Do ridge axis geometry and geochemical properties reflect source composition variations of the underlying magmatic plumbing system? Carbotte et al. (2015) explore this question by examining the relationship between magmatic and tectonic segmentation at mid-ocean ridges using a synthesis of geophysical and geochemical data from a large number of sources. Combining higher resolution seafloor mapping from the GMRT Synthesis, which can identify tectonic segments including small discontinuities, with more detailed geophysical imaging of below-seafloor melt distribution and comprehensive geochemical data from PetDB, the authors confirm that global mid ocean ridges are composed of a number of magmatic spreading segments, each with its own magma plumbing system extending into the asthenosphere below.
Fig. 13. Sketch showing along-axis section of idealized magmatic spreading segment at fast and slow ridges based onstudies summarized in this article. (a) At fast-spreading ridges, rising mantle melts accumulate at the base of the crust (orange–grey) beneath each principal magmatic segment. The crustal magmatic system is composed of a more or less steady state magma lens or sill (red) that is partitioned into finer-scale segments coincident with the finest-scale seafloor segmentation. This shallow magma lens resides above a lower crustal zone of crystal mush and possible lower crustal sills (red lozenges embedded in red –grey). Red arrows in the dyke section indicate trajectories of magma transport during dyking (primarily vertical with minor lateral transport in places). (b) At slow-spreading ridges, strong focusing of mantle melts leads to thick crust/thin axial lithosphere at centre and thin crust/thick axial lithosphere at ends of each principal magmatic segment. Crustal magma bodies are more localized and ephemeral; both vertical and lateral magma transport during dyking may occur. Normal faulting is highly localized in detachments at segment ends and more distributed between several axial valley faults at segment centres. See text for further discussion.
Carbotte et al., (2015) Tectonic and magmatic segmentation of the Global Ocean Ridge System: a synthesis of observation. Geological Society of London, Special Publications 420. DOI:10.1144/SP420.5.