Late-Paleoproterozoic tectonothermal events of the metamorphic basement in Alxa area: Evidence from geochronology
阿拉善变质基底古元古代晚期的构造热事件

The metamorphic basement (block) in Alxa area, Inner Mongolia, can be divided into Archean Debusige complex, Paleoproterozoic Bayan-Wulashan complex, Paleo-Middle Proterozoic Alxa complex, Boluositanmiao orthogneiss and Bijigetai orthogneiss. 1926Ma and 1802Ma metamorphic events was recorded in zircons from the gneisses of Debusige complex, 1918Ma metamorphic event and 1722Ma cooling age was respectively recorded in hornblende and plagioclase from Debusige complx. 1839Ma magmatic event was distinguished in zircons from Boluositanmiao deformed orthogneiss. The Late-Paleoproterozoic tectonothemal events can be divided into early event (2000~1900Ma) and late event (1850~1800Ma). The Late Paleoproterozoic tectonothermal events in the eastern part of Alxa area are similar to magmatic and metamorphic events in the Daqingshan-Jining-Datong area in time and feature. Therefore, Paleoproterozoic orogenic belt (khondalite belt) in the West Block, the North China Craton, extended westly to the northeastern part of Alxa area.