DOCSLIB.ORG

Comprehensive Analysis of Global Mid Ocean Ridge and Mariana

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

COMPREHENSIVE ANALYSIS OF GLOBAL MID OCEAN RIDGE AND MARIANA CONVERGENT MARGIN HYDROTHERMAL SYSTEMS TECTONICS, FLUID CHEMISTRY AND VENT BIOTA by Diluni Ayeshika Wimalaratne Hetti Pathirannehelage APPROVED BY SUPERVISORY COMMITTEE: ___________________________________________ Dr. Robert J. Stern, Chair ___________________________________________ Dr. Thomas Brikowski ___________________________________________ Dr. Juan Gonzalez ___________________________________________ Dr. Carlos Aiken Copyright 2020 Diluni Ayeshika Wimalaratne Hetti Pathirannehelage All Rights Reserved Through the trenches up to the ridges You made my journey a success … To my little Neth, Sachith, family, friends and mentors COMPREHENSIVE ANALYSIS OF GLOBAL MID OCEAN RIDGE AND MARIANA CONVERGENT MARGIN HYDROTHERMAL SYSTEMS TECTONICS, FLUID CHEMISTRY AND VENT BIOTA by DILUNI AYESHIKA WIMALARATNE HETTI PATHIRANNEHELAGE, BS, MS DISSERTATION Presented to the Faculty of The University of Texas at Dallas in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY IN GEOSCIENCES THE UNIVERSITY OF TEXAS AT DALLAS May 2020 ACKNOWLEDGMENTS I would like to thank Dr. Frank Konietschke and Asanka M. Gunawardana of the Department of Mathematical Sciences at the University of Texas at Dallas for their guidance in statistical analysis. April 2020 v COMPREHENSIVE ANALYSIS OF GLOBAL MID OCEAN RIDGE AND MARIANA CONVERGENT MARGIN HYDROTHERMAL SYSTEMS TECTONICS, FLUID CHEMISTRY AND VENT BIOTA Diluni Ayeshika Wimalaratne Hetti Pathirannehelage, PhD The University of Texas at Dallas, 2020 Supervising Professor: Robert J. Stern This study is a multidisciplinary data integration and metadata analysis for mid-ocean ridge (MOR) and Mariana intra oceanic convergent margin hydrothermal vents including fluids and biota. We compiled separate databases for MOR and Mariana hydrothermal vent parameters and their vent biota using published and on-line information managed by government agencies and other research institutes. The vent parameter databases are compiled under the categories of setting, vent field name, vent field number, name, latitude, longitude, alias, vent sites, smoker type and chimney 3 4 composition, host rocks, full spreading rate, depth, temperature, pH, total Fe, ( He/ He)/Ra, CO2, 2- CH4, H2, H2S, SO4 ions, chlorinity, operations and references. MOR database for vent parameters includes 449 individual hydrothermal vents grouped into 73 vent fields at global divergent margins. The vent organism database of MOR vents includes 672 species belong to 72 individual vents. Mariana vent summary database includes 47 individual hydrothermal vents belong to four different tectonic settings: the forearc (FAR), arc (ARC), backarc (BAB) and the southern Mariana trough (SMT). Database for Mariana biota include vent animals for 31 vents of the above settings. vi We considered vent depth, fluid temperature, pH, total Fe, Mn, helium isotopic ratio 3 4 2- (( He/ He)/Ra), fluid gases (CO2, CH4, H2, H2S), SO4 ions and chlorinity of the fluids for statistical analysis. In addition to these parameters, for MOR vents full spreading rate was also considered for statistical analysis. To overcome non-linear data distributions and small number of observations for some vent parameters, we used purely nonparametric statistical procedures. We assessed vent fluid parameters first for correlations with key parameters spreading rate (for MOR only), summit depth, fluid temperature and fluid chlorinity. Second, we compared different segments (MOR segments and Mariana tectonic settings) based on vent parameters. Similarities between the vent organisms in different tectonic segments were assessed using Sörensen similarity indices; for MOR vents at both genera and species levels; and for Mariana only for genus level. Our results for MORs show that even if MOR hydrothermal systems are associated with simple divergent margin tectonism, they are remarkably similar despite having differences in both fluid chemistry and biota distribution regardless of the ocean and the rate of spreading. Vent fluid 2- temperature, pH, Fe, Mn, CO2, H2, SO4 ion and chlorinity are independent of the spreading rate. Fluid temperature does control pH, Fe and H2S. Brine separation might influence gases such as helium isotopic ratio and CO2 in venting fluids. Highest similarities of the macro organisms are seen in the Indian Ocean ridges and the greatest differences are observed in the Pacific Ocean ridges. Integration of tectonics, fluid chemistry and vent biota of Mariana convergent margin vents demonstrate that Mariana vent groups are more diverse than global mid-ocean ridge vents and that the southernmost Marianas most resembles mid-ocean ridge (MOR) type venting, the other tectonic groups are quite different than MOR vents. vii TABLE OF CONTENTS ACKNOWLEDGMENTS ...............................................................................................................v ABSTRACT ................................................................................................................................... vi LIST OF FIGURES ....................................................................................................................... xi LIST OF TABLES ....................................................................................................................... xiv LIST OF ABBREVIATIONS ........................................................................................................xv CHAPTER 1: GLOBAL MID OCEAN RIDGE HYDROTHERMAL VENTS AND THEIR BIOTA 1.1. Abstract .........................................................................................................................1 1.2. Introduction ...................................................................................................................2 1.3. Geological Settings .......................................................................................................4 1.3.1. Pacific Ocean Spreading Ridges .........................................................................4 a. Juan de Fuca Ridge (JFR), Explorer Ridge (EXR), and Gorda Ridge (GOR) b. East Pacific Rise (EPR) c. Galapagos Spreading Center (GSC) 1.3.2. Atlantic and Arctic Ocean Spreading Ridges .....................................................8 a. Mid Atlantic Ridge (MAR), Reykjanes Ridge (RKR), Kolbeinsy Ridge (KOR), and Mohn’s Ridge (MHR) b. Mid Cayman Rise (MCR) c. Gakkel Ridge (GKR) 1.3.3. Indian Ocean Spreading Ridges ........................................................................10 a. Central Indian Ridge (CIR) viii b. Southwest Indian Ridge (SWIR) 1.4. Methods.......................................................................................................................11 1.4.1. Data Sources .....................................................................................................11 1.4.2. Statistical Analyses of Vent Parameters ...........................................................13 1.4.3. Statistical Analyses of Vent Biota ....................................................................15 1.5. Results .........................................................................................................................16 1.5.1. Analyses of Vent Parameters ............................................................................16 1.5.2. Similarity Analysis of Vent Biota……………………………………………..29 1.6. Discussion ...................................................................................................................30 1.6.1. Effect of Spreading Rate and Summit Depth on Hydrothermal Fluid………..30 1.6.2. Temperature and Chlorinity Controls on Fluid Compositions .........................32 1.6.3. Anomalous Fe and Chlorinity of Central Indian Ridge Vent Fluids ................34 1.6.4. Is geography the most important control on MOR vent biota? ........................34 1.7. Conclusions .................................................................................................................35 1.8. Acknowledgments.......................................................................................................35 1.9. Appendix A: Statistical analyses of fluid parameters and vent macro organisms in global mid ocean ridge hydrothermal system .............................................................36 1.10. References .................................................................................................................40 CHAPTER 2: A COMPILATION OF HYDROTHERMAL AND COLD-SEEP VENTS IN THE MARIANA CONVERGENT MARGIN: TECTONICS, FLUID CHEMISTRY AND BIOLOGY 2.1. Abstract .......................................................................................................................47 2.2. Introduction .................................................................................................................48 2.3. Geological Settings .....................................................................................................54 ix 2.4. Methods.......................................................................................................................56 2.4.1. Data Sources .....................................................................................................56 2.4.2. Statistical Analyses of Vent Parameters ...........................................................58 2.4.3. Statistical Analyses of Vent Biota ....................................................................60 2.4.4. Statistical Analysis of Chimney
Recommended publications
  • Canada's Active Western Margin

    Canada's Active Western Margin

    Geoscience Canada. Volume 3. Nunber 4 269 in the area of Washington and Oregon seemed necessary geometrically. This suggestion was reiterated by Tobin and Sykes (1968) in their study of the seismicity ofthe regionanddevelopedin established the presence and basic bathymetric trench at the foot of the Canada's Active configuration of an active spreading continental slope, the absence of a ocean ridge system ofl the west coast of clearly defined eastward dipping Beniofl Western Margin - Vancwver Island. The theory of the earthquake zone and the apparently geometrical mwement of rigid quiescent state of present volcanism The Case for lithospheric plates on a spherical earth have all contributed toward a (introducedas the 'paving stone' theory) widespreaa uncertalnfy as to whether Subduction was tirst ~ro~osedand tasted bv subddctlon 1s cbrrently taking place ~c~enziiand Parker (1967) using data (e.8.. Crosson. 1972: ~rivast&a,1973; R. P. Riddihough and R. D. Hyndnan from the N. Pacific and in the global Stacey. 1973). Past subduction, fran Victoria Geophysical Observatory, extension of the theory by Morgan several tens of m.y. ago until at leastone Earth Physics Branch, (1 968) this reglon again played a major or two m y. ago. IS more generally Department Energy, Mines and role Morgan alsoconcluded that a small accepted ana it seems to us that the Resources, block eitof theJuandeFuca ridge (the case for contemporary subduction, in a 5071 W. Saanich Rd. Juan de Fuca plate. Fig. 2) was moving large part, must beargued upona Victoria B. C. independently of the main Pacific plate. continuation into the present of the The possibility that theJuan de Fuca processes shown to be active in the Summary plate is now underthrustingNorth recent geological past.
  • Cambridge University Press 978-1-108-44568-9 — Active Faults of the World Robert Yeats Index More Information

    Cambridge University Press 978-1-108-44568-9 — Active Faults of the World Robert Yeats Index More Information

    Cambridge University Press 978-1-108-44568-9 — Active Faults of the World Robert Yeats Index More Information Index Abancay Deflection, 201, 204–206, 223 Allmendinger, R. W., 206 Abant, Turkey, earthquake of 1957 Ms 7.0, 286 allochthonous terranes, 26 Abdrakhmatov, K. Y., 381, 383 Alpine fault, New Zealand, 482, 486, 489–490, 493 Abercrombie, R. E., 461, 464 Alps, 245, 249 Abers, G. A., 475–477 Alquist-Priolo Act, California, 75 Abidin, H. Z., 464 Altay Range, 384–387 Abiz, Iran, fault, 318 Alteriis, G., 251 Acambay graben, Mexico, 182 Altiplano Plateau, 190, 191, 200, 204, 205, 222 Acambay, Mexico, earthquake of 1912 Ms 6.7, 181 Altunel, E., 305, 322 Accra, Ghana, earthquake of 1939 M 6.4, 235 Altyn Tagh fault, 336, 355, 358, 360, 362, 364–366, accreted terrane, 3 378 Acocella, V., 234 Alvarado, P., 210, 214 active fault front, 408 Álvarez-Marrón, J. M., 219 Adamek, S., 170 Amaziahu, Dead Sea, fault, 297 Adams, J., 52, 66, 71–73, 87, 494 Ambraseys, N. N., 226, 229–231, 234, 259, 264, 275, Adria, 249, 250 277, 286, 288–290, 292, 296, 300, 301, 311, 321, Afar Triangle and triple junction, 226, 227, 231–233, 328, 334, 339, 341, 352, 353 237 Ammon, C. J., 464 Afghan (Helmand) block, 318 Amuri, New Zealand, earthquake of 1888 Mw 7–7.3, 486 Agadir, Morocco, earthquake of 1960 Ms 5.9, 243 Amurian Plate, 389, 399 Age of Enlightenment, 239 Anatolia Plate, 263, 268, 292, 293 Agua Blanca fault, Baja California, 107 Ancash, Peru, earthquake of 1946 M 6.3 to 6.9, 201 Aguilera, J., vii, 79, 138, 189 Ancón fault, Venezuela, 166 Airy, G.
  • Geology and Geochemistry of the Southern Explorer Ridge Seafloor Hydrothermal Site Using an Integrated GIS Database and 3D Modeling

    Geology and Geochemistry of the Southern Explorer Ridge Seafloor Hydrothermal Site Using an Integrated GIS Database and 3D Modeling

    Physiology, Geology and Geochemistry of the Southern Explorer Ridge Seafloor Hydrothermal Site Using an Integrated GIS Database and 3D Modeling Yannick C. Beaudoin A thesis subrnitted in conformity with the requirements for the degree of Master of Science Graduate Department of Geology University of Toronto O March 2001 National Library Bibliothèque nationale If1 of Canada du Canada Acquisitions and Acquisitions et Bibliogmphic Sewices services bibliogrâphiques 395 Wellington Street 395. rue Wellington Ottawa ON K1A ON4 Ottawa ON K1A ON4 Canada Canada Yow Ne votro nlfémma Our fiie Notre réfdrenw The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exciusive permettant à la National Lhrary of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/film, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fkom it Ni la thèse ni des extraits substantiels may be printed or othe*se de celle-ci ne doivent être imprimes reproduced without the author's ou autrement reproduits sans son permission. autorisation. Physiology, Geology and Geochemistry of the Southern Explorer Ridge Seafloor Hydrothermal Site Using an Integrated GIS Database and 3D Modeling by Yannick Beaudoin in partial fulfillment of the requirements for the degree of Master's of Science, March 2001, Graduate Department of Geology, University of Toronto Southem Explorer Ridge (SER) is an anomalously-rate shallow, intemediate spreading ridge located 200 kilometers off the west Coast of Vancouver Island, Canada.
  • Recent Movements of the Juan De Fuca Plate System

    Recent Movements of the Juan De Fuca Plate System

    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 89, NO. B8, PAGES 6980-6994, AUGUST 10, 1984 Recent Movements of the Juan de Fuca Plate System ROBIN RIDDIHOUGH! Earth PhysicsBranch, Pacific GeoscienceCentre, Departmentof Energy, Mines and Resources Sidney,British Columbia Analysis of the magnetic anomalies of the Juan de Fuca plate system allows instantaneouspoles of rotation relative to the Pacific plate to be calculatedfrom 7 Ma to the present.By combiningthese with global solutions for Pacific/America and "absolute" (relative to hot spot) motions, a plate motion sequencecan be constructed.This sequenceshows that both absolute motions and motions relative to America are characterizedby slower velocitieswhere younger and more buoyant material enters the convergencezone: "pivoting subduction."The resistanceprovided by the youngestportion of the Juan de Fuca plate apparently resulted in its detachmentat 4 Ma as the independentExplorer plate. In relation to the hot spot framework, this plate almost immediately began to rotate clockwisearound a pole close to itself such that its translational movement into the mantle virtually ceased.After 4 Ma the remainder of the Juan de Fuca plate adjusted its motion in responseto the fact that the youngest material entering the subductionzone was now to the south. Differencesin seismicityand recent uplift betweennorthern and southernVancouver Island may reflect a distinction in tectonicstyle betweenthe "normal" subductionof the Juan de Fuca plate to the south and a complex "underplating"occurring as the Explorer plate is overriddenby the continent.The history of the Explorer plate may exemplifythe conditionsunder which the self-drivingforces of small subductingplates are overcomeby the influenceof larger, adjacent plates. The recent rapid migration of the absolutepole of rotation of the Juan de Fuca plate toward the plate suggeststhat it, too, may be nearingthis condition.
  • Description of Map Units Northeast Asia Geodynamics Map

    Description of Map Units Northeast Asia Geodynamics Map

    DESCRIPTION OF MAP UNITS NORTHEAST ASIA GEODYNAMICS MAP OVERLAP ASSEMBLAGES (Arranged alphabetically by map symbol) ad Adycha intermountain sedimentary basin (Miocene and Pliocene) (Yakutia) Basin forms a discontinuous chain along the foot of southwestern slope of Chersky Range in the Yana and Adycha Rivers basins. Contain Miocene and Pliocene sandstone, pebble gravel conglomerate, claystone, and minor boulder gravel conglomerate that range up to 400 m thick. REFERENCES: Grinenko and others, 1998. ag Agul (Rybinsk) molasse basin (Middle Devonian to Early Carboniferous) (Eastern Sayan) Consists of Middle Devonian through Early Carboniferous aerial and lacustrine sand-silt-mudstone, conglomerate, marl, and limestone with fauna and flora. Tuff, tuffite, and tuffaceous rock occur in Early Carboniferous sedimentary rocks. Ranges up to 2,000 m thick in southwestern margin of basin. Unconformably overlaps Early Devonian rocks of South Siberian volcanic-plutonic belt and Precambrian and early Paleozoic rocks of the Siberian Platform and surrounding fold belts. REFERENCES: Yanov, 1956; Graizer, Borovskaya, 1964. ags Argun sedimentary basin (Early Paleozoic) (Northeastern China) Occurs east of the Argun River in a discontinuously exposed, northeast-trending belt and consists of Cambrian and Ordovician marine, terrigenous detrital, and carbonate rocks. Cambrian units are composed of of feldspar- quartz sandstone, siltstone, shale and limestone and contain abundant Afaciacyathus sp., Bensocyathus sp., Robustocyathus yavorskii, Archaeocyathus yavorskii(Vologalin), Ethomophyllum hinganense Gu,o and other fossils. Ordovicain units consist of feldspar-quartz sandstone, siltstone, fine-grained sandstone and phylitic siltstone, and interlayered metamorphosed muddy siltstone and fine-grained sandstone with brachiopods, corals, and trilobites. Total thickness ranges up to 4,370 m. Basin unconformably overlies the Argunsky metamorphic terrane.
  • Did the 1999 Earthquake Swarm on Gakkel Ridge Open a Volcanic Conduit? a Detailed Teleseismic Data Analysis Carsten Riedel, Vera Schlindwein

    Did the 1999 Earthquake Swarm on Gakkel Ridge Open a Volcanic Conduit? a Detailed Teleseismic Data Analysis Carsten Riedel, Vera Schlindwein

    Did the 1999 earthquake swarm on Gakkel Ridge open a volcanic conduit? A detailed teleseismic data analysis Carsten Riedel, Vera Schlindwein To cite this version: Carsten Riedel, Vera Schlindwein. Did the 1999 earthquake swarm on Gakkel Ridge open a volcanic conduit? A detailed teleseismic data analysis. Journal of Seismology, Springer Verlag, 2009, 14 (3), pp.505-522. 10.1007/s10950-009-9179-6. hal-00537995 HAL Id: hal-00537995 https://hal.archives-ouvertes.fr/hal-00537995 Submitted on 20 Nov 2010 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. J Seismol (2010) 14:505–522 DOI 10.1007/s10950-009-9179-6 ORIGINAL ARTICLE Did the 1999 earthquake swarm on Gakkel Ridge open a volcanic conduit? A detailed teleseismic data analysis Carsten Riedel · Vera Schlindwein Received: 19 February 2009 / Accepted: 2 November 2009 / Published online: 20 November 2009 © Springer Science + Business Media B.V. 2009 Abstract In 1999, a seismic swarm of 237 tele- ascending toward the potential conduit during the seismically recorded events marked a submarine beginning of April 1999, indicating an opening of eruption along the Arctic Gakkel Ridge, later on the vent.
  • 3D Seismic Velocity Structure Around Plate Boundaries and Active Fault Zones 47

    3D Seismic Velocity Structure Around Plate Boundaries and Active Fault Zones 47

    ProvisionalChapter chapter 3 3D Seismic Velocity Structure AroundAround PlatePlate BoundariesBoundaries and Active Fault Zones and Active Fault Zones Mohamed K. Salah Mohamed K. Salah Additional information is available at the end of the chapter Additional information is available at the end of the chapter http://dx.doi.org/10.5772/65512 Abstract Active continental margins, including most of those bordering continents facing the Pacific Ocean, have many earthquakes. These continental margins mark major plate boundaries and are usually flanked by high mountains and deep trenches, departing from the main elevations of continents and ocean basins, and they also contain active volcanoes and, sometimes, active fault zones. Thus, most earthquakes occur predomi‐ nantly at deep‐sea trenches, mid‐ocean spreading ridges, and active mountain belts on continents. These earthquakes generate seismic waves; strong vibrations that propagate away from the earthquake focus at different speeds, due to the release of stored stress. Along their travel path from earthquake hypocenters to the recording stations, the seismic waves can image the internal Earth structure through the application of seismic tomography techniques. In the last few decades, there have been many advances in the theory and application of the seismic tomography methods to image the 3D structure of the Earth's internal layers, especially along major plate boundaries. Applications of these new techniques to arrival time data enabled the detailed imaging of active fault zones, location of magma chambers beneath active volcanoes, and the forecasting of future major earthquakes in seismotectonically active regions all over the world. Keywords: 3D seismic structure, seismic tomography, Vp/Vs ratio, plate boundaries, crustal structure 1.
  • Azores and Iceland

    Azores and Iceland

    13th World Conference on Earthquake Engineering Vancouver, B.C., Canada August 1-6, 2004 Paper No. 2369 A COMPARATIVE STUDY ON STRONG GROUND MOTION IN TWO VOLCANIC ENVIRONMENTS: AZORES AND ICELAND Carlos S. OLIVEIRA1, Ragnar SIGBJÖRNSSON2, Simon ÓLAFSSON3 SUMMARY The objective of this paper is to present the main results of a comparative study of strong ground motion on the Azores and Iceland. These islands are a super-structural part of the Mid Atlantic Ridge, which marks the boundary between the North-American Plate and the Eurasian Plate and creates a north-south oriented belt of seismic and volcanic activity. The tectonic environments are described and compared emphasising the similarities in the geological structure, including surface geology and its effects on strong ground motion. Furthermore, the seismicity of the Azores and Iceland is compared based on earthquake catalogues using statistical analysis. The strong-motion networks on the islands are described along with the strong-motion data used in the subsequent analysis. The strong-motion data are compared using statistical analysis. The main emphasis is put on attenuation of strong-motion data, characterised by root mean square acceleration and peak ground acceleration. The attenuation is also compared to some of the common attenuation relationships, used by the engineering community in Europe and America. The main findings are that there are significant similarities between the tectonic environments of the Azores and Iceland. Furthermore, the similarities found in seismicity are statistically significant. The attenuation is characterised by rapid decay with increasing distance and high acceleration in the near source area. It is found that the same ground motion estimation models can be applied on the Azores and in Iceland.
  • Hydrothermal Exploration Near the Azores Triple Junction: Tectonic Control of Venting at Slow-Spreading Ridges?

    Hydrothermal Exploration Near the Azores Triple Junction: Tectonic Control of Venting at Slow-Spreading Ridges?

    EPSL ELSEVIER Earth and Planetary Science Letters 138 (1996) 93- 104 Hydrothermal exploration near the Azores Triple Junction: tectonic control of venting at slow-spreading ridges? C.R. German * , L.M. Parson, HEAT Scientific Team. ’ Southampton Oceanography Centre, Empress Dock, Southampton, SO14 3ZH, UK Received 8 June 1995; accepted 14 November 1995 Abstract Simultaneous acoustic imaging of the seafloor and detection of particle-rich plumes in the overlying water column have been used to identify and determine the tectonic setting of high-temperature ‘black smoker’ hydrothermal activity along 200 km of the Mid-Atlantic Ridge between 36” and 38”N. Using this approach, we have identified hydrothermal signals at 7 different locations. These results indicate a higher incidence of hydrothermal activity along this section of ridge axis than has been reported elsewhere along slow spreading ridges. Our data show that the majority of hydrothermal sites here are located near to non-transform offsets rather than at the centres of individual ridge segments. We suggest that this intersection of fabrics, associated with ridge discontinuities and the spreading process, is instrumental in focussing hydrothermal flow at these localities. Future strategies of exploration for hydrothermal activity on slow-spreading ridges may need to be revised accordingly. Keywords: Azores; Mid-Atlantic Ridge; triple junctions; black smokers; acoustical surveys 1. Introduction Neutrally buoyant plumes overlying high-temper- ature ‘black smoker’ hydrothermal fields exhibit pro- * Corresponding author. Fax: +44 1703 596554. E-mail: nounced enrichments compared to ambient seawater [email protected] in a range of characteristic tracers. Consequently, ’ HEAT Scientific Team: C.R.
  • Effusive and Explosive Volcanism on the Ultraslow-Spreading Gakkel Ridge, 85�E

    Effusive and Explosive Volcanism on the Ultraslow-Spreading Gakkel Ridge, 85E

    Article Volume 13, Number 10 6 October 2012 Q10005, doi:10.1029/2012GC004187 ISSN: 1525-2027 Effusive and explosive volcanism on the ultraslow-spreading Gakkel Ridge, 85E Claire W. Pontbriand MIT-WHOI Joint Program in Oceanography, 266 Woods Hole Road, MS 24, Woods Hole, Massachusetts 02543, USA ([email protected]) S. Adam Soule, Robert A. Sohn, Susan E. Humphris, Clayton Kunz, and Hanumant Singh Woods Hole Oceanographic Institution, 266 Woods Hole Road, MS 24, Woods Hole, Massachusetts 02543, USA ([email protected]; [email protected]; [email protected]; [email protected]; [email protected]) Ko-ichi Nakamura Institute of Geology and Geoinformation, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba 305-8567, Japan ([email protected]) Martin Jakobsson Department of Geological Sciences, Stockholm University, SE-10691 Stockholm, Sweden ([email protected]) Timothy Shank Woods Hole Oceanographic Institution, 266 Woods Hole Road, MS 24, Woods Hole, Massachusetts 02543, USA ([email protected]) [1] We use high-definition seafloor digital imagery and multibeam bathymetric data acquired during the 2007 Arctic Gakkel Vents Expedition (AGAVE) to evaluate the volcanic characteristics of the 85E seg- ment of the ultraslow spreading Gakkel Ridge (9 mm yrÀ1 full rate). Our seafloor imagery reveals that the axial valley is covered by numerous, small-volume (order 1000 m3) lava flows displaying a range of ages and morphologies as well as unconsolidated volcaniclastic deposits with thicknesses up to 10 cm. The valley floor contains two prominent volcanic lineaments made up of axis-parallel ridges and small, cra- tered volcanic cones.
  • Quaternary Stratigraphy of the Northwind Ridge, Arctic Ocean

    Quaternary Stratigraphy of the Northwind Ridge, Arctic Ocean

    Quaternary Stratigraphy of the Northwind Ridge, Arctic Ocean THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Kevin Allen Crawford B.S. Graduate Program in Geological Sciences The Ohio State University 2010 Master's Examination Committee: Peter-Noel Webb, Advisor Leonid Polyak Lawrence A. Krissek Copyright by Kevin A Crawford 2010 Abstract The Arctic Ocean plays an important role in modulating the world‘s climate. Changes in sea-ice albedo and the export of freshwater into the North Atlantic could have serious repercussions to the climate patterns far beyond the Arctic. To understand fully the impacts of the retreating sea-ice cover and the warming Arctic Ocean we need to look into the past for clues. Paleoenvironments of the Arctic Ocean can be reconstructed by using sea-floor sediment constituents, such as paleobiological and mineral components as well as chemical and paleomagnetic parameters. Three cores raised from the Northwind Ridge, north of the Alaskan continental margin, were chosen to investigate sedimentary patterns and related paleoenvironments in the western Arctic Ocean across a time frame from the Holocene to estimated early Pleistocene. These cores show a range of sedimentation rates decreasing from south to north, thus allowing a development of a relatively high-resolution Upper Quaternary stratigraphy at the southern part of the ridge and a lower-resolution, yet longer stratigraphy for its northern part. In addition to this long stratigraphic coverage, the northern core has well-preserved calcareous microfauna, which provides new insights into paleoceanographic environments.
  • On the Dynamics of the Juan De Fuca Plate

    On the Dynamics of the Juan De Fuca Plate

    Earth and Planetary Science Letters 189 (2001) 115^131 www.elsevier.com/locate/epsl On the dynamics of the Juan de Fuca plate Rob Govers *, Paul Th. Meijer Faculty of Earth Sciences, Utrecht University, P.O. Box 80.021, 3508 TA Utrecht, The Netherlands Received 11 October 2000; received in revised form 17 April 2001; accepted 27 April 2001 Abstract The Juan de Fuca plate is currently fragmenting along the Nootka fault zone in the north, while the Gorda region in the south shows no evidence of fragmentation. This difference is surprising, as both the northern and southern regions are young relative to the central Juan de Fuca plate. We develop stress models for the Juan de Fuca plate to understand this pattern of breakup. Another objective of our study follows from our hypothesis that small plates are partially driven by larger neighbor plates. The transform push force has been proposed to be such a dynamic interaction between the small Juan de Fuca plate and the Pacific plate. We aim to establish the relative importance of transform push for Juan de Fuca dynamics. Balancing torques from plate tectonic forces like slab pull, ridge push and various resistive forces, we first derive two groups of force models: models which require transform push across the Mendocino Transform fault and models which do not. Intraplate stress orientations computed on the basis of the force models are all close to identical. Orientations of predicted stresses are in agreement with observations. Stress magnitudes are sensitive to the force model we use, but as we have no stress magnitude observations we have no means of discriminating between force models.