东秦岭秦岭岩群中角闪石环带所记录的pTt轨迹

东秦岭秦岭岩群是一套中深变质结晶岩系，主要由片麻岩、斜长角闪岩、变粒岩和大理岩组成。秦岭岩群中角闪石多具成分环带，由角闪石成分环带确定的ｐＴｔ轨迹由三段组成：①等压升温轨迹，②等压降温轨迹，③降温降压轨迹。同位素年代学表明东秦岭秦岭岩群曾经历晋宁和加里东两个变质旋回，在晋宁旋回晚期形成等压升温轨迹，在加里东旋回早期形成等温降压轨迹，晚期形成降温降压轨迹。

THE pTt PATH RECORDED BY THE AMPHIBOLE ZONATION OF THE QINLING GROUP IN EASTERN QINLING MOUNTAIN

The Qinling Group is lithologically composed of four closely related but different rock sequences,gneiss,amphibolite,metadolerite and marble.Amphiboles in Qinling group are zoned.The pTt path from amphibole zonation suggests the collision between North China massif and Yangtze massif,which had resulted in the thickening of the lithophere.The major characteristic of the pTt path is the isobaric heating followed by isothermal decompression,and at last decompression and cooling,which is caused by intracontinental orogenesis.The isotopic geochronology suggests Jining and caledonian cycles are the two most important metamorphic cycles in Qinling group.During the Jining cycle the sharp increasing of pressure and the steady increasing of tempe rature was caused by the horizontal shortening and vertical thickening of the crust.The isothermal decompression in caledonian cycle was caused by fast uplifting by extension and upper strata slipping towards east in Eastern Qinling mountain.