caa a22 4500 47704736X CHVBK 20180405111334.0 cr unu---uuuuu 170330e19960901xx s 000 0 eng 10.1007/BF00874736 doi (NATIONALLICENCE)springer-10.1007/BF00874736 Chen Yongshun College of Oceanic and Atmospheric Sciences, Oregon State University, 97331, Corvallis, OR, USA aut Dynamics of the mid-ocean ridge plate boundary: Recent observations and theory [Elektronische Daten] [Yongshun Chen] The global mid-ocean ridge system is one of the most active plate boundaries on the earth and understanding the dynamic processes at this plate boundary is one of the most important problems in geodynamics. In this paper I present recent results of several aspects of mid-ocean ridge studies concerning the dynamics of oceanic lithosphere at these diverging plate boundaries. I show that the observed rift valley to no-rift valley transition (globally due to the increase of spreading rate or locally due to the crustal thickness variations and/or thermal anomalies) can be explained by the strong temperature dependence of the power law rheology of the oceanic lithosphere, and most importantly, by the difference in the rheological behavior of the oceanic crust from the underlying mantle. The effect of this weaker lower crust on ridge dynamics is mainly influenced by spreading rate and crustal thickness variations. The accumulated strain pattern from a recently developed lens model, based on recent seismic observations, was proposed as an appealing mechanism for the observed gabbro layering sequence in the Oman Ophiolite. It is now known that the mid-ocean ridges at all spreading rates are offset into individual spreading segments by both transform and nontransform discontinuities. The tectonics of ridge segmentation are also spreading-rate dependent: the slow-spreading Mid-Atlantic Ridge is characterized by distinct "bulls-eye” shaped gravity lows, suggesting large along-axis variations in melt production and crustal thickness, whereas the fast-spreading East-Pacific Rise is associated with much smaller along-axis variations. These spreading-rate dependent changes have been attributed to a fundamental differences in ridge segmentation mechanisms and mantle upwelling at mid-ocean ridges: the mantle upwelling may be intrinsically plume-like (3-D) beneath a slow-spreading ridge but more sheet-like (2-D) beneath a fast-spreading ridge. Birkhäuser Verlag, 1996 Oceanic spreading center nationallicence mantle upwelling nationallicence rift valley to no-rift valley transition nationallicence ridge segmentation nationallicence pure and applied geophysics Birkhäuser-Verlag 146/3-4(1996-09-01), 621-648 0033-4553 146:3-4<621 1996 146 24 https://doi.org/10.1007/BF00874736 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00874736 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Chen Yongshun College of Oceanic and Atmospheric Sciences, Oregon State University, 97331, Corvallis, OR, USA aut NATIONALLICENCE 773 0- pure and applied geophysics Birkhäuser-Verlag 146/3-4(1996-09-01), 621-648 0033-4553 146:3-4<621 1996 146 24 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer