山西吕梁地区岚河群沉积时代及形成环境：来自碎屑锆石U—Pb年龄和Hf同位素的证据  

Deposition age and sedimentary setting of the Lanhe Groups in Liiliang area of Shanxi Province： Evidences from detrital zircon U-Pb dating and their Hf isotopes

作　　者：胡育华 张成立[1] 赵娇 郭晓俊 刘欣雨[1] 王璐 刘炳旭 

机构地区：[1]大陆动力学国家重点实验室、西北大学地质学系,西安710069 [2]中国人民武装警察部队黄金第5支队,西安710100

出　　处：《地质科学》2017年第4期1195-1219,共25页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家重点基础研究发展计划“973”项目（编号：2012CB416606）和西北大学大陆动力学国家重点实验室专项资助.

摘　　要：山西吕梁地区是华北克拉通保存古元古界变质表壳岩良好地区， 其中的岚河群在吕梁山北部岚县南北两侧大量出露， 由碎屑岩、碳酸盐岩夹少量基性火山岩等多个沉积旋回的沉积组合构成， 经历绿片岩相浅变质作用改造， 保留了大量原始沉积构造， 是探讨该群沉积 特征、形成时代及与其它表壳岩群关系的理想对象。 对岚河群 3 件样品的碎屑锆石 LA-ICP-MS U-Pb 定年， 获得底部含砾砂岩最年轻碎屑锆石 2.2 Ga 的峰值年龄， 该群经历了 1.87 Ga 的 区域变质作用， 因而限定岚河群沉积于 2.2～1.87 Ga 之间。 碎屑锆石年龄谱显示了～2.2 Ga 的 主峰期和～2.3 Ga 及太古代中晚期等较小峰期年龄， 指示主要源自古元古代陆壳物质源区， 它们的主峰期年龄锆石与吕梁地区同期岛弧花岗岩锆石 Hf 同位素特征一致， 且其沉积组合反映了物源区活动性较强， 证明岚河群形成于活动陆缘岛弧相关的沉积盆地。 野鸡山群下部的 青杨树湾组和白龙山组沉积组合与岚河群沉积地层序列类似， 它们均形成于 2.2 Ga 左右， 说明野鸡山下部沉积与岚河群相同， 也形成于活动陆缘岛弧环境的沉积盆地， 分别代表了盆地同时异相的沉积产物。 野鸡山群上部程道沟组与黑茶山群沉积序列类似， 具有造山过程相关盆地的磨拉石建造组合特征， 它们均形成于 1.85 Ga 之后， 代表与碰撞造山过程相关前陆盆地快速堆积。 因此， 3 个岩群表壳岩的沉积演化揭示了华北克拉通中部～2.2 Ga 俯冲汇聚相关的活动陆缘岛弧环境， 在～1.85 Ga 转为陆—陆碰撞造山演化过程。The supracrustal rocks are widely developed in the Lüliang area of Shanxi Province. The Lanhe Group, as an important part, is outcropped in both north and south sides of the Lanxian County, which mainly composed of clastic rocks, carbonatite with minor meta-basalts and is an ideal object to probe the sedimentary characteristics, formation age and relationship with other supracrustal rocks due to the greenschist facies metomorphism and primary sedimentary structure preserved in some calsitic rocks. The LA-ICP-MS U-Pb dating of detrital zircons from three samples yield the youngest peak age of ～2.2 Ga in their lower sequence. Combined with their metamorphism similar to those occured in the Lvliang area at 1.87 Ga, the forming age of the Lanhe Group can be limited between 2.2 Ga and 1.87 Ga. Their U-Pb age spectrum is characterized by a main peak at ～2.2 Ga and smaller peaks at ～2.3 Ga and the end of Neoarchean, suggesting that they are mainly derived from the Paleoproterozoic continental provenance other than Archaean crust. The Hf isotopic features of detrital zicons with the ags of ～2.2 Ga are much consistent with the temporal granitoids related to island arc setting. In addtion, their sedimentary assemblages indicate an active sedimentary enviroment. All suggest that Lanhe Group is formed in a arc-related basin in the active continental margin. The sedimentary sequences of the Qingyangshuwan and Bailongshan Formations of the lower part of Yejishan Group are well compared with those of the Lanhe Group, and both are deposited at ～2.2 Ga. Therefore, the lower part of the Yejishan group, as Lanhe Group, can be considered to be diposited in the arc-related basin in the continental margin. Both represented likely the transformation of sedimentaru facies at the same period. While the sedimentary sequeces of Chengdaogou Formation in the upper part of the Yejishan Group is similar to the sequenc of the Heichashan Group with molasse deposits in a foreland basin associated with the collision between continental

关 键 词：岚河群 碎屑锆石U—Pb定年 形成时代与环境 吕梁地区 

分 类 号：P534.1[天文地球—古生物学与地层学] P597[天文地球—地质学]