拉脊山东段峡门地区新元古代花岗闪长岩体锆石U-Pb年龄及地质意义

Zircon U-Pb Age and Geological Significance of Neoproterozoic Granodiorite in Xiamen Area,Shandong Province

在拉脊山东段峡门地区新发现新元古代花岗闪长岩体,呈构造岩块分布于峡门(拉脊山)蛇绿构造混杂岩带。通过LA-ICP-MS方法测得花岗闪长岩锆石同位素年龄为821. 1 Ma±5. 6 Ma,侵位时代为新元古代。岩石SiO_2含量为72. 87%,Al_2O_3含量为15. 02%,Al_2O_3含量为15. 02%,A/CNK值为1. 06,总体显示为弱过铝质钙碱性岩石。轻稀土元素富集、重稀土元素相对亏损。微量元素中K、Rb、Ba、Th富集,Nb、Ta相对亏损。环境判别显示新元古代花岗闪长岩体与大陆碰撞、地壳增厚密切相关,是形成于大陆碰撞构造背景之下的S型花岗岩。

Neoproterozoic granodiorite is newly discovered in Xiamen area of the Shandong section of the La Ridge. The tectonic blocks are distributed in Xiamen （Lhajishan） ophiolitic tectonic belt. The zircon isotopic age of granodiorite was 821.1 Ma ± 5.6 Ma by LA-ICP-MS method and the emplacement age was Neoproterozoic. The SiO2 content of the rock is 72.87% , the Al2O3 content is 15.02% , the Al2O3 content is 15.02% , and the A/CNK value is 1.06, which is generally weak aluminum calc-alkaline rock. Light rare earth elements are enriched. Heavy rare earth elements are relatively depleted. In the trace elements, K, Rb, Ba, and Th are enriched, Nb and Ta are relatively depleted. The environmental discrimination shows that the Neoproterozoic granodiorite is closely related to continental collision and crustal thickening, It is an S-type granite that is fomled under the background of continental collisional structures.