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山西临县紫金山杂岩主要由深成相岩瘤、浅成相岩墙和岩基、喷出相熔岩和火山角砾岩等岩石单元组成。对该杂岩体内的浅成相次透辉二长岩、霞辉正长岩进行了锆石LA-ICP-MS原位U-Pb同位素测年。结果显示,次透辉二长岩锆石边部U-Pb年龄加权平均值为(136.7±6.5)Ma,Th/U比值0.781～2.559,明显呈三段性,表明岩浆同化混染过程中岩浆成分变化的岩浆混合过程信息;锆石核部U-Pb年龄加权平均值为(1937±37)Ma,Th/U比值为0.339～0.669,显示岩浆成因特征;(霓)霞(次透)辉正长岩的锆石U-Pb加权平均年龄为(137±2.7)Ma,Th/U比值1.484～5.0,反映岩浆富Th且与二长岩互补的特征,揭示出这2期岩浆之间存在有限混合现象。2个样品年龄均显示紫金山碱性杂岩体最早的二长岩与霞辉正长岩浆活动在早白垩世。二长岩的2个孤点年龄(222±4)Ma和(323±3)Ma可能代表了霓霞钛辉岩、正霞正长岩及白霞正长岩包体岩石岩浆底侵的年龄。
Zijinshan complex in Linxian County, Shanxi Province is mainly composed of deep-phase faulting, shallow-faulted rock wall and rock foundation, and exuded rock units such as lava and volcanic breccia. Zircon LA-ICP-MS in-situ U-Pb isotope dating was performed on the epithermal diopside and Xia-Xia syenite in this complex. The results show that the zircon U-Pb ages of the second Permian monzhang rocks are (136.7 ± 6.5) Ma and the Th / U ratios are 0.781-2.559, which are obviously in three stages, indicating that the magma (1937 ± 37) Ma, and the Th / U ratio was 0.339 ~ 0.669, showing the genetic characteristics of magmatic rocks; (Ni) Xia The zircon zircon U-Pb weighted mean age of (137 ± 2.7) Ma and Th / U ratio of 1.484-5.0 reflect the characteristics of magma-enriched magma and complementarity with the monzonite, revealing the existence of the two magmas Limited mixed phenomenon. The age of two samples shows that the earliest magmatism of the monzonite and Xia-fai magma in the Zijinshan alkaline complex was in the Early Cretaceous. The 2 solitary-point ages (222 ± 4) Ma and (323 ± 3) Ma of the monzonite may represent the age of the magmatic underplating of the Nixia Xia Hui, Zhengxiazhengchang and Baixia Zhengchang inclusions .