Magmatic processes in the depth of Tianxiu segment,Carlsberg Ridge:Implication from crystallization conditions of clinopyroxene in MORB
Mid-ocean ridge basalt(MORB)is a type of excellent material for understanding the thermal condition,magma supply and evolution of the mid-ocean ridge.To investigate the deep magmatic processes of the Tianxiu segment at the slow spreading Carlsberg Ridge,detailed petrological and mineralogical studies on MORB(49V-DR02)dredged basalts from the Tianxiu segment from the DY49V cruise were carried out to estimate the crystallization temperature and pressure of clinopyroxene in the dredged basalts by clinopyroxene-liquid thermobarometers.The dredged basalts are tholeiitic N-MORB,and clinopyroxene in the basalts are dominantly augite and diopside that generally are scaly,dendritic or skeletal microcrystals in the matrix.Clinopyroxene-liquid thermobarometers yield crystallization temperatures of 1153～1225 ℃ and pressures of 0.08～0.64GPa,equivalent to a depth of 2.6～21.1km,most of them focus within 10～16km of depth.The crystallization temperatures have a narrow range of variation,but the crystallization depth is very dispersed from a shallow upper ocean crust to a deeper ocean lithosphere mantle region,but most of them are dominantly in the ocean lithosphere mantle region,indicating no melt lens or magma chamber occurs in the ocean crust in the Tianxu segment.It implies that the mantle lithosphere of the Tianxiu segment was very thick,and the terminate depth of magma produced by the mantle partial melting was relatively deeper.Voluminous melts gathered within the depth of 10～16km to affect the Tianxiu hydrothermal cycle as a heat source.
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