西藏阿里地区北部新生代火山岩—兼论陆内俯冲作用

CENOZOIC VOLCANIC ROCKS IN THE NORTHERN NGARI DISTRICT OF THE TIBET (XIZANG)——DISCUSSION ON THE CONCURRENT INTRACONTINENTAL SUBDUCTION

本文研究了新南藏北昆仑山南侧新生代火山岩的地质学、岩石学和主要元素、痕量元素地球化学特征;划分出以新第三纪喷发为主的碱性火山岩带(南带)和与之伴随的第四纪钙碱性火山岩带(北带);用塔里木大陆岩石圈向青藏高原下面的俯冲机制解释了本区火山岩的成因,并且认为陆内俯冲作用不但可以说明中国西部诸山系的近期上升,而且可以运用于所有地壳厚度异常的碰撞带,因而具有普遍的意义。作者划分出具有不同地质特色的昆仑山型和喜马拉雅型两种陆内俯冲模式。

Cenozoic volcanic rocks in the Kunlun Mts. district between the Northern Tibet and Southern Xinjiang have been studied in geology, petrology, major and trace element geochemistry. They are divided into two belts: one is an alkalicvolcanic rock belt erupted mostly in Late Tertiary (South belt) and ether is a calcalkalic volcanic rock belt erupted mostly in Quaternary(North belt). Origin of volcanics in this area could be explained by subduction of the Talim continental lithosphere southwards beneath the Tibetan Plateau. and it is suggested that the intracontinental subduction not only can interpret recent uplift of some mountains in western China, but also is suitable for all collision zones which have unusually thick crust and therefore this mechanism is universally applicable. The Kunlun type and Himalayan type of the intracontinental subduction are proposed on the basis of different geological characteristics.