Download or read book Magnetization of Oceanic Crust Near Selected Areas of Hydrothermal Activity on the Mid Atlantic and Gorda Ridges written by Anita L. Wooldridge and published by . This book was released on 1990 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Publications Abstracts written by United States. National Telecommunications and Information Administration and published by . This book was released on 1989 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Publications Abstracts written by Environmental Research Laboratories (U.S.) and published by . This book was released on 1992 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the Ocean Drilling Program written by Ocean Drilling Program and published by . This book was released on 1994 with total page 800 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dissertation Abstracts International written by and published by . This book was released on 1990 with total page 730 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bibliography and Index of Geology written by and published by . This book was released on 1992 with total page 1544 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Tectonics of the East Pacific Rise written by Sang-Mook Lee and published by . This book was released on 1995 with total page 530 pages. Available in PDF, EPUB and Kindle. Book excerpt: The global mid-ocean ridge system is one of the most striking geological features on the surface of the Earth. In this system, the East Pacific Rise (EPR) is the fastest spreading ridge and is thus considered as the most active magmatically among the plate boundaries. In January and February of 1988, an extensive survey by the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution was conducted along the EPR between 9°05' and 9°55'N to study the crustal structure of the axial region. This thesis, the result of that cruise, comprises four main topics: (1) characterization of normal faulting from Sea Beam bathymetric data, (2) application of mechanical models to explore the hypothesis that buoyancy arising from crustal magma chambers and gravitational spreading of the upper crust are the principal processes leading to the initiation and development of normal faults, (3) investigation of seafloor magnetization anomalies to constrain upper crustal structure, and (4) analysis of gravity anomalies to examine possible correlations between observed variations in seafloor manifestations of volcanism and deformation and underlying structure. Thus, each topic focuses on different levels of the mid-ocean ridge. Together with the results of seismic and other observations, the findings are woven into a better understanding of the tectonic processes and structure of fastspreading mid-ocean ridges.
Download or read book American Doctoral Dissertations written by and published by . This book was released on 1989 with total page 760 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Some Aspects of the Structure and Magnetization of the Oceanic Crust written by Roi Granot and published by . This book was released on 2009 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: The structure and magnetization of the oceanic crust reflect its tectonic and magmatic evolution since its initial formation. The magnetization of the crust also provides a record of the polarity reversals and strength of the Earth's geomagnetic field. In this dissertation I first describe absolute paleointensity measurements made on gabbroic rocks collected from the lower oceanic crust of the Troodos ophiolite, Cyprus. The resultant data-set provides a view into the geomagnetic field during the end of the Cretaceous normal polarity superchron (CNS, 120.6 to 83 million years ago). This data-set is then compared to the locally and globally existing data and predictions made by geodynamo numerical simulations. The results hint that the geomagnetic field had similar properties during times of frequent reversals and times of stable polarity. The second chapter of this dissertation is focused on the marine magnetic anomalies observed across the North Pacific fracture zones. Here I analyze archival and newly collected magnetic anomaly and bathymetric profiles measured across three fracture zones in the Cretaceous Quiet Zone (CNS in age). Forward and inverse modeling indicate that these anomalies arise from remanent magnetization, with enhanced remanence located on one side of each fracture zone. These long-duration enhanced zones require some long-lived asymmetry in crustal construction processes near ridge-transform intersections. The calculated magnetization contrasts provide long-term constraints on the properties of the geomagnetic field during the Cretaceous superchron. Finally, using seismic reflection and magnetic anomaly grids collected in the Adare Basin, Antarctica, I explore the kinematic evolution of the West Antarctic rift system during the Neogene. Correlation of the Adare seismic sequence to the closest drillholes and the Ross Sea seismic stratigraphy establishes the temporal framework of three regional tectonic events. Overall, minimal but significant extensional activity took place in the Adare Basin after seafloor spreading stopped. Comparison of the results with observations from the central and southern parts of the rift system suggests that a major change in plate motion took place in the middle miocene.
Download or read book Physics Briefs written by and published by . This book was released on 1992 with total page 820 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Anomalous Magnetic Field of the World Ocean written by Alexander M. Gorodnitsky and published by CRC Press. This book was released on 1994-10-12 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book investigates the anomalous magnetic field of the ocean and its connection with geological structure, tectonic evolution of the oceanic lithosphere, and magnetic properties of different rock types in the oceanic crust. The book describes new instruments and techniques of gradient magnetic measurements with three sensors, as well as the new technique of processing and interpretating hydromagnetic data on the basis of adoptive filtration and reparametrization. The text provides unique data of geomagnetic surveys carried out by Russian research vessels in different regions of the World Ocean, including submersible apparatus and ingenious theoretical and experimental technology of the magnetic modeling and investigations of the nature of magnetic anomalies. The results of systems analysis of geochemical content and composition during the mid-oceanic ridge basalt are presented.
Download or read book Thermal Structure of Mid Ocean Ridges Lucky Strike Mid Atlantic Ridge and Magma Chambers written by Doga Dusunur and published by . This book was released on 2008 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modeling the thermal state of the oceanic crust is an important task to understand the construction of oceanic crust which covers two thirds of the surface of our planet. The interplays among magma delivery to the axis and cooling of the oceanic lithosphere as a function of both space and time are key factors to understand the creation of the oceanic crust, which is primarily determined by the overall thermal structure of mid-ocean ridges. Classical thermal models do not predict steady state axial magma chambers (AMCs) along mid-ocean ridges at spreading rates less than 30 mm/year. The identification and seismic imaging of an axial magma chamber underlying the Lucky Strike central volcano and hydrothermal field at the Mid-Atlantic Ridge provides a unique opportunity to study the thermal structure of slow spreading ridges. Here we present coupled microseismic data and thermal modeling to provide insight on the nature of ephemeral magma chambers at slow-spreading ridges, to constrain the timescales associated with changes in melt supply and the parameters that can create them, and to shed light on the different mechanisms that can result on the cooling and disappearance of these structures. Both the coupled microseismic and thermal modeling results, and the time-constraints derived from the geological constraints put forward, suggest that focused melt supply to the segment center is required regularly, and that this supply is maintained over extended periods of time, that can lead to a durable magma chamber. This thesis, while focusing on the processes occurring at the Lucky Strike, provide a more general template to both understand and study other slow-spreading ridge segments, and to gain insight on how the oceanic crust is formed along them.
Download or read book Magnetic Anomalies Over Fracture Zones in the Central North Atlantic Ocean written by Willem Twigt and published by . This book was released on 1980 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Oceanic Lithosphere Magnetization written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2007.
Download or read book Using Magnetic Methods to Better Understand the Thermal Structure of Fast spread Lower Ocean Crust at Pito Deep written by Sarah May Maher and published by . This book was released on 2021 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: More than 30% of oceanic crust is formed at fast-spreading ridges, but there remains much to learn about how the lower, gabbroic crust is accreted and cooled. This is partially due to conflicting evidence from direct and indirect studies of the lower crust and ophiolite analogues, leading to two end-member models for gabbroic crust formation which have different predictions for the thermal structure of the crust. The gabbro glacier model asserts the majority of heat is lost through the upper crust via hydrothermal circulation while the gabbroic crust cools conductively off-axis. The sheeted sills model requires efficient cooling throughout the crust within 2-3 km of the spreading center via deep hydrothermal circulation. These models are testable using magnetic techniques. As the lower ocean crust cools, magnetic minerals will lock in the magnetic field direction. If the crust is cooling during a magnetic reversal, the boundary between polarity intervals acts as a proxy isotherm in the lower crust. The slope of that isotherm will distinguish between the gabbro glacier model, which should have shallow isotherms dipping away from the ridge, and the sheeted sills model, where isotherms would steeply dip near the ridge. A 2017 cruise to Pito Deep, a tectonic exposure in fast-spread crust, recorded near-bottom magnetic data and collected oriented gabbroic samples to document a polarity boundary in the lower crust. This thesis developed a magnetic inversion technique to incorporate near-bottom anomaly data from multiple platforms over steep escarpments to identify the location of the polarity boundary at depth. Results show a large offset of the polarity boundary between the dike and gabbroic layers, implying that the gabbroic layer remains hotter for an extended period off-axis. Using oriented samples from a 1x1 km study area, I verified the location of a polarity boundary which remains horizontal for a minimum of 8 km off-axis. Finally, I use samples with multiple polarity components to determine a cooling rate in gabbroic crust. Our results are incompatible with deep hydrothermal cooling within 2-3 km of the spreading center, and instead promote the idea of slow cooling within 8 km of the spreading center.
Download or read book Geologic Hydrothermal and Biologic Studies at Escanaba Trough Gorda Ridge Offshore Northern California written by Geological Survey (U.S.) and published by . This book was released on 1994 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Implications of Fine Scale Magnetics for the Structure and Evolution of Slowly Accreted Oceanic Crust written by and published by . This book was released on 1997 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The long range objective of this program is to understand the structure of oceanic crust created at slow-spreading ridges by investigating the patterns of magnetization that reside in the crust. The project seeks to investigate how crustal magnetic fields are related to the structural deformation history of oceanic crust formed in slow spreading environments and how magnetization may be used to predict the properties of the underlying crust. Scientific Objectives are: (1) Investigate the relationship between crustal magnetization and the tectonic structure and architecture of oceanic crust by comparing the magnetization patterns of crust created at 'inside corners' versus 'outside corners' of ridge segment offsets. (2) Investigate the relationship between crustal magnetization and cyclic magmatic and tectonic processes involved in crustal formation and how this magnetization signal varies with age. (3) Investigate along-axis variability in crustal magnetization within a ridge segment and compare with the ridge axis signal. (4) Map magnetic isochrons to provide temporal framework for other related studies e.g. investigate how crustal structure and seafloor morphology change with spreading rate.
