Tectonic attribute of the Qoltag orogenic belt in the East Tianshan Mountains, northwestern China

Abstract：The Joltag orogenic belt is located between the Turpan-Hami basin and Central Tianshan block, in the East Tianshan Mountains. For a long time different views exist as to the tectonic attribute of this orogenic belt, e.g. it is considered as a Late Paleozoic arc island belt, a backarc basin, an aulacogen, a Paleozoic continental-marginal accretion belt or Carboniferous volcanic-type passive continental margins. Based on systematic petrological, petrochemical and rock geochemical studies of the volcanic-sedimentary formations of the Early Carboniferous Yamasu Formation in the belt and the fact that the Qoltag area was in an intraplate extensional dynamic setting rather than a noncompresional collisional dynamic setting during the Early Paleozoic，the authors conclude that the Qoltag orogenic belt should be an extensional tectono-magmatic one.