鲁东地区玲珑型(超单元)花岗岩的锆石SHRIMP定年

SHRIMP Zircon Dating of Linglong Type (Superunit) Granite in Eastern Shandong Province

玲珑型(超单元)花岗岩主要岩性为不同粒度的二长花岗岩,原划为新元古代震旦纪。根据在招掖地区新测的锆石SHRIMP U-Pb年龄,崔召单元中粒二长花岗岩为(158±3)Ma、郭家店单元中粗粒二长花岗岩为(144±3)Ma;昆嵛山地区九曲单元弱片麻状中粒二长花岗岩锆石SHRIMP U-Pb年龄(153±2)Ma。玲珑型(超单元)锆石SHRIMP U-Pb同位素年龄值集中在160～140 Ma,结合宏观与其他地质体相互关系,改划为侏罗纪。玲珑型(超单元)花岗岩体属于侏罗纪钙碱系列的侵入体,主要显示长英质陆壳深熔花岗岩的特征。推断其形成于中下地壳深度,可能来源于加厚陆壳的部分熔融,是加厚下地壳拆沉作用的产物,而且可能标志着中国东部岩石圈减薄的开始。

Main property of Linglong type（superunit） granite is monzogranite with different sizes.It was classified into Neoproterozoic Sinian period originally.According to newly measured zircon SHRIMP U-Pb age,monzogranite with medium size in Cuizhao unit is（158±3） Ma,medium coarse grained monzogranite in Guodian unit is（144±3） Ma,while SHRIMP zircon U-Pb age of weak gneissic monzogranite in Jiuqu unit of Kunyushan formation is（153±2） Ma.The SHRIMP U-Pb zircon isotopic age of Linglong type（superunit） is（160～140） Ma.Combining with the correlation with other geological bodies in macro,it is classified into Jurassic period.Linglong type（superunit） granites belong to Jurassic calc-alkaline granite intrusives.It mainly displayed felsic crust anatectic granites.It is conducted that it was formed in medium to lower crust,and maybe derived from partial melting of thickened continental crust.It is the production of thickened lower crust delamination,and may mark the beginning of lithospheric thinning in eastern China.