Geodynamic process of melt generation, migration and focusing at ultraslow mid-ocean ridges

Abstract

Accretion of oceanic crust has experienced the mantle partial melting by decompression, melt extraction, migration and focusing into the oceanic crust, which emplaced in the oceanic crust forming of dike and erupted on the bottom of sea after fractional crystallization. The dramatic variation of crustal thickness along the ultraslow mid-ocean ridge and ammagmatic segmentation is concerned to be the typical characteristics to others. Based on previous studies of melt generation key factors and migration model of mid-ocean ridge basalt, this paper discussed the process of melt at ultraslow mid-ocean ridge and analyzed the key factors controlling the crustal thickness. Besides, this process and its result is constrained by geophysical and geochemical observation. The result shows that the crustal thickness along the ultraslow mid-ocean ridge is constrained by melt volume and lateral migration collectively. Among this process, mantle potential temperature, mantle compositions and spreading velocity controlled the melt volume. The segmentation of ultraslow mid-ocean ridge and the corresponding permeability barrier construct guide the migration and focusing of melt.