DOCSLIB.ORG

Observational Test of the Global Moving Hot Spot Reference Frame

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Observational Test of the Global Moving Hot Spot Reference Frame RESEARCH LETTER Observational Test of the Global Moving Hot Spot 10.1029/2019GL083663 Reference Frame Key Points: Chengzu Wang1 , Richard G. Gordon1 , Tuo Zhang1 , and Lin Zheng1 • The fit of the Global Moving Hotspot Reference Frame (GMHRF) to 1Department of Earth, Environmental, and Planetary Sciences, William Marsh Rice University, Houston, TX, USA observed geologically young trends of hot spot tracks is evaluated • The data are fit significantly worse (p = 0.005) by the GMHRF than by Abstract The Global Moving Hotspot Reference Frame (GMHRF) has been claimed to fit hot spot tracks fixed hot spots better than the fixed hot spot approximation mainly because the GMHRF predicts ≈1,000 km southward • Either plume conduits do not advect motion through the mantle of the Hawaiian mantle plume over the past 80 Ma. As the GMHRF is passively with mantle flow or the GMHRF mantle velocity field is determined by starting at present and calculating backward in time, it should be most accurate and incorrect reliable for the recent geologic past. Here we compare the fit of the GMHRF and of fixed hot spots to the observed trends of young tracks of hot spots. Surprisingly, we find that the GMHRF fits the data significantly Supporting Information: worse (p = 0.005) than does the fixed hot spot approximation. Thus, either plume conduits are not passively • Supporting Information S1 advected with the mantle flow calculated for the GMHRF or Earth's actual mantle velocity field differs substantially from that calculated for the GMHRF. Correspondence to: Hot spots are the surface manifestations of plumes of hot rock that R. G. Gordon, Plain Language Summary [email protected] rise from deep in the mantle. The tracks of hot spots, such as the Hawaiian island and seamount chain, have been used in two very different ways to estimate the motion of tectonic plates relative to the deep mantle. Originally, it was assumed that the hot spots are “fixed” and do not move relative to each other or Citation: Wang, C., Gordon, R. G., Zhang, T., & relative to the deep mantle. In a later approach, termed the “Global Moving Hotspot Reference Frame” Zheng, L. (2019). Observational test of (GMHRF), the motion of each hot spot relative to the deep mantle was predicted from a calculation of the the global moving hot spot reference global flow of mantle rocks. The latter approach assumes that hot spot motion can be reliably calculated over frame. Geophysical Research Letters, 46, 8031–8038. https://doi.org/10.1029/ the past 130 million years, but does not test its predictions using data from the trends of young hot spot 2019GL083663 chains. We compare the statistical fit of the GMHRF and fixed hot spots using data from the observed trends of young hot spot tracks. Surprisingly, we find that the GMHRF fits the data significantly worse than Received 14 MAY 2019 does the fixed hot spot approximation. Thus, simple fixed hot spots provide the more useful reference frame Accepted 20 JUN 2019 Accepted article online 3 JUL 2019 and some assumptions made to construct the GMHRF are incorrect. Published online 29 JUL 2019 1. Introduction Nearly 50 years ago, Morgan (1971, 1972) proposed that hot spots, sites of intraplate volcanism or excessive volcanism along a plate boundary, are approximately fixed in location and provide a reference frame for determining plate motion relative to the deep mantle. He further proposed that plumes of hot rock rise up from deep in the mantle and are the cause of hot spots at the surface, which had been proposed by Wilson (1963) to explain the origin of chains of seamounts and islands, such as the Hawaiian island chain. Since Morgan's (1971, 1972) work, hot spot tracks have been widely used to estimate plate motion relative to the deep mantle, especially for geologically current plate motions (e.g., Chase, 1978; Gripp & Gordon, 1990, 2002; Minster et al., 1974; Minster & Jordan, 1978; Morgan & Morgan, 2007; Wang et al., 2017, 2018, 2019). How fast individual hot spots move relative to each other and relative to the lower mantle has long been debated. If relative velocities of individual hot spots are low, it would provide support for the usefulness of the fixed hot spot approximation, while high individual hot spot velocities would indicate the need for alternative methods, possibly including a moving hot spot reference frame with its attendant complexity and additional adjustable parameters. Prior studies resulted in inconsistent opinions concerning hot spot velocities. For example, Morgan (1981, 1983) and Duncan (1981) found that individual hot spots move rela- tive to a mean hot spot reference frame at ≈3 to 5 mm/a. Recent work is consistent with these early results and find that nominal relative velocities between Pacific hot spots and Indo‐Atlantic hot spots over the past 50 Ma are only 2−6 mm/a over the past 48 Ma (Andrews et al., 2006; Koivisto et al., 2014). In contrast, to ≈ – fi ©2019. American Geophysical Union. explain the track of the Emperor chain ( 50 80 Ma) on the Paci c plate, several studies found that the velo- All Rights Reserved. city of the Hawaiian hot spot was as high as 40 to 80 mm/a in early Cenozoic and Late Cretaceous time WANG ET AL. 8031 Geophysical Research Letters 10.1029/2019GL083663 (Konrad et al., 2018; Norton, 1995; Raymond et al., 2000; Tarduno et al., 2003). Morgan (1981), Duncan (1981), and Koivisto et al. (2014) have argued, however, that the high apparent velocity of the Hawaiian hot spot during the formation of the Emperor chain is an artifact of missing motion in the global plate motion circuit, most likely due to unmodeled motion between East and West Antarctica, as seems required by paleomagnetic data (Gordon & Cox, 1980; Acton & Gordon, 1994; but see a differing opinion in Doubrovine & Tarduno, 2008). Acting in part on the belief that the Hawaiian hot spot moved southward relative to the mantle during the formation of the Emperor chain, a belief that we do not share (Petronotis et al., 1994; Petronotis & Gordon, 1989; Woodworth & Gordon, 2018b), Doubrovine et al. (2012) asserted that the fixed hot spot reference frame should be abandoned and replaced by a so‐called Global Moving Hotspot Reference Frame (GMHRF) for which hot spot velocities are predicted from a velocity field calculated for the mantle over the past ≈130 Ma. If indeed the motion of hot spots could be reliably calculated (or predicted) over the past ≈130 Ma from models of flow in the mantle, it would advance global geophysics. How far can one rely, however, on these predicted velocities between hot spots? After all, the mantle‐plume system is complex and any estimate of mantle flow must be based on many simplifying assumptions. Our understanding of many key variables in a mantle flow model, such as mantle viscosity structure, may not be sufficiently well constrained for reliable calculations. Given these potential sources of uncertainty, it would be useful to be able to test the predictions of any such model with observations not used in the construction of the model. Fortunately, Morgan and Morgan (2007) developed a data set of the trends of young hot spot chains. This rich data set was evidently not used by Doubrovine et al. (2012) in developing the GMHRF and thus could be used to test its predictions. Because errors accumulate with age and the calculations for the GMHRF proceed from the present Earth backward in time, the predictions from the GMHRF should be at their most reliable and accurate for the recent geologic past. Here we investigate the following question: is the improvement in fit to trends of young hot spot tracks realized by the GMHRF large enough to justify the considerable complexity and its additional adjustable parameters relative to the simple fixed hot spot approximation? Surprisingly, we find that the GMHRF fits the observed trends of young hot spot tracks much worse than the assumption of fixed hot spots. 2. Data: Hot Spot Trends and Uncertainties Morgan and Morgan (2007) estimated the trends of 57 young tracks of hot spots produced by 54 hot spots (their Table 1). Following Wang et al. (2017, 2019), we omit the Comores track, leaving 56 hot spot tracks. Doubrovine et al. (2012) estimate the locations as a function of time of 44 hot spots (their Table S6). Thirty eight of the hot spots modeled by Doubrovine et al. (2012) correspond to 41 of the 56 trends of hot spot tracks adopted by Wang et al. (2019). Thus, we use the observed trends of these 41 tracks (Figure 1 and Table S1 in the supporting information) to test the predictions of the GMHRF. We adopt the current hot spot locations and current trends from Morgan and Morgan (2007). The uncertainties in trends are calculated objectively using hot spot track length and width (Gripp & Gordon, 2002; Wang et al., 2019). 3. Methods 3.1. Predicted Velocities of Hot Spots Steinberger and O'Connell (1998) proposed a method to estimate plume and hot spot velocity through numerical modeling of mantle convection and advection of plume conduits in the mantle flow field. Following Steinberger and O'Connell (1998), Doubrovine et al. (2012) computed a large‐scale mantle flow field from global plate motions, a radial mantle viscosity structure, and a mantle density structure inferred from seismic tomography. A plume conduit is inserted into the flow field under the assumption that plume conduits do not influence larger‐scale mantle flow. Plume velocity is determined by a sum of the mantle flow velocity and plume vertical buoyant rising velocity. The hot spot velocities adopted herein are determined from the hot spot locations at present and at 5 Ma given by Doubrovine et al.
Load more

Recommended publications
  • Identification of Erosional Terraces on Seamounts
    ORIGINAL RESEARCH published: 03 July 2018 doi: 10.3389/feart.2018.00088 Identification of Erosional Terraces on Seamounts: Implications for Interisland Connectivity and Subsidence in the Galápagos Archipelago Darin M. Schwartz 1*, S. Adam Soule 2, V. Dorsey Wanless 1 and Meghan R. Jones 2 1 Department of Geosciences, Boise State University, Boise, ID, United States, 2 Geology and Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, MA, United States Shallow seamounts at ocean island hotspots and in other settings may record emergence histories in the form of submarine erosional terraces. Exposure histories are valuable for constraining paleo-elevations and sea levels in the absence of more traditional Edited by: markers, such as drowned coral reefs. However, similar features can also be produced Ricardo S. Ramalho, Universidade de Lisboa, Portugal through primary volcanic processes, which complicate the use of terraced seamounts Reviewed by: as an indicator of paleo-shorelines. In the western Galápagos Archipelago, we utilize Neil Mitchell, newly collected bathymetry along with seafloor observations from human-occupied University of Manchester, submersibles to document the location and depth of erosional terraces on seamounts United Kingdom Daneiele Casalbore, near the islands of Santiago, Santa Cruz, Floreana, Isabela, and Fernandina. We directly Sapienza Università di Roma, Italy observed erosional features on 22 seamounts with terraces. We use these observations Rui Quartau, Instituto Hidrográfico, Portugal and bathymetric analysis to develop a framework to identify terrace-like morphologic *Correspondence: features and classify them as either erosional or volcanic in origin. From this framework Darin M. Schwartz we identify 79 erosional terraces on 30 seamounts that are presently found at depths [email protected] of 30 to 300 m.
    [Show full text]
  • Upper Mantle Flow Beneath and Around the Hangay Dome, Central Mongolia Guilhem Barruol, Anne Deschamps, Jacques Déverchère, Valentina V
    Upper mantle flow beneath and around the Hangay Dome, central Mongolia Guilhem Barruol, Anne Deschamps, Jacques Déverchère, Valentina V. Mordvinova, Ulziibat Munkhuu, Julie Perrot, A. Artemiev, T. Dugarmaa, Götz H.R. Bokelmann To cite this version: Guilhem Barruol, Anne Deschamps, Jacques Déverchère, Valentina V. Mordvinova, Ulziibat Munkhuu, et al.. Upper mantle flow beneath and around the Hangay Dome, central Mongolia. Earth and Planetary Science Letters, Elsevier, 2008, 274 (1-2), pp.221-233. 10.1016/j.epsl.2008.07.027. hal- 00407853 HAL Id: hal-00407853 https://hal.archives-ouvertes.fr/hal-00407853 Submitted on 24 Oct 2016 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Upper mantle flow beneath and around the Hangay dome, Central Mongolia Guilhem Barruol a,⁎, Anne Deschamps b, Jacques Déverchère c,d, Valentina V. Mordvinova e, Munkhuu Ulziibat f, Julie Perrot c,d, Alexandre A. Artemiev e, Tundev Dugarmaa f, Götz H.R. Bokelmann a a Université Montpellier II, CNRS, Géosciences Montpellier, F-34095 Montpellier cedex 5, France b Université Nice Sophia Antipolis, CNRS, Observatoire de la Côte d'Azur, Géosciences Azur, 250, Rue Albert Einstein, F-06560 Valbonne, France c Université Européenne de Bretagne, France d Université de Brest; CNRS, UMR 6538 Domaines Océaniques; Institut Universitaire Européen de la Mer, Place Copernic, 29280 Plouzané, France e Institute of the Earth's Crust SB RAS, Lermontov st.
    [Show full text]
  • The Depths of Magma Chambers Under the Galapagos Ridge Presented in Partial Fulfillment of the Requirements for Graduation With
    The Depths of Magma Chambers under the Galapagos Ridge Presented in Partial Fulfillment of the Requirements for Graduation with a Bachelor of Science in Geological Sciences in the undergraduate colleges of The Ohio State University by Emily V. England The Ohio State University August 2008 Dr. Michael Barton Advisor Table of Contents Acknowledgements……………………………………………………………………..p.1 Abstract…………………………………………………………………………………p.2 Introduction…………………………………………………………………………….p.4 Background……………………………………………………………………………..p.6 Methods………………………………………………………………………………..p.9 Samples……………………………………………………………………………..…p.11 Results…………………………………………………………………………………p.13 Discussion……………………………………………………………………………..p.15 Conclusions……………………………………………………………………………p. 18 References…………………………………………………………………………….p.19 Appendix (Summary of P and T)……………………………………………………..p. 21 ACKNOWLEDGEMENTS I would like to give thanks to the following people for helping me with my research on the Galapagos ridge while at The Ohio State University: my research advisor Dr. Michael Barton who suggested this project and mentored me along the way, Dr. Wendy Panero for her time and conversation, graduate student Daniel Kelley, and classmate Jameson “Dino” Scott. I would also like to acknowledge the entire Geological Sciences Department at OSU. I have been thoroughly pleased with my education and believe that I have found a field that I will enjoy and pursue for the rest of my life. And of course I thank my parents and family for more than words can say. 1 ABSTRACT The Galapagos Ridge System is one of the
    [Show full text]
  • Hunting for Hydrothermal Vents Along the Galã¡Pagos Spreading Center
    University of South Carolina Scholar Commons Faculty Publications Earth, Ocean and Environment, School of the 12-2007 Hunting for Hydrothermal Vents Along the Galápagos Spreading Center Rachel M. Haymon University of California - Santa Barbara Edward T. Baker Joseph A. Resing Scott M. White University of South Carolina - Columbia, [email protected] Ken C. Macdonald University of California - Santa Barbara Follow this and additional works at: https://scholarcommons.sc.edu/geol_facpub Part of the Earth Sciences Commons Publication Info Published in Oceanography, Volume 20, Issue 4, 2007, pages 100-107. Haymon, R. M., Baker, E. T., Resing, J. A., White, S. M., & Macdonald, K. C. (2007). Hunting for hydrothermal vents along the Galápagos Spreading Center. Oceanography, 20 (4), 100-107. © Oceanography 2007, Oceanography Society This Article is brought to you by the Earth, Ocean and Environment, School of the at Scholar Commons. It has been accepted for inclusion in Faculty Publications by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. or collective redistirbution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of The Oceanography Society. Send all correspondence to: [email protected] ofor Th e The to: [email protected] Oceanography approval Oceanography correspondence all portionthe Send Society. ofwith any permitted articleonly photocopy by Society, is of machine, reposting, this means or collective or other redistirbution This article has This been published in S P E C I A L Iss U E O N O C E A N E XPL O RATI on B Y R AC H E L M .
    [Show full text]
  • On the Emergence and Submergence of the Galapagos Islands
    On the emergence and submergence of the Galápagos Islands Item Type article Authors Geist, Dennis Download date 23/09/2021 23:04:08 Link to Item http://hdl.handle.net/1834/23895 March7996 NOTICIAS DE GALAPAGOS ON THE EMERGENCE AND SUBMERCENCE OF THE GALÁPAGOS ISLANDS By: Dennis Geist INTRODUCTION emerge above the sea due to two principal effects. First, as the Nazca plate travels over the Galápagos hotspot, the The age of sustained emergence of the individual seafloor rises due to thermal expansion. The Galápagos Galápagos islands above the sea is an important issue in thermal swell is predicted to be only 400 m high (Epp, developing evolutionary models for their unique terres- 1984). The sea floor to the west of Fernandina is about trial biota. For one, the age of emergence of the oldest 3200 m deep, so 2800 m of lava needs to pile up on the island permits estimation of when terrestrial organisms swell for an island to form. In reality, much more magma may have originally colonized the archipelago. Second, is required, because as lava erupts from an oceanic volca- the ages of the individual islands and minor islets are no, the extra weight causes the earth's crust to sag into the required for quantitative assessments of rates of coloni- mantle, forming a deep root. Feighner and Richard s (799a) zation and diversification within the archipelago. estimate, for example, that the base of the crust is up to 7 Emergence is not a straightforward geologic problem, km deeper beneath Isabela than it is to the west; in other because the islands constitute an extremely dynamic en- words, for every 1 km of elevation growth of a volcano, vironment - the shorelines that we see today are transient about 4 km of "sinking" occurs.
    [Show full text]
  • 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).
    [Show full text]
  • Pleistocene Volcanism in the Anahim Volcanic Belt, West-Central British Columbia
    University of Calgary PRISM: University of Calgary's Digital Repository Graduate Studies The Vault: Electronic Theses and Dissertations 2014-10-24 A Second North American Hot-spot: Pleistocene Volcanism in the Anahim Volcanic Belt, west-central British Columbia Kuehn, Christian Kuehn, C. (2014). A Second North American Hot-spot: Pleistocene Volcanism in the Anahim Volcanic Belt, west-central British Columbia (Unpublished doctoral thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/25002 http://hdl.handle.net/11023/1936 doctoral thesis University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission. Downloaded from PRISM: https://prism.ucalgary.ca UNIVERSITY OF CALGARY A Second North American Hot-spot: Pleistocene Volcanism in the Anahim Volcanic Belt, west-central British Columbia by Christian Kuehn A THESIS SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY GRADUATE PROGRAM IN GEOLOGY AND GEOPHYSICS CALGARY, ALBERTA OCTOBER, 2014 © Christian Kuehn 2014 Abstract Alkaline and peralkaline magmatism occurred along the Anahim Volcanic Belt (AVB), a 330 km long linear feature in west-central British Columbia. The belt includes three felsic shield volcanoes, the Rainbow, Ilgachuz and Itcha ranges as its most notable features, as well as regionally extensive cone fields, lava flows, dyke swarms and a pluton. Volcanic activity took place periodically from the Late Miocene to the Holocene.
    [Show full text]
  • Petrogenesis of Alkalic Seamounts on the Galápagos Platform T ⁎ Darin M
    Deep-Sea Research Part II 150 (2018) 170–180 Contents lists available at ScienceDirect Deep-Sea Research Part II journal homepage: www.elsevier.com/locate/dsr2 Petrogenesis of alkalic seamounts on the Galápagos Platform T ⁎ Darin M. Schwartza, , V. Dorsey Wanlessa, Rebecca Berga, Meghan Jonesb, Daniel J. Fornarib, S. Adam Souleb, Marion L. Lytlea, Steve Careyc a Department of Geosciences, Boise State University, 1910 University Drive, Boise, ID 83725, United States b Geology and Geophysics Department, Woods Hole Oceanographic Institution, United States c Graduate School of Oceanography, University of Rhode Island, United States ARTICLE INFO ABSTRACT Keywords: In the hotspot-fed Galápagos Archipelago there are transitions between volcano morphology and composition, Seamounts effective elastic thickness of the crust, and lithospheric thickness in the direction of plate motion from west to Geochemistry east. Through sampling on the island scale it is unclear whether these transitions are gradational or sharp and Monogenetic whether they result in a gradational or a sharp boundary in terms of the composition of erupted lavas. Clusters of Hotspot interisland seamounts are prevalent on the Galápagos Platform, and occur in the transition zone in morphology Galápagos between western and eastern volcanoes providing an opportunity to evaluate sharpness of the compositional Basalt E/V Nautilus boundary resulting from these physical transitions. Two of these seamounts, located east of Isabela Island and southwest of the island of Santiago, were sampled by remotely operated vehicle in 2015 during a telepresence- supported E/V Nautilus cruise, operated by the Ocean Exploration Trust. We compare the chemistries of these seamount lavas with samples erupted subaerially on the islands of Isabela and Santiago, to test whether sea- mounts are formed from melt generation and storage similar to that of the western or eastern volcanoes, or transitional between the two systems.
    [Show full text]
  • 98-031 Oceanus F/W 97 Final
    A hotspot created the island of Iceland and its characteristic volcanic landscape. Hitting the Hotspots Hotspots are rela- tively small regions on the earth where New Studies Reveal Critical Interactions unusually hot rocks rise from deep inside Between Hotspots and Mid-Ocean Ridges the mantle layer. Jian Lin Associate Scientist, Geology & Geophysics Department he great volcanic mid-ocean ridge system hotspots may play a critical role in shaping the stretches continuously around the globe for seafloor—acting in some cases as strategically T 60,000 kilometers, nearly all of it hidden positioned supply stations that fuel the lengthy beneath the world’s oceans. In some places, how- mid-ocean ridges with magma. ever, mid-ocean ridge volcanoes are so massive that Studies of ridge-hotspot interactions received a they emerge above sea level to create some of the major boost in 1995 when the US Navy declassified most spectacular islands on our planet. Iceland, the gravity data from its Geosat satellite, which flew Azores, and the Galápagos are examples of these from 1985 to 1990. The satellite recorded in unprec- “hotspot” islands—so named because they are edented detail the height of the ocean surface. With believed to form above small regions scattered accuracy within 5 centimeters, it revealed small around the earth where unusually hot rocks rise bumps and dips created by the gravitational pull of from deep inside the mantle layer. dense underwater mountains and valleys. Research- But hotspots may not be such isolated phenom- ers often use precise gravity measurements to probe ena. Exciting advances in satellite oceanography, unseen materials below the ocean floor.
    [Show full text]
  • Petrogenesis of Alkalic Seamounts on the Galápagos Platform 2 a a a 3 Darin M
    Version of Record: https://www.sciencedirect.com/science/article/pii/S096706451730156X Manuscript_4a3a952cd2024196ea9e98a9d9d28724 1 Petrogenesis of Alkalic Seamounts on the Galápagos Platform 2 a a a 3 Darin M. Schwartz [email protected], V. Dorsey Wanless , Rebecca Berg , 4 Meghan Jonesb, Daniel J. Fornarib, S. Adam Souleb, Marion L. Lytlea, Steve Careyc 5 6 a Department of Geosciences, Boise State University, 1910 University Drive, Boise, ID 7 83725 8 b Geology and Geophysics Department, Woods Hole Oceanographic Institution 9 c Graduate School of Oceanography, University of Rhode Island 10 11 Keywords: seamounts, geochemistry, monogenetic, hotspot, Galápagos, basalt, E/V 12 Nautilus 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 1 © 2017 published by Elsevier. This manuscript is made available under the Elsevier user license https://www.elsevier.com/open-access/userlicense/1.0/ 1 2 Abstract 3 In the hotspot-fed Galápagos Archipelago there are transitions between volcano 4 morphology and composition, effective elastic thickness of the crust, and lithospheric 5 thickness in the direction of plate motion from west to east. Through sampling on the 6 island scale it is unclear whether these transitions are gradational or sharp and whether 7 they result in a gradational or a sharp boundary in terms of the composition of erupted 8 lavas. Clusters of interisland seamounts are prevalent on the Galápagos Platform, and 9 occur in the transition zone in morphology between western and eastern volcanoes 10 providing an opportunity to evaluate sharpness of the compositional boundary resulting 11 from these physical transitions.
    [Show full text]
  • Absolute Plate Motions Constrained By
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 114, B10405, doi:10.1029/2009JB006416, 2009 Click Here for Full Article Absolute plate motions constrained by shear wave splitting orientations with implications for hot spot motions and mantle flow Corne´ Kreemer1 Received 27 February 2009; revised 11 June 2009; accepted 14 July 2009; published 22 October 2009. [1] Here, I present a new absolute plate motion model of the Earth’s surface, determined from the alignment of present-day surface motions with 474 published shear wave (i.e., SKS) splitting orientations. When limited to oceanic islands and cratons, splitting orientations are assumed to reflect anisotropy in the asthenosphere caused by the differential motion between lithosphere and mesosphere. The best fit model predicts a 0.2065°/Ma counterclockwise net rotation of the lithosphere as a whole, which revolves around a pole at 57.6°S and 63.2°E. This net rotation is particularly well constrained by data on cratons and/or in the Indo-Atlantic region. The average data misfit is 19° and 24° for oceanic and cratonic areas, respectively, but the normalized root-mean-square misfits are about equal at 5.4 and 5.2. Predicted plate motions are very consistent with recent hot spot track azimuths (<8° on many plates), except for the slowest moving plates (Antarctica, Africa, and Eurasia). The difference in hot spot propagation vectors and plate velocities describes the motion of hot spots (i.e., their underlying plumes). For most hot spots that move significantly, the motions are considerably smaller than and antiparallel to the absolute plate velocity. Only when the origin depth of the plume is considered can the hot spot motions be explained in terms of mantle flow.
    [Show full text]
  • Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions
    Surv Geophys (2009) 30:407–461 DOI 10.1007/s10712-009-9075-1 ORIGINAL PAPER Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions Maureen D. Long Æ Paul G. Silver Received: 5 February 2009 / Accepted: 3 June 2009 / Published online: 27 June 2009 Ó The Author(s) 2009. This article is published with open access at Springerlink.com Abstract Measurements of the splitting or birefringence of seismic shear waves that have passed through the Earth’s mantle yield constraints on the strength and geometry of elastic anisotropy in various regions, including the upper mantle, the transition zone, and the D00 layer. In turn, information about the occurrence and character of seismic anisotropy allows us to make inferences about the style and geometry of mantle flow because anisotropy is a direct consequence of deformational processes. While shear wave splitting is an unambiguous indicator of anisotropy, the fact that it is typically a near-vertical path-integrated measure- ment means that splitting measurements generally lack depth resolution. Because shear wave splitting yields some of the most direct constraints we have on mantle flow, however, understanding how to make and interpret splitting measurements correctly and how to relate them properly to mantle flow is of paramount importance to the study of mantle dynamics. In this paper, we review the state of the art and recent developments in the measurement and interpretation of shear wave splitting—including new measurement methodologies and forward and inverse modeling techniques,—provide an overview of data sets from different tectonic settings, show how they help us relate mantle flow to surface tectonics, and discuss new directions that should help to advance the shear wave splitting field.
    [Show full text]