柴达木盆地北缘都兰地区榴辉岩中透长石+石英包裹体:超高压变质作用的证据

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

近年来在祁连地体与柴达木地块之间大柴旦—都兰北一线确定出一条榴辉岩带。在此带东端都兰北部地区野马滩一带榴辉岩中,我们发现产在石榴子石内部由透长石和多晶石英(柯石英假像)构成的包裹体。包裹体的内部结构特征及周围的放射状裂纹反映早期超高压变质相特征,据此,推测柴达木盆地北缘榴辉岩带可能是一形成深度超过80km的超高压变质带。

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.