The main uplift processes of deep crustal rocks of the early proterozoic orogenic belt in Daqingshan area, Inner Mongolia

Abstract

Deep crustal rocks of the Early Proterozoic orogenic belt (DCR) in Daqingshan area mainly included the synorogenic-metamorphic khondalite series and reworked Archean-basement granulites. During the early stage about 1900–1800 Ma, the DCR consisted of five huge slices which obducted over and stacked up along a series of high-temperature shear zone (HTSZ). and were subsequently uplifted from the deep crustal level to the middle one accompanied with granulite-amphibolite facies retrometamorphic reworking in HTSZ. From 1800 – 1700 Ma, some slices and HTSZ mentioned above were oveprinted by several low-temperature shear zone (LTSZ), of which the low-angle oblique thrusts caused these DCR to uplift again from the middle crustal level to the shallow one, and experienced retrometamorphic reworking of greenschist facies. These two stages of uplifting processes should be included in an entire Early Proterozoic orogenic cycle.

Keywords

deep crustal rocks / orogenic belt / uplift-process / Early Proterozoic