祁连地区窑井子岩龄及同位素特征

Zircon Ages and Isotopic Features of Yaojingzi Granite in North Qilian,Gansu Province

窑井子岩体位于北祁连早古生代造山带,岩性主要为肉红色正长花岗岩、肉红色似斑状正长花岗岩,局部为肉红色二长花岗岩;锆石LA-MC-ICP-MSU-Pb测年获得正长花岗岩结晶年龄为452±1.5 Ma;ε_(Nd)(t)为-11.18~-8.22之间,平均-9.46,T_(DM)值为1.51~1.83 Ga,平均1.65 Ga;I_(Sr)值为0.7087~0.7112之间,均值为0.7094,表明源岩为上地壳古中元古代地层,结合区域地质资料,其源岩可能为北大河岩群黑云石英片岩、二云石英片岩、钾长片麻岩等。

Yaojingzi rock body located in the early paleozoic orogenic belt of north Qilian consists of flesh-red syenogranite,porphyritic syenogranite and local monzonitic granite.The age of syenite is dated to be 452±1.5 Ma by La-MC-ICP-MS zircon U-Pb dating.ε_(Nd)(t)is between-11.18 and-8.22 with an average of-9.46.T_(DM)is 1.51-1.83Ga with an average age of 1.65Ga.I_(Sr)is 0.7087-0.7112 with an average of 0.7094.Based on the regional geological data,the source rocks are inferred to be biotite quartz schist,two-mica quartz schist and K-feldspar gneiss from paleo Mesoproterozoic strata in the upper crust.