祁连山地质构造特征

祁连山呈近北西向展布,长约1000余公里,宽100-250公里。本文据甘肃、青海等省的区调、科研资料及成果综合整理。

THE CHARACTERISTICS OF GEOLOGICAL STRUCTURES IN THE CHILIENSHAN REGION,CHINA

Chilienshan was a typical Caledonian geosyncline in the Kunlun-Qinling geosync-line fold system,which attained its full growth of folding in the Caledonian movement(Chilien cycle)at the end of Silurian.The structural units of Chilienshan can be subdivided into(from North to South): 1)the Hosi-Zoulang marginal geosyncline fold belt; 2)the North Chilienshan eugeo-syncline fold belt(with ophiolites); 3)the middle Chilienshan uplifted fold belt; 4)the Lajishan taphrogeosyncline fold belt(involved with ophiolites); 5)the South Chilienshan miogeosyncline fold belt.Chilienshan tectonic belt is situated between northern plate aad southern plate in China,and has two lithospheric fractures,which made of an important suture line of the ancient plate tectonics.The first one is Northern Chilienshan deep fracture system,the second one is Qinhai lake-Northern Huaiyang deep fracture system.On the basis of recent field investigation,five ancient ophiolite suites may be recognized,which lie respectively in Sinian(Zc-Zj),Middle Cambrian and the Upper Ordovician,the Middle Ordovician and Lower Ordovieian.The glaucophane-sehists ore found along Northern Chilienshan deep fracture belt extended to one or two hundred km is generally associated with scattering melanges.Most of the basic volcanic rocks of ancient ophiolites are characterized by low potashium(K₂O<0.3%),high sodium(Na₂>3%),Na₂/K₂O=2.61-28.51.