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The Geological Record of Oceanic Crustal Accretion and Tectonism at Slow-spreading Ridges

出版	Massachusetts Institute of Technology, Woods Hole Oceanographic Institution, Joint Program in Oceanography/Applied Ocean Science and Engineering, 1996
URL	http://books.google.com.hk/books?id=_DAeAQAAIAAJ&hl=&source=gbs_api

註釋Studies of the morphology of slow-spreading ridges have contributed enormously to our understanding of the generation of oceanic crust. However, such work has largely been confined to the ridge axis, and therefore is limited in its application. The objective of this Thesis was to interpret the structural development of slow-spreading ridge segments by: (1) delineating the nature, magnitude, and relative importance of primary tectonic and volcanic processes that control crustal morphology, (2) investigating the spatial and temporal variability of these processes, and (3) examining how rheological variations in the lithosphere constrain its structural configuration. To that end, this Thesis provides detailed documentation of faults and volcanoes (seamounts) at the Mid-Atlantic Ridge from 25 deg 25'N to 27 deg 10'N and extending from zero-age crust at the ridge axis to tilde 29 Ma crust on the ridge flank. This information is used to analyze the evolution of ocean crust from initial formation on the rift-valley floor to degradation by aging processes on the ridge flank. In addition, deformation conditions in the lithosphere are examined from study of naturally deformed mantle rocks recovered from fault zones at slow-spreading ridges. Accumulation of sediments affects the seafloor morphological expression of ocean crustal structure. Therefore, to study the morphological record of crustal accretion and tectonism at the Mid-Atlantic Ridge, sediment thicknesses were mapped over the same region where the faults and seamounts were analyzed. All available seismic-reflection data were interpreted, and conversions from reflection time to thickness in meters were made based on compressional-wave velocity data.