吉林中部硅质岩中锆石U-Pb年龄及其地质意义

吉林中部烟筒山地区的硅质岩带是研究古亚洲洋构造演化的一个关键地区。前人在本区确认出红帘石硅质岩的存在,并结合周边岩石特征研究,提出本区为古亚洲洋最后闭合的地点。岩石化学成分研究发现,所研究硅质岩的原岩为火山岩。锆石阴极发光图像中,韵律环带结构明显,说明其为早期岩浆锆石。LA-ICP-MS颗粒锆石U-Pb法同位素年龄测定表明,硅质岩变形和变质作用年代为(239±11)M a,结合呼兰群变质作用时代的研究,确定古亚洲洋最终闭合的时代为中生代(三叠纪)。

Zircon U-Pb Age of Siliceous Rock from the Central Jilin and Its Geological Significance

The siliceous rock zone in Yantong mountain area,central Jilin Province,is the key region for study-ing the paleo-Asian ocean tectonic evolution.The predecessors confirm that piedmontite siliceous rock exists in this area,and combining with the research of peripheral rock characteristics,the paper suggests that this area should be the site of the final closing of the paleo-Asian ocean.According to the lithochemical analysis,the authors find the parent rocks of silicalite are volcanos.In the zircons CL image,the rhythm annulus structure of ziron is obvious,which shows that they are the earlier magma rock zircons.LA-ICP-MS single-zircon U-Pb isotopic age dating indicates the siliceous rock deformation and metamorphism took place at(239±11)Ma.Combining with the metamorphism age of Hulan Group,the authors confirm that the final closing of the paleo-Asian ocean took place in the Mesozoic(Triassic).