|Mixing at mid-ocean ridges controlled by small-scale convection and plate motion|Samuel, H.; King, S.D. (2014). Mixing at mid-ocean ridges controlled by small-scale convection and plate motion. Nature Geoscience 7: 602-605. hdl.handle.net/10.1038/ngeo2208
In: Nature Geoscience. Nature Publishing Group: London. ISSN 1752-0894, more
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Oceanic lavas are thought to be derived from different sources within the Earth’s mantle, each with a distinct composition. Large-scale plate motions provide the primary mechanism for mixing these sources, yet the geochemical signature of lavas erupted at different mid-ocean ridges can still vary significantly. Geochemical variability is low where plate spreading rates are high, consistent with plate-scale mixing. However, slow-spreading centres, such as the Southwest Indian Ridge in the Indian Ocean, are also geochemically homogeneous, which is inconsistent with plate-scale mixing. Here we use numerical simulations of mantle flow to study mantle mixing at mid-ocean ridges, under conditions with variable plate length and spreading rate. Our simulations reveal that small-scale convection in the mantle contributes significantly to mantle mixing at slow spreading rates; faster plate velocities and smaller plates inhibit small-scale convection. We conclude that whereas fast-spreading ridge lavas are well mixed by plate-scale flow, slow-spreading ridge lavas are mixed by small-scale convection.