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 Cooling and Accretion of the Lower Oceanic Crust at Fast spreading Mid ocean Ridges written by Kathrin Faak and published by . This book was released on 2013 with total page 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 Mid ocean Ridges Processes written by Violaine Combier and published by . This book was released on 2007 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: At fast spreading ridges such as the East Pacific Rise, the nature and geometry of the magma chamber are relatively well constrained, due in part to the fact that melt has been quasi ubiquitously identified in the crust beneath the ridge axis with seismic methods experiments since the end of the 1970s. In contrast, at slow-spreading ridges such as the Mid-Atlantic Ridge, the nature of the magma chamber is less well understood, because until recently, seismic methods revealed little evidence of melt in the crut. During the SISMOMAR scientific cruise in 2005, a seismic reflector interpreted as the roof of a maga chamber was discovered beneath the Lucky Strike Volcano at the Mid-Atlantic Ridge, providing new contraints on accretion processes at slow-spreading ridges. The first part of this thesis concerns the overlapping spreading center (OSC) at 9°N on the East-Pacifc Rise. Accretion at fast-spreading ridges is often treated as bi-dimensional, with no variation along the ridge axis. At OSCs, which are non-transform discontinuities of the ridge axis found at fast-spreaing ridges, volcanic and tectonic processes are tri-dimensional (3D). The study of OSCs provides new insights into the coupling between the melt supply and the tectonics of the brittle lithosphere. I will present my study of the relationships between seafloor volcanic and tectonic structures and the geometry of melt concentrations in the crust at the 9°N OSC. My study is based mainly on a new interpretation of 3D reflection seismic data acquired during the 1997 ARAD cruise. I produced a high-resolution bathymtric map derived from the seismics and a map of the melt lens reflectors in depth. The main results inlude firstly, the identification of decoupled stresses between the brittle upper crust and the lower cust, with the melt lens acting as an effective decoupling zone; and secondly, the determination of factors controlling the geometry of the melt lens: the location of the melt source beneath the melt lens, the ambient stress-field at melt lens depth which is the regional stress-field controlled by plate separation, and the brittle upper crust local stress-field. A second part of the thesis concerns the 3D processing and interpretation of the seismic reflection data acquired at the Lucky Strike Volcano during the SISMOMAR cruise. The newly processed data constrain the depth and geometry of the reflector corresponding to the roof of the magma chamber. Faults are also imaged at depth, including the axial valley bounding faults and faults on the volcano itself. The spatial relationships between the magma chamber roof and the faults suggest a vigorous cooling of the magma chamber through hydrothermal circulation.
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 Magma to Microbe written by Robert P. Lowell and published by John Wiley & Sons. This book was released on 2013-04-30 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magma to Microbe Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 178. Hydrothermal systems at oceanic spreading centers reflect the complex interactions among transport, cooling and crystallization of magma, fluid circulation in the crust, tectonic processes, water-rock interaction, and the utilization of hydrothermal fluids as a metabolic energy source by microbial and macro-biological ecosystems. The development of mathematical and numerical models that address these complex linkages is a fundamental part the RIDGE 2000 program that attempts to quantify and model the transfer of heat and chemicals from “mantle to microbes” at oceanic ridges. This volume presents the first “state of the art” picture of model development in this context. The most outstanding feature of this volume is its emphasis on mathematical and numerical modeling of a broad array of hydrothermal processes associated with oceanic spreading centers. By examining the state of model development in one volume, both cross-fertilization of ideas and integration across the disparate disciplines that study seafloor hydrothermal systems is facilitated. Students and scientists with an interest in oceanic spreading centers in general and more specifically in ridge hydrothermal processes will find this volume to be an up-to-date and indispensable resource.
Download or read book Mid Ocean Ridges written by Johnson Robin Cann and published by Cambridge University Press. This book was released on 1999-07-22 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: Covers the most important problems that arise at mid-ocean ridges; for researchers working in the earth sciences.
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 The Oceanic Crust from Accretion to Mantle Recycling written by Thierry Juteau and published by Springer. This book was released on 1999-04-15 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book deals mainly with the petrography and mineralogy of the rocks of the oceanic crust, and with petrological and geochemical processes. Structural processes are described in as far as they help in the understanding of the general processes controlling the formation and evolution of the oceanic crust and lithosphere. The book includes numerous examples and case studies, and is written in a clear and readable style which will make it popular with students.
Download or read book Magma Rock and Magma Mush Interactions as Fundamental Processes of Magmatic Differentiation written by Anastassia Borisova and published by Frontiers Media SA. This book was released on 2024-08-08 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: During transport, a percolating melt or magma may contact rock or a magmatic mush, resulting in inevitable interactions that may be described as magma/melt-rock or magma/melt-mush interactions. Examples of these types of interactions include mantle metasomatism, mineral-melt reaction in the mantle, mineral dissolution in magma, crustal wallrock partial melting, and thermal remobilization of preexisting mushy magma (rejuvenation of mush) by intruding high specific enthalpy magma. This spectrum of processes plays a major role in the composition, thickness, and age of the mantle lithosphere and its associated crust. These interactions also impact the asthenosphere because melts that form in the deepest parts of the mantle may ascend and interact with shallower mantle during transport.
Download or read book Mid Ocean Ridges written by Christopher R. German and published by American Geophysical Union. This book was released on 2004-01-09 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 148. Mid-ocean ridges play an important role in the plate-tectonic cycle of our planet. Extending some 50–60,000 km across the ocean-floor, the global mid-ocean ridge system is the site of creation of the oceanic crust and lithosphere that covers more than two thirds of the Earth's exterior. Approximately 75% of Earth's total heat flux occurs through oceanic crust, much of it at mid-ocean ridges through complex processes associated with magma solidification, heat transfer, and cooling of young oceanic lithosphere. While the majority of this heat loss occurs through conduction, approximately one third of the total heat loss at mid-ocean ridges is influenced by a convective process: hydrothermal circulation.
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 2009 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 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 Ofioliti written by and published by . This book was released on 2002 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 The Mid oceanic Ridges written by Adolphe Nicolas and published by Copernicus. This book was released on 1995 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contains the most recent oceanographic data with ophiolites, representing fossil ocean crust, abducted onto the continents by tectonic processes.
Download or read book The Dynamic Accretion of Fast spread Oceanic Crust written by Michelle R. Gess and published by . This book was released on 2020 with total page 744 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 2017, the AT37-08 cruise collected over 400 gabbro samples from in-situ fast-spread ocean crust at Pito Deep on the East Pacific Rise. The main focus site, Area B, exposes a section of gabbroic crust, ~1km flow line parallel by 1km deep. Detailed analysis of samples from the chemically and texturally distinct Northern Magmatic Suite (olivine gabbro, gabbro, and oxide gabbro) reveal varying mineral chemistry (olivine Fo79-68, plagioclase An87-68, clinopyroxene Mg#84-60, and orthopyroxene Mg#76-63). These mineral compositions overall evolve upwards, but also show a second order cyclic pattern of six Series (~200m scale), each with upward decreasing compositions, suggesting repetitive magmatic pulses. The uppermost Series is similar to the Root Zone of the Sheeted Dike Complex described in the Oman ophiolite. The other five Series may be the subsiding crystal mush of earlier axial melt lenses or a Series of sills intruded at different depths within the crustal section.
