太岳山17.9亿年英安斑岩的发现及其对华北克拉通南部裂谷系成因的约束  

Discovery of 1.79Ga dacite porphyry in the Taiyueshan Mts: Constraints on the genesis of the southern rift system in the North China Craton

作　　者：范昱宏 祝禧艳[1] 段庆松 马建锋 贾朝媛 刘书琪 赵太平[4] FAN YuHong;ZHU XiYan;DUAN QingSong;MA JianFeng;JIA ChaoYuan;LIU ShuQi;ZHAO TaiPing(Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;University of Chinese Academy of Sciences,Beijing 100049,China;State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China)

机构地区：[1]中国科学院地质与地球物理研究所,中国科学院矿产资源研究重点实验室,北京100029 [2]中国科学院大学,北京100049 [3]中国科学院地质与地球物理研究所,岩石圈演化国家重点实验室,北京100029 [4]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广州510640 [5]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《岩石学报》2024年第4期1327-1342,共16页Acta Petrologica Sinica

基　　金：国家重点研发计划项目(2020YFA0714803);国家自然科学基金项目(92062103、42220104008)联合资助。

摘　　要：熊耳群火山岩系主要分布于华北克拉通南部地区,主体喷发时限是1.75~1.80Ga。作为华北克拉通早期板块构造调整阶段的首次大规模岩浆活动,该火山-侵入岩系的形成时限、时空分布规律和地球动力学背景尚有争议,制约了对华北克拉通中元古代构造演化的进一步认识。本次研究在华北中部太岳山地区识别出中元古代英安斑岩,与古元古代花岗质片麻岩围岩呈侵入关系,无明显变质变形。锆石U-Pb年龄分析结果表明,该英安斑岩形成于1.79Ga,属于熊耳期岩浆活动的产物。样品中约90%的锆石显示出~1.92Ga和~2.16Ga两期年龄峰值,推测其为围岩的捕获锆石。英安斑岩SiO_(2)含量为65.12%~66.11%,A/CNK=0.91~1.05,全碱(K_(2)O+Na_(2)O)含量为6.85%~7.28%,Na_(2)O/K_(2)O=0.48~0.54,属于钾玄岩系列。样品稀土元素含量较高,亏损Nb、Ta、Zr、Hf等高场强元素,富集Rb、Ba、La等大离子亲石元素,与华北克拉通南部地区熊耳期英安-流纹斑岩的地球化学特征完全一致,指示板内伸展环境。太岳山熊耳期英安斑岩的发现,贯通了中条山地区的熊耳群火山岩系、吕梁地区汉高山群和小两岭火山岩系,完善了熊耳三叉裂谷系北支的空间分布范围,是华北克拉通中部地区开启中元古代裂陷作用演化的重要岩浆记录。The volcanic rocks of the Xiong'er Group mainly distribute in the southern North China Craton (NCC), and the main eruption peak time is ca. 1.75~1.80Ga. As a distinctive large-scale magmatic activity of the Earth's middle age in the NCC, its formation time, temporal and spatial distribution and geodynamic background is still controversial, that hinders further research of tectonic evolution of the NCC during the Early Mesoproterozoic. In this study, Mesoproterozoic dacite porphyry is distinguished in the Taiyueshan Mts in central NCC. It intrudes into the surrounding Paleoproterozoic gneissic granitoids with weak metamorphism and deformation. The SHRIMP and LA-ICP-MS zircon U-Pb age of the dacite porphyry is ca. 1.79Ga, which is consistent with the formation time of the Xiong'er volcanic rocks. 90% zircon grains show two age peaks of ~1.92Ga and ~2.16Ga, which are speculated to be captured from surrounding rocks. The dacites belong to shoshonite series with SiO_(2) content from 65.12% to 66.11%, alkali content (K_(2)O+Na_(2)O) from 6.85% to 7.28%, A/CNK ratios of 0.91~1.05, and Na_(2)O/K_(2)O ratios of 0.48~0.54. They have a high content of REE with depletion in HFSE such as Nb, Ta, Zr and Hf, and enrichment in LILE such as Rb, Ba, and La, which is completely consistent with the geochemical characteristics of Xiong'er dacite-rhyolite porphyry in the southern part of NCC. Currently, more scholars believe that the Xiong'er Group was formed in a trigeminal rift system, indicating the background of within-plate extension. This dacite porphyry connects the Xiong'er Group volcanic rock series in the Zhongtiaoshan area with the Hangaoshan Group and Xiaoliangling volcanic rock series in the Lüliang area. They complete the northern branch of the Xiong'er trigeminal rift system, recording the initial Mesoproterozoic rifting in the central part of the NCC.

关 键 词：英安斑岩 熊耳火山-侵入岩系 三叉裂谷 太岳山 华北克拉通 

分 类 号：P588.13[天文地球—岩石学] P597.3[天文地球—地质学]