通化地区光华岩群变质岩锆石U-Pb定年及其地质意义

吉林通化地区光华岩群出露于太古宙TTG片麻岩之中，其形成时代一直存在争议.利用SHRIMP与LA-ICPMS技术，对其代表性岩石样品开展了锆石U-Pb定年分析，包括石榴黑云片岩、黑云二长片麻岩、石榴角闪片岩和侵入光华岩群底部的钾长花岗岩.结果显示，光华岩群4件变质岩石样品尽管位置不同，但碎屑锆石年龄非常接近，207Pb/206Pb谐和年龄集中在2.6~2.5 Ga之间，加权平均值分别为2 529±7 Ma、2 568±4 Ma、2 526±11 Ma和2 530±6 Ma，表明其成岩物质来源于新太古代地体.部分变质岩石记录了2 525±10 Ma、1 926±40 Ma和1 878±16 Ma的变质锆石年龄，表明其既经历了太古代末期的构造热事件改造，又遭受了古元古代晚期碰撞造山事件的扰动.确定侵入光华岩群底部的钾长花岗岩的侵位年龄为2 154±7 Ma，岩石未遭受变形改造，其成因可能与陆内裂谷发育过程有关. 

Zircon U-Pb Dating of Metamorphic Rock from Guanghua Group in Tonghua Area and Its Geological Significance

Metamorphic rock series of the Guanghua Group occurs as a block in Archean TTG gneiss in Tonghua area of Jilin Province, whose forming age remains controversial for a long time. Using SHRIMP and LA-ICPMS zircon U-Pb dating techniques, representative rock samples from the Guanghua Group were analyzed, including garnet biotite schist, biotite monzo-gneiss, garnet hornblende schist and potassium granite intruding into the bottom of the Guanghua Group. The results show that four metamorphic rock samples have similar detrital zircon ages (concordant ages are between 2.6 Ga and 2.5 Ga) though they were collected from different strata. Most detrital zircons from four samples yeild concordant mean ages of 2 529±7 Ma, 2 568±4 Ma, 2 526±11 Ma and 2 530±6 Ma, respectively, suggesting a derivation from Neoarchean magmatic unit. Some zircons from metamorphic rocks record 3 stages metamorphic age (2 525±10 Ma, 1 926±40 Ma and 1 878±16 Ma), indicating that the Guanghua Group experienced both Neoarchean and Paleoproterozoic thermo-tectonic events. Zircons from the potassium granite yield a concordant mean age of 2 154±7 Ma, which is interpreted as intruding time of the ploton. The potassium granite has not suffered any deformation, suggesting a intracontinental rift tectonic setting.