山东蒙阴金伯利岩中锆石的成因研究

Study on Origin of Zircon in Mengyin Kimberlite from Shandong Province

摘要: 采用离子探针、阴极发光和拉曼光谱等方法，对采自山东蒙阴金伯利岩中的锆石进行了年龄测定及成因研究。结果显示，多数锆石的²⁰⁷Pb/ ²⁰⁶Pb的年龄变化于 2 5 6 7± 13~ 2 6 36± 4 2Ma，该年龄值与研究区太古宙花岗岩质岩石的年龄 (2 4 5 7.3± 4 7Ma)相近。锆石的微量元素w(ZrO₂)/w(HfO₂)显示花岗岩型锆石的变化特征。锆石的环带发育，矿物包裹体为长石、石英和磷灰石。上述结果表明，锆石为地壳来源，暗示金伯利岩岩浆上升受到一定程度的地壳混染

Abstract: The age and the origin of zircons in Mengyin kimberlite from Shandong Province are studied by means of SHRIMP, CL and Raman spectrum, et al. The results show that the ages of ²⁰⁷Pb/²⁰⁶Pb of zircons vary from 2 567±13 to 2 636±42 Ma, which are close to the age of Archaean granitoid (2 457.3±47 Ma)in the research area. The ratio of w(ZrO₂)/w(HfO₂) in the zircons decreases gradually from the core to rim, just like that of the granite-type zircon. Colour zones are obvious under CL. The inclusions in the zircons are feldspar, quartz and apatite. It can be concluded that the zircons come from the crust, which means that the kimberlite magma may be contaminated by the crust.