Sanidine + Quartz Inclusions in Dulan Eclogites: Evidence for UHP Metamorphism on the North Margin of the Qaidam Basin, N W China

An Early Palaeozoic eclogite-bearing complex belt has been identified as a continental collision suture zone between the Qilian terrain and the Qaidam terrain in recent years. K-feldspar (sanidine) occurs alongside quartz (a pseudomorph after coesite) as microinclusions in garnets of eclogite from the north belt eclogite in Dulan, the east part of the north Qaidam eclogite belt. The mosaic polycrystalline texture of K-feldspar + quartz aggregation and radial fractures around the inclusions indicate that they are the product of peak metamorphism under the ultrahigh-pressure condition. Therefore, the authors consider that the eclogite-bearing complex belt is most probably a UHP belt formed at a depth over 80 km.