeneity may indicate that some ophiolite bodies are composite terranes. Collisions with buoyant lithosphere transfo= parts of these ocean basins into ophiolites. The connection between ophiolites and marginal basins is strongest where parts of actively spreading SSZ basins are partially represented as ophiolites in collision zones. Many of the various tectonic models proposed for rollback, subduction polarity asymmetry, astheno­ the origin and tectonic evolution of ophiolites are spheric flow and plate kinematics.
    [Show full text]
  • Redalyc.Ophiolite-Related Ultramafic Rocks (Serpentinites) in the Caribbean Region: a Review of Their Occurrence, Composition, O
    Geologica Acta: an international earth science journal ISSN: 1695-6133 [email protected] Universitat de Barcelona España Lewis, J.F.; Draper, G.; Proenza, J.A.; Espaillat, J.; Jiménez, J. Ophiolite-Related Ultramafic Rocks (Serpentinites) in the Caribbean Region: A Review of their Occurrence, Composition, Origin, Emplacement and NiLaterite Soil Formation Geologica Acta: an international earth science journal, vol. 4, núm. 1-2, 2006, pp. 237-263 Universitat de Barcelona Barcelona, España Available in: http://www.redalyc.org/articulo.oa?id=50540214 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Geologica Acta, Vol.4, Nº1-2, 2006, 237-263 Available online at www.geologica-acta.com Ophiolite-Related Ultramafic Rocks (Serpentinites) in the Caribbean Region: A Review of their Occurrence, Composition, Origin, Emplacement and Ni-Laterite Soil Formation 1 2 3 4 5 J.F. LEWIS G. DRAPER J.A. PROENZA J. ESPAILLAT and J. JIMÉNEZ 1 Dept. of Earth and Environmental Sciences, The George Washington University Washington DC 20052. E-mail: [email protected] 2 Dept. of Earth Sciences, Florida International University Miami, FL 33199. E-mail: [email protected] 3 Departament de Cristalografia, Mineralogia i Dipòsits Minerals, Facultat de Geologia, Universitat de Barcelona, Martí i Franquès s/n 08028 Barcelona, Spain. E-mail: [email protected] 4 Corporación Minera Dominicana Máximo Gómez s/n, Dominican Republic. E-mail: [email protected] 5 Falconbridge Dominicana Bonao, Dominican Republic.
    [Show full text]
  • Polygenetic Ophiolite Belt of the California Sierra Nevada' Geochronologicaland Tectonostratigraphicdevelopment
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 87, NO. B3, PAGES 1803-1824, MARCH 10, 1982 Polygenetic Ophiolite Belt of the California Sierra Nevada' Geochronologicaland TectonostratigraphicDevelopment JASON B. $ALEEBY Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125 The assumptionthat ophiolite sequencesare generatedat essentiallyone point in geologictime by the processof sea-floorspreading is critical for modern conceptsin the tectonicsof ophiolites and for topicsdealing with their structureand petrology.However, this assumptionhas only been verifiedin a few locationsby an integratedgeochronological and structural-stratigraphicapproach. Many ophiolite sectionsare reconstructedfrom structurallydisrupted sequences with the idealized ocean floor model in mind. Such reconstructionsare prone to error without adequate age control on each of the reconstructedfragments. This is a significantproblem in structurallycomplex regions where more than one generationof ophiolite may be present. In this paper new Pb/U zircon agesare presentedfor key locations along a 375 km segmentof the western Sierra Nevada ophiolite belt. These age data are combined with structural-stratigraphicobservations and published ages, and significant tectonic implicationsfor the ophiolite belt emerge.Three different ophiolitic assemblagesare recognizedwith igneousages of about 300, 200 and 160m.y.B.P. Rocks of the 300 m.y. assemblageare in a completely disruptedarray of metamorphictectonite slabsand serpentinite-matrixmelange. Fragmentsof upper Paleozoic seamountsoccur in associationwith the ophiolitic melange, and together these assemblages constitutethe basementframework for the western Sierra. Pb/U and K/Ar isotopic systematicsare complex within this framework and indicate a polymetamorphichistory. Systematicsin the 200 and 160m.y. assemblagesare lesscomplex and give tighter igneousage constraints.Rocks of the 200 m.y. assemblageare in a semi-intact state with only local tectonite and melange zones.
    [Show full text]
  • Precambrian Greenstone Sequences Represent Different Ophiolite Types
    GR-01066; No of Pages 37 Gondwana Research xxx (2013) xxx–xxx Contents lists available at SciVerse ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr GR Focus Review Precambrian greenstone sequences represent different ophiolite types H. Furnes a,⁎, Y. Dilek b,c, M. de Wit d a Department of Earth Science and Centre for Geobiology, University of Bergen, Allégaten 41, 5007 Bergen, Norway b Department of Geology & Environmental Earth Science, Miami University, Oxford, OH 45056, USA c State Key Laboratory of Geological Processes and Mineral Resources, and School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China d AEON – Africa Earth Observatory Network, and Faculty of Science, Nelson Mandela Metropolitian University 7701, Port Elizabeth, 6031, South Africa article info abstract Article history: We present here a global geochemical dataset from one hundred-and-five greenstone sequences, ranging in Received 14 March 2013 age from the Eoarchean through the Archean and Proterozoic Eons that we have examined to identify differ- Received in revised form 14 June 2013 ent ophiolite types (c.f. Dilek and Furnes, 2011) with distinct tectonic origins in the Precambrian rock record. Accepted 14 June 2013 We apply well-established discrimination systematics (built on immobile elements) of basaltic components Available online xxxx of the greenstone sequences as our geochemical proxies. The basaltic rocks are classified under two major groups, subduction-related and subduction-unrelated. This analysis suggests that ca. 85% of the greenstone Keywords: fi Precambrian greenstone belts sequences can be classi ed as subduction-related ophiolites, generated in backarc to forearc tectonic envi- Ophiolite classification ronments.
    [Show full text]