P–T path, zircon U–Pb ages and tectonic implications of Devonian pelitic granulites in the southern Chinese Altay orogen

The Chinese Altay orogen is an important part of the giant Central Asian Orogenic Belt. However, its tectono–metamorphic evolution is still a matter of debate. Here, we report Devonian pelitic granulites at the Wuqiagou area in the southern Chinese Altay orogen. They are characterized by an assemblage of garnet + orthopyroxene + cordierite ± spinel + biotite + plagioclase ± K–feldspar + quartz + Fe–Ti oxides. Based on petrographic features and P–T estimates, together with phase equilibrium modeling in the NCKFMASHTO system, three metamorphic stages can be distinguished as follows: (1) pre–peak prograde (M1) stage, with small biotite–plagioclase– or spinel–bearing assemblages preserved as inclusions in garnets and P–T conditions of <4.0 kbar and 700–770 °C; (2) peak metamorphic (M2) stage, with an garnet–orthopyroxene–cordierite–bearing assemblage and P–T conditions of 4.2–5.2 kbar and 780–830 °C; and (3) post–peak retrograde (M3) stage, with the biotite–plagioclase–bearing intergrowth ...