Tectonic units division and Precambrian significant geological events in Altyn Tagh Mountain, China

Five tectonic units are divided in Altyn Tagh Mountain area respectively Dunhuang block, ophiolitic mélange of north Altyn Tagh, Meso-Neoproterozoic tectonic slice of middle Altyn Tagh, tectonic complex belt of Altyn Tagh and basic-ultrabasic igenous rocks zone of south Altyn Tagh with different rocks assemblages and deformation-metamorphism characteristics. Based on the correct recognition of tectonic significance of geological events, five important geological events are identified in this area according to the isotopic data. Data from 3600Ma to 2500Ma shows that within Dunhuang block there are Eoarchean, Paleaoarchean and mesoarchean crust relicts and multi-phase magmatic activities. In Palaeoproterozoic from 2500Ma to 1800Ma, strong deformation and metamorphic reworking took place in Dunhuang block with some medium-basic and granite intrusion. In the period from 1000Ma to 800Ma, a lot of syn-collisional granite bodies reflect Neoproterozoic collisional orogeny in the tectonic complex belt of Altyn Tagh. The events in the age from 530Ma to 500Ma include mélange accumulation and high pressure metamorphism of muddy rocks in the ophiolitic mélange of north Altyn Tagh, high pressure metamorphism of eclogites in the tectonic complex belt of Altyn Tagh, the tectonic complex belt of Altyn Tagh is the western part of the huge scale of collisional zone of Qinling-North margin of Qadam basin.