• 责任者：Shen Xiaoming (Key Laboratory of Crustal Dynamics ; Institute of Crustal Dynamics ; China Earthquake Administration ; Beijing 100085 ; China) ; Zhang Haixiang
• 刊名：Journal of Guilin University of Technology
• 出版年：2013
• 卷期：33(3)
• 关键词：蛇绿岩 ; ophiolite ; 铀—铅计时 ; U-Pb dating ; 氩—氩计时 ; Ar-Ar dating ; 阿尔泰山 ; Altai Mountains
• 页码：p.394-405
• 图表：6 illus., 2 tables, 71 refs.
• 分类号：0801
• issnNo：ISSN1674-9057
• isbnNo：CN45-1375/N

     Palaeozoic ophiolites are dotted sporadically along the suture zone in southern Altay Range, a key part of the Central Asian Orogenic Belt （CAOB）. Without enongh precise age constraints, the tectonic settings of the ophiolites in this area have been controversial, which cause the debate on accretionary orogenic processes in CAOB. Plagiogranite dykes interbeded with amphibolite dykes are found within the gabbro unit of the lower part of Kuerti ophiolite in southern Ahay Range. New LA - ICP - MS zircon U - Pb dating indicates that pla- giogranite was generated at 389 ＋ 3 Ma. This -390 Ma age is the best estimate for the formation of ophiolite, although a little late. 40Ar/39Ar amphibole dating for an amphibolite sample from Kuerti ophiolite gives a plateau age of 277 ＋ 4 Ma, revealing an Early Permain thermal event in the study area. Previous studies suggest that the Kuerti Ophiolite be formed in a spreading back-are basin when the Paleo-Asian ocean subducted under the Altay arc. However, recently, more evidence, including approximately synchronous adakites, boninites, high-Ti basahs, picrites, marie dykes, and high-T metamorphism strongly indicates that Kuerti ophiolite was formed in a ridge subduction extensional setting. It is possible that ridge subduetion around 390 Ma caused up- welling of the hot asthenosphere and triggered the spreading of the Kuerti back-arc basin, following the differen- tiation of the plagiogranites and amphibolites in Kuerti ophiolite. Then, at - 277 Ma Kuerti ophiolite under- went a metamorphic event. Taking into account tectonics, sedimentology, and the coeval mafic-uhramafie rocks and voluminous A-type granites in this region, it is suggested that this metamorphic event occurr during a post-collisional extensional regime, and ophiolite may undergo metamorphism after emplacement which requires caution when using 40Ar/39Ar technique to date the age of ophiolite.