松潘—甘孜造山带中丹巴地区变质岩演化及其地质意义

丹巴地区位于松潘—甘孜造山带中部。区域动热变质作用主要发生于印支晚期—喜马拉雅早期，与深层滑脱-逆冲作用有关。根据特征矿物组合．丹巴地区变质岩可划分出六个变质带：绢云母—绿泥石带、黑云母带、石榴子石带、十字石带、蓝晶石带和夕线石带。石榴子石生长环带代表每段时间矿物晶体边部的平衡，可用于推测石榴子石生长时的P－t轨迹。利用石榴子石—黑云母温度计和石榴子石—斜长石—Al2SiO5-石英压力计得到石榴子石的参考温度、压力，根据环带定量计算得到的变质作用p-t轨迹为顺时外形式，与其所处的构造背景为大陆碰撞造山带是一致的。

THE EVOLUTION OF METAMORPHIC ROCKS IN THE SONGPAN-GANZI OROGENIC BELT IN THE DANBA AREA AND ITS GEOLOGICAL IMPLICATIONS

The Danba area is located in the central part of the Songpan-Ganzi orogenic belt. The major metamorphic period occurred between Late Indosinian and Early Himalayan, which is related to regional dynamothermal metamorphlsm. In terms of mineral paragenesis, the metamorphic rocks can be subdivided into six metamorphic zones: sillimanite zone, kyanite zone, staurolite zone, garnet zone, biotite zone and sericite-chlorite zone.Garnet growth zoning, which represents the balance of the mineral rims during every period,can be used to calculate the p-t path of garnet growth- Reference temperatures and pressures are estimated from garnet-biotite geothermometry and garnet-plagioclase-Al,SiO,-quart geobarome-try. The p-t path of metamorphism calculated from garnet zoning shows a clockwise character,and it is similar to that of the continental collision orogenic belt.