DOCSLIB.ORG

Kings River Ophiolite, Southwest Sierra Nevada Foothills, California

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Kings River Ophiolite, Southwest Sierra Nevada Foothills, California Kings River ophiolite, southwest Sierra Nevada foothills, California JASON SALEEBY Department of Geology and Geophysics, University of California, Berkeley, California 94720 ABSTRACT INTRODUCTION In the lower Kings River area, rocks older than the Sierra Nevada Distinctive rock sequences consisting (from bottom to top) of batholith include a disrupted and metamorphosed ophiolite. The peridotite, gabbro, mafic dikes, and pillow basalt are referred to as Kings River ophiolite consists of tectonically emplaced slabs as ophiolites. Ophiolites are believed to represent fragments of oceanic much as 20 km long that are separated by serpentinite-matrix crust and upper mantle that were detached and emplaced into melange zones and by crosscutting plutons of the batholith. Within orogenic zones along once-active plate junctures (Dietz, 1963; the slabs, various segments of the original ophiolite section are Thayer, 1969; Coleman, 1971a; Dewey and Bird, 1971; Church, preserved. From the base upward, the reconstructed section con- 1972; Brookfield, 1977). The widespread occurrence of ophiolite sists of (1) a harzburgite zone (more than 4 km thick), (2) a transi- remnants now documented in the Sierra Nevada of California tion zone between ultramafic and mafic tectonites and cumulates (Morgan, 1973; Menzies and others, 1975; Moores and Menzies, (2.5 km thick), (3) a gabbro zone with cumulates (2 km thick), (4) a 1975; Ehrenberg, 1975; Saleeby, 1975a, 1975b, 1975c, 1977a, mafic-dike zone (0.7 km thick), and (5) a pillow-basalt zone (1.8 1977b; Behrman, 1978) is important because they record the role km thick). The pillow basalt is overlain by at least 20 m of metal- of plate-margin processes and the involvement of oceanic liferous radiolarian chert. After tectonic mixing and emplacement lithosphere in the pre-batholith tectonic evolution of the Sierran into the Sierran terrane, the ophiolite was metamorphosed to the terrane. hornblende-hornfels facies by the batholith. Ophiolite remnants exposed almost continuously as a 125-km- The Kings River ophiolite is interpreted as a disrupted fragment long northwest-trending belt in the southwestern Sierra Nevada of oceanic crust and upper mantle. Isotopic ages along with struc- foothills are referred to informally as the Kings-Kaweah ophiolite tural and petrographic data indicate that the igneous part of the belt (Fig. 1, inset map). The Kings-Kaweah ophiolite belt forms section originated in latest Paleozoic or possibly earliest Mesozoic part of the western wall of the Sierra Nevada batholith in the re- time. Intense deformation of the ophiolite began at its point of ori- gion. The Kings River ophiolite is located at the northern end of the gin. Deep levels of the ophiolite were penetratively mylonitized, in- belt; it is exposed for 33 km along strike and covers an area of 340 termediate levels were deformed by ductile faulting, and upper km2. The purpose of this paper is to (1) describe the general setting levels were deformed by brittle shear. As deformation and disrup- of the Kings River ophiolite and its relation with the rest of the tion progressed, serpentinization of the ophiolite's lower levels also Kings-Kaweah ophiolite belt, (2) describe in detail the petrology progressed. Serpentinization and differential tectonic movements and structure of the Kings River ophiolite, and (3) discuss the were concentrated along zones that became serpentinite-matrix emplacement and related deformation of the ophiolite. A more in- melange. The inclusion of only ophiolite-assemblage rocks in the depth discussion of the emplacement and regional tectonic sig- melange zones indicates that the melange mixing was oceanic. nificance of the entire ophiolite belt is presented elsewhere (Saleeby, The ophiolite originated and began its deformational history at a 1977b, and ms. in prep.). mid-ocean spreading center where that center was cut by a trans- Prior to my work, the northern part of the ophiolite had been verse fracture zone. The progression from brittle to ductile be- mapped in reconnaissance and studied petrographically by Mac- havior with stratigraphic depth during initial deformation is at- donald (1941). The southern part had been mapped in reconnais- tributed to a steep thermal gradient, typical of an ocean ridge. sance (Mathews and Burnett, 1966). Neither of these studies rec- Progressive deformation and disruption and, ultimately, ophiolite ognized the existence of an ophiolite. Mafic and ultramafic rocks of emplacement occurred along a wrench zone that cut obliquely into the region have been generally interpreted as magmatically western North America and truncated earlier-formed tectonic ele- emplaced "forerunners" of the Sierra Nevada batholith (Mayo, ments. The wrench zone is believed to have been an extension of 1941; Bateman and others, 1963). It will be shown that rocks of the mid-ocean fracture zone that widened and became more com- the Kings River ophiolite are not magmatic forerunners of the plex with time. During the later stages of wrench movement, a batholith and that the ophiolite is of a petrogenetic domain re- component of eastward underthrusting commenced. Disrupted moved from that of the batholith in terms of both time and space. ocean floor of the wrench zone was left as an accretionary hanging Magmatically emplaced mafic rocks do occur in the vicinity of the wall of a newly formed subduction zone. A Jurassic volcanic arc Kings River ophiolite (Saleeby, 1975c, 1976a, 1976b; Saleeby and was built across the already weakened oceanic basement as it un- Sharp, 1977), but these rocks along with other batholithic rocks derwent transverse shortening and continued wrench movements in will not be discussed in depth here. response to oblique subduction. Final truncation of North Ameri- can tectonic elements and emplacement of the ophiolite probably GEOLOGIC SETTING overlapped in time with arc activity. Similar deformation and trun- cation zones are a common feature in modern subduction-arc The Kings-Kaweah ophiolite belt is exposed along the western complexes of the circum-Pacific. edge of the Sierran foothills between lat 36°00'N and 37°00' (Fig. Geological Society of America Bulletin, v. 89, p. 617-636, 7 figs., April 1978, Doc. no. 80413. 617 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/89/4/617/3444453/i0016-7606-89-4-617.pdf by guest on 26 September 2021 618 J. SALEEBY Figure 1. Geologic location map showing entire Kings-Kaweah ophiolite belt and area covered in adjoining detailed geologic map of the 1, inset map). The southern half of the belt consists of a tectonic since some of them contain mappable internal stratigraphic units. melange in which the various rock types of the ophiolite assem- Collectively, these slabs are the Kings River ophiolite. blage are mixed within a schistose serpentinite matrix. The A complete ophiolite succession is preserved within the tectonic melange is referred to informally as the Kaweah serpentinite slabs of the Kings River area. The slabs are separated by melange melange and is discussed in detail elsewhere (Saleeby, 1975a, zones containing ophiolitic material and by crosscutting plutons of 1975b, 1975c, 1977a, 1977b). North of the Kaweah River area the the Sierra Nevada batholith (Fig. 1). The slabs are elongated in a tectonic blocks increase in size (Fig. 1, inset map). The large blocks northwest direction and range from 5 to 20 km in length. The slabs of the Kings River area are referred to as slabs (after Hsu, 1968), form the topographic highs in the area and are named informally Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/89/4/617/3444453/i0016-7606-89-4-617.pdf by guest on 26 September 2021 KINGS RIVER OPHIOLITE, CALIFORNIA 619 Kings River ophiolite. Geology by Saleeby supplemented by Macdonald (1941), Matthews and Burnett (1966), and W. D. Sharp (unpub. data). after the highest peaks that they underlie. The Bald Mountain and The melange zone that bounds the east side of the Hog Mountain Hughes Mountain slabs consist mainly of metamorphosed pillow slab separates the ophiolite from metasedimentary rocks of the basalt, breccia, and mafic dikes. The Tivy Mountain and Hog Calaveras Complex (Saleeby and Goodin, 1977). The melange zone Mountain slabs consist mainly of metamorphosed gabbro and that bounds the western margin of the Tivy Mountain slab is simi- peridotite. lar to the Kaweah melange and forms the western known border of Contacts between ophiolitic slabs and adjacent melange zones the ophiolite. are vertical and gradational over short distances. Exotic blocks of Plutons ranging in composition from olivine-hornblende mainly metabasalt and metachert characterize the melange zones. melagabbro to biotite quartz diorite intruded and metamorphosed Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/89/4/617/3444453/i0016-7606-89-4-617.pdf by guest on 26 September 2021 620 J. SALEEBY GENERALIZED RECONSTRUCTED OPHIOLITE SECTION OCEANIC uj co BASEMENT PROTOLITHS METAMORPHIC DERIVATIVES 20m km o —I METALLIFEROUS AND PURE METAQUARTZITE LAYER OQ RAD IOLARIAN CHERT 2 PILLOW BASALT ZONE PILLOW BASALT WITH LOCAL INTER- MAFIC HORNBLENDE BASALT, 7.0km PILLOW CHERT, PILLOW BRECCIA, HORNFELS AND SCHISTOSE DIABASE MASSIVE BASALT AND MAFIC DIKE ROCK AMPHI BOLITE Figure 2. Reconstructed co- MAFIC DIKE ZONE lumnar section of the Kings LAYER BASALT-DIABASE DIKES WITH LOCAL MAFIC HORNBLENDE River ophiolite. Brief lithologie 0.7km DIKES AND SCREENS OF CLINOPYROXENE HORNFELS AND
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]