How and When Plume Zonation Appeared During the 132&Thinsp
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C"""- Signature of Author, Joint Program in Oceanography Massachusetts Institute of Technology/ Woods Hole Oceanographic Institution
GLOBAL ISOTOPIC SIGNATURES OF OCEANIC ISLAND BASALTS by LYNN A. OSCHMANN A.B. BRYN MAWR COLLEGE (1989) SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN OCEANOGRAPHY at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY and the WOODS HOLE OCEANOGRAPHIC INSTITUTION August 1991 @Lynn A. Oschmann 1991 The author hereby grants to MIT, WHOI, and the U.S. Government permission to reproduce and distribute copies of this thesis in whole or in part. %/7_ ) C"""- Signature of Author, Joint Program in Oceanography Massachusetts Institute of Technology/ Woods Hole Oceanographic Institution Certified by - 1% Dr. Stanley R. Hart Senior Scientist, Woods Hole Oceanographic Institution Thesis Supervisor Accepted by Dr. G. Pat Lohman Chairman, Joint Committee for Geology and Geophysics, Massachusetts Institute of Technology/ Woods Hole Oceanographic Institution MVIr 2 GLOBAL ISOTOPIC SIGNATURES OF OCEANIC ISLAND BASALTS by LYNN A. OSCHMANN Submitted to the Department of Earth, Atmospheric and Planetary Sciences Massachusetts Institute of Technology and the Department of Geology and Geophysics Woods Hole Oceanographic Institution August 9, 1991 in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN OCEANOGRAPHY ABSTRACT Sr, Nd and Pb isotopic analyses of 477 samples representing 30 islands or island groups, 3 seamounts or seamount chains, 2 oceanic ridges and 1 oceanic plateau [for a total of 36 geographic features] are compiled to form a comprehensive oceanic island basalt [OIB] data set. These samples are supplemented by 90 selected mid-ocean ridge basalt [MORB] samples to give adequate representation to MORB as an oceanic basalt end-member. This comprehensive data set is used to infer information about the Earth's mantle. -
Vulnerable Marine Ecosystems – Processes and Practices in the High Seas Vulnerable Marine Ecosystems Processes and Practices in the High Seas
ISSN 2070-7010 FAO 595 FISHERIES AND AQUACULTURE TECHNICAL PAPER 595 Vulnerable marine ecosystems – Processes and practices in the high seas Vulnerable marine ecosystems Processes and practices in the high seas This publication, Vulnerable Marine Ecosystems: processes and practices in the high seas, provides regional fisheries management bodies, States, and other interested parties with a summary of existing regional measures to protect vulnerable marine ecosystems from significant adverse impacts caused by deep-sea fisheries using bottom contact gears in the high seas. This publication compiles and summarizes information on the processes and practices of the regional fishery management bodies, with mandates to manage deep-sea fisheries in the high seas, to protect vulnerable marine ecosystems. ISBN 978-92-5-109340-5 ISSN 2070-7010 FAO 9 789251 093405 I5952E/2/03.17 Cover photo credits: Photo descriptions clockwise from top-left: Acanthagorgia spp., Paragorgia arborea, Vase sponges (images courtesy of Fisheries and Oceans, Canada); and Callogorgia spp. (image courtesy of Kirsty Kemp, the Zoological Society of London). FAO FISHERIES AND Vulnerable marine ecosystems AQUACULTURE TECHNICAL Processes and practices in the high seas PAPER 595 Edited by Anthony Thompson FAO Consultant Rome, Italy Jessica Sanders Fisheries Officer FAO Fisheries and Aquaculture Department Rome, Italy Merete Tandstad Fisheries Resources Officer FAO Fisheries and Aquaculture Department Rome, Italy Fabio Carocci Fishery Information Assistant FAO Fisheries and Aquaculture Department Rome, Italy and Jessica Fuller FAO Consultant Rome, Italy FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome, 2016 The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. -
20. a Seismic Reflection Study of the Rio Grande Rise1
20. A SEISMIC REFLECTION STUDY OF THE RIO GRANDE RISE1 Peter F. Barker, Department of Geological Sciences, Birmingham University, Birmingham B15 2TT, England Richard T. Buffler,2 Galveston Marine Geophysics Laboratory, University of Texas at Austin, Galveston, Texas and Luiz A. Gamboa,3 Lamont-Doherty Geological Observatory, Palisades, New York ABSTRACT Seismic reflection profiles have been interpreted in combination with deep-sea drilling data to examine the sedimen- tary evolution of the Rio Grande Rise. Restricted and unevenly distributed seismic reflection coverage (particularly multichannel) and limited well control confined most of our interest to the northern flank of the main western elevated block of the Rise, near to DSDP Site 516. The basement of much of the Rise above approximately 3000 m present depth has the "dipping reflector" character of some continental margins, produced by interbedded lavas and sediments formed directly above sea level. The overlying Late Cretaceous and early Tertiary sediments are mainly pelagic, but lap onto originally subaerial base- ment in places. A major middle Eocene tectonic event (involving uplift, tilting, faulting, and probably local volcanism) resulted in subaerial erosion, submarine slumping, and turbidite deposition. Submarine slides associated with the early stages of this tectonism probably caused the chaotic midsection reflector sequence identified with the middle Eocene Unit 4 at Site 516. Middle Eocene tectonism also produced the central graben of the Rise, which contains rotated fault blocks, and the broad guyot between the graben and Site 516. The guyot shows thick sequences dipping away from the graben and truncated, presumably by subaerial erosion. Prograded biogenic debris, swept off the top by bottom cur- rents after resubmergence in the Oligocene, extended the guyot's top farther. -
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. -
Three Hotspot Reference Frames – Shallow and Lithospherically Controlled – Reflect “Mesoplates”, a Plate Tectonics Heuristic
Three Hotspot Reference Frames – Shallow and Lithospherically Controlled – Reflect “Mesoplates”, a Plate Tectonics Heuristic Submitted to: Penrose Conference- Plume IV: Beyond the Plume Hypothesis, Iceland, 2003 May 1, 2003 (Not to be circulated beyond the organizing committee) Rex H. Pilger, Jr. Landmark Graphics Corporation 1805 Shea Center Drive Suite 400 Highlands Ranch, Colorado 80129 United States of America Extended Abstract The hotspot reference frames of the Atlantic-Indian Ocean and the Pacific Ocean are kinematically distinct. Relative motion of the two reference frames in the Late Cretaceous and Early Tertiary corresponds with motion of the American plates in the Atlantic-Indian Ocean frame, suggesting a lithospheric control on the reference frames. A third reference frame, beneath Iceland and Eurasia, cannot be satisfactorily quantified at this time, but the inability to fit Iceland in either of the two other reference frames implies its existence. The two hotspot reference frames can be shown to be relatively shallow. Hotspot traces, cross- grain oceanic gravity lineations of the Pacific Ocean reflect a shallow hotspot reference frame. Intracontinental stress fields of North America correspond with the Atlantic-Indian Ocean reference frame, also reflecting a shallow reference frame. Pacific evidence: Minor hotspot island-seamount chains of the Pacific plate (Figure 1) are controlled by lithospheric structure. Almost every such trace appears to originate on the south side of a fracture zone separating older lithosphere on the north from younger lithosphere on the south. Assuming that older plate is thicker than younger plate, passage of a fracture zone separating lithosphere of contrasting age and thickness over the asthenosphere and deeper mesosphere would result in isostatic rise of affected portions of both layers. -
Experimental Partitioning of Rb, Cs, Sr, and Ba Between Alkali Feldspar and Peraluminous Melt
American Mineralogist, Volume 81, pages 719-734,1996 Experimental partitioning of Rb, Cs, Sr, and Ba between alkali feldspar and peraluminous melt JONATHAN IcENHOWER AND DAVID LoNDON School of Geology and Geophysics, University of Oklahoma, 100 East Boyd Street, SEC 810, Norman, Oklahoma 73019, U.S.A. ABSTRACT Hydrous partial melting experiments performed between 650 and 750 °C at 200 MPa (H20) on synthetic metapelite compositions (quartz + albite + muscovite + biotite min- eral mixtures) doped with Ba, Sr, Rb, and Cs yielded alkali feldspar crystals with a wide range of compositions in equilibrium at their rims with peraluminous melt. Measured partition coefficients for normally trace lithophile elements between feldspar and melt [D(M)FSP/gl,M = Ba, Sr, Rb, Cs] do not depend on either temperature or bulk composition of melt for the compositions studied. Values of D(Sr)FSP/glare between 10 and 14 and appear to be independent of the albite and orthoclase contents of the feldspar crystals. In contrast, values of D(Ba)FSP/gland D(Rb)FsP/glare strongly dependent on the orthoclase content of feldspar, relationships that can be expressed by the following linear equations: D(Ba)FSP/gl= 0.07 + 0.25(orthoclase) and D(Rb)FsP/gl= 0.03 + 0.0 1(orthoclase), where orthoclase is in mole percent. These equations reproduce the range of previously reported values for D(Ba) and D(Rb) determined on natural and synthetic samples. A single par- tition coefficient for Cs was also determined at D(CS)Fsp/gl= 0.13. These data can be used in conjunction with recently published partition coefficients for muscovite, biotite, and plagioclase feldspars (Blundy and Wood 1991; Icenhower and London 1995) to model quantitatively the trace element signatures of peraluminous mag- mas during anatexis and crystallization. -
Using Rare Earth Elements to Model Silicate Melting and Crystallization
Using Rare Earth Elements to Model Silicate Melting and Crystallization The Rare Earth Elements (REE) The lanthanide series is formed by filling of 4f orbitals, and its constituents are commonly termed the rare earth elements (REE). The common valence state is +3 for all REE over a wide range of oxygen fugacity; Ce+4 can occur in highly oxidized environments at the earth's surface, and Eu+2 in reducing environments in the crust and mantle. The rare earth elements are lithophile elements (low electronegativities lead to the formation of highly ionic bonds), which substitute into many silicates and phosphates. Ionic radii of the lanthanides decreases with increasing atomic number from La to Lu, the lanthanide contraction… Because of their high charge and large radii, the rare earth elements are usually relatively incompatible in silicate minerals. However, due to the lanthanide contraction, the heavier rare earths are smaller and thus can "fit" within some lattice sites (although there must be charge compensation for the 3+ valence), so incompatibility decreases with increasing Z. Class Discussion #1: What mineral lattice sites could host the heavy rare earth elements? What about Eu2+? REE diagrams If we plot the concentrations of the rare earth elements as a group on a diagram of abundance versus atomic number, we observe two cosmochemical phenomena: 1) the decrease in absolute abundance with increasing atomic number; 2) the “even-odd effect” in relative abundances (higher abundances of even atomic number elements). Because these cosmochemical effects are common to all terrestrial rocks, we would rather ignore them in order to accentuate more subtle variations in absolute and relative concentrations of REE between samples. -
Trace Elements in Igneous Petrology
Trace Elements in igneous petrology •Abundances of trace elements are used to test petrogenetic hypotheses •No universal definition of TE: Concentration usually less than 100 ppm, often < 10 ppm •Useful trace elements: a)First transition series: Sc Ti V Cr Mn Fe Co Ni Cu Zn Ti and Fe are usually major elements, Cr, Mn, and Ni are minor elements Progressive filling of 3d orbitals Variable crystal field stabilization Commonly multivalent (Sc3, Ti4,3, V2,3,4,5, Cr2,3,6, Mn2,3, Fe2,3, Co2, Ni2 b) Lanthanides (REE): La Ce Pr Nd (Pm) Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Light REE and heavy REE (Y behaves like a HREE) normalization factors (chondrites) 1 Eu2+ REE Chondritic abundances Lanthanide Contraction odd vs. even abundances 1.2 .8 .6 1.1 .4 Eu3+ Ionic radius (Å) Ionic radius Abundance (ppm) .2 Based on 8-fold 1.0 coordination 0 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu (c) Large Ion Lithophile Elements (LILE): may also be partitioned into fluid phase Alkalis: K Rb Cs (monovalent) Alkaline earths: Ba Sr (divalent) Actinides: U, Th, Ra, Pa (multiple valency) (d) High field strength elements (HFSE): small, highly-charged ions Zr, Hf (4 valent) Nb, Ta (4 and 5 valent) (e) Chalcophile elements: Cu, Zn, Pb, Ag, Hg, PGE, (Fe, Co, Ni) (f) Siderophile elements: Fe, Ni, Co, Ge, P, Ga, Au (PGE)… • Decoupled from major elements: lack of stoichiometric constraints (not strictly true) • Goldschmidt’s Rules • Generalities: Incompatible elements are elements that tend to be excluded from common minerals (olivines, pyroxenes, garnets, feldspars, oxides…) in equilibrium with a melt, i.e., they have low D values. -
High Seas Deep-Sea Fishing Grounds in the South East Atlantic Ocean 51
50 Worldwide review of bottom fisheries in the high seas MAP 1 High seas deep-sea fishing grounds in the South East Atlantic Ocean 51 South East Atlantic Ocean FAO Statistical Area 47 (and a portion of 34) GEOGRAPHIC DESCRIPTION OF THE REGION Angola, Namibia and South Africa are the three countries bordering the South East Atlantic Region (FAO Statistical Area 47) along the African coast. This region extends from the Central Atlantic in the north at 6°S to the Southern Ocean in the south at 50°S. The western limit of the South East Atlantic is the 20°W meridian, which means that the southern Mid-Atlantic Ridge is within the region, at around 15°W, and extends over the entire region from north to south. Other important bottom topographic features in this region are the Walvis Ridge and the Valdivia Bank, joining the exclusive economic zone (EEZ) of Tristan da Cunha on the northern part of the Namibian continental shelf at around 18°S, and in the southern part, the Meteor Rise and the Agulhas Ridge. These are the areas largely targeted in the deep-sea bottom fisheries in the region, together with associated or isolated seamounts areas such as Ewing and Molloy Seamounts, Vema Seamount and those in SEAFO Subdivision A1 (SEAFO, 2007a). It is important to note that in the South East Atlantic, the continental shelf along the coasts does not extend beyond the EEZs of the coastal states. MANAGEMENT REGIME APPLICABLE TO DEEP-SEA BOTTOM FISHERIES IN THE HIGH SEAS Regional Fisheries Management Organization/Arrangement The South East Atlantic Fisheries Organisation (SEAFO) was established in 2003 with the entry into force of the Convention on the conservation and management of fisheries resources in the South East Atlantic Ocean. -
The Geodynamic Development of the Rio Grande Rise and Walvis Ridge, Central South Atlantic Ocean, from Crustal Thickness Mapping
Geophysical Research Abstracts Vol. 21, EGU2019-11012, 2019 EGU General Assembly 2019 © Author(s) 2019. CC Attribution 4.0 license. The Geodynamic Development of the Rio Grande Rise and Walvis Ridge, Central South Atlantic Ocean, from Crustal Thickness Mapping Michelle Graça (1,3), Nick Kusznir (2), and Natasha Stanton (3) (1) Geological Survey of Brazil - CPRM, 404, Pasteur Avenue, Urca, Rio de Janeiro, Brazil, (2) Department of Earth & Ocean Sciences, University of Liverpool, Liverpool L69 3BX, UK, (3) Faculty of Oceanography, Rio de Janeiro State University, Rio de Janeiro, Brazil The recent report of the discovery from submersible sampling of continental material of Proterozoic age on the Rio Grande Rise suggests that the formation processes of the Rio Grande Rise and Walvis Ridge in the southern S. Atlantic need to be re-examined. Existing proposed formation processes involve ocean ridge – mantle plume interaction or simply excess ‘on-ridge’ magmatism. We use gravity anomaly inversion to map crustal thickness for the central South Atlantic area encompassing the Rio Grande Rise, Walvis Ridge and adjacent South American and African rifted continental margins. We show that the Rio Grande Rise consists of three distinct bodies of anomalously thick crust (Western, Central and Eastern) separated by normal thickness oceanic crust. The Central Rio Grande Rise forms a large elliptical body with maximum crustal thickness of 25 km and Walvis Ridge also has a maximum crustal thickness of 25 km but has a narrower and more linear geometry. We use plate reconstructions to restore maps of crustal thickness and magnetic anomaly to Early Cretaceous times to examine the development of the Rio Grande Rise and Walvis Ridge. -
Aula 4 – Tipos Crustais Tipos Crustais Continentais E Oceânicos
14/09/2020 Aula 4 – Tipos Crustais Introdução Crosta e Litosfera, Astenosfera Crosta Oceânica e Tipos crustais oceânicos Crosta Continental e Tipos crustais continentais Tipos crustais Continentais e Oceânicos A interação divergente é o berço fundamental da litosfera oceânica: não forma cadeias de montanhas, mas forma a cadeia desenhada pela crista meso- oceânica por mais de 60.000km lineares do interior dos oceanos. A interação convergente leva inicialmente à formação dos arcos vulcânicos e magmáticos (que é praticamente o berço da litosfera continental) e posteriormente à colisão (que é praticamente o fechamento do Ciclo de Wilson, o desparecimento da litosfera oceânica). 1 14/09/2020 Curva hipsométrica da terra A área de superfície total da terra (A) é de 510 × 106 km2. Mostra a elevação em função da área cumulativa: 29% da superfície terrestre encontra-se acima do nível do mar; os mais profundos oceanos e montanhas mais altas uma pequena fração da A. A > parte das regiões de plataforma continental coincide com margens passivas, constituídas por crosta continental estirada. Brito Neves, 1995. Tipos crustais circunstâncias geométrico-estruturais da face da Terra (continentais ou oceânicos); Característica: transitoriedade passar do Tempo Geológico e como forma de dissipar o calor do interior da Terra. Todo tipo crustal adveio de um outro ou de dois outros, e será transformado em outro ou outros com o tempo, toda esta dança expressando a perda de calor do interior para o exterior da Terra. Nenhum tipo crustal é eterno; mais "duráveis" (e.g. velhos Crátons de de "ultra-longa duração"); tipos de curta duração, muitas modificações e rápida evolução potencial (como as bacias de antearco). -
Implications of Subduction Rehydration for Earth's Deep Water
Implications of Subduction Rehydration for Earth’s Deep Water Cycle Lars Rüpke Physics of Geological Processes, University of Oslo, Oslo, Norway, and SFB 574 Volatiles and Fluids in Subduction Zones, Kiel, Germany Jason Phipps Morgan Cornell University, Ithaca, New York, USA and SFB 574 Volatiles and Fluids in Subduction Zones, Kiel, Germany Jacqueline Eaby Dixon RSMAS/MGG, University of Miami, Miami, Florida, USA The “standard model” for the genesis of the oceans is that they are exhalations from Earth’s deep interior continually rinsed through surface rocks by the global hydrologic cycle. No general consensus exists, however, on the water distribution within the deeper mantle of the Earth. Recently Dixon et al. [2002] estimated water concentrations for some of the major mantle components and concluded that the most primitive (FOZO) are significantly wetter than the recycling associated EM or HIMU mantle components and the even drier depleted mantle source that melts to form MORB. These findings are in striking agreement with the results of numerical modeling of the global water cycle that are presented here. We find that the Dixon et al. [2002] results are consistent with a global water cycle model in which the oceans have formed by efficient outgassing of the mantle. Present-day depleted mantle will contain a small volume fraction of more primitive wet mantle in addition to drier recycling related enriched components. This scenario is consis- tent with the observation that hotspots with a FOZO-component in their source will make wetter basalts than hotspots whose mantle sources contain a larger fraction of EM and HIMU components.