ebook img

Back-Arc Spreading Systems: Geological, Biological, Chemical, and Physical Interactions PDF

305 Pages·2006·38.7 MB·English
by  
Save to my drive
Quick download
Download
Most books are stored in the elastic cloud where traffic is expensive. For this reason, we have a limit on daily download.

Preview Back-Arc Spreading Systems: Geological, Biological, Chemical, and Physical Interactions

Geophysical Monograph Series Including IUGG Volumes Maurice Ewing Volumes Mineral Physics Volumes Geophysical Monograph Series 129 Environmental Mechanics: Water, Mass and Energy  148 Mid-Ocean Ridges: Hydrothermal Interactions  Transfer in the Biosphere Peter A. C. Raats, Between the Lithosphere and Oceans Christopher R. David Smiles, and Arthur W. Warrick (Eds.) German, Jian Lin, and Lindsay M. Parson (Eds.) 130 Atmospheres in the Solar System: Comparative  149 Continent-Ocean Interactions Within East Asian  Aeronomy Michael Mendillo, Andrew Nagy, and Marginal Seas Peter Clift, Wolfgang Kuhnt, Pinxian J. H. Waite (Eds.) Wang, and Dennis Hayes (Eds.) 131 The Ostracoda: Applications in Quaternary Research  150 The State of the Planet: Frontiers and Challenges  Jonathan A. Holmes and Allan R. Chivas (Eds.) in Geophysics Robert Stephen John Sparks and 132 Mountain Building in the Uralides Pangea to the  Christopher John Hawkesworth (Eds.) Present Dennis Brown, Christopher Juhlin, and 151 The Cenozoic Southern Ocean: Tectonics,  Victor Puchkov (Eds.) Sedimentation, and Climate Change Between  133 Earth’s Low-Latitude Boundary Layer Patrick T. Newell Australia and Antarctica Neville Exon, James P. and Terry Onsage (Eds.) Kennett, and Mitchell Malone (Eds.) 134 The North Atlantic Oscillation: Climatic Significance  152 Sea Salt Aerosol Production: Mechanisms, Methods,  and Environmental Impact James W. Hurrell, Measurements, and Models Ernie R. Lewis and Stephen Yochanan Kushnir, Geir Ottersen, and Martin Visbeck E. Schwartz (Eds.) 153 Ecosystems and Land Use Change Ruth S. DeFries, 135 Prediction in Geomorphology Peter R. Wilcock and Gregory P. Anser, and Richard A. Houghton (Eds.) Richard M. Iverson (Eds.) 154 The Rocky Mountain Region—An Evolving  136 The Central Atlantic Magmatic Province: Insights  Lithosphere: Tectonics, Geochemistry, and  from Fragments of Pangea W. Hames, J. G. McHone, Geophysics  Karl E. Karlstrom and G. Randy Keller (Eds.) P. Renne, and C. Ruppel (Eds.) 155 The Inner Magnetosphere: Physics and Modeling Tuija 137 Earth’s Climate and Orbital Eccentricity: The Marine  I. Pulkkinen, Nikolai A. Tsyganenko, and Reiner H. W. Isotope Stage 11 Question André W. Droxler, Friedel (Eds.) Richard Z. Poore, and Lloyd H. Burckle (Eds.) 156 Particle Acceleration in Astrophysical Plasmas:  138 Inside the Subduction Factory John Eiler (Ed.) Geospace and Beyond Dennis Gallagher, James Horwitz, Joseph Perez, Robert Preece, and John Quenby (Eds.) 139 Volcanism and the Earth’s Atmosphere Alan Robock and Clive Oppenheimer (Eds.) 157 Seismic Earth: Array Analysis of Broadband  Seismograms Alan Levander and Guust Nolet (Eds.) 140 Explosive Subaqueous Volcanism James D. L. White, John L. Smellie, and David A. Clague (Eds.) 158 The Nordic Seas: An Integrated Perspective Helge Drage, Trond Dokken, Tore Furevik, Rüdiger Gerdes, 141 Solar Variability and Its Effects on Climate   and Wolfgang Berger (Eds.) Judit M. Pap and Peter Fox (Eds.) 159 Inner Magnetosphere Interactions: New Perspectives  142 Disturbances in Geospace: The Storm-Substorm  From Imaging James Burch, Michael Schulz, and Harlan Relationship A. Surjalal Sharma, Yohsuke Kamide, and Spence (Eds.) Gurbax S. Lakhima (Eds.) 160 Earth’s Deep Mantle: Structure, Composition, and  143 Mt. Etna: Volcano Laboratory Alessandro Bonaccorso, Evolution Robert D. van der Hilst, Jay D. Bass, Jan Sonia Calvari, Mauro Coltelli, Ciro Del Negro, and Matas, and Jeannot Trampert (Eds.) Susanna Falsaperla (Eds.) 161 Circulation in the Gulf of Mexico: Observations and  144 The Subseafloor Biosphere at Mid-Ocean Ridges  Models Wilton Sturges and Alexis Lugo-Fernandez (Eds.) William S. D. Wilcock, Edward F. DeLong, Deborah S. Kelley, John A. Baross, and S. Craig Cary (Eds.) 162 Dynamics of Fluids and Transport Through Fractured  Rock Boris Faybishenko, Paul A. Witherspoon, and John 145 Timescales of the Paleomagnetic Field James E. Gale (Eds.) T. Channell, Dennis V. Kent, William Lowrie, and Joseph G. Meert (Eds.) 163 Remote Sensing of Northern Hydrology: Measuring  Environmental Change Claude R. Duguay and Alain 146 The Extreme Proterozoic: Geology, Geochemistry,  Pietroniro (Eds.) and Climate Gregory S. Jenkins, Mark A. S. McMenamin, Christopher P. McKay, and Linda Sohl 164 Archean Geodynamics and Environments Keith Benn, (Eds.) Jean-Claude Mareschal, and Kent C. Condie (Eds.) 147 Earth’s Climate: The Ocean–Atmosphere Interaction  165 Solar Eruptions and Energetic Particles Chunzai Wang, Shang-Ping Xie, and James A. Carton Natchimuthukonar Gopalswamy, Richard Mewalt, and (Eds.) Jarmo Torsti (Eds.) Geophysical Monograph 166 Back-Arc Spreading Systems: Geological, Biological, Chemical, and Physical Interactions David M. Christie  Charles R. Fisher  Sang-Mook Lee  Sharon Givens  Editors Published under the aegis of the AGU Books Board Jean-Louis Bougeret, Chair; Gray E. Bebout, Cassandra G. Fesen, Carl T. Friedrichs, Ralf R. Haese, W. Berry Lyons, Kenneth R. Minschwaner, Andrew Nyblade, Darrell Strobel, and Chunzai Wang, members. Library of Congress Cataloging-in-Publication Data Back-arc spreading systems : geological, biological, chemical, and physical interactions / David M. Christie ... [et al.], editors. p. cm. ISBN-13: 978-0-87590-431-3 ISBN-10: 0-87590-431-9 1. Sea-floor spreading. 2. Back-arc basins. 3. Hydrothermal vents. 4. Marine geophysics. I. Christie, David M. QE511.7.B33 2006 551.1'36--dc22 2006031438 ISBN-13: 978-0-87590-431-3 ISBN-10: 0-87590-431-9 ISSN: 0065-8448 Cover: Saint James' Spires, a chimney complex at 1900 m depth in the Tu'i Malila hydrothermal field on the East Lau Spreading Center. The snails in the foreground are Ifremeria nautilei and the mussels are Bathymodiolus brevior. The picture was taken from the ROV Jason II and is provided compliments of Charles Fisher and the Ridge 2000 Program. Copyright 2006 by the American Geophysical Union 2000 Florida Avenue, N.W. Washington, DC 20009 Figures, tables and short excerpts may be reprinted in scientific books and journals if the source is properly cited. Authorization to photocopy items for internal or personal use, or the internal or personal use of specific clients, is granted by the American Geophyscial Union for libraries and other users registered with the Copyright Clearance Center (CCC) Transactional Reporting Service, provided that the base fee of $1.50 per copy plus $0.35 per page is paid directly to CCC, 222 Rosewood Dr., Danvers, MA 01923. 0065-8448/06/$01.50+0.35. This consent does not extend to other kinds of copying, such as copying for creating new collective works or for resale. The reproduction of multiple copies and the use of full articles or the use of extracts, including figures and tables, for commercial purposes requires permission from the American Geophysical Union. Printed in the United States of America. CONTENTS Preface David M. Christie and Charles R. Fisher ...........................................................................................................vii Geological, Biological, Chemical, and Physical Interactions in Back-Arc Spreading Systems—  An Introduction David M. Christie and Charles R. Fisher .............................................................................................................1 Synthesis Papers Modes of Crustal Accretion in Back-Arc Basins: Inferences From the Lau Basin Fernando Martinez and Brian Taylor. ..................................................................................................................5 Present-Day Tectonics in Four Active Island Arcs Based on GPS Observations and Forearc   Stress Fields Teruyuki Kato and Atsuki Kubo ........................................................................................................................31 Mantle Structure and Flow Patterns Beneath Active Back-Arc Basins Inferred From Passive   Seismic and Electromagnetic Methods Douglas A. Wiens, Nobukazu Seama, and James A. Conder ............................................................................43 Origin of Back-Arc Basin Magmas: Trace Element and Isotope Perspectives Julian A. Pearce and Robert J. Stern ..................................................................................................................63 Chemical Systematics and Hydrous Melting of the Mantle in Back-Arc Basins C.H. Langmuir, A. Bézos, S. Escrig, and S.W. Parman .......................................................................................87 Unique Geochemistry of Submarine Hydrothermal Fluids From Arc–Back-Arc Settings   of the Western Pacific Toshitaka Gamo, Junichiro Ishibashi, Urumu Tsunogai, Kei Okamura, and Hitoshi Chiba ................................147 Magmatic Fluids as a Source of Metals in Seafloor Hydrothermal Systems Kaihui Yang and Steven D. Scott ....................................................................................................................163 Microbial Ecology of Mid-Ocean Ridges and Back-Arc Basins Ken Takai, Satoshi Nakagawa, Anna-Louise Reysenbach, and Joost Hoek .......................................................185 Composition and Biogeography of Hydrothermal Vent Communities in Western Pacific   Back-Arc Basins Daniel Desbruyères, Jun Hashimoto, and Marie-Claire Fabri. ..........................................................................215 Physiological Ecology of Back-Arc Basin Fauna: Explorations of the Known and Unknown James J. Childress, Dijanna Figueroa, and Michael Henry ...............................................................................235  Case Studies The East Scotia Sea: Mantle to Microbe Roy Livermore ...............................................................................................................................................243 Tectonic and Magmatic Evolution of the Bismarck Sea, Papua New Guinea: Review   and New Synthesis Sang-Mook Lee and Etienne Ruellan ..............................................................................................................263 Origin of Diverse Geochemical Signatures in Igneous Rocks From the West Philippine   Basin: Implications for Tectonic Models Rosemary Hickey-Vargas, Ivan P. Savov, Michael Bizimis, Teruaki Ishii, and Kantaro Fujioka ...........................287 i Geological, Biological, Chemical, and Physical Interactions in Back-Arc Spreading Systems—An Introduction David M. Christie Global Undersea Research Unit, School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, Alaska, USA Charles R. Fisher Biology Department, Penn State University, University Park, Pennsylvania, USA Each chapter of this volume is based on a presentation at the international Theoretical Institute, “Interactions among Physical, Chemical, Biological, and Geological Processes in Back-arc Spreading Systems”, which was jointly sponsored by Ridge 2000 and InterRidge, on Jeju Island, South Korea, in May 2004. The vol- ume is divided into two sections. Papers in the first section synthesize the state of knowledge of back-arc basins in general, from the perspectives of a broad range of disciplines. The papers are arranged according to their subject matter, roughly fol- lowing the flow of energy and material from their origins in the mantle, through the magmatic systems that create and modify the oceanic crust, to the hydrothermal and biological systems that derive their existence from magmatic heat and chemicals. Papers in the second section are case studies, focused on the geology and geophys- ics of individual back-arc basins. These include two back-arc systems that are more than usually complex, as a result of their more complex tectonic settings. Back-arc basins are elongate oceanic basins formed by the Mid-Atlantic Ridge. Back-arc basin studies repre- seafloor spreading and related extensional tectonic pro- sent an important emerging area of ocean sciences for a cesses. They form adjacent to island arcs, on the opposite number of reasons. Because they are closely associated side from the subducting oceanic plate. Back-arc basins with islands, back-arc basins commonly have considerable are a characteristic feature of oceanic convergent plate economic, cultural, and political importance, especially boundaries, and the dominant role of extensional tec- to western Pacific nations that include back-arc regions tonics in their formation and evolution is a paradox that within their Exclusive Economic Zones. Scientifically, remains imperfectly understood. Mature back-arc basins back-arc spreading centers are important analogs for, and are floored by predominantly basaltic lavas erupted along complements to, mid-ocean spreading systems, relative back-arc spreading centers that are very similar to “nor- to which they are more diverse, shorter-lived, and more mal” mid-ocean ridges such as the East Pacific Rise or rapidly evolving. Their proximity to islands allows for real-time geodetic studies using global positioning system Back-Arc Spreading Systems: Geological, Biological, Chemical, technology that is not possible at most mid-ocean spread- and Physical Interactions ing centers. Back-arc magma systems are more chemically Geophysical Monograph Series 66 and physically diverse and variable, providing a window Copyright 2006 by the American Geophysical Union 0.029/66GM02 to understand their dynamic and complex mantle source  2 INTRODUCTION regions. Because of their diverse and often extreme chem- arc). This new geophysical evidence for arc-parallel flow istry, back-arc hydrothermal systems support a diversity of supports earlier hypotheses, based on both geochemistry microbial fauna with considerable biotechnological poten- and seismology, that mantle material is flowing southward tial. The chemical diversity of hydrothermal microhabitats behind the Tonga arc from the vicinity of Samoa. in relatively isolated back-arc basins supports a variety of Patterns and processes of mantle flow may also be inferred endemic vent macrofauna, each with its own potential to from igneous geochemistry. Pearce et al. use trace element contribute to our understanding of the physiological limits ratios in back-arc lavas to infer that three types of mantle to animal life. These shorter-lived, more variable systems material contribute to back-arc magma sources and to esti- also provide a natural laboratory for studies of larval dis- mate their relative contributions. They identify the three persal and genetic linkages, both regionally and among the mantle types as ambient mantle from the mantle wedge major global biogeographic vent faunal provinces. beneath the backarc; material derived from the subducting slab as a fluid phase; and mantle that has physically migrated MANTLE STRUCTURE AND DYNAMICS into the region above the slab, through gaps or tears in the subducting slab or around its end(s). Studies of the dynamics and deep structure of Island By combining a broad array of geochemical data with new Arc–Back-Arc Systems are primarily centered in the dis- geochemical models for melting in the presence of water, ciplines of Geodesy, Geodynamics, and Seismology, which Langmuir et al. have developed a new view of the shape of depend heavily on instrumental observations, and in Igneous the region within which melting occurs beneath the backarc, Geochemistry, which uses high-precision trace element and and of variations in the melting process throughout this isotopic data to infer conditions of melt formation and details relatively complex region. Key features of this new melting of mantle composition. model are the spatial asymmetry that is imposed on the melt For more than a decade, the Global Positioning System region by the proximity of the active island arc and a funda- (GPS) has allowed accurate measurement of plate motions mental contrast between shallow, hydrous, iron-poor melts in real time. Arrays of GPS instruments are especially on the arc side of the spreading center and deeper, dryer, suited to arc and back-arc geodynamic studies, because more iron-rich melts on the farther side. GPS stations, which must be stable and above water, can be placed on islands within and adjacent to areas of interest. HYDROTHERMAL VENTS AND Arrays of GPS stations allow for measurement of actual HYDROTHERMAL DEPOSITS earth motions with high precision and accuracy. Such measurements are rarely possible for normal mid-oceanic The inherent geological variability of backarc basins pro- spreading centers. Kato and Kubo summarize four major vides a greater variety of substrates for active hydrothermal GPS studies of convergent margins that include back-arc systems relative to mid-oceanic spreading centers. This systems. Although each of the areas has a different inter- variety, in turn, provides a broader range of opportunities for nal structure, these studies show that back-arc extension evaluating the interactions between substrate (volcanic rock) is measurable on timescales of just a few years and that compositions and those of hydrothermal fluids and deposits. arc-parallel extension is common, though not universal, in Of particular interest is the significantly greater abundance island arc and forearc terrains. of volatile species (ultimately derived from devolatiliza- The subduction of a cold slab beneath arc–back-arc sys- tion of the subducting slab) in arc and back-arc magmatic tems generates frequent, deep (~00 to ~500 km) earth- systems. Known back-arc hydrothermal systems include a quakes that vary in intensity and are widely distributed in range of styles and temperatures of hydrothermal venting, both arc-parallel and cross-arc directions. In some cases, and a number of valuable ancient ore deposits have been such as the Lau Basin, these high-frequency, powerful interpreted as having formed in back-arc settings. seismic sources are distributed beneath the entire back Gamo et al. have reviewed current knowledge of back- arc region, providing an almost ideal “illumination” of arc hydrothermal chemistry. As expected from the vari- the back-arc spreading system. Wiens et al. have com- able underlying geology, back-arc hydrothermal fluids are bined passive seismic data that exploit this natural seismic much more variable than their mid-ocean ridge counterparts. source beneath the Lau Basin with electromagnetic data Backarc hydrothermal fluids are often quite distinct in their to evaluate three-dimensional mantle flow patterns. Key very high volatile contents, relative to those of mid-ocean observations include contrasting mantle anisotropies that spreading centers. Back-arc hydrothermal volatile enrich- are consistent with arc-parallel flow beneath the Tonga ment reflects the volatile-rich character of the host lavas, arc and with cross-arc flow beneath the Lau Basin (back- and perhaps of still-molten magmas. In some back-arc hydro- CHRISTIE AND FISHER  thermal systems, high SO contents give rise to high acidity, the well-studied symbiont-containing vent fauna from mid- 2 with significantly lower pH values (as low as 2) than those ocean ridges to provide a background for understanding the of mid-ocean ridge systems. back-arc fauna, to constrain their physiological capabilities The pivotal role of volatiles in hydrothermal metal trans- and the habitat conditions they are likely to tolerate, and to port and ore deposition is discussed by Yang and Scott. They suggest productive areas for future research on back-arc conclude that volatiles derived directly from molten magma, vent fauna. even if they constitute only a small fraction of the total vola- tile budget, can supply most of the metals carried by seafloor CASE STUDIES OF INDIVIDUAL BACK-ARC BASINS hydrothermal systems and incorporated into sub-seafloor mineral deposits. Back-arc magmas are generally more vola- The Lau Basin has an overall south-pointing V-shape, tile-rich, and felsic magmas (which concentrate many metals indicating that the back-arc spreading center is extending as they evolve) are much more common in back-arc settings (propagating) to the south. One consequence of this south- than along normal mid-ocean ridges. As a result, back-arc ward growth is that the tectonic environment, and therefore hydrothermal systems are often metal-rich, and large ore the geological character, of the back-arc spreading center deposits are much more likely to occur in backarc settings changes systematically from north to south. Martinez and than on most mid-ocean ridges. Taylor describe this variation in some detail and use it to examine the interplay of processes and conditions that influ- HYDROTHERMAL VENT BIOTA AND ECOSYSTEMS ence the spreading process in this basin and, by inference, in other back-arc spreading environments. Takai et al. extend the discussion of geological and hydro- Livermore summarizes current knowledge of the east thermal diversity in back-arc systems to the field of micro- Scotia Sea “from mantle to microbe”. This unique, isolated bial ecology, reviewing the available information on the backarc basin lies behind (to the west of) the South Sandwich microbial inhabitants of these geologically diverse spreading Arc in the southwest Atlantic Ocean. This arc–back-arc centers. The greater variability in back-arc fluids, lavas, and system provides a particularly good case study because it mineral deposits (relative to mid-ocean spreading centers) has a relatively short geological history and is built entirely is paralleled by a wide diversity among microbiological on “oceanic” crust with no underlying older arc material. It communities. This variability facilitates detailed studies of is of great geobiological interest because it is both isolated individual groups and of the relationships between microbial from other known (or potential) hydrothermal vent systems populations and their microhabitat parameters. In addition, and situated at an important gateway between the Pacific the diversity of microbial life associated with back-arc basin and Atlantic Oceans. hydrothermal systems provides new insights into the rela- Some back-arc basins, especially those to the west of the tionships among hydrothermal microbial populations from western Pacific rim, occupy more complex tectonic settings around the world. than the “simple” island arc–back-arc systems, such as the Desbruyères et al. have summarized the distribution and East Scotia, Lau, and Mariana back-arc basins described composition of hydrothermal animal communities from in earlier chapters. These more complex back-arcs undergo five back-arc spreading centers. They provide a compre- changes in local (micro) plate motion in response to exter- hensive compilation of the occurrence of species endemic nal forces and are therefore more tectonically and magmati- to the western Pacific back-arc basins. On the basis of cur- cally complex. Lee and Ruellan review the history of the rent knowledge, they identify a global-scale biogeographic Bismarck Sea, a complex back-arc basin to the north of New provincialism. At the generic level, they recognize three Guinea. The history of this basin has been complicated both population clusters: the Mid-Atlantic Ridge; the East Pacific by its location between two opposing subduction zones Rise, subdivided into northern and southern subgroups; and and by its ongoing collision with the northward migrating a third, widespread group consisting of the western Pacific Australian Plate. These external forces have induced local back-arc spreading centers, the Central Indian Ridge, and plate motion changes within the basin, resulting in micro- perhaps including the Gorda and Juan de Fuca ridges in the plate rotation and highly asymmetric back-arc spreading. NE Pacific. Hickey-Vargas et al. focus on the magmatic evolution of Childress et al. focus on the physiological ecology of vent the West Philippine Basin, which was actively spreading fauna, in particular, the role of microbial symbionts in the from 60 to 5 Ma and which remained magmatically active animals that dominate the biomass at vents around the world. until 26 Ma, when the Izu–Bonin–Mariana arc to the east Because no back-arc species has been the focus of intensive began to dominate the tectonics of the region. An interest- physiological study, Childress et al. use what is known about ing and unexplained feature of both of these complex basins 4 INTRODUCTION is the occurrence of relatively voluminous, late-stage mag- David M. Christie, Global Undersea Research Unit, School of matism that is not directly related to spreading processes. Fisheries and Ocean Sciences, University of Alaska Fairbanks, These magmas are described as “enriched” in character, Fairbanks, Alaska 99752, USA. ([email protected]) meaning that their trace element contents are more similar Charles R. Fisher, Biology Department, 208 Mueller Lab., Penn to those of many ocean island volcanoes, commonly attrib- State University, University Park, Pennsylvania 6802, USA. uted to deep mantle sources. ([email protected])

Description:
Published by the American Geophysical Union as part of the Geophysical Monograph Series. New ocean crust is continuously created where tectonic plates diverge. A distinctive type of oceanic crust is formed by back-arc spreading systems that parallel oceanic island arcs on the side away from the subd
See more

The list of books you might like

Most books are stored in the elastic cloud where traffic is expensive. For this reason, we have a limit on daily download.