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The North-Subducting Rheic Ocean During the Devonian: Consequences for the Rhenohercynian Ore Sites
Published in "International Journal of Earth Sciences 106(7): 2279–2296, 2017" which should be cited to refer to this work. The north-subducting Rheic Ocean during the Devonian: consequences for the Rhenohercynian ore sites Jürgen F. von Raumer1 · Heinz-Dieter Nesbor2 · Gérard M. Stampfli3 Abstract Base metal mining in the Rhenohercynian Zone activated Early Devonian growth faults. Hydrothermal brines has a long history. Middle-Upper Devonian to Lower Car- equilibrated with the basement and overlying Middle-Upper boniferous sediment-hosted massive sulfide deposits Devonian detrital deposits forming the SHMS deposits in the (SHMS), volcanic-hosted massive sulfide deposits (VHMS) southern part of the Pyrite Belt, in the Rhenish Massif and and Lahn-Dill-type iron, and base metal ores occur at sev- in the Harz areas. Volcanic-hosted massive sulfide deposits eral sites in the Rhenohercynian Zone that stretches from the (VHMS) formed in the more eastern localities of the Rheno- South Portuguese Zone, through the Lizard area, the Rhen- hercynian domain. In contrast, since the Tournaisian period ish Massif and the Harz Mountain to the Moravo-Silesian of ore formation, dominant pull-apart triggered magmatic Zone of SW Bohemia. During Devonian to Early Carbonif- emplacement of acidic rocks, and their metasomatic replace- erous times, the Rhenohercynian Zone is seen as an evolv- ment in the apical zones of felsic domes and sediments in ing rift system developed on subsiding shelf areas of the the northern part of the Iberian Pyrite belt, thus changing the Old Red continent. A reappraisal of the geotectonic setting general conditions of ore precipitation. -
The Geology of England – Critical Examples of Earth History – an Overview
The Geology of England – critical examples of Earth history – an overview Mark A. Woods*, Jonathan R. Lee British Geological Survey, Environmental Science Centre, Keyworth, Nottingham, NG12 5GG *Corresponding Author: Mark A. Woods, email: [email protected] Abstract Over the past one billion years, England has experienced a remarkable geological journey. At times it has formed part of ancient volcanic island arcs, mountain ranges and arid deserts; lain beneath deep oceans, shallow tropical seas, extensive coal swamps and vast ice sheets; been inhabited by the earliest complex life forms, dinosaurs, and finally, witnessed the evolution of humans to a level where they now utilise and change the natural environment to meet their societal and economic needs. Evidence of this journey is recorded in the landscape and the rocks and sediments beneath our feet, and this article provides an overview of these events and the themed contributions to this Special Issue of Proceedings of the Geologists’ Association, which focuses on ‘The Geology of England – critical examples of Earth History’. Rather than being a stratigraphic account of English geology, this paper and the Special Issue attempts to place the Geology of England within the broader context of key ‘shifts’ and ‘tipping points’ that have occurred during Earth History. 1. Introduction England, together with the wider British Isles, is blessed with huge diversity of geology, reflected by the variety of natural landscapes and abundant geological resources that have underpinned economic growth during and since the Industrial Revolution. Industrialisation provided a practical impetus for better understanding the nature and pattern of the geological record, reflected by the publication in 1815 of the first geological map of Britain by William Smith (Winchester, 2001), and in 1835 by the founding of a national geological survey. -
Mapping a Hidden Terrane Boundary in the Mantle Lithosphere with Lamprophyres
ARTICLE DOI: 10.1038/s41467-018-06253-7 OPEN Mapping a hidden terrane boundary in the mantle lithosphere with lamprophyres Arjan H. Dijkstra 1 & Callum Hatch1,2 Lamprophyres represent hydrous alkaline mantle melts that are a unique source of information about the composition of continental lithosphere. Throughout southwest Britain, post-Variscan lamprophyres are (ultra)potassic with strong incompatible element enrich- 1234567890():,; ments. Here we show that they form two distinct groups in terms of their Sr and Nd isotopic compositions, occurring on either side of a postulated, hitherto unrecognized terrane boundary. Lamprophyres emplaced north of the boundary fall on the mantle array with εNd −1 to +1.6. Those south of the boundary are enriched in radiogenic Sr, have initial εNd values of −0.3 to −3.5, and are isotopically indistinguishable from similar-aged lamprophyres in Armorican massifs in Europe. We conclude that an Armorican terrane was juxtaposed against Avalonia well before the closure of the Variscan oceans and the formation of Pangea. The giant Cornubian Tin-Tungsten Ore Province and associated batholith can be accounted for by the fertility of Armorican lower crust and mantle lithosphere. 1 School of Geography, Earth and Environmental Sciences, Plymouth University, Plymouth PL4 8AA, UK. 2 Department of Core Research Laboratories, Natural History Museum, Cromwell Road, London, SW7 5BD UK. Correspondence and requests for materials should be addressed to A.H.D. (email: [email protected]) NATURE COMMUNICATIONS | (2018) 9:3770 | DOI: 10.1038/s41467-018-06253-7 | www.nature.com/naturecommunications 1 ARTICLE NATURE COMMUNICATIONS | DOI: 10.1038/s41467-018-06253-7 ilson’s cycle1 of the opening and closing of ocean typically form 10 cm to m-wide dykes and other types of minor Wbasins throughout Earth history was based on the intrusions cutting across Variscan foliations in Carboniferous and similarity of Early Palaeozoic faunal assemblages in Devonian rocks. -
The Iberian Variscan Orogen
CHAPTER 1 THE IBERIAN VARISCAN OROGEN Aerial view of the tectonic repetition of limestone beds in the Láncara Formation, Primajas duplex structure of the Esla thrust (photo by J.L. Alonso) Martínez Catalán, J.R. Aller, J. Alonso, J.L. Bastida, F. Rocks of Upper Proterozoic to Carboniferous age - forming the Variscan or Hercynian orogen - crop out widely in the western part of the Iberian Peninsula, in what is called the Iberian or Hesperian Massif. These deformed rocks, often metamorphosed and intruded by different types of granitoids, were witness to the great mountain range formed in the late Paleozoic, basically in the Late Devonian and Carboniferous (between 370 and 290 million years ago), by the convergence and collision of two major continents: Laurasia and Gondwana. The Iberian Massif constitutes a geological framework of global interest. It is unique due to the continuity of its exposures and because it displays excellent records allowing the analysis of continental crust features, the tectonic, metamorphic and magmatic evolution of orogens, and therefore provides enormously relevant data about the lithospheric dynamics during the latest Precambrian and the Paleozoic. The Variscan orogen forms the basement of the Figure 1. Scheme showing the position of the Iberian Iberian Peninsula and of most of western and central Peninsula in relation to the Appalachians and the Europe. A crustal basement is the result of an orog- Caledonian and Variscan belts. Modified from eny, that is, the consequence of a deep remobilization Neuman and Max (1989). of the continental crust caused by the convergence of plates, and is associated to uplift and the creation of relief. -
Paleozoic Evolution of Pre-Variscan Terranes: from Gondwana to the Variscan Collision
Geological Society of America Special Paper 364 2002 Paleozoic evolution of pre-Variscan terranes: From Gondwana to the Variscan collision Gérard M. Stamp×i Institut de Géologie et Paléontologie, Université de Lausanne, CH-1015 Lausanne, Switzerland Jürgen F. von Raumer Institut de Minéralogie et Pétrographie, Université de Fribourg, CH-1700 Fribourg, Switzerland Gilles D. Borel Institut de Géologie et Paléontologie, Université de Lausanne, CH-1015 Lausanne, Switzerland ABSTRACT The well-known Variscan basement areas of Europe contain relic terranes with a pre-Variscan evolution testifying to their peri-Gondwanan origin (e.g., relics of Neo- proterozoic volcanic arcs, and subsequent stages of accretionary wedges, backarc rift- ing, and spreading). The evolution of these terranes was guided by the diachronous subduction of the proto-Tethys oceanic ridge under different segments of the Gond- wana margin. This subduction triggered the emplacement of magmatic bodies and the formation of backarc rifts, some of which became major oceanic realms (Rheic, paleo- Tethys). Consequently, the drifting of Avalonia was followed, after the Silurian and a short Ordovician orogenic event, by the drifting of Armorica and Alpine domains, ac- companied by the opening of the paleo-Tethys. The slab rollback of the Rheic ocean is viewed as the major mechanism for the drifting of the European Variscan terranes. This, in turn, generated a large slab pull force responsible for the opening of major rift zones within the passive Eurasian margin. Therefore, the µrst Middle Devonian Variscan orogenic event is viewed as the result of a collision between terranes detached from Gondwana (grouped as the Hun superterrane) and terranes detached from Eurasia. -
The Complex Tectonic Evolution of the Malvern Region: Crustal Accretion Followed by Multiple Extensional and Compressional Reactivation
The complex tectonic evolution of the Malvern region: crustal accretion followed by multiple extensional and compressional reactivation Tim Pharaoh British Geological Survey, Keyworth, Nottingham, NG12 5GG ([email protected]) Abstract, The Malvern Hills include some of the oldest rocks in southern Britain, dated by U-Pb zircon analysis to c. 680Ma. They reflect calc-alkaline arc magmatic activity along a margin of the Rodinia palaeocontinent, hints of which are provided by inherited zircon grains as old as 1600Ma. Metamorphic recrystallisation under upper greenschist/amphibolite facies conditions occurred from c. 650–600Ma. Subsequently, rifting of the magmatic arc (c.f. the modern western Pacific) at c. 565Ma led to the formation of a small oceanic marginal basin, evidenced by basaltic pillow lavas and tuffs of the Warren House Formation, and Kempsey Formation equivalents beneath the Worcester Graben. By early Cambrian time this juvenile crust had stabilised sufficiently for thick quartz arenite-dominated sequences to accumulate, followed by mudstones in mid- to late-Cambrian time. In earliest Ordovician time, subsidence accelerated in a rift basin east of the Malverns, but was terminated by accretion of the Monian Composite Terrane to the Gondwana margin. Rifting led to a microcontinental flake (‘East Avalonia’) breaking away, eventually to impact with Laurentian terranes on the other margin of the Iapetus Ocean in early Silurian time. Minor inversion of the floor of the Worcester Graben might have occurred during the Acadian (early Devonian) deformation phase, but more significantly, during the Variscan (end Carboniferous) Orogeny, when a ‘Rocky Mountain Front’-type uplift was generated opposite a pinch-point within the orogen. -
A Landscape Fashioned by Geology
64751 SNH SW Cvr_5mm:cover 14/1/09 10:00 Page 1 Southwest Scotland: A landscape fashioned by geology From south Ayrshire and the Firth of Clyde across Dumfries and Galloway to the Solway Firth and northeastwards into Lanarkshire, a variety of attractive landscapes reflects the contrasts in the underlying rocks. The area’s peaceful, rural tranquillity belies its geological roots, which reveal a 500-million-year history of volcanic eruptions, continents in collision, and immense changes in climate. Vestiges of a long-vanished ocean SOUTHWEST are preserved at Ballantrae and the rolling hills of the Southern Uplands are constructed from the piled-up sediment scraped from an ancient sea floor. Younger rocks show that the Solway shoreline was once tropical, whilst huge sand dunes of an arid desert now underlie Dumfries. Today’s landscape has been created by aeons of uplift, weathering and erosion. Most recently, over the last 2 million years, the scenery of Southwest Scotland was moulded by massive ice sheets which finally melted away about 11,500 years ago. SCOTLAND SOUTHWEST A LANDSCAPE FASHIONED BY GEOLOGY I have a close personal interest in the geology of Southwest Scotland as it gave me my name. It comes of course from the town of Moffat, which is only a contraction of Moor Foot, which nestles near the head of a green valley, surrounded by hills and high moorland. But thank God something so prosaic finds itself in the midst of so SCOTLAND: much geological drama. What this excellent book highlights is that Southwest Scotland is the consequence of an epic collision. -
Ediacaran–Middle Paleozoic Oceanic Voyage of Avalonia from Baltica Via Gondwana to Laurentia Paleomagnetic, Faunal and Geological Constraints J
Document generated on 09/29/2021 6:04 a.m. Geoscience Canada Journal of the Geological Association of Canada Journal de l’Association Géologique du Canada Ediacaran–Middle Paleozoic Oceanic Voyage of Avalonia from Baltica via Gondwana to Laurentia Paleomagnetic, Faunal and Geological Constraints J. Duncan Keppie and D. Fraser Keppie Volume 41, Number 1, 2014 Article abstract Current Ediacaran–Cambrian, paleogeographic reconstructions place Avalonia, URI: https://id.erudit.org/iderudit/1023627ar Carolinia and Ganderia (Greater Avalonia) at high paleolatitudes off northwestern Gondwana (NW Africa and/or Amazonia), and locate NW See table of contents Gondwana at either high or low paleolatitudes. All of these reconstructions are incompatible with 550 Ma Avalonian paleomagnetic data, which indicate a paleolatitude of 20–30ºS for Greater Avalonia and oriented with the present- Publisher(s) day southeast margin on the northwest side. Ediacaran, Cambrian and Early Ordovician fauna in Avalonia are mainly endemic, which suggests that Greater The Geological Association of Canada Avalonia was an island microcontinent. Except for the degree of Ediacaran deformation, the Neoproterozoic geological records of mildly deformed ISSN Greater Avalonia and the intensely deformed Bolshezemel block in the Timanian orogen into eastern Baltica raise the possibility that they were 0315-0941 (print) originally along strike from one another, passing from an island 1911-4850 (digital) microcontinent to an arc-continent collisional zone, respectively. Such a location and orientation is consistent with: (i) Ediacaran (580–550 Ma) Explore this journal ridge-trench collision leading to transform motion along the backarc basin; (ii) the reversed, ocean-to-continent polarity of the Ediacaran cratonic island arc recorded in Greater Avalonia; (iii) derivation of 1–2 Ga and 760–590 Ma detrital Cite this article zircon grains in Greater Avalonia from Baltica and the Bolshezemel block (NE Timanides); and (iv) the similarity of 840–1760 Ma TDM model ages from Keppie, J. -
A Seismic Model for Moho and Crustal Structure in Europe, Greenland, and the North Atlantic Region☆
Tectonophysics 609 (2013) 97–153 Contents lists available at ScienceDirect Tectonophysics journal homepage: www.elsevier.com/locate/tecto Review Article EUNAseis: A seismic model for Moho and crustal structure in Europe, Greenland, and the North Atlantic region☆ Irina M. Artemieva ⁎, Hans Thybo IGN, University of Copenhagen, Denmark article info abstract Article history: We present a new digital crustal model for Moho depth and crustal structure in Europe, Greenland, Iceland, Received 27 November 2012 Svalbard, European Arctic shelf, and the North Atlantic Ocean (72W–62E, 30N–84N). Our compilation is based Received in revised form 18 July 2013 on digitization of original seismic profiles and Receiver Functions from ca. 650 publications which provides a Accepted 4 August 2013 dense regional data coverage. Exclusion of non-seismic data allows application of the database to potential Available online 15 August 2013 field modeling. EUNAseis model includes Vp velocity and thickness of five crustal layers, including the sedimen- tary cover, and Pn velocity. For each parameter we discuss uncertainties associated with theoretical limitations, Keywords: Moho regional data quality, and interpolation. Crustal thickness By analyzing regional trends in crustal structure and links to tectonic evolution illustrated by a new tectonic map, Crystalline crust we conclude that: (1) Each tectonic setting shows significant variation in depth to Moho and crustal structure, Sedimentary cover essentially controlled by the age of latest tectono-thermal processes; (2) Published global averages of crustal pa- Pn velocity rameters are outside of observed ranges for any tectonic setting in Europe; (3) Variation of Vp with depth in the Crustal evolution sedimentary cover does not follow commonly accepted trends; (4) The thickness ratio between upper-middle (Vp b 6.8 km/s) and lower (Vp N 6.8 km/s) crystalline crust is indicative of crustal origin: oceanic, transitional, platform, or extended crust; (5) Continental rifting generally thins the upper-middle crust significantly without changing Vp. -
Supercontinent Reconstruction the Palaeomagnetically Viable, Long
Geological Society, London, Special Publications The palaeomagnetically viable, long-lived and all-inclusive Rodinia supercontinent reconstruction David A. D. Evans Geological Society, London, Special Publications 2009; v. 327; p. 371-404 doi:10.1144/SP327.16 Email alerting click here to receive free email alerts when new articles cite this service article Permission click here to seek permission to re-use all or part of this article request Subscribe click here to subscribe to Geological Society, London, Special Publications or the Lyell Collection Notes Downloaded by on 21 December 2009 © 2009 Geological Society of London The palaeomagnetically viable, long-lived and all-inclusive Rodinia supercontinent reconstruction DAVID A. D. EVANS Department of Geology & Geophysics, Yale University, New Haven, CT 06520-8109, USA (e-mail: [email protected]) Abstract: Palaeomagnetic apparent polar wander (APW) paths from the world’s cratons at 1300–700 Ma can constrain the palaeogeographic possibilities for a long-lived and all-inclusive Rodinia supercontinent. Laurentia’s APW path is the most complete and forms the basis for super- position by other cratons’ APW paths to identify possible durations of those cratons’ inclusion in Rodinia, and also to generate reconstructions that are constrained both in latitude and longitude relative to Laurentia. Baltica reconstructs adjacent to the SE margin of Greenland, in a standard and geographically ‘upright’ position, between c. 1050 and 600 Ma. Australia reconstructs adja- cent to the pre-Caspian margin of Baltica, geographically ‘inverted’ such that cratonic portions of Queensland are juxtaposed with that margin via collision at c. 1100 Ma. Arctic North America reconstructs opposite to the CONgo þ Sa˜o Francisco craton at its DAmaride–Lufilian margin (the ‘ANACONDA’ fit) throughout the interval 1235–755 Ma according to palaeomag- netic poles of those ages from both cratons, and the reconstruction was probably established during the c. -
The Ordovician History of the Iapetus Ocean in Britain
Journal of the Geological Society, London, Vol. 148, 1991, pp. 423-425, 3 figs. Printed in Northern Ireland SHORT PAPER al. 1990), from which palaeomagnetic data indicate high southerly latitudes (Perroud & Van der Voo 1985; Perroud The Ordovician history of the Iapetus et al. 1986). Therefore, although several palaeogeographic Ocean in Britain: new palaeomagnetic reconstructions depict S Britain as a peri-Gondwanan block constraints in early Ordovician time (Pickering et al. 1988; Scotese & McKerrow 1990), nopalaeomagnetic data have been T. H. TORSVIK' & A. TRENCH^ available to quantify its palaeo-position. Similarly, palaeo- Department of Earth Sciences, University of magnetic data have been insufficient to discriminate whether Oxford, Oxford, OX1 3PR, UK S Britain (part of EasternAvalonia; Soper et al. 1987; 'Present address: Geological Survey of Norway, McKerrow1988) formed a constituent of the Armorican P.B. 3006 Lade N-7002 Trondheim, Norway plate (Armorican and Iberian Massifs: Van der Voo 1979; 2Present address: Dept of Geology, University of Perroud et al. 1984) during the Ordovician period. Western Australia, Nedlands, Perth, WA6009, To addressthese uncertainties, 15 siteswere sampled within a sequence of late Tremadoc-early Arenig andesitic Australia lavas and volcaniclastic sediments at Treffgarne, Dyfed, SW Wales (Traynor 1988). This sequence dips on average 30" to thenorth. Low-grade metamorphism(Oliver 1988) and New late Tremadoc-edy Arenig palaeomagnetic results from SW tectonismis most likely Acadian (Woodcock et al. 1988), Wales imply that S Britain (part of Eastern Avalonia) occupied a although Hercyniandeformation cannot be excluded southerly latitude of c. 60"s in early Ordovician times. When com- (Hancock et al. 1981). -
Caledonian-Appalachian Orogen Palaeomagnetic Constraints on The
Downloaded from http://sp.lyellcollection.org/ at Columbia University on January 17, 2012 Geological Society, London, Special Publications Palaeomagnetic constraints on the evolution of the Caledonian-Appalachian orogen J. C. Briden, D. V. Kent, P. L. Lapointe, J. L. Roy, R. A. Livermore, A. G. Smith, M. K. Seguin, R. Van der Voo and D. R. Watts Geological Society, London, Special Publications 1988, v.38; p35-48. doi: 10.1144/GSL.SP.1988.038.01.03 Email alerting click here to receive free e-mail alerts when service new articles cite this article Permission click here to seek permission to re-use all or request part of this article Subscribe click here to subscribe to Geological Society, London, Special Publications or the Lyell Collection Notes © The Geological Society of London 2012 Downloaded from http://sp.lyellcollection.org/ at Columbia University on January 17, 2012 Palaeomagnetic constraints on the evolution of the Caledonian- Appalachian orogen J. C. Briden, D. V. Kent, P. L. Lapointe, R. A. Livermore, J. L. Roy, M. K. Seguin, A. G. Smith, R. Van der Voo & D. R. Watts SUMMARY: Late Proterozoic and Palaeozoic (pre-Permian) palaeomagnetic data from all regions involved in, or adjacent to, the Caledonian-Appalachian orogenic belt are reviewed. Between about 1100 and about 800 Ma the Laurentian and Baltic shields were close together, prior to the opening phase of the Caledonian-Appalachian Wilson cycle. The problems of tectonic interpretation of Palaeozoic palaeomagnetic data from within and around the belt derive mostly from differences of typically 10°-20° between the pole positions. These can variously be interpreted in terms of (i) relative displacements between different continents or terranes, (ii) differences in ages of remanence and (iii) aberrations due to inadequacy of data or geomagnetic complexity, and it is not always easy to discriminate between these alternatives.