松辽盆地林深3 井火山岩的锆石U——Pb 年龄与Hf 同位素组成

根据松辽盆地北部林深3 井火山岩的岩相、全岩主微量元素、锆石U--Pb 同位素和锆石Hf 同位素特征的分析结果，探讨了该火山岩的形成时代和岩浆源区。锆石LA--MC--ICPMS U--Pb 研究结果表明: 林深3 井火山岩形成时代约为120 Ma，处于早白垩世中晚期，属于营城组火山岩。锆石的LA-- MC--ICPMS Hf 同位素研究显示，本区火山岩的锆石εHf ( t) 全部为较高的正值，二阶段Hf 模式年龄为789 ～ 1 494 Ma，表明其主要起源于中--新元古代增生的地壳物质，暗示中--新元古代时期兴蒙造山带东段存在地壳增生事件。

Zircon U-Pb ages and Hf isotopic composition of volcanic rocks from Well Linshen 3 in Songliao Basin

The formation time and the source rocks of volcanic rocks from Well Linshen 3 in the northern Songliao Basin have been discussed through the petrography，major and trace elements，zircon U--Pb isotopic data and zircon Hf isotopic data of three samples． Zircon U--Pb dating by LA--ICP MS technique indicated that the volcanic rocks from Well Linshen 3 were erupted at ca． 120 Ma，the middle--late Early Cretaceous，belonging to of the Yingcheng Formation． Zircon Hf analysis conducted by LA--MC--ICPMS showed that all of the volcanic rocks had high εHf( t) positive values with Hf modal ages of 789 ～ 1 494 Ma，indicating the crust in the Songliao Basin extracted from mantle during Meso- and Neoproterozoic，which provides the important evidence of crustal growth during Meso-and Neoproterozoic in eastern Xing--Meng orogenic belt．