Cenozoic thermal evolution of lithospheric mantle in northern Victoria Land (Antarctica): Evidences from mantle xenoliths

摘要

Thermobarometry of spinel peridotites collected in northern Victoria Land in Cenozoic basalts of the Mt Melbourne Volcanic Province, reveals warming of local lithospheric mantle, marked by a shift of geothermal gradient from 0.5 °C/km to ～3 °C/km during the development of Cenozoic magmatism related to the opening of the Ross Sea rift system.Wesuggest that a significant uplift fraction of the rift shoulder on the West Antarctic margin is due to the change in olivine molar volume induced by mantle heating. The heat source is provided by enhancement of asthenospheric convection induced by an “edge effect” in the mantle circulation, following the opening phase of the Ross Sea. Besides explaining the asymmetric uplift of the rift shoulder corresponding to the Transantarctic Mountains, this mechanism satisfactorily accounts for the time scale (～10 Ma) and most of total uplift (～3000 m) of the western border of the Ross Sea in northern Victoria Land.