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穆棱古近纪(第三纪)碱性玄武岩位于郯庐断裂东北段分支敦化～密山深大断裂带的中北部,与吉林敦化、汪清,黑龙江镜泊湖、牡丹江等新生代火山岩一起分布于兴蒙造山带和太平洋板块俯冲带结合带上;本文利用电子探针、激光剥蚀等离子质谱技术(LA-ICP-MS)及多接收器电感耦合等离子体质谱仪(MC-ICP-MS)分析了来自玄武岩风化冲积物中锆石巨晶的主、微量元素及其Hf同位素组成。这些锆石巨晶具有明显的熔蚀结构,锆石电子探针分析其Zr/Hf比最高可达217,平均150,是目前东部新生代玄武岩锆石巨晶的最高值。它们具有相似的微量元素特征,具有明显的Ce正异常,富集重稀土和HFSE元素,锆石Hf/Y比值大多小于10,Th/U均小于1(一个数据例外),Yb/Sm为21～59。与岩浆锆石和变质锆石相比,显示过渡的特征;锆石~(176)Hf/~(177)Hf变化为0.283105～0.283151,ε_(Hf)变化在+11.8～+13.4之间,显示亏损地幔来源,反映锆石形成时岩石圈地幔主体具有“新生”的特征,表明岩石圈减薄或置换事件在东北地区东北部穆棱地区也同样存在。穆棱新生代碱性玄武岩有关锆石巨晶的成因特征与中国东部海南文昌、福建明溪及山东昌乐等地新生代玄武岩的锆石巨晶相同,可能与有下地壳物质参与的近期岩石圈地幔的交代作用有关。
Alkaline basalts in the Muling Paleogene (Tertiary) are located in the central-northern part of the Dunhua-Mishan deep-fault zone in the northeast segment of the Tanlu Fault and distributed along with Cenozoic volcanic rocks such as Dunhua, Wangqing in Jilin Province, Jingpo Lake in Heilongjiang, and Mudanjiang In the belt of Xingmeng orogen and the subduction zone of the Pacific plate, we use electron probe, laser ablation plasma mass spectrometry (LA-ICP-MS) and multi-receiver inductively coupled plasma mass spectrometry (MC-ICP-MS) From the basaltic weathered alluvial zircon giant macroscopic host, trace elements and their Hf isotope composition. These giant zircons have obvious eroded structures. The Zr / Hf ratio of Zircon electron probe is up to 217, an average of 150, which is the highest value of giant zircons in the Cenozoic basalts of the eastern part of China. They have similar trace element characteristics with obvious positive Ce anomalies, enriched in heavy rare earths and HFSE elements, zircon Hf / Y ratios mostly less than 10, Th / U less than 1 (with one exception) and Yb / Sm 21 ~ 59. Compared with the magmatic zircons and metamorphic zircons, the transitional characteristics are shown. The Hf / ~ (177) Hf values of zircon ~ (176) range from 0.283105 ~ 0.283151, and the changes of ε_ (Hf) range from +11.8 ~ +13.4, The source of the mantle indicates that the lithospheric mantle has the characteristics of “newborn” when the zircon was formed, indicating that the lithospheric thinning or replacement events also exist in the Muling region in northeastern Northeast China. The genetic characteristics of the Muling Cenozoic alkaline basalts related to the giant zircons are the same as those of the Cenozoic basalts in Wenchang, Hainan Province of China, Mingxi of Fujian Province, Changle of Shandong Province, and may be related to the recent interpretation of lithospheric mantle beneath the lower crust Relevant role.