Spreading-rate dependence of melt extraction at mid-ocean ridges from mantle seismic refraction data

摘要: A variety of observations indicate that mid-ocean ridges produce less crust at spreading rates below 20 mm yr(-1) (refs 1-3), reflecting changes in fundamental ridge processes with decreasing rate. The nature these changes, however, remains uncertain, end-member explanations being shallow melting or incomplete melt extraction, each due to the influence a thicker thermal lid. Here we present results seismic refraction experiment designed study by imaging residual mantle structure. Our reveal an abrupt lateral change bulk properties associated from slow ultraslow palaeo-spreading Changes velocity gradient, basement topography and crustal thickness all correlate this spreading-rate change. These can be explained variations extraction ridge, gabbroic phase preferentially retained slower rates. estimated volume balances approximately 1.5-km difference thickness, suggesting rate affect melt-extraction rather than total melting.