DOCSLIB.ORG

Implications of the Temporal Distribution of High‐Mg Magmas for Mantle Plume Volcanism Through Time Author(S): Ann E

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Implications of the Temporal Distribution of High‐Mg Magmas for Mantle Plume Volcanism Through Time Author(S): Ann E Implications of the Temporal Distribution of High‐Mg Magmas for Mantle Plume Volcanism through Time Author(s): Ann E. Isley and Dallas H. Abbott Source: The Journal of Geology, Vol. 110, No. 2 (March 2002), pp. 141-158 Published by: University of Chicago Press Stable URL: http://www.jstor.org/stable/10.1086/338553 Accessed: 22-01-2016 15:05 UTC Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://www.jstor.org/page/ info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. University of Chicago Press is collaborating with JSTOR to digitize, preserve and extend access to The Journal of Geology. http://www.jstor.org This content downloaded from 129.236.224.227 on Fri, 22 Jan 2016 15:05:16 UTC All use subject to JSTOR Terms and Conditions Implications of the Temporal Distribution of High-Mg Magmas for Mantle Plume Volcanism through Time Ann E. Isley and Dallas H. Abbott1 Department of Earth Sciences, Oswego State University of New York, Oswego, New York 13126, U.S.A. (e-mail: [email protected]) ABSTRACT We compile a 3.7-b.yr.-long time series of ultramafic and mafic rocks including extrusives and shallow intrusives (dikes and sills). We infer that peaks in the time series represent mantle plume events. Rocks erupted from plumes are becoming more Ti rich through time, and several rock types having 118 wt % MgO are Phanerozoic analogs for komatiites. These include meimechites, ankaramites, and rocks previously called “picrites.” Spectral analysis reveals the time series is driven by periods of ∼800 and ∼273 m.yr. Two 256-m.yr.-long data subsets, one sampling the Archean -.m.yr., respectively. The ∼800-m.yr 4.5 ע and 34.5 3 ע and one sampling the Phanerozoic, are driven by periods of26 long energy may reflect changes in the rate of impacts of extraterrestrial objects, tectonic slab cascades into the mesosphere, or resonance between free-core nutations and those forced by solar torques. We suggest that the 273 m.yr. period reflects the cosmic year. The latter modulates fluctuation in cometary impacts that occur with a 30–35 m.yr. period (Matese et al. 1996). Thus, there may be more than one driving force for mantle plume volcanism, including forces endogenic and exogenic to Earth. Introduction In a recent article, we discussed the temporal dis- mantle plume events because they capture both tribution of Archean and Paleoproterozoic mafic continental and putative oceanic flood basalt se- and ultramafic igneous events and inferred that ep- quences. Although they were once thought to be isodes of substantially increased basic magmatism typical of Archean mid-ocean ridge crust, komati- reflect mantle plume volcanism (Isley and Abbott ites actually had sources a few to several 100ЊC 1999). Since that work, we have compiled a data hotter than the average mantle, even in the Ar- set of the ages of high-Mg volcanic units and high- chean (Abbott et al. 1994; Puchtel et al. 1998b; Mg dikes and sills spanning more than 3.7 Ga of therefore, even Precambrian komatiites are now Earth history. (For brevity’s sake, this data set has generally acknowledged as expressions of mantle been included in The Journal of Geology’s data de- plume volcanism (Campbell et al. 1989; Campbell pository.) In this article, we analyze the time series to evaluate secular changes in the chemistry of and Griffiths 1990). However, the degree to which high-Mg lavas and to determine whether there are all komatiites reflect high mantle temperatures is well-defined periodicites in the data set. This work debatable since komatiites could have formed by may provide insights into the forces that ultimately melting of a hydrous mantle with temperatures drive mantle plume events. only 150ЊC higher at the top of the asthenosphere In our previous work, we investigated four prox- than at present (Gromshei et al. 1990). Some have ies of mantle plume activity: komatiites, continen- argued that komatiites are not necessarily the prod- tal flood basalts, mafic dikes, and layered (ul- ucts of mantle plumes (Burke 1997; De Wit 1998). tra)mafic intrusions (Isley and Abbott 1999). However, the lack of both degassing structures and Komatiites proved particularly robust proxies of porphyritic textures in most komatiites and their chemical and isotopic signatures led Arndt et al. Manuscript received October 31, 2000; accepted August 14, (1998) to conclude that, although some rare ko- 2001. 1 Lamont-Doherty Earth Observatory of Columbia Univer- matiites were hydrous, most were not. We concur sity, Palisades, New York 10964, U.S.A. and maintain that, while komatiites may not be [The Journal of Geology, 2002, volume 110, p. 141–158] ᭧ 2002 by The University of Chicago. All rights reserved. 0022-1376/2002/11002-0002$15.00 141 This content downloaded from 129.236.224.227 on Fri, 22 Jan 2016 15:05:16 UTC All use subject to JSTOR Terms and Conditions 142 A. E. ISLEY AND D. H. ABBOTT perfect recorders of mantle plume activity, they are (2000), and modeled by Sparks (1986) and Jellinek among the most robust indicators available. and Kerr (1999). Rocks with MgO of 10–14 wt % We found other proxies of mantle plume activity whose geochemistries did not dictate admixture of less dynamic (Isley and Abbott 1999). For example, a high-Mg melt with another source were excluded mantle plume events promote mafic dike swarms, from the data set. but not all mafic dike swarms are the result of man- Rocks referred to in this work are described using tle plume volcanism nor are all layered igneous in- the 1989 IUGS classification so that we use the trusions necessarily the result of mantle plume vol- same term that was applied to rocks in the original canism. It may be necessary to cull these data sets studies we cite. We note that the rocks we refer to to obtain clear signals of mantle plume activity. here as “komatiite” and “meimechite” retain that Ernst and Buchan (1997), for example, drew infer- nomenclature in the recent IUGS reclassification ences about plumes by focusing only on giant ra- (Le Bas 2000). However, some of the rocks that were diating dike swarms. previously termed “basaltic komatiite,” “komati- Here, we focus on the geologic record of high-Mg itic basalt,” “picritic basalt,” and “high-Mg basalt” lavas, including komatiites. Most komatiites might now be called “picrite.” Rocks having 118 erupted before the beginning of the Mesoprote- ϩ wt % MgO and 1–2 wt %Na22 O KO , previously rozoic (1.6 Ga). Assessing mantle plume activity labeled picrites, would now be referred to as “mei- from the Mesoproterozoic onward requires a proxy mechites” (Le Bas 2000). or proxies in addition to komatiites. Several other There are several examples of Phanerozoic ko- lithologies are as rich in MgO as komatiites (e.g., matiites in the data set. There is a long-standing meimechites). Because the ratios Mg/Si and Fe/Si conviction that the only Phanerozoic komatiites increase in mafic volcanics as a function of either are those of Gorgona Island (e.g., Kerr et al. 1996). melt-source temperature or degree of melting However, several other sequences have units with (which may also reflect mantle temperature), we an MgO component consistent with komatiitic include other high-Mg rocks in the data set. chemistry. Spinifex texture has been reported for most of these sequences (Buturlinov and Kisil’ Data Set Description 1985; Paraskevopoulos and Economou 1986; Struy- eva 1988; Spadea et al. 1989; Fang and Ma 1994; The Lithologies. The International Union of Geo- Alvarado et al. 1997). logical Sciences (IUGS) recently reclassified high- Many ankaramites from the pre-Cenozoic record Mg rocks (Le Bas 2000). Previously, rocks having have been interpreted as island arc volcanics. These 118 wt % MgO were called “picrites,” “ferropic- ankaramites all are associated with calc-alkaline rites,” “ankaramites,” “komatiites,” or “meime- volcanic sequences. Cenozoic ankaramites com- chites” (using the IUGS recommendations for no- prise some of the volcanic units in the Lesser An- menclature from 1989 and earlier). Rocks with 118 ϩ tilles, Indonesian, Vanuata, and Izu-Bonin arcs wt % MgO andNa22 O KO of 1–2 wt % were called “picrites.” If such rocks were enriched in Fe, (Hawkesworth et al. 1979; Maillet 1982; Foden they were called “ferropicrites” (Gibson et al. 1983; Fukuyama 1983). However, there are many 2000). Ankaramites were a subset of picrites rich more examples of Cenozoic ankaramites associated in titanian augite. Rocks less alkaline than picrites with hotspots and mantle plumes (Isley and Abbott were termed “komatiites” or “meimechites.” Ko- 2000). For example, ankaramites contribute to the ! volcanic extrusives erupting from 120 hotspots, in- matiites had 1wt%TiO2, while meimechites cluding the Jan Mayan, Icelandic, Azores, Trindade, were richer in TiO2. There is a host of lithologies that are compositionally analogous to mixtures of Society, Samoan, and Hawaiian hotspots (Johnson komatiitic, (ferro)picritic, and/or basaltic magmas. et al. 1986; Kennedy et al. 1991; Pegram and Allegre Such rocks include picritic komatiite, basaltic ko- 1992; Stecher 1998; Guest et al. 1999; Fodor and matiite, komatiitic basalt, picritic basalt, and high- Hanan 2000). In this work, we assume that all vol- Mg basalt. The data set includes such mixtures, and canic sequences containing ankaramites but lack- a few of these sequences have units with MgO be- ing dominant associations with calc-alkaline rocks tween 10 and 14 wt %.
Load more

Recommended publications
  • Hikurangi Plateau: Crustal Structure, Rifted Formation, and Gondwana Subduction History
    Article Geochemistry 3 Volume 9, Number 7 Geophysics 3 July 2008 Q07004, doi:10.1029/2007GC001855 GeosystemsG G ISSN: 1525-2027 AN ELECTRONIC JOURNAL OF THE EARTH SCIENCES Published by AGU and the Geochemical Society Click Here for Full Article Hikurangi Plateau: Crustal structure, rifted formation, and Gondwana subduction history Bryan Davy Institute of Geological and Nuclear Sciences, P.O. Box 30368, Lower Hutt, New Zealand ([email protected]) Kaj Hoernle IFM-GEOMAR, Wischhofstraße 1-3, D-24148 Kiel, Germany Reinhard Werner Tethys Geoconsulting GmbH, Wischhofstraße 1-3, D-24148 Kiel, Germany [1] Seismic reflection profiles across the Hikurangi Plateau Large Igneous Province and adjacent margins reveal the faulted volcanic basement and overlying Mesozoic-Cenozoic sedimentary units as well as the structure of the paleoconvergent Gondwana margin at the southern plateau limit. The Hikurangi Plateau crust can be traced 50–100 km southward beneath the Chatham Rise where subduction cessation timing and geometry are interpreted to be variable along the margin. A model fit of the Hikurangi Plateau back against the Manihiki Plateau aligns the Manihiki Scarp with the eastern margin of the Rekohu Embayment. Extensional and rotated block faults which formed during the breakup of the combined Manihiki- Hikurangi plateau are interpreted in seismic sections of the Hikurangi Plateau basement. Guyots and ridge- like seamounts which are widely scattered across the Hikurangi Plateau are interpreted to have formed at 99–89 Ma immediately following Hikurangi Plateau jamming of the Gondwana convergent margin at 100 Ma. Volcanism from this period cannot be separately resolved in the seismic reflection data from basement volcanism; hence seamount formation during Manihiki-Hikurangi Plateau emplacement and breakup (125–120 Ma) cannot be ruled out.
    [Show full text]
  • Geochemistry This
    TORONTOTORONTO Vol. 8, No. 4 April 1998 Call for Papers GSA TODAY — page C1 A Publication of the Geological Society of America Electronic Abstracts Submission — page C3 Antarctic Neogene Landscapes—In the 1998 Registration Refrigerator or in the Deep Freeze? Annual Issue Meeting — June GSA Today Introduction The present Molly F. Miller, Department of Geology, Box 117-B, Vanderbilt Antarctic landscape undergoes very University, Nashville, TN 37235, [email protected] slow environmental change because it is almost entirely covered by a thick, slow-moving ice sheet and thus effectively locked in a Mark C. G. Mabin, Department of Tropical Environmental Studies deep freeze. The ice sheet–landscape system is essentially stable, and Geography, James Cook University, Townsville, Queensland 4811, Australia, [email protected] Antarctic—Introduction continued on p. 2 Atmospheric Transport of Diatoms in the Antarctic Sirius Group: Pliocene Deep Freeze Arjen P. Stroeven, Department of Quaternary Research, Stockholm University, S-106 91 Stockholm, Sweden Lloyd H. Burckle, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964 Johan Kleman, Department of Physical Geography, Stockholm University, S-106, 91 Stockholm, Sweden Michael L. Prentice, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824 INTRODUCTION How did young diatoms (including some with ranges from the Pliocene to the Pleistocene) get into the Sirius Group on the slopes of the Transantarctic Mountains? Dynamicists argue for emplacement by a wet-based ice sheet that advanced across East Antarctica and the Transantarctic Mountains after flooding of interior basins by relatively warm marine waters [2 to 5 °C according to Webb and Harwood (1991)].
    [Show full text]
  • Playing Jigsaw with Large Igneous Provinces a Plate Tectonic
    PUBLICATIONS Geochemistry, Geophysics, Geosystems RESEARCH ARTICLE Playing jigsaw with Large Igneous Provinces—A plate tectonic 10.1002/2015GC006036 reconstruction of Ontong Java Nui, West Pacific Key Points: Katharina Hochmuth1, Karsten Gohl1, and Gabriele Uenzelmann-Neben1 New plate kinematic reconstruction of the western Pacific during the 1Alfred-Wegener-Institut Helmholtz-Zentrum fur€ Polar- und Meeresforschung, Bremerhaven, Germany Cretaceous Detailed breakup scenario of the ‘‘Super’’-Large Igneous Province Abstract The three largest Large Igneous Provinces (LIP) of the western Pacific—Ontong Java, Manihiki, Ontong Java Nui Ontong Java Nui ‘‘Super’’-Large and Hikurangi Plateaus—were emplaced during the Cretaceous Normal Superchron and show strong simi- Igneous Province as result of larities in their geochemistry and petrology. The plate tectonic relationship between those LIPs, herein plume-ridge interaction referred to as Ontong Java Nui, is uncertain, but a joined emplacement was proposed by Taylor (2006). Since this hypothesis is still highly debated and struggles to explain features such as the strong differences Correspondence to: in crustal thickness between the different plateaus, we revisited the joined emplacement of Ontong Java K. Hochmuth, [email protected] Nui in light of new data from the Manihiki Plateau. By evaluating seismic refraction/wide-angle reflection data along with seismic reflection records of the margins of the proposed ‘‘Super’’-LIP, a detailed scenario Citation: for the emplacement and the initial phase of breakup has been developed. The LIP is a result of an interac- Hochmuth, K., K. Gohl, and tion of the arriving plume head with the Phoenix-Pacific spreading ridge in the Early Cretaceous. The G.
    [Show full text]
  • Subsidence and Growth of Pacific Cretaceous Plateaus
    ELSEVIER Earth and Planetary Science Letters 161 (1998) 85±100 Subsidence and growth of Paci®c Cretaceous plateaus Garrett Ito a,Ł, Peter D. Clift b a School of Ocean and Earth Science and Technology, POST 713, University of Hawaii at Manoa, Honolulu, HI 96822, USA b Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA Received 10 November 1997; revised version received 11 May 1998; accepted 4 June 1998 Abstract The Ontong Java, Manihiki, and Shatsky oceanic plateaus are among the Earth's largest igneous provinces and are commonly believed to have erupted rapidly during the surfacing of giant heads of initiating mantle plumes. We investigate this hypothesis by using sediment descriptions of Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) drill cores to constrain plateau subsidence histories which re¯ect mantle thermal and crustal accretionary processes. We ®nd that total plateau subsidence is comparable to that expected of normal sea¯oor but less than predictions of thermal models of hotspot-affected lithosphere. If crustal emplacement was rapid, then uncertainties in paleo-water depths allow for the anomalous subsidence predicted for plumes with only moderate temperature anomalies and volumes, comparable to the sources of modern-day hotspots such as Hawaii and Iceland. Rapid emplacement over a plume head of high temperature and volume, however, is dif®cult to reconcile with the subsidence reconstructions. An alternative possibility that reconciles low subsidence over a high-temperature, high-volume plume source is a scenario in which plateau subsidence is the superposition of (1) subsidence due to the cooling of the plume source, and (2) uplift due to prolonged crustal growth in the form of magmatic underplating.
    [Show full text]
  • Large Igneous Provinces: a Driver of Global Environmental and Biotic Changes, Geophysical Monograph 255, First Edition
    2 Radiometric Constraints on the Timing, Tempo, and Effects of Large Igneous Province Emplacement Jennifer Kasbohm1, Blair Schoene1, and Seth Burgess2 ABSTRACT There is an apparent temporal correlation between large igneous province (LIP) emplacement and global envi- ronmental crises, including mass extinctions. Advances in the precision and accuracy of geochronology in the past decade have significantly improved estimates of the timing and duration of LIP emplacement, mass extinc- tion events, and global climate perturbations, and in general have supported a temporal link between them. In this chapter, we review available geochronology of LIPs and of global extinction or climate events. We begin with an overview of the methodological advances permitting improved precision and accuracy in LIP geochro- nology. We then review the characteristics and geochronology of 12 LIP/event couplets from the past 700 Ma of Earth history, comparing the relative timing of magmatism and global change, and assessing the chronologic support for LIPs playing a causal role in Earth’s climatic and biotic crises. We find that (1) improved geochronol- ogy in the last decade has shown that nearly all well-dated LIPs erupted in < 1 Ma, irrespective of tectonic set- ting; (2) for well-dated LIPs with correspondingly well-dated mass extinctions, the LIPs began several hundred ka prior to a relatively short duration extinction event; and (3) for LIPs with a convincing temporal connection to mass extinctions, there seems to be no single characteristic that makes a LIP deadly. Despite much progress, higher precision geochronology of both eruptive and intrusive LIP events and better chronologies from extinc- tion and climate proxy records will be required to further understand how these catastrophic volcanic events have changed the course of our planet’s surface evolution.
    [Show full text]
  • Ontong Java and Kerguelen Plateaux: Cretaceous Icelands?
    Journal of the Geological Society, London, Vol. 152, 1995, pp. 1047-1052, 4 figs. Printed in Northern Ireland Ontong Java and Kerguelen Plateaux: Cretaceous Icelands? M. F. COFFIN & L.M. GAHAGAN Institute for Geophysics, The University of Texas at Austin, 8701 North Mopac Expressway, Austin, Texas 78759-8397, USA Abstract: Together with Iceland, the two giant oceanic plateaux, Ontong Java in the western Pacific and Kerguelen/Broken Ridge in the Indian Ocean, are accumulations of mafic igneous rock which were not formed by 'normal' seafloor spreading. We compare published geochronological, crustal structure, and subsidence results with tectonic fabric highlighted in new satellite-derived free-air gravity data from the three igneous provinces, and conclude that existing evidence weighs lightly against the Ontong Java and Kerguelen plateaux originating at a seafloor spreading centre. Keywords: Iceland, Ontong Java Plateau, Kerguelen Plateau, plumes, hot spots. The two giant oceanic plateaux, Ontong Java in the western Age constraints Pacific, and Kerguelen in the south-central Indian Ocean (Fig. 1), and Iceland are among the best-studied examples of The vast bulk of crust in the ocean basins is dated using large-scale mafic magmatism not resulting solely from magnetic anomalies created by the interplay between the 'normal' seafloor spreading. Analogues on the continents, seafloor spreading process and the alternating polarity of the continental flood basalts, are demonstrably not created by Earth's magnetic field. Mesozoic and Cenozoic marine seafloor spreading, although controversy persists as to magnetic anomalies, summarized globally by Cande et al. whether or not lithospheric extension must precede their (1989), are most commonly tied to geological time through emplacement.
    [Show full text]
  • Large Igneous Provinces and Mass Extinctions: an Update
    Downloaded from specialpapers.gsapubs.org on April 29, 2015 OLD G The Geological Society of America Special Paper 505 2014 OPEN ACCESS Large igneous provinces and mass extinctions: An update David P.G. Bond* Department of Geography, Environment and Earth Science, University of Hull, Hull HU6 7RX, UK, and Norwegian Polar Institute, Fram Centre, 9296 Tromsø, Norway Paul B. Wignall School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK ABSTRACT The temporal link between mass extinctions and large igneous provinces is well known. Here, we examine this link by focusing on the potential climatic effects of large igneous province eruptions during several extinction crises that show the best correlation with mass volcanism: the Frasnian-Famennian (Late Devonian), Capi- tanian (Middle Permian), end-Permian, end-Triassic, and Toarcian (Early Jurassic) extinctions. It is clear that there is no direct correlation between total volume of lava and extinction magnitude because there is always suffi cient recovery time between individual eruptions to negate any cumulative effect of successive fl ood basalt erup- tions. Instead, the environmental and climatic damage must be attributed to single- pulse gas effusions. It is notable that the best-constrained examples of death-by- volcanism record the main extinction pulse at the onset of (often explosive) volcanism (e.g., the Capitanian, end-Permian, and end-Triassic examples), suggesting that the rapid injection of vast quantities of volcanic gas (CO2 and SO2) is the trigger for a truly major biotic catastrophe. Warming and marine anoxia feature in many extinc- tion scenarios, indicating that the ability of a large igneous province to induce these proximal killers (from CO2 emissions and thermogenic greenhouse gases) is the single most important factor governing its lethality.
    [Show full text]
  • A Mantle Plume Origin for the Palaeoproterozoic Circum-Superior Large Igneous Province
    Accepted Manuscript A Mantle Plume Origin for the Palaeoproterozoic Circum-Superior Large Ig- neous Province T. Jake R. Ciborowski, Matthew J. Minifie, Andrew C. Kerr, Richard E. Ernst, Bob Baragar, Ian L. Millar PII: S0301-9268(16)30449-1 DOI: http://dx.doi.org/10.1016/j.precamres.2017.03.001 Reference: PRECAM 4687 To appear in: Precambrian Research Received Date: 14 October 2016 Revised Date: 24 January 2017 Accepted Date: 5 March 2017 Please cite this article as: T.J.R. Ciborowski, M.J. Minifie, A.C. Kerr, R.E. Ernst, B. Baragar, I.L. Millar, A Mantle Plume Origin for the Palaeoproterozoic Circum-Superior Large Igneous Province, Precambrian Research (2017), doi: http://dx.doi.org/10.1016/j.precamres.2017.03.001 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A Mantle Plume Origin for the Palaeoproterozoic Circum-Superior Large Igneous Province T. Jake R. Ciborowski*1,2, Matthew J. Minifie2, Andrew C. Kerr2, Richard E. Ernst3, Bob Baragar4, Ian L. Millar5 1School of Environment and Technology, University of Brighton, Brighton BN2 4GJ, UK 2School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK 3Department of Earth Sciences, Carleton University, Ottawa, Ontario, Canada K1S 5B6; Faculty of Geology and Geography, Tomsk State University, pr.
    [Show full text]
  • The Timing and Duration of the Karoo Igneous Event, Southern Gondwana
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 102, NO. B8, PAGES 18,127-18,138,AUGUST 10, 1997 The timing and duration of the Karoo igneousevent, southern Gondwana R.A. Duncan,• P.R. Hooper,: J. Rehacek,2J.S. Marsh, 3 andA.R. Duncan4 Abstract.A volcanicevent of immensescale occurred within a relativelyshort period in early Jurassictime overlarge regions of the contiguousGondwana supercontinent. In southernAfrica, associated remnants of thick volcanic successionsof lava flows and extensive dike and sill complexesof similarcomposition have been grouped together as the Karoo Igneous Province. Correlativevolcanic and plutonic rocks occur in Antarcticaand Australia as the FerrarProvince. Thirty-twonew •OAr-•Ar incrementalt•eatmg experiments on feldsparsand whole rocks from Namibia,South Africa andEast Antarctica produce highly resolved ages with a vastmajority at 183+_ 1 Ma anda totalrange of 184 to 179 Ma. Theseare indistinguishablefrom recent,high- resolution40Ar-39Ar and U-Pb agedeterminations reported from the Antarctic portion of the province.Initial Karoo volcanism(Lesotho-type compositions) occurred across the entireSouth African craton.The ubiquitousdistribution of a plexusof generallynonoriented feeder dikes and sillsintruding Precambrian crystalline rocks and Phanerozoic sediments indicates that these magmaspenetrated the cratonover a broadregion. Lithosphere thinning of the continentfollowed the main pulseof igneousactivity, with volcanismfocused in the Lebombo-Nuanetsiregion, near the eventualsplit between Africa andAntarctica. Seafloor spreading and dispersion of eastand west Gondwanafollowed some 10-20 m.y. afterward.The volumeof the combinedKaroo-Ferrar province(•2.5 x 106km3) makes it oneof thelargest continental flood basalt events. The timing of thisevent correlates with a moderatemass extinction (Toarcian-Aalenian), affecting largely marine invertebrates. This extinction event was not as severe as those recorded at the Permian- Triassicor Cretaceous-Tertiaryboundaries associated with the Siberianand Deccan flood basalts events,respectively.
    [Show full text]
  • Provided for Non-Commercial Research and Educational Use. Not for Reproduction, Distribution Or Commercial Use
    Provided for non-commercial research and educational use. Not for reproduction, distribution or commercial use. This article was originally published in the Treatise on Geophysics, published by Elsevier and the attached copy is provided by Elsevier for the author’s benefit and for the benefit of the author’s institution, for non-commercial research and educational use including use in instruction at your institution, posting on a secure network (not accessible to the public) within your institution, and providing a copy to your institution’s administrator. All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites are prohibited. For exceptions, permission may be sought for such use through Elsevier’s permissions site at: http://www.elsevier.com/locate/permissionusematerial Information taken from the copyright line. The Editor-in-Chief is listed as Gerald Schubert and the imprint is Academic Press. Author's personal copy 7.09 Hot Spots and Melting Anomalies G. Ito, University of Hawaii, Honolulu, HI, USA P. E. van Keken, University of Michigan, Ann Arbor, MI, USA ª 2007 Elsevier B.V. All rights reserved. 7.09.1 Introduction 372 7.09.2 Characteristics 373 7.09.2.1 Volcano Chains and Age Progression 373 7.09.2.1.1 Long-lived age-progressive volcanism 373 7.09.2.1.2 Short-lived age-progressive volcanism 381 7.09.2.1.3 No age-progressive volcanism 382 7.09.2.1.4 Continental hot spots 383 7.09.2.1.5 The hot-spot reference frame 386
    [Show full text]
  • Copyrighted Material
    Index Page numbers in italics refer to fi gures; those in bold to tables Acasta gneisses 347 sea fl oor divided into 84 diversity of 288–9 accretionary orogens, structure 287, 309, Aleutian accretionary prism growth latest phase of compression 289 336–42 rate 267 Andean foreland, styles of tectonic active, seismic refl ection profi les 295, 315, Aleutian arc, focal mechanism solutions of shortening 292, 292, 293, 294 340, 342 earthquakes 256, 257 foreland basement thrusts 292, 293 Canadian Cordillera 336–7, 338, 339, 341, Aleutian–Alaska arc, prominent gap in segmentation of foreland 292, 294 376 seismicity 259, 261 thick-skinned and thin-skinned fold and common features of 338, 340, 502 alkaline series, includes shoshonitic thrust belts 292, 293 western North America 336, 337 lavas 271 Andean-type subduction, specifi c types of accretionary prisms 251, 264–9, 270 Alpine Fault, New Zealand 228–30, 338 deposit 417–18 accumulation of sediments including accommodation of oblique slip 244, 245, backarc environment, granite belts with olistostromes 267 246 tin and tungsten 417–18 creation of mélange 268 Breaksea Basin once continuous with stratabound copper sulfi des 417 décollement 264, 266 Dagg Basin 220, 221, 222 Andes, central 301–2 sliding on 267 central segment, weakly/non-partitioned arcuate shape (orocline) 294 deformation front 264 style of transpressional evolution of shortening (model) 300 development of 243, 244 deformation 213, 223 fl at and steep subduction zones 289, 291 and development of forearc basin 267 change in relative plate
    [Show full text]
  • File Report 6226
    Precambrian Research 294 (2017) 189–213 Contents lists available at ScienceDirect Precambrian Research journal homepage: www.elsevier.com/locate/precamres A mantle plume origin for the Palaeoproterozoic Circum-Superior Large Igneous Province ⇑ T. Jake R. Ciborowski a,b, , Matthew J. Minifie b, Andrew C. Kerr b, Richard E. Ernst c,d, Bob Baragar e, Ian L. Millar f a School of Environment and Technology, University of Brighton, Brighton BN2 4GJ, UK b School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK c Department of Earth Sciences, Carleton University, Ottawa, Ontario K1S 5B6, Canada d Faculty of Geology and Geography, Tomsk State University, pr. Lenina 36, Tomsk 634050, Russia e Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada f NERC Isotope Geosciences Laboratory, Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG, UK article info abstract Article history: The Circum-Superior Large Igneous Province (LIP) consists predominantly of ultramafic-mafic lavas and Received 14 October 2016 sills with minor felsic components, distributed as various segments along the margins of the Superior Revised 24 January 2017 Province craton. Ultramafic-mafic dykes and carbonatite complexes of the LIP also intrude the more cen- Accepted 5 March 2017 tral parts of the craton. Most of this magmatism occurred 1880 Ma. Previously a wide range of models Available online 09 March 2017 have been proposed for the different segments of the CSLIP with the upper mantle as the source of mag- matism. New major and trace element and Nd-Hf isotopic data reveal that the segments of the CSLIP can be treated as a single entity formed in a single tectonomagmatic environment.
    [Show full text]