DOCSLIB.ORG

Formation of Sulphides in the Canadian High Arctic Large

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Formation of Sulphides in the Canadian High Arctic Large Examensarbete vid Institutionen för geovetenskaper Degree Project at the Department of Earth Sciences ISSN 1650-6553 Nr 440 Formation of Sulphides in the Canadian High Arctic Large Igneous Province; Testing the Influence of Sedimentary Rocks Bildandet av sulfider i den kanadensiska högarktiska magmatiska provinsen: prövning av sedimentära bergarters inflytande Erika Hagerfors INSTITUTIONEN FÖR GEOVETENSKAPER DEPARTMENT OF EARTH SCIENCES Examensarbete vid Institutionen för geovetenskaper Degree Project at the Department of Earth Sciences ISSN 1650-6553 Nr 440 Formation of Sulphides in the Canadian High Arctic Large Igneous Province; Testing the Influence of Sedimentary Rocks Bildandet av sulfider i den kanadensiska högarktiska magmatiska provinsen: prövning av sedimentära bergarters inflytande Erika Hagerfors ISSN 1650-6553 Copyright © Erika Hagerfors Published at Department of Earth Sciences, Uppsala University (www.geo.uu.se), Uppsala, 2018 Abstract Formation of Sulphides in the Canadian High Arctic Large Igneous Province; Testing the Influence of Sedimentary Rocks Erika Hagerfors Large Igneous Provinces (LIPs) form during short-lived pulses of extensive magmatic activity. LIPs are known for their ability to affect global climate as well as for their Ni-Cu-PGE ore potential. A key factor that controls the intensity of the climate impact of a LIP and its ore potential is the assimilation of volatile-rich sedimentary host rocks. Magmas of the High Arctic Large Igneous Province (HALIP), exposed in the Arctic, intruded volatile-rich black shales, carbonates and evaporites in the Canadian Arctic Islands, offering a great opportunity for studying magma-sediment interaction. The purpose of this study is to test whether assimilation of sedimentary sulphide can promote sulphide immiscibility in magma and thus aid formation of Ni-Cu-PGE ore bodies. This is done by analysing sulphur isotopes in pyrite grains hosted in a HALIP dolerite sill, which was emplaced into black shale, by using Secondary Ion Mass Spectrometry (SIMS). Four dolerite samples are analysed; two coming from the lower contact margin of the sill, one from 60 cm into the sill and one sample from a basaltic vein at the upper contact margin of the sill. A total of 14 pyrite grains (n = 246 individual SIMS spot analyses) were analysed for their sulphur isotope ratios. The results of the SIMS analyses show that all analysed sulphides have highly negative δ34S values ranging from -19.5 to -5.7‰ (average δ34S = -8.2 0.83‰, 2SD), which therefore differ largely from that of the primitive mantle (0 1.8‰). In order to put our four analysed dolerite samples into a broader context, δ34S data of our sulphides are compared with whole-rock δ34S and δ18O data from Hare Fiord shale and dolerite samples. The δ34S values of the sulphide samples from the sill typically trend toward the negative sulphur isotope composition of the sulphides in the surrounding shale, and the shale surrounding the sill experiences a loss of 32S near the contact of the sill. This indicates that sedimentary light sulphur (32S) has been locally incorporated into the sill by the surrounding shale, resulting in negative δ34S values in the magmatic sulphides. Since sulphide immiscibility in the Hare Fiord sill was triggered by assimilation of sulphur from host rock shale, the igneous rocks of the HALIP may be prospective for Ni-Cu-PGE mineralization, though more studies are needed. Furthermore, our results suggest that incorporation of crustal sulphur increased the volatile budget of HALIP magmas, which therefore could have contributed to deterioration of the environmental conditions during the emplacement of the HALIP. Keywords: LIPs, HALIP, SIMS, sulphur isotopes, Ni-Cu-PGE ores, environmental deterioration Degree Project E1 in Earth Science, 1GV025, 30 credits Supervisor: Frances M. Deegan Department of Earth Sciences, Uppsala University, Villavägen 16, SE-752 36 Uppsala (www.geo.uu.se) ISSN 1650-6553, Examensarbete vid Institutionen för geovetenskaper, No. 440, 2018 The whole document is available at www.diva-portal.org Populärvetenskaplig sammanfattning Bildandet av sulfider i den kanadensiska högarktiska magmatiska provinsen: prövning av sedimentära bergarters inflytande Erika Hagerfors Stora magmatiska provinser (på engelska Large Igneous Provinces, LIPs) är vulkaniska event då enorma mängder magma avsätts över en väldigt stor yta under ett, i ett geologiskt perspektiv, kort tidsspann. Dessa stora vulkaniska utbrott har väckt stort intresse då de är samtida med flera av de största massutdöendena i jordens historia, men också för att en viss typ av sulfidmalm rik på nickel, koppar och platinametaller (Ni-Cu-PGE malmer) ofta förekommer i provinsernas magmagångar och magmakammare. En viktig faktor som till stor del avgör en magmatisk provins påverkan på klimatet och potentiella malmförekomster är inkorporering av sedimentära bergarter till magman som, när de hettas upp, kan frigöra gaser rika på svavel och kol. I Kanadas arktiska öar trängde magma tillhörande den högarktiska magmatiska provinsen (HALIP) in i svart skiffer, karbonater och evaporiter, som är sedimentära bergarter rika på flyktiga ämnen. Denna magmatiska provins erbjuder därför stora möjligheter till att studera interaktionen mellan magma och sedimentära bergarter. Syftet med denna studie är att testa om inkorporering av sedimentärt svavel kan främja bildandet av sulfidsmälta i magma och därigenom bidra till bildandet av sulfidmalmer. Detta görs genom att analysera svavelisotoper i sulfidmineral i prover från en magmagång, som trängde in i en skifferformation, tillhörande den högarktiska magmatiska provinsen i norra Kanada. Genom att analysera svavelisotopkvoten (δ34S) i sulfidmineral kan man få information om huruvida svavlet i mineralen är av sedimentärt ursprung (där skiffer generellt har negativa δ34S värden) eller om svavlet har δ34S värden liknande de från manteln (som har δ34S värden runt 0‰), vilket i så fall skulle innebära att magman inte har inkorporerat sedimentärt svavel. Genom att använda masspektrometri av typen SIMS analyseras totalt 14 sulfidmineralkorn (n = 246 individuella SIMS punkter) för deras svavelisotopkvoter. Resultatet av studien visar att alla analyserade sulfidmineral har mycket negativa δ34S värden mellan -19.5 to -5.7‰ (med ett δ34S medelvärde på -8.2 0.83‰, två standardavvikelser). Genom att jämföra våra δ34S värden med δ34S och δ18O värden för andra prover från både magmagången och den omgivande skiffern kunde vi se att δ34S värdena för sulfidmineralen i de yttre delarna av magmagången har liknande negativa värden som den omgivande skiffern, och att δ34S värdena för skiffern närmast magmagången är mer positiva. Detta tyder på att sedimentärt svavel i kontakten mellan magmagången och skiffern har blivit inkorporerat i magman från den omgivande skiffern. Våra resultat tyder därför på att sulfidmineralen i våra prover från magmagången bildades genom assimilering av svavel från den omgivande skiffern. Detta innebär i sin tur att den kanadensiska högarktiska magma provinsen potentiellt kan vara en källa för sulfidmalm, även om ytterligare studier behövs. Dessutom visar våra resultat att inkorporering av sedimentärt svavel förmodligen ökade de vulkaniska gaserna i magman, vilket kan ha bidragit till klimatförändringar relaterade till den vulkaniska aktiviteten av den högarktiska magmatiska provinsen. Nyckelord: LIPs, HALIP, SIMS, svavelisotoper, Ni-Cu-PGE malmer, klimatförändring Examensarbete E1 i geovetenskap, 1GV025, 30 hp Handledare: Frances M. Deegan Institutionen för geovetenskaper, Uppsala universitet, Villavägen 16, 752 36 Uppsala (www.geo.uu.se) ISSN 1650-6553, Examensarbete vid Institutionen för geovetenskaper, Nr 440, 2018 Hela publikationen finns tillgänglig på www.diva-portal.org Table of Contents 1. Introduction ....................................................................................................................................... 1 1.1 Aims and purpose of this study ..................................................................................................... 1 2. Background ........................................................................................................................................ 3 2.1 General characteristics of LIPs ...................................................................................................... 3 2.2 LIP gas emissions and environmental impact ............................................................................... 4 2.2.1 LIP SO2 emissions .................................................................................................................. 5 2.3 Extinction events and LIPs ............................................................................................................ 6 2.3.1 The role of sedimentary basins ............................................................................................... 7 2.4 Ni-Cu-PGE ore deposits and LIPs ............................................................................................... 10 2.5 Geological setting ........................................................................................................................ 11 3. Methods ............................................................................................................................................ 14 3.1 Sampling and sample preparation ............................................................................................... 14 3.2 Electron microprobe ...................................................................................................................
Load more

Recommended publications
  • 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]
  • Midcontinent Rift
    VOL. 97 NO. 18 15 SEP 2016 NORTH AMERICA’S MIDCONTINENT RIFT Augmented Reality for Earth Science Quirky Geoscience Tunes Future of AGU Meetings NEW in Fall 2016 GeoHealth will foster the intersection of Earth science disciplines (Earth processes, climate change, atmospheric and ocean sciences, hydrology, among others), with those of the health sciences, defined broadly (environmental and ecosystem health and services, human and agricultural health, geomedicine, and the impact of natural hazards). Now Accepting Applications for Two Editors in Chief of GeoHealth AGU is launching GeoHealth under Founding Editor Rita R. Colwell. We are seeking applications for two dynamic, well-organized scientists with high editorial standards and strong leadership skills to serve 4-year terms as the editors in chief (EICs) to lead this exciting journal starting in 2017 and beyond. One editor’s main area of focus will be on the geosciences, while the other editor’s main area of focus will be on health. This is an important opportunity to help shape and lead this increasingly important, cross-cutting discipline. The EICs will be the principal architects of the scientific content of the journal. They are active scientists, well-known and well-regarded in their respective discipline. The EICs must be active in soliciting the best science from the best scientists to be published in the journal. Working with the other editors and AGU staff, EICs are the arbiter of the content of the journal. Among other functions, EICs will be responsible for: • Acting as an ambassador to the author/editor/reviewer/scientist community. • Setting the strategy for the journal.
    [Show full text]
  • Project Report: the Siberian Traps and the End-Permian Mass Extinction
    Project Report: The Siberian Traps and the end-Permian mass extinction During the summer of 2008, I spent a month and a half in the field in Arctic Siberia. The eruption of the Siberian Traps ca. 252 million years ago was one of the greatest volcanic cataclysms in the geologic record, and may have been associated with the most severe biotic crisis since the Cambrian radiation. The remnants of this volcanism are exposed along the remote Kotuy River in Siberia (Figure 1). The causes of the end-Permian mass extinction, during which > 90% of marine species vanished forever, remain poorly understood. The apparently coincident eruption of the Siberian Traps large igneous province—which is one of the most voluminous continental flood basalt provinces in Phanerozoic time—has been widely invoked as a potential trigger mechanism for the mass extinction (e.g. Campbell et al., 1992). By traveling to the scene of this ancient eruption in Siberia, I hoped to gather clues to the character and possible environmental consequences of the eruption. I accompanied a small team of scientists from Russia and MIT, including my doctoral advisor (Linda Elkins-Tanton). The Siberian Traps are difficult to reach, and logistics were complex. As shown in Figure Figure 1. White star marks the approximate location of field work in the summer of 2008, along the Kotuy River in Siberia (71°54 N, 102° 7’ E). Figure 2. We used small water craft to navigate the Kotuy River and reach the Siberian Traps volcanic stratigraphy. The cliffs shown here are limestones from the underlying sedimentary sequence.
    [Show full text]
  • New Constraints on the Age, Geochemistry
    New constraints on the age, geochemistry, and environmental impact of High Arctic Large Igneous Province magmatism: Tracing the extension of the Alpha Ridge onto Ellesmere Island, Canada T.V. Naber1,2, S.E. Grasby1,2, J.P. Cuthbertson2, N. Rayner3, and C. Tegner4,† 1 Geological Survey of Canada–Calgary, Natural Resources Canada, Calgary, Canada 2 Department of Geoscience, University of Calgary, Calgary, Canada 3 Geological Survey of Canada–Northern, Natural Resources Canada, Ottawa, Canada 4 Centre of Earth System Petrology, Department of Geoscience, Aarhus University, Aarhus, Denmark ABSTRACT Island, Nunavut, Canada. In contrast, a new Province (HALIP), is one of the least studied U-Pb age for an alkaline syenite at Audhild of all LIPs due to its remote geographic lo- The High Arctic Large Igneous Province Bay is significantly younger at 79.5 ± 0.5 Ma, cation, and with many exposures underlying (HALIP) represents extensive Cretaceous and correlative to alkaline basalts and rhyo- perennial arctic sea ice. Nevertheless, HALIP magmatism throughout the circum-Arctic lites from other locations of northern Elles- eruptions have been commonly invoked as a borderlands and within the Arctic Ocean mere Island (Audhild Bay, Philips Inlet, and potential driver of major Cretaceous Ocean (e.g., the Alpha-Mendeleev Ridge). Recent Yelverton Bay West; 83–73 Ma). We propose anoxic events (OAEs). Refining the age, geo- aeromagnetic data shows anomalies that ex- these volcanic occurrences be referred to col- chemistry, and nature of these volcanic rocks tend from the Alpha Ridge onto the northern lectively as the Audhild Bay alkaline suite becomes critical then to elucidate how they coast of Ellesmere Island, Nunavut, Canada.
    [Show full text]
  • Hot Rocks from Cold Places: a Field, Geochemical and Geochronological Study from the High Arctic Large Igneous P Rovince (HALIP) at Axel Heiberg Island, Nunavut
    ! !"#$%"&'($)*"+$,"-.$/-0&1(2$3$451-.6$71"&81+5&0-$09.$ 71"&8*"9"-":5&0-$;#<.=$)*"+$#81$!5:8$3*&#5&$>0*:1$ ?:91"<($/*"@59&1$A!3>?/B$0#$3C1-$!15D1*:$?(-09.6$ E<90@<#$ $ $ by Cole Girard Kingsbury A thesis submitted to the Faculty of Graduate and Postdoctoral Affairs in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Earth Sciences Ottawa – Carleton Geoscience Centre and Carleton University Ottawa, Ontario © 2016 Cole Girard Kingsbury ! ! !"#$%&'$() ) ) ) ) ) ) ) ) ) ) The geology of the Arctic is greatly influenced by a period of widespread Cretaceous magmatic activity, the High Arctic Large Igneous Province (HALIP). Two major tholeiitic magmatic pulses characterize HALIP: an initial 120 -130 Ma pulse that affected Arctic Canada and formally adjacent regions of Svalbard (Norway) and Franz Josef Land (Russia). In Canada, this pulse fed lava flows of the Isachsen Formation. A second 90-100 Ma pulse that apparently only affected the Canadian side of the Arctic, fed flood basalts of the Strand Fiord Formation. The goal of this thesis is to improve understanding of Arctic magmatism of the enigmatic HALIP through field, remote sensing, geochemical and geochronology investigations of mafic intrusive rocks collected in the South Fiord area of Axel Heiberg Island, Nunavut, and comparison with mafic lavas of the Isachsen and Strand Fiord Formations collected from other localities on the Island. Ground-based and remote sensing observations of the South Fiord area reveal a complex network of mafic sills and mainly SSE-trending dykes. Two new U-Pb baddeleyite ages of 95.18 ± 0.35 Ma and 95.56 ± 0.24 Ma from South Fiord intrusions along with geochemical similarity confirm these intrusions (including the SSE-trending dykes) are feeders for the Strand Fiord Formation lavas.
    [Show full text]
  • Environmental Effects of Large Igneous Province Magmatism: a Siberian Perspective Benjamin A
    20 Environmental effects of large igneous province magmatism: a Siberian perspective benjamin a. black, jean-franc¸ois lamarque, christine shields, linda t. elkins-tanton and jeffrey t. kiehl 20.1 Introduction Even relatively small volcanic eruptions can have significant impacts on global climate. The eruption of El Chichón in 1982 involved only 0.38 km3 of magma (Varekamp et al., 1984); the eruption of Mount Pinatubo in 1993 involved 3–5km3 of magma (Westrich and Gerlach, 1992). Both these eruptions produced statistically significant climate signals lasting months to years. Over Earth’s his- tory, magmatism has occurred on vastly larger scales than those of the Pinatubo and El Chichón eruptions. Super-eruptions often expel thousands of cubic kilo- metres of material; large igneous provinces (LIPs) can encompass millions of cubic kilometres of magma. The environmental impact of such extraordinarily large volcanic events is controversial. In this work, we explore the unique aspects of LIP eruptions (with particular attention to the Siberian Traps), and the significance of these traits for climate and atmospheric chemistry during eruptive episodes. As defined by Bryan and Ernst (2008), LIPs host voluminous (> 100,000 km3) intraplate magmatism where the majority of the magmas are emplaced during short igneous pulses. The close temporal correlation between some LIP eruptions and mass extinction events has been taken as evidence supporting a causal relationship (Courtillot, 1994; Rampino and Stothers, 1988; Wignall, 2001); as geochronological data become increasingly precise, they have continued to indicate that this temporal association may rise above the level of coincidence (Blackburn et al., 2013). Several obstacles obscure the mechanisms that might link LIP magmatism with the degree of global environmental change sufficient to trigger mass extinction.
    [Show full text]
  • Guadalupian, Middle Permian) Mass Extinction in NW Pangea (Borup Fiord, Arctic Canada): a Global Crisis Driven by Volcanism and Anoxia
    The Capitanian (Guadalupian, Middle Permian) mass extinction in NW Pangea (Borup Fiord, Arctic Canada): A global crisis driven by volcanism and anoxia David P.G. Bond1†, Paul B. Wignall2, and Stephen E. Grasby3,4 1Department of Geography, Geology and Environment, University of Hull, Hull, HU6 7RX, UK 2School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK 3Geological Survey of Canada, 3303 33rd Street N.W., Calgary, Alberta, T2L 2A7, Canada 4Department of Geoscience, University of Calgary, 2500 University Drive N.W., Calgary Alberta, T2N 1N4, Canada ABSTRACT ing gun of eruptions in the distant Emeishan 2009; Wignall et al., 2009a, 2009b; Bond et al., large igneous province, which drove high- 2010a, 2010b), making this a mid-Capitanian Until recently, the biotic crisis that oc- latitude anoxia via global warming. Although crisis of short duration, fulfilling the second cri- curred within the Capitanian Stage (Middle the global Capitanian extinction might have terion. Several other marine groups were badly Permian, ca. 262 Ma) was known only from had different regional mechanisms, like the affected in equatorial eastern Tethys Ocean, in- equatorial (Tethyan) latitudes, and its global more famous extinction at the end of the cluding corals, bryozoans, and giant alatocon- extent was poorly resolved. The discovery of Permian, each had its roots in large igneous chid bivalves (e.g., Wang and Sugiyama, 2000; a Boreal Capitanian crisis in Spitsbergen, province volcanism. Weidlich, 2002; Bond et al., 2010a; Chen et al., with losses of similar magnitude to those in 2018). In contrast, pelagic elements of the fauna low latitudes, indicated that the event was INTRODUCTION (ammonoids and conodonts) suffered a later, geographically widespread, but further non- ecologically distinct, extinction crisis in the ear- Tethyan records are needed to confirm this as The Capitanian (Guadalupian Series, Middle liest Lopingian (Huang et al., 2019).
    [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]
  • Evidence for Slab Material Under Greenland and Links to Cretaceous
    PUBLICATIONS Geophysical Research Letters RESEARCH LETTER Evidence for slab material under Greenland 10.1002/2016GL068424 and links to Cretaceous High Key Points: Arctic magmatism • Mid-mantle seismic and gravity anomaly under Greenland identified G. E. Shephard1, R. G. Trønnes1,2, W. Spakman1,3, I. Panet4, and C. Gaina1 • Jurassic-Cretaceous slab linked to paleo-Arctic ocean closure, prior to 1Centre for Earth Evolution and Dynamics (CEED), Department of Geosciences, University of Oslo, Oslo, Norway, 2Natural Amerasia Basin opening 3 • Possible arc-mantle signature in History Museum, University of Oslo, Oslo, Norway, Department of Earth Sciences, Utrecht University, Utrecht, Netherlands, 4 Cretaceous High Arctic LIP volcanism Institut National de l’Information Géographique et Forestière, Laboratoire LAREG, Université Paris Diderot, Paris, France Supporting Information: Abstract Understanding the evolution of extinct ocean basins through time and space demands the • Supporting Information S1 integration of surface kinematics and mantle dynamics. We explore the existence, origin, and implications Correspondence to: of a proposed oceanic slab burial ground under Greenland through a comparison of seismic tomography, G. E. Shephard, slab sinking rates, regional plate reconstructions, and satellite-derived gravity gradients. Our preferred [email protected] interpretation stipulates that anomalous, fast seismic velocities at 1000–1600 km depth imaged in independent global tomographic models, coupled with gravity gradient perturbations, represent paleo-Arctic oceanic slabs Citation: that subducted in the Mesozoic. We suggest a novel connection between slab-related arc mantle and Shephard, G. E., R. G. Trønnes, geochemical signatures in some of the tholeiitic and mildly alkaline magmas of the Cretaceous High Arctic W.
    [Show full text]
  • Wrangellia Flood Basalts in Alaska, Yukon, and British Columbia: Exploring the Growth and Magmatic History of a Late Triassic Oceanic Plateau
    WRANGELLIA FLOOD BASALTS IN ALASKA, YUKON, AND BRITISH COLUMBIA: EXPLORING THE GROWTH AND MAGMATIC HISTORY OF A LATE TRIASSIC OCEANIC PLATEAU By ANDREW R. GREENE A THESIS SUBMITTED iN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Geological Sciences) UNIVERSITY OF BRITISH COLUMBIA (Vancouver) August 2008 ©Andrew R. Greene, 2008 ABSTRACT The Wrangellia flood basalts are parts of an oceanic plateau that formed in the eastern Panthalassic Ocean (ca. 230-225 Ma). The volcanic stratigraphy presently extends >2300 km in British Columbia, Yukon, and Alaska. The field relationships, age, and geochemistry have been examined to provide constraints on the construction of oceanic plateaus, duration of volcanism, source of magmas, and the conditions of melting and magmatic evolution for the volcanic stratigraphy. Wrangellia basalts on Vancouver Island (Karmutsen Formation) form an emergent sequence consisting of basal sills, submarine flows (>3 km), pillow breccia and hyaloclastite (<1 1cm), and subaerial flows (>1.5 km). Karmutsen stratigraphy overlies Devonian to Permian volcanic arc (—‘380-355 Ma) and sedimentary sequences and is overlain by Late Triassic limestone. The Karmutsen basalts are predominantly homogeneous tholeiitic basalt (6-8 wt% MgO); however, the submarine part of the stratigraphy, on northern Vancouver Island, contains picritic pillow basalts (9-20 wt% MgO). Both lava groups have overlapping initial and ENd, indicating a common, ocean island basalt (OIB)-type Pacific mantle source similar to the source of basalts from the Ontong Java and Caribbean Plateaus. The major-element chemistry of picrites indicates extensive melting (23 -27%) of anomalously hot mantle (‘—1500°C), which is consistent with an origin from a mantle plume head.
    [Show full text]
  • Building and Breaking a Large Igneous Province: an Example from The
    PUBLICATIONS Geophysical Research Letters RESEARCH LETTER Building and breaking a large igneous province: An 10.1002/2016GL072420 example from the High Arctic Key Points: Arne Døssing1 , Carmen Gaina2 , and John M. Brozena3 • An early Aptian giant High-Arctic LIP dyke swarm, >2000 km long, formed 1DTU Space, Lyngby, Denmark, 2Centre for Earth Evolution and Dynamics, University of Oslo, Oslo, Norway, 3United States as part of early rifting of the Amerasia Basin Naval Research Laboratory, Washington, District of Columbia, USA • Middle-to-Late Cretaceous HALIP flood basalts subsequently covered the northern Amerasia Basin, centered Abstract The genesis of the Amerasia Basin in the Arctic Ocean has been difficult to discern due to over the proto-Alpha Ridge overprint of the Cretaceous High-Arctic Large Igneous Province (HALIP). Based on detailed analysis of • Latest Cretaceous to middle Paleocene rifting and seafloor bathymetry data, new Arctic magnetic and gravity compilations, and recently published radiometric and spreading within the Makarov Basin seismic data, we present a revised plate kinematic model of the northernmost Amerasia Basin. We show broke apart the proto-Alpha Ridge that the smaller Makarov Basin is formed by rifting and seafloor spreading during the latest Cretaceous (to middle Paleocene). The opening progressively migrated into the Alpha Ridge structure, which was the Supporting Information: focus of Early-to-Middle Cretaceous HALIP formation, causing breakup of the proto-Alpha Ridge into the • Supporting Information S1 present-day Alpha Ridge and Alpha Ridge West Plateau. We propose that breakup of the Makarov Basin was triggered by extension between the North America and Eurasian plates and possibly North Pacific Correspondence to: A.
    [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]