秦岭富水杂岩的变辉长岩中斜锆石与锆石U-Pb同位素年龄的差异及其地质意义

秦岭富水杂岩体的一些变辉长岩含有粒度较大，U、Pb含量较高的斜锆石和锆石，是U-Pb同位素测年的极好矿物。本文对秦岭富水杂岩的中粗粒角闪黑云辉长岩中的斜错石和错石分别进行了SHRIMP法和TIMS法U-Pb同位素年龄测定，获得斜锆石和锆石的U-Pb同位素年龄分别为501.4±1.2 Ma和480.0±3.4 Ma，二者相差约20 Ma；对该岩石中的斜锆石和锆石的关系及锆石的成因进行了初步研究，认为斜锆石的U-Pb同位素年龄应可解释为秦岭富水杂岩中基性岩石的形成时代，而锆石的成因比较复杂，对其U-Pb同位素年龄地质意义的合理解释需作进一步的研究。

Age Difference between Baddeleyite and Zircon from Metagabbro in Fushui Complex of the Qinling Mountains and Its Geological Implications

There are baddeleyites and zircons with high U and Pb in metagabbro from Fushui complex in the Qinling Mountains. They are very ideal minerals for U-Pb isotope dating. The baddeleyites and zircons were dated by SHRIMP and TIMS U-Pb dating methods. Age data of 501.4±1.2 Ma for baddeleyites and 480.0±3.4 Ma for zircons were obtained. The age difference between baddeleyite and zircon is about 20 Ma. The baddeyite-zircon relationship in the metagabbro and the zircon genesis were studied. The Baddeleyite age of 501.4±1.2 Ma is interpreted as the formation age of the metagabbro in Fushui Complex of the Qinling Mountains. As the genesis of the zircon is very complex, the reasonable interpretation for the zircon age of 480.0±3.4 Ma requires further studies.