阿拉善变质基底古元古代晚期的构造热事件

阿拉善地块可分为太古宙的叠布斯格杂岩(岩群)、古元古代的巴彦乌拉山杂岩(岩组)和古-中元古代的阿拉善杂岩(岩群)、波罗斯坦庙片麻杂岩和毕级格台片麻杂岩。太古宙的叠布斯格岩群和片麻岩中的锆石记录了1926Ma和1802Ma的变质事件年龄,角闪石记录了1918Ma的变质事件年龄,斜长石记录了1722Ma的冷却年龄。同时,在波罗斯坦庙变形的片麻状杂岩中的锆石记录了1839Ma的岩浆事件年龄。该区古元古代晚期的构造热事件,可初步将划分为2000～1900Ma的早期事件和1850～1800Ma的晚期事件,并在时间和特点上与大青山-集宁-大同一带变质地体中广泛发育古元古代晚期的岩浆-变质事件非常相似,进而表明,华北克拉通西部陆块中的古元古代晚期造山带(孔兹岩带)向西可延伸到阿拉善东部地区。

Late-Paleoproterozoic tectonothermal events of the metamorphic basement in Alxa area: Evidence from geochronology

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.