辽东袁家堡石英二长斑岩的锆石U-Pb年龄、地球化学特征及地质意义

Zircon U-Pb dating, geochemical characteristics and geological significance of beschtauite in Yuanjiapu, eastern Liaoning

对辽东地区袁家堡石英二长斑岩进行了年代学和地球化学研究,LA-MC-ICP-MS锆石U-Pb测年获得其年龄加权平均值为129±1 Ma,表明其形成于早白垩世。岩石地球化学分析结果表明,该岩体SiO2含量为72.20%~74.36%,K2O+Na2O为8.22%~9.01%,K2O/Na2O为1.39%~1.67%,A/CNK和A/NK分别为1.05~1.16和1.12~1.28;ΣREE为162.31~261.42,LREE/HREE为12.31~15.85,轻稀土相对富集,δEu为0.16~0.58,Eu负异常明显;亏损Ba、Sr等大离子亲石元素和Nb、P、Ti等高场强元素,相对富集Rb、Th、La、Nd、Hf等元素。袁家堡石英二长斑岩为花岗质地壳部分熔融形成的铝质A型花岗岩,形成于辽东地区地壳伸展环境下,是岩石圈减薄过程中的产物。

This paper studies the geochronology and geochemistry of beschtauite in Yuanjiapu,eastern Liaoning,LA-MC-ICP-MS zircon U-Pb isotope dating obtained an age-weighted average of 129±1 Ma, indicates its formation in the Early Cretaceous. The elemental geochemical analysis indicates that the SiO2 content of the rock mass is 72.20%-74.36%;K2O+Na2O is 8.22%-9.01%;K2O/Na2O is 1.39%-1.67%;A/CNK and A/NK are 1.05-1.16 and 1.12-1.28.LREE is relatively enriched,ΣREE is 162.31-261.42;LREE/HREE is 12.31-15.85;δEu is 0.16-0.58,obvious negative Eu anomalies.The rock is depleted of large ion lithophile elements such as Ba and Sr, and high field strength elements such as Nb, P, and Ti, and relatively enriched in Rb, Th, La, Nd, and Hf. The above characteristics indicate that the beschtauite in Yuanjiapu is an aluminum A-type granite formed by partial melting of granitic crust, which was formed in the crustal extension environment of the eastern Liaoning and the product of the lithospheric thinning process.