A geological model for the structure of ridge segments in slow spreading ocean crust

摘要: First-order (transform) and second-order ridge-axis discontinuities create a fundamental segmentation of the lithosphere along mid-ocean ridges, in slow spreading crust they commonly are associated with exposure subvolcanic upper mantle. We analyzed available morphological, gravity, rock sample data from Atlantic Ocean to determine whether consistent structural patterns occur at these constrain processes that control patterns. The results show their older, inside-corner sides, both first-and characterized by thinned and/or mantle exposures as well irregular fault paucity volcanic features. Crust on young, outside-corner sides has more normal thickness, regular patterns, common forms. These tectonic thinning inside corners low-angle detachment faults previously suggested for transform Dick et al. [1981] Karson [1990]. Volcanic accretes hanging wall detachment, is stripped footwall, carried outside comer. Gravity morphological suggest faulting relatively continuous, long-lived process <25–30 mm/yr, it rnay be intermittent intermediate rates 25–40 unlikely faster rates. Detachment surfaces dissected later, high-angle formed during crustal uplift into rift mountains; can cut through entire may kinds imaged seismic reflection profiling over Cretaceous North crust. Off-axis variations gravity anomalies indicate experiences cyclic magmatic/amagmatic extension typical cycle about 2 m.y. long. During magmatic phases footwall probably exposes lower gabbros, although rocks locally have an unconformable carapace. amagmatic dip steeply crust, providing mechanism whereby ultramafic exhumed very rapidly, perhaps little 0.5 Together, strongly heterogeneous across isochrons ocean