DOCSLIB.ORG

Curved Orogenic Belts, Back-Arc Basins, and Obduction As Consequences of Collision at Irregular Continental Margins.', Geology

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Curved Orogenic Belts, Back-Arc Basins, and Obduction As Consequences of Collision at Irregular Continental Margins.', Geology Durham Research Online Deposited in DRO: 23 August 2021 Version of attached le: Published Version Peer-review status of attached le: Peer-reviewed Citation for published item: Schlike, Nicholas and van Hunen, Jeroen and Gueydan, Fr¡ed¡ericand Magni, Valentina and Allen, Mark B. (2021) 'Curved orogenic belts, back-arc basins, and obduction as consequences of collision at irregular continental margins.', Geology . Further information on publisher's website: https://doi.org/10.1130/G48919.1 Publisher's copyright statement: c 2021 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license Additional information: Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full DRO policy for further details. Durham University Library, Stockton Road, Durham DH1 3LY, United Kingdom Tel : +44 (0)191 334 3042 | Fax : +44 (0)191 334 2971 https://dro.dur.ac.uk https://doi.org/10.1130/G48919.1 Manuscript received 6 February 2021 Revised manuscript received 10 May 2021 Manuscript accepted 21 June 2021 © 2021 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Curved orogenic belts, back-arc basins, and obduction as consequences of collision at irregular continental margins Nicholas Schliffke1, Jeroen van Hunen1, Frédéric Gueydan2, Valentina Magni3 and Mark B. Allen1 1 Department of Earth Sciences, Durham University, DH1 3LE Durham, UK 2 Géosciences Montpellier, Université Montpellier 2, Place Eugène Bataillon, 34095 Montpellier cedex 5, France 3 The Centre for Earth Evolution and Dynamics (CEED), University of Oslo, SemSaelandsvei 24, P.O. Box 1048, Blindern, NO-0316 Oslo, Norway ABSTRACT by thrusting of an older Jurassic rifted margin Continental collisions commonly involve highly curved passive plate margins, leading to (Tubia et al., 2009), or by hyperextension of diachronous continental subduction during trench rollback. Such systems may feature back- the overriding plate before, and thrusting dur- arc extension and ophiolite obduction postdating initial collision. Modern examples include ing, continental collision (Frasca et al., 2017; the Alboran and Banda arcs. Ancient systems include the Newfoundland and Norwegian Cale- Gueydan et al., 2019; see Fig. 1C). It is unclear donides. While external forces or preexisting weaknesses are often invoked, we suggest that in these examples how the geologic evolution ophiolite obduction can equally be caused by internal stress buildup during collision. Here, is linked to the highly arcuate geometry and we modeled collision with an irregular subducting continental margin in three-dimensional irregular shape of the subducting continental (3-D) thermo-mechanical models and used the generated stress field evolution to understand margin, if at all. resulting geologic processes. Results show how tensional stresses are localized in the overrid- The aim of this study was to examine evolv- ing plate during the diachronous onset of collision. These stresses thin the overriding plate ing plate stresses during irregular continental and may open a back-arc spreading center. Collision along the entire trench follows rapidly, subduction and the formation of curved orogenic with inversion of this spreading center, ophiolite obduction, and compression in the overrid- belts, to provide a better understanding of the ing plate. The models show how subduction of an irregular continental margin can form a drivers and controls of the geologic evolution. highly curved orogenic belt. With this mechanism, obduction of back-arc oceanic lithosphere We show that localized tensional stresses during naturally evolves from a given initial margin geometry during continental collision. the initial stages of irregular margin collision cause short-lived back-arc rifting or spreading INTRODUCTION coinciding with trench rotation, and this was centers that are rapidly inverted once continental The formation of highly curved orogenic followed by continental subduction (4 Ma) at subduction spreads along the trench. belts is still debated (Rosenbaum, 2014). Pro- Timor, in the south (Fig. 1A). Oceanic subduc- posed mechanisms include processes associated tion is now ceased, with collision occurring COLLISION WITH IRREGULAR with deformation along thinned fold-and-thrust along the entire continental margin. The tec- PASSIVE MARGINS belts (Marshak, 1988), gravitational spreading tonic history of the Alboran Basin in the west- We investigated the stress regime evolution (e.g., Edey et al., 2020), or along-strike migration ern Mediterranean is debated (van Hinsbergen during continental collision with an irregular rate variations of plate boundaries (Rosenbaum et al., 2014). Most models agree that the slab margin (Fig. 2) in a model space of 3300 by and Lister, 2004). The latter includes processes retreated westward into the narrowing Alboran 3960 by 660 km in size. The finite element code such as plate rotation, trench rollback, or inden- embayment since 30–20 Ma (Fig. 1B). Citcom (Moresi et al., 1996; Zhong et al., 2000; tation during continental collision (Rosenbaum, Both regions share puzzling geological fea- Magni et al., 2014) solves the conservation equa- 2014; Rosenbaum and Lister, 2004). tures, such as extensional basins in the upper tions for momentum, energy, mass, and compo- The Alboran and Banda arcs are two mod- plate (Pownall et al., 2016; Watts et al., 1993), sition. We used a visco-plastic rheology includ- ern systems that are associated with trench and exhumed subcrustal continental lithosphere ing diffusion and dislocation creep, lithospheric rollback and diachronous continental subduc- (Frasca et al., 2017; Gueydan et al., 2019; Pow- yielding, and an upper-limit viscosity (Magni tion along strike (Spakman and Hall, 2010; van nall et al., 2014). The Banda system involves et al., 2014; van Hunen and Allen, 2011). We did Hinsbergen et al., 2014). Both regions experi- ophiolite obduction (Ishikawa et al., 2007), but not apply external forcing; all dynamics were enced trench rollback against a highly nonlinear this has not been identified in the Alboran arc. driven by internal buoyancy forces. Subducting passive margin (see Fig. 1), where continental The world’s largest subcontinental mantle ex- and overriding plates were separated by a weak lithosphere subducted diachronously along the posures, the Ronda and Beni peridotites in the zone and decoupled from neighboring plates by trench ( Pownall et al., 2016; Spakman and Hall, Alboran arc (Gueydan et al., 2019), have been weak transform faults to permit toroidal mantle 2010; van Hinsbergen et al., 2014). In the Banda suggested to have been exhumed by gravita- flow (van Hunen and Allen, 2011; Magni et al., region, continental material initially (15 Ma) tional collapse after slab break-off (Platt and 2014). Continental lithosphere was free to move subducted at Seram (Spakman and Hall, 2010), Vissers, 1989; Van der Wal and Vissers, 1993), toward the trench and collide with the overriding CITATION: Schliffke, N., et al., 2021, Curved orogenic belts, back-arc basins, and obduction as consequences of collision at irregular continental margins: Geology, v. 49, p. XXX–XXX, https://doi.org/10.1130/G48919.1 Geological Society of America | GEOLOGY | Volume XX | Number XX | www.gsapubs.org 1 Downloaded from http://pubs.geoscienceworld.org/gsa/geology/article-pdf/doi/10.1130/G48919.1/5379011/g48919.pdf by guest on 23 August 2021 while extension close to the oceanic embay- A ment continues to exert slab pull and trench retreat. The differential stresses cause yielding and rupture of the overriding plate. Opening of a back-arc spreading center (Fig. 3C) briefly increases convergence velocities by a factor of three (Fig. 4A). Shortly (∼5 m.y.) after onset of back-arc spreading, the oceanic embayment is completely subducted, and this is followed by continental subduction (Figs. 3D–3F). At this point, the young oceanic back-arc basin measures only 166 km in ridge-perpendicular spreading distance (Fig. 3D). High continental crustal buoyancy reduces subduction velocities and stops trench rollback (Fig. 4A). Without lo- cal, rapid trench rollback driving the extension- al stresses in the back-arc area, back-arc spread- ing ceases, and its stress state changes from an extensional to a compressional stress state within 10 m.y. after initial collision (Figs. 3E and 3F). During this last stage, slab break-off B along the entire subducted margin ends sub- duction and allows the subducted continent to begin exhumation. Subduction of smaller embayments (Fig. 4B) does not rupture the overriding plate to produce back-arc spreading, but it still thins the overrid- ing continent; crustal thickness reduces from the initial 40 km to as little as 8 km (Fig. 4B; Fig. S1 in the Supplemental Material1) at the C onset of collision. The embayment breadth, bb, determines the duration of the overriding plate extensional phase, and hence the presence or absence of an oceanic back-arc basin. Too narrow embayments (small wb) do not create sufficient tensional stresses, while the widest embayments (wb = 1200 km) lack the required stress localization. When a back-arc spreading center is formed, its spreading duration varies from 1 m.y. in the smallest basin, to 5 m.y. (ref- Figure 1. (A–B) Tectonic history of Banda (A) and Alboran (B) systems with diachronous conti- erence model, Fig. 3), to 10 m.y. in the models nental subduction and trench rollback before continental subduction along entire trench ended with the largest embayments (wb = 1200 km and subduction (overriding plate not shown in A–B). Orange—continental domains; blue—oceanic bb = 600 km) and forming the largest back-arc domains.
Load more

Recommended publications
  • Two Contrasting Phanerozoic Orogenic Systems Revealed by Hafnium Isotope Data William J
    ARTICLES PUBLISHED ONLINE: 17 APRIL 2011 | DOI: 10.1038/NGEO1127 Two contrasting Phanerozoic orogenic systems revealed by hafnium isotope data William J. Collins1*(, Elena A. Belousova2, Anthony I. S. Kemp1 and J. Brendan Murphy3 Two fundamentally different orogenic systems have existed on Earth throughout the Phanerozoic. Circum-Pacific accretionary orogens are the external orogenic system formed around the Pacific rim, where oceanic lithosphere semicontinuously subducts beneath continental lithosphere. In contrast, the internal orogenic system is found in Europe and Asia as the collage of collisional mountain belts, formed during the collision between continental crustal fragments. External orogenic systems form at the boundary of large underlying mantle convection cells, whereas internal orogens form within one supercell. Here we present a compilation of hafnium isotope data from zircon minerals collected from orogens worldwide. We find that the range of hafnium isotope signatures for the external orogenic system narrows and trends towards more radiogenic compositions since 550 Myr ago. By contrast, the range of signatures from the internal orogenic system broadens since 550 Myr ago. We suggest that for the external system, the lower crust and lithospheric mantle beneath the overriding continent is removed during subduction and replaced by newly formed crust, which generates the radiogenic hafnium signature when remelted. For the internal orogenic system, the lower crust and lithospheric mantle is instead eventually replaced by more continental lithosphere from a collided continental fragment. Our suggested model provides a simple basis for unravelling the global geodynamic evolution of the ancient Earth. resent-day orogens of contrasting character can be reduced to which probably began by the Early Ordovician12, and the Early two types on Earth, dominantly accretionary or dominantly Paleozoic accretionary orogens in the easternmost Altaids of Pcollisional, because only the latter are associated with Wilson Asia13.
    [Show full text]
  • Tectonic Features of the Precambrian Belt Basin and Their Influence on Post-Belt Structures
    ... Tectonic Features of the .., Precambrian Belt Basin and Their Influence on Post-Belt Structures GEOLOGICAL SURVEY PROFESSIONAL PAPER 866 · Tectonic Features of the · Precambrian Belt Basin and Their Influence on Post-Belt Structures By JACK E. HARRISON, ALLAN B. GRIGGS, and JOHN D. WELLS GEOLOGICAL SURVEY PROFESSIONAL PAPER X66 U N IT ED STATES G 0 V ERN M EN T P R I NT I N G 0 F F I C E, \VAS H I N G T 0 N 19 7 4 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress catalog-card No. 74-600111 ) For sale by the Superintendent of Documents, U.S. GO\·ernment Printing Office 'Vashington, D.C. 20402 - Price 65 cents (paper cO\·er) Stock Number 2401-02554 CONTENTS Page Page Abstract................................................. 1 Phanerozoic events-Continued Introduction . 1 Late Mesozoic through early Tertiary-Continued Genesis and filling of the Belt basin . 1 Idaho batholith ................................. 7 Is the Belt basin an aulacogen? . 5 Boulder batholith ............................... 8 Precambrian Z events . 5 Northern Montana disturbed belt ................. 8 Phanerozoic events . 5 Tectonics along the Lewis and Clark line .............. 9 Paleozoic through early Mesozoic . 6 Late Cenozoic block faults ........................... 13 Late Mesozoic through early Tertiary . 6 Conclusions ............................................. 13 Kootenay arc and mobile belt . 6 References cited ......................................... 14 ILLUSTRATIONS Page FIGURES 1-4. Maps: 1. Principal basins of sedimentation along the U.S.-Canadian Cordillera during Precambrian Y time (1,600-800 m.y. ago) ............................................................................................... 2 2. Principal tectonic elements of the Belt basin reentrant as inferred from the sedimentation record ............
    [Show full text]
  • Post-Collisional Formation of the Alpine Foreland Rifts
    Annales Societatis Geologorum Poloniae (1991) vol. 61:37 - 59 PL ISSN 0208-9068 POST-COLLISIONAL FORMATION OF THE ALPINE FORELAND RIFTS E. Craig Jowett Department of Earth Sciences, University of Waterloo, Waterloo, Ontario Canada N2L 3G1 Jowett, E. C., 1991. Post-collisional formation of the Alpine foreland rifts. Ann. Soc. Geol. Polon., 6 1 :37-59. Abstract: A series of Cenozoic rift zones with bimodal volcanic rocks form a discontinuous arc parallel to the Alpine mountain chain in the foreland region of Europe from France to Czechos­ lovakia. The characteristics of these continental rifts include: crustal thinning to 70-90% of the regional thickness, in cases with corresponding lithospheric thinning; alkali basalt or bimodal igneous suites; normal block faulting; high heat flow and hydrothermal activity; regional uplift; and immature continental to marine sedimentary rocks in hydrologically closed basins. Preceding the rifting was the complex Alpine continental collision orogeny which is characterized by: crustal shortening; thrusting and folding; limited calc-alkaline igneous activity; high pressure metamorphism; and marine flysch and continental molasse deposits in the foreland region. Evidence for the direction of subduction in the central area is inconclusive, although northerly subduction likely occurred in the eastern and western Tethys. The rift events distinctly post-date the thrusthing and shortening periods of the orogeny, making “impactogen” models of formation untenable. However, the succession of tectonic and igneous events, the geophysical characteristics, and the timing and location of these rifts are very similar to those of the Late Cenozoic Basin and Range province in the western USA and the Early Permian Rotliegendes troughs in Central Europe.
    [Show full text]
  • Sedimentological Constraints on the Initial Uplift of the West Bogda Mountains in Mid-Permian
    www.nature.com/scientificreports OPEN Sedimentological constraints on the initial uplift of the West Bogda Mountains in Mid-Permian Received: 14 August 2017 Jian Wang1,2, Ying-chang Cao1,2, Xin-tong Wang1, Ke-yu Liu1,3, Zhu-kun Wang1 & Qi-song Xu1 Accepted: 9 January 2018 The Late Paleozoic is considered to be an important stage in the evolution of the Central Asian Orogenic Published: xx xx xxxx Belt (CAOB). The Bogda Mountains, a northeastern branch of the Tianshan Mountains, record the complete Paleozoic history of the Tianshan orogenic belt. The tectonic and sedimentary evolution of the west Bogda area and the timing of initial uplift of the West Bogda Mountains were investigated based on detailed sedimentological study of outcrops, including lithology, sedimentary structures, rock and isotopic compositions and paleocurrent directions. At the end of the Early Permian, the West Bogda Trough was closed and an island arc was formed. The sedimentary and subsidence center of the Middle Permian inherited that of the Early Permian. The west Bogda area became an inherited catchment area, and developed a widespread shallow, deep and then shallow lacustrine succession during the Mid- Permian. At the end of the Mid-Permian, strong intracontinental collision caused the initial uplift of the West Bogda Mountains. Sedimentological evidence further confrmed that the West Bogda Mountains was a rift basin in the Carboniferous-Early Permian, and subsequently entered the Late Paleozoic large- scale intracontinental orogeny in the region. The Central Asia Orogenic Belt (CAOB) is the largest accretionary orogen on Earth, which was formed by the amalgamation of multiple micro-continents, island arcs and accretionary wedges1–5.
    [Show full text]
  • THE GROWTH of SHEEP MOUNTAIN ANTICLINE: COMPARISON of FIELD DATA and NUMERICAL MODELS Nicolas Bellahsen and Patricia E
    THE GROWTH OF SHEEP MOUNTAIN ANTICLINE: COMPARISON OF FIELD DATA AND NUMERICAL MODELS Nicolas Bellahsen and Patricia E. Fiore Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 e-mail: [email protected] be explained by this deformed basement cover interface Abstract and does not require that the underlying fault to be listric. In his kinematic model of a basement involved We study the vertical, compression parallel joint compressive structure, Narr (1994) assumes that the set that formed at Sheep Mountain Anticline during the basement can undergo significant deformations. Casas early Laramide orogeny, prior to the associated folding et al. (2003), in their analysis of field data, show that a event. Field data indicate that this joint set has a basement thrust sheet can undergo a significant heterogeneous distribution over the fold. It is much less penetrative deformation, as it passes over a flat-ramp numerous in the forelimb than in the hinge and geometry (fault-bend fold). Bump (2003) also discussed backlimb, and in fact is absent in many of the forelimb how, in several cases, the basement rocks must be field measurement sites. Using 3D elastic numerical deformed by the fault-propagation fold process. models, we show that early slip along an underlying It is noteworthy that basement deformation often is thrust fault would have locally perturbed the neglected in kinematic (Erslev, 1991; McConnell, surrounding stress field, inducing a compression that 1994), analogue (Sanford, 1959; Friedman et al., 1980), would inhibit joint formation above the fault tip. and numerical models. This can be attributed partially Relating the absence of joints in the forelimb to this to the fact that an understanding of how internal stress perturbation, we are able to constrain the deformation is delocalized in the basement is lacking.
    [Show full text]
  • Pan-African Orogeny 1
    Encyclopedia 0f Geology (2004), vol. 1, Elsevier, Amsterdam AFRICA/Pan-African Orogeny 1 Contents Pan-African Orogeny North African Phanerozoic Rift Valley Within the Pan-African domains, two broad types of Pan-African Orogeny orogenic or mobile belts can be distinguished. One type consists predominantly of Neoproterozoic supracrustal and magmatic assemblages, many of juvenile (mantle- A Kröner, Universität Mainz, Mainz, Germany R J Stern, University of Texas-Dallas, Richardson derived) origin, with structural and metamorphic his- TX, USA tories that are similar to those in Phanerozoic collision and accretion belts. These belts expose upper to middle O 2005, Elsevier Ltd. All Rights Reserved. crustal levels and contain diagnostic features such as ophiolites, subduction- or collision-related granitoids, lntroduction island-arc or passive continental margin assemblages as well as exotic terranes that permit reconstruction of The term 'Pan-African' was coined by WQ Kennedy in their evolution in Phanerozoic-style plate tectonic scen- 1964 on the basis of an assessment of available Rb-Sr arios. Such belts include the Arabian-Nubian shield of and K-Ar ages in Africa. The Pan-African was inter- Arabia and north-east Africa (Figure 2), the Damara- preted as a tectono-thermal event, some 500 Ma ago, Kaoko-Gariep Belt and Lufilian Arc of south-central during which a number of mobile belts formed, sur- and south-western Africa, the West Congo Belt of rounding older cratons. The concept was then extended Angola and Congo Republic, the Trans-Sahara Belt of to the Gondwana continents (Figure 1) although West Africa, and the Rokelide and Mauretanian belts regional names were proposed such as Brasiliano along the western Part of the West African Craton for South America, Adelaidean for Australia, and (Figure 1).
    [Show full text]
  • Deepwater Fold-And-Thrust Belt Along New Caledonia's Western Margin
    Deepwater fold-and-thrust belt along New Caledonia’s western margin: relation to post-obduction vertical motions J. Collot, M. Patriat, S. Etienne, P. Rouillard, F. Soetaert, C Juan, B. Marcaillou, Giulia Palazzin, Camille Clerc, P. Maurizot, et al. To cite this version: J. Collot, M. Patriat, S. Etienne, P. Rouillard, F. Soetaert, et al.. Deepwater fold-and-thrust belt along New Caledonia’s western margin: relation to post-obduction vertical motions. Tectonics, American Geophysical Union (AGU), 2017, 36, pp.2108-2122. 10.1002/2017TC004542. insu-01614136 HAL Id: insu-01614136 https://hal-insu.archives-ouvertes.fr/insu-01614136 Submitted on 24 Oct 2017 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. PUBLICATIONS Tectonics RESEARCH ARTICLE Deepwater Fold-and-Thrust Belt Along New 10.1002/2017TC004542 Caledonia’s Western Margin: Relation Key Points: to Post-obduction Vertical Motions • New deepwater fold-and-thrust belt discovered off New Caledonia’s J. Collot1 , M. Patriat1,2 , S. Etienne1,3 , P. Rouillard1,3,4, F. Soetaert1,2, C. Juan1, western margin 5 6 7 1 1,3 1,3 1 • Origin of the deepwater B. Marcaillou , G. Palazzin , C.
    [Show full text]
  • Collision Orogeny
    Downloaded from http://sp.lyellcollection.org/ by guest on October 6, 2021 PROCESSES OF COLLISION OROGENY Downloaded from http://sp.lyellcollection.org/ by guest on October 6, 2021 Downloaded from http://sp.lyellcollection.org/ by guest on October 6, 2021 Shortening of continental lithosphere: the neotectonics of Eastern Anatolia a young collision zone J.F. Dewey, M.R. Hempton, W.S.F. Kidd, F. Saroglu & A.M.C. ~eng6r SUMMARY: We use the tectonics of Eastern Anatolia to exemplify many of the different aspects of collision tectonics, namely the formation of plateaux, thrust belts, foreland flexures, widespread foreland/hinterland deformation zones and orogenic collapse/distension zones. Eastern Anatolia is a 2 km high plateau bounded to the S by the southward-verging Bitlis Thrust Zone and to the N by the Pontide/Minor Caucasus Zone. It has developed as the surface expression of a zone of progressively thickening crust beginning about 12 Ma in the medial Miocene and has resulted from the squeezing and shortening of Eastern Anatolia between the Arabian and European Plates following the Serravallian demise of the last oceanic or quasi- oceanic tract between Arabia and Eurasia. Thickening of the crust to about 52 km has been accompanied by major strike-slip faulting on the rightqateral N Anatolian Transform Fault (NATF) and the left-lateral E Anatolian Transform Fault (EATF) which approximately bound an Anatolian Wedge that is being driven westwards to override the oceanic lithosphere of the Mediterranean along subduction zones from Cephalonia to Crete, and Rhodes to Cyprus. This neotectonic regime began about 12 Ma in Late Serravallian times with uplift from wide- spread littoral/neritic marine conditions to open seasonal wooded savanna with coiluvial, fluvial and limnic environments, and the deposition of the thick Tortonian Kythrean Flysch in the Eastern Mediterranean.
    [Show full text]
  • Tectonic Evolution of the Southern Laurentian Grenville Orogenic Belt
    Tectonic evolution of the southern Laurentian Grenville orogenic belt Sharon Mosher* Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78712 ABSTRACT bordered on its eastern margin by the north- with northwest-directed transport are observed northeast–trending Grenville orogen, which re- along the belt (Davidson, 1986) with crustal im- The Grenville orogenic belt along the south- cords both intracratonic and collisional orogen- brication resulting in burial to depths in excess ern margin of Laurentia records more than esis (Davidson, 1986; Rivers et al., 1989). In of 45 km (Indares, 1993). This orogenic belt 300 m.y. of orogenic activity culminating in Labrador, crustal shortening telescoped older continues northward into Greenland and Scandi- arc-continent and continent-continent colli- basement rocks in an intracratonic setting as a navia, and scattered inliers in the Appalachians sion ca. 1150–1120 Ma. Exposures in Texas result of continent-continent collision farther suggest a lateral continuity along the length of provide a unique profile across the Grenville outboard (Connelly et al., 1995). In Ontario, a the Appalachian orogen (Fig. 1). Recent plate re- orogen from the orogen core to the cratonal long history of island-arc and allochthonous ter- constructions interpret South America as the col- margin. In the Llano uplift of central Texas, rane accretion culminated in continent-continent liding continent (Dalziel, 1991, 1992, 1997, ca. 1360–1232 Ma upper amphibolite–lower collision (Davidson, 1986; Gower et al., 1990; Hoffman, 1991; Moores, 1991; Unrug, 1996) granulite facies, polydeformed supracrustal Culotta et al., 1990). Deep crustal shear zones adjacent to this eastern margin of Laurentia, and plutonic rocks represent the core of the collisional orogen.
    [Show full text]
  • Zagros Orogeny
    Zagros orogeny: a subduction-dominated process Philippe Agard, Jafar Omrani, Laurent Jolivet, Hubert Whitechurch, Bruno Vrielynck, Wim Spakman, Patrick Monié, Bertrand Meyer, R. Wortel To cite this version: Philippe Agard, Jafar Omrani, Laurent Jolivet, Hubert Whitechurch, Bruno Vrielynck, et al.. Zagros orogeny: a subduction-dominated process. Geological Magazine, Cambridge University Press (CUP), 2011, 148 (5-6), pp.692-725. 10.1017/S001675681100046X. insu-00616582 HAL Id: insu-00616582 https://hal-insu.archives-ouvertes.fr/insu-00616582 Submitted on 4 Feb 2013 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. Geol. Mag. 148 (5–6), 2011, pp. 692–725. c Cambridge University Press 2011 692 doi:10.1017/S001675681100046X Zagros orogeny: a subduction-dominated process P. AGARD∗†, J. OMRANI‡, L. JOLIVET§, H. WHITECHURCH¶, B. VRIELYNCK∗, W. SPAKMAN,P.MONIÉ#,B.MEYER∗ &R. WORTEL ∗ISTEP, UMR 7193, Université Pierre et Marie Curie – Université Paris 6, 4 pl. Jussieu, Paris 75005, France ‡Geological Survey of Iran, Tehran, Iran §ISTO, Université d’Orléans, France ¶EOST, Strasbourg, France Geosciences, Utrecht University, The Netherlands #Géosciences Montpellier, UMR 5573, Université Montpellier 2, France (Received 17 January 2011; accepted 3 May 2011; first published online 5 July 2011) Abstract – This paper presents a synthetic view of the geodynamic evolution of the Zagros orogen within the frame of the Arabia–Eurasia collision.
    [Show full text]
  • Stress Fields Around Dislocations the Crystal Lattice in the Vicinity of a Dislocation Is Distorted (Or Strained)
    Stress Fields Around Dislocations The crystal lattice in the vicinity of a dislocation is distorted (or strained). The stresses that accompanied the strains can be calculated by elasticity theory beginning from a radial distance about 5b, or ~ 15 Å from the axis of the dislocation. The dislocation core is universally ignored in calculating the consequences of the stresses around dislocations. The stress field around a dislocation is responsible for several important interactions with the environment. These include: 1. An applied shear stress on the slip plane exerts a force on the dislocation line, which responds by moving or changing shape. 2. Interaction of the stress fields of dislocations in close proximity to one another results in forces on both which are either repulsive or attractive. 3. Edge dislocations attract and collect interstitial impurity atoms dispersed in the lattice. This phenomenon is especially important for carbon in iron alloys. Screw Dislocation Assume that the material is an elastic continuous and a perfect crystal of cylindrical shape of length L and radius r. Now, introduce a screw dislocation along AB. The Burger’s vector is parallel to the dislocation line ζ . Now let us, unwrap the surface of the cylinder into the plane of the paper b A 2πr GL b γ = = tanθ 2πr G bG τ = Gγ = B 2πr 2 Then, the strain energy per unit volume is: τ× γ b G Strain energy = = 2π 82r 2 We have identified the strain at any point with cylindrical coordinates (r,θ,z) τ τZθ θZ B r B θ r θ Slip plane z Slip plane A z G A b G τ=G γ = The elastic energy associated with an element is its θZ 2πr energy per unit volume times its volume.
    [Show full text]
  • Evidence for Controlled Deformation During Laramide Orogeny
    Geologic structure of the northern margin of the Chihuahua trough 43 BOLETÍN DE LA SOCIEDAD GEOLÓGICA MEXICANA D GEOL DA Ó VOLUMEN 60, NÚM. 1, 2008, P. 43-69 E G I I C C O A S 1904 M 2004 . C EX . ICANA A C i e n A ñ o s Geologic structure of the northern margin of the Chihuahua trough: Evidence for controlled deformation during Laramide Orogeny Dana Carciumaru1,*, Roberto Ortega2 1 Orbis Consultores en Geología y Geofísica, Mexico, D.F, Mexico. 2 Centro de Investigación Científi ca y de Educación Superior de Ensenada (CICESE) Unidad La Paz, Mirafl ores 334, Fracc.Bella Vista, La Paz, BCS, 23050, Mexico. *[email protected] Abstract In this article we studied the northern part of the Laramide foreland of the Chihuahua Trough. The purpose of this work is twofold; fi rst we studied whether the deformation involves or not the basement along crustal faults (thin- or thick- skinned deformation), and second, we studied the nature of the principal shortening directions in the Chihuahua Trough. In this region, style of deformation changes from motion on moderate to low angle thrust and reverse faults within the interior of the basin to basement involved reverse faulting on the adjacent platform. Shortening directions estimated from the geometry of folds and faults and inversion of fault slip data indicate that both basement involved structures and faults within the basin record a similar Laramide deformation style. Map scale relationships indicate that motion on high angle basement involved thrusts post dates low angle thrusting. This is consistent with the two sets of faults forming during a single progressive deformation with in - sequence - thrusting migrating out of the basin onto the platform.
    [Show full text]