Download or read book Crustal Accretion at Intermediate Spreading Rates written by Ana Lucia Goncalves Macario and published by . This book was released on 1995 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Crustal Accretion at the Intermediate Spreading Rate Southeast Indian Ridge written by L. Ying Ma and published by . This book was released on 1997 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Crustal Accretion and Evolution at Slow and Ultra slow Spreading Mid ocean Ridges written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Funding was provided by the National Science Foundation through Contract No. OCE-9300450 and by the Joint Oceanographic Institutions through Subcontract No. JSC1-00.
Download or read book Ophiolites and Oceanic Crust written by Yildirim Dilek and published by Geological Society of America. This book was released on 2000-01-01 with total page 570 pages. Available in PDF, EPUB and Kindle. Book excerpt: The proceedings from the September 1998 conference in Marshall, California contain 39 papers on the following topics: ophiolites, ocean crust, and global tectonics; oceanic lower crust and upper mantle; structure and physical properties of upper oceanic crust; hydrothermal processes; Pacific Rim ophiolites; and, Ophiolites from Iapetus, Rheic-Pleionic, Neotethyan, and Indian Oceans. Contributors include scientists with backgrounds in structural geology, tectonics, geophysics, petrology, and geochemistry. Numerous black and white illustrations (and one in color) are included. Annotation copyrighted by Book News Inc., Portland, OR
Download or read book Duration Rates and Patterns of Crustal Growth at Slow spreading Mid ocean Ridges written by Craig B. Grimes and published by ProQuest. This book was released on 2008 with total page 309 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation addresses temporal and spatial characteristics of magmatic and tectonic accretion processes occurring at mid-ocean ridges during formation of new ocean lithosphere. The accretion histories of plutonic crust recovered by deep drilling of footwalls to large-displacement normal faults at three locations on the MAR are emphasized. Pb/U zircon dating of evolved gabbros and oceanic plagiogranites show that magmatic accretion typically occurs over 100-200 kyr. Magmatic accretion occurs by emplacement of many short-lived intrusive pulses that are focused at different depths within the crust and mantle. During formation of the Atlantis Massif core complex (30° N, MAR), spreading may have been partitioned up to 100% on the North American plate for at least 200 kyr, implying crustal accretion was highly asymmetric. Cooling rates of 1000-2000° C/m.y. over 900-200° C are documented at Atlantis Massif and two locations from 14-16°N, MAR, consistent with rapid denudation of the footwall sections to the seafloor following emplacement. Spreading rates combined with the time interval over which cooling to
Download or read book New Insights Into Accretion and Cooling of Lower Ocean Crust at Ultraslow and Fast spreading Mid ocean Ridges written by Christopher James Doorn and published by . This book was released on 2022 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mid-ocean ridges are the primary divergent tectonic margins and generate the ocean crust, which covers ~60% of Earth’s surface. The gabbroic lower ocean crust hosts lithologic and structural diversity varying with spreading rate and magma supply. This dissertation examines lower crustal accretion at ultraslow- and fast-spreading ridges to better constrain crustal accretion and cooling across spreading rates. Trace element compositions of zircon from Atlantis Bank (Southwest Indian Ridge) characterize the final stages of magmatism and the thermal architecture in the lower crust produced along an ultraslow-spreading ridge. U-Pb zircon dates of evolved gabbroic rocks from the fast-spread lower crust at Pito Deep (East Pacific Rise) reveal significant off-axis magmatism, implying locally robust magmatism and relatively slow cooling of this nascent ocean crust. Textural characteristics of gabbroic rocks from Pito Deep highlight the lateral complexity of the fast-spread lower crust, and record increasing degrees of magmatic strain with depth. Synthesizing textural data, U-Pb geochronology, mineral chemistry, and magnetic data from Pito Deep supports a pulsed gabbro glacier flow process for generating the lower ocean crust at magmatically robust fast-spreading ridges.
Download or read book Crustal Structure in Areas of Active Crustal Accretion written by Leonard Dale Bibee and published by . This book was released on 1979 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Crustal Accretion at a Spreading Rate End member the Mid Cayman Spreading Center written by Jennifer Logan Harding and published by . This book was released on 2019 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ocean crustal accretion is an important Earth process, affecting the global heat budget, geochemical cycles, and life on Earth. New crust is produced at divergent plate boundaries, or spreading centers, at a range of full plate separation rates from ultraslow spreading rates of 15 mm/yr, to fast spreading rates of 75 mm/yr. Oceanic crustal structure, lithology, and thickness vary with spreading rate, and ultraslow-spreading centers accrete some of the thinnest and most heterogeneous crust on Earth. In order to investigate fundamental tectonic, magmatic and accretionary processes that underlie these observations, we study one of the slowest-spreading centers in the world, the Mid-Cayman Spreading Center (MCSC), situated between the North American Plate and the Caribbean Plate in the Caribbean Sea. We image the new oceanic crust formed at the MCSC by modeling wide-angle refraction seismic data, gravity data, and geochemistry of seafloor rocks. Seismic images of P-wave velocity (Vp) reveal very heterogeneous structure both parallel and perpendicular to the axial valley. A low Vp zone ~5 km beneath an off-axis massif that hosts a hydrothermal vent field likely represents fracturing associated with hydrothermal circulation, and possibly intruded magmatic sills. In order to constrain the lithology of the crust, we model amplitudes of seismic refraction data and construct gravity profiles. We find that the thickness of the igneous crust varies from ~0- 6 km with a mean of ~3 km, where gabbro within a matrix of variably serpentinized mantle is distributed unevenly along the spreading center. Geochemical modeling of incompatible element concentrations in basalts provides estimates of the magmatic budget of the MCSC and two other spreading segments with faster spreading rates. The MCSC has a modeled melt thickness of ~2.8 km, with suppressed melting to ~12 km depth. These results support the hypothesis that there is increased surface cooling of the lithosphere at ultraslow-spreading rates, which reduces melt supply, and that these magmatic processes vary smoothly with spreading rate. Variability of ultraslow-spread crustal thickness can be explained by a segment-scale spatiotemporal fluctuation of lithospheric deformation and melt delivery, with an average of ~2 km of serpentinized mantle within the upper lithosphere
Download or read book Seismic Structure and Crustal Accretion Along an Intermediate rate Mid ocean Ridge Segment written by Robert Todd Weekly and published by . This book was released on 2013 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: Epicenters and magnitudes for 36,523 earthquakes recorded along the Endeavour segment between August 2003 and October 2006 are automatically determined using a local ocean-bottom seismometer (OBS) network. The catalog is dominated by two swarm sequences in January and February 2005 in the vicinity of the Endeavour overlapping spreading center, which included earthquakes in West Valley, the northern portion of the Endeavour segment, southwest Endeavour Valley and the Endeavour vent fields. These swarms are attributed to volcanism including a dike intrusion on the northern Endeavour in February 2005 and smaller diking events on the propagating tip of the West Valley segment in both swarms. The dike on the northern Endeavour propagated to the south, which is inconsistent with magma sourced from the axial magma chamber beneath the elevated central portion of the segment. Following the swarms, seismic activity on the Endeavour segment decreased on average to ~15% of pre-swarm values and almost ceased at the segment ends. I infer that a six-year non-eruptive event that started with a swarm in 1999 and finished with the 2005 swarms ruptured the entire segment and relieved plate-spreading stresses. The inferred coupling between the 1999 and 2005 events, the observation of extensive precursory activity prior to the 2005 swarms, and the interaction between seismically active regions during the swarms is consistent with static triggering with delays influenced by viscoelastic relaxation, hydraulic diffusion and magma withdrawal and replenishment. The isotropic and anisotropic P-wave velocity structure of the upper oceanic crust on the Endeavour Segment of the Juan de Fuca Ridge is studied using refracted travel time data collected by an active-source, three-dimensional tomography experiment. The isotropic velocity structure is characterized by low crustal velocities in the overlapping spreading centers (OSCs) at the ends of the segment. These low velocities are indicative of pervasive tectonic fracturing and persist off-axis, recording the history of ridge propagation. Near the segment center, velocities within the upper 1 km show ridge-parallel bands with low velocities on the outer flanks of topographic highs. These features are attributed to localized thickening of the volcanic extrusive layer from eruptions extending outside of the axial valley that flow down the fault-tilted blocks that form the abyssal hill topography. On-axis velocities are relatively high beneath the hydrothermal vent fields due to the infilling of porosity by mineral precipitation. Lower velocities are observed beneath the most vigorous vent fields in a seismically active region above the axial magma chamber and may reflect increased fracturing and higher temperatures. Seismic anisotropy is high on-axis but decreases substantially off-axis over ~8 km (0.3 Ma). This decrease coincides with an increase in seismic velocities at depths greater than 1 km and is attributed to the infilling of cracks in the sheeted dike layer by mineral precipitation associated with near-axis hydrothermal circulation. The orientation of the fast-axis of anisotropy is ridge-parallel near the segment center but curves near the segment ends reflecting the tectonic fabric within the OSCs.
Download or read book Magmatic Rifting and Active Volcanism written by T.J. Wright and published by Geological Society of London. This book was released on 2016-09-06 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: A major rifting episode began in the Afar region of northern Ethiopia in September 2005. Over a ten-day period, c. 2.5 km3 of magma were intruded along a 60 km-long dyke separating the Arabian and Nubian plates. Over the next five years, a further 13 dyke intrusions caused continued extension, eruptions and seismicity. This activity led to a renewed international focus on the role of magmatism in rifting, with major international collaborative projects working in Afar and Ethiopia to study the ongoing activity and to place it in a broader context. This book brings together articles that explore the role of magmatism in rifting, from the initiation of continental break-up through to full seafloor spreading. We also explore the hazards related to rifting and the associated volcanism. This work has implications for our understanding of how continents break-up and the associated distribution of resources in rift basins and continental margins.
Download or read book Hydrothermal Processes at Seafloor Spreading Centers written by Peter A. Rona and published by Springer Science & Business Media. This book was released on 2013-11-21 with total page 802 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the past ten years, evidence has developed to indicate that seawater convects through oceanic crust driven by heat derived from creation of lithosphere at the Earth-encircling oceanic ridge-rift system of seafloor spreading centers. This has stimulated multiple lines of research with profound implications for the earth and life sciences. The lines of research comprise the role of hydrothermal convection at seafloor spreading centers in the Earth's thermal regime by cooling of newly formed litho sphere (oceanic crust and upper mantle); in global geochemical cycles and mass balances of certain elements by chemical exchange between circulating seawater and basaltic rocks of oceanic crust; in the concentration of metallic mineral deposits by ore-forming processes; and in adaptation of biological communities based on a previously unrecognized form of chemosynthesis. The first work shop devoted to interdisciplinary consideration of this field was organized by a committee consisting of the co-editors of this volume under the auspices of a NATO Advanced Research Institute (ARI) held 5-8 April 1982 at the Department of Earth Sciences of Cambridge University in England. This volume is a product of that workshop. The papers were written by members of a pioneering research community of marine geologists, geophysicists, geochemists and biologists whose work is at the stage of initial description and interpretation of hydrothermal and associated phenomena at seafloor spreading centers.
Download or read book Faulting and Magmatism at Mid Ocean Ridges written by W. Roger Buck and published by American Geophysical Union. This book was released on 1998-02-04 with total page 349 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book can benefit the nonspecialist who wants to keep up with work on magmatism and tectonics, as well as researchers working on mid-ocean ridges."--BOOK JACKET.
Download or read book Treatise on Geophysics written by and published by Elsevier. This book was released on 2015-04-17 with total page 5604 pages. Available in PDF, EPUB and Kindle. Book excerpt: Treatise on Geophysics, Second Edition, is a comprehensive and in-depth study of the physics of the Earth beyond what any geophysics text has provided previously. Thoroughly revised and updated, it provides fundamental and state-of-the-art discussion of all aspects of geophysics. A highlight of the second edition is a new volume on Near Surface Geophysics that discusses the role of geophysics in the exploitation and conservation of natural resources and the assessment of degradation of natural systems by pollution. Additional features include new material in the Planets and Moon, Mantle Dynamics, Core Dynamics, Crustal and Lithosphere Dynamics, Evolution of the Earth, and Geodesy volumes. New material is also presented on the uses of Earth gravity measurements. This title is essential for professionals, researchers, professors, and advanced undergraduate and graduate students in the fields of Geophysics and Earth system science. Comprehensive and detailed coverage of all aspects of geophysics Fundamental and state-of-the-art discussions of all research topics Integration of topics into a coherent whole
Download or read book Accretionary Prisms and Convergent Margin Tectonics in the Northwest Pacific Basin written by Yujiro Ogawa and published by Springer Science & Business Media. This book was released on 2011-05-18 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accretionary prisms in convergent margins are natural laboratories for exploring initial orogenic processes and mountain building episodes. They are also an important component of continental growth both vertically and laterally. Accretionary prisms are seismically highly active and their internal deformation via megathrusting and out-of-sequence faulting are a big concern for earthquake and tsunami damage in many coastal cities around the Pacific Rim. The geometries and structures of modern accretionary prisms have been well imaged seismically and through deep drilling projects of the Ocean Drilling Program (and recently IODP) during the last 15 years. Better understanding of the spatial distribution and temporal progression of accretionary prism deformation, structural and hydrologic evolution of the décollement zone (tectonic interface between the subducting slab and the upper plate), chemical gradients and fluid flow paths within accretionary prisms, contrasting stratigraphic and deformational framework along-strike in accretionary prisms, and the distribution and ecosystems of biological communities in accretionary prism settings is most important in interpreting the evolution of ancient complex sedimentary terrains and orogenic belts in terms of subduction-related processes. This book is a collection of interdisciplinary papers documenting the geological, geophysical, geochemical, and paleontological features of modern accretionay prisms and trenches in the northwestern Pacific Ocean, based on many submersible dive cruises, ODP drilling projects, and geophysical surveys during the last 10 years. It also includes several papers presenting the results of systematic integrated studies of recent to ancient on-land accretionary prisms in comparison to modern analogues. The individual chapters are data and image rich, providing a major resource of information and knowledge from these critical components of convergent margins for researchers, faculty members, and graduate and undergraduate students. As such, the book will be a major and unique contribution in the broad fields of global tectonics, geodynamics, marine geology and geophysics, and structural geology and sedimentology.
Download or read book Hydrogeology of the Oceanic Lithosphere with CD ROM written by Earl E. Davis and published by Cambridge University Press. This book was released on 2004-12-09 with total page 736 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book, first published in 2004, reviews the subject of the nature, causes, and consequences of fluid flow in oceanic crust.
Download or read book Magmatic Systems written by Michael P. Ryan and published by Academic Press. This book was released on 1994-08-26 with total page 427 pages. Available in PDF, EPUB and Kindle. Book excerpt: With its integrated and cohesive coverage of the current research, Magmatic Systems skillfully explores the physical processes, mechanics, and dynamics of volcanism. The text utilizes a synthesized perspective--theoretical, experimental, and observational--to address the powerful regulatory mechanisms controlling the movement of melts and cooling, with emphasis on mantle plumes, mid-ocean ridges, and intraplate magmatism. Further coverage of subduction zone magmatism includes:Fluid mechanics of mixed magma migrationInternal structure of active systemsGrain-scale melt flowRheology of partial meltsNumerical simulation of porous media melt migrationNonlinear (chaotic and fractal) processes in magma transportIn all, Magmatic Systems will prove invaluable reading to those in search of an interdisciplinary perspective on this active topic. Key Features* Fluid mechanics of magma migration from surface region to eruption site* Internal structure of active magmatic systems* Grain-scale melt flow in mantle plumes and beneath mid-ocean ridges* Physics of magmatic systems and magma dynamics
Download or read book Modern Ocean Floor Processes and the Geological Record written by Rachel A. Mills and published by Geological Society of London. This book was released on 1998 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt:
