Modern Mantle Activity in Central Asia in Retrospection of 400 Ka inferred from U–Th-isotope Systematics of Volcanic Rocks: Control of Mantle Melting by Growing and Thawing Glaciers
To estimate retrospective variations of the mantle activity in Central Asia, isotopes of 238U-series were measured by ICP–MS technique in volcanic rocks erupted in Sayans (Siberia) and Hangay (Central Mongolia) in the past 400 Ka. From calculations, a general increasing of melting rate and mantle upwelling beneath these areas is inferred. It is suggested that the elevated melting rate and mantle upwelling beneath Sayans was due to anomalous reducing lithostatic pressure caused by thawing ice sheets. The decreased mantle activity beneath Hangay reflected relatively stable isostatic conditions of the area in the absence of glaciation.