山西吕梁地区汉高山群火山岩成因及其形成环境  

Petrogenesis and tectonic setting of volcanics from the Hangaoshan Group in Lüliang area,Shanxi Province

作　　者：雷天 张成立[1] 白海峰 刘欣雨[1] 杨欢[1] LEI Tian;ZHANG Chengli;BAI Haifeng;LIU Xinyu;YANG Huan(Precambrian Research Center,State Key Laboratory of Continental Dymamics.Northrest University,Xi'an,Shaanxi 710069,China;Research Institute of Petroleum Ex ploration and Development.Changqing Oil Field Branch.PetroChina Com pany Limited,Xi'an,Shaanri 710018,China)

机构地区：[1]大陆动力学国家重点实验室,西北大学,陕西西安710069 [2]中国石油长庆油田分公司勘探研究院,陕西西安710018

出　　处：《地质学报》2022年第2期465-481,共17页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41772189、41890831);国家自然科学基金创新群体(编号41421002);国家科技重大专项(编号2017ZX05008-005);大陆动力学国家重点实验室科技部专项(编号201210133)联合资助的成果。

摘　　要：吕梁地区汉高山群火山沉积岩是华北克拉通中部带中部中元古代初期火山-沉积记录,其成因及形成环境研究对认识华北克拉通结晶基底固结后地质演化有重要意义。该群火山岩为拉斑玄武系列安山岩,SiO_(2)(54.68%~56.19%)略低,有较高的MgO(4.97%~6.16%,Mg;=49.4~53.8)及Cr(165×10^(-6)~174×10^(-6))和Ni(31.1×10^(-6)~34.2×10^(-6))含量,高TiO_(2)(1.34%~1.40%),TFeO/MgO=1.70~2.03,富集LREEs和Ba、U、K等LILEs,亏损Nb、Ta、Ti等HFSEs,与弧岩浆地球化学特征类似。它们的ε;(t)偏负且变化小(-4.48~-4.31),T;=2509~2520 Ma,其高的Ba/Th和低的(La/Sm);说明它们源自受板片俯冲流体改造的岩石圈地幔,地幔改造为新太古代大洋板片消减所致。结合邻区小两岭组火山岩和华北克拉通南部熊耳群火山岩也显示弧岩浆地球化学特征,且Sr-Nd同位素组成揭示源自新太古代板片俯冲改造的岩石圈地幔,与同期基性岩墙群一道代表板内伸展环境岩浆活动的产物,而非为弧岩浆活动的记录,代表了华北克拉通中元古代初期转入大陆伸展拉张环境,首套火山沉积建造,是全球Columbian超大陆裂解初期在华北地块的物质记录。The volcanic sedimentary rocks of the Hangaoshan Group in Lüliang area are representative of Early Masoproterozoic sedimentary records in the Trans-North China Orogen of the Norh China Craton(NCC). The study on their genesis and formation background is of great significance to understand the geological evolution of NCC after the consolidation of the crystalline basement. The volcanic rocks in this group are tholeiite series andesite, with lower SiO_(2)(54.68%~56.19%), higher MgO(4.97%~6.16%, Mg;=49.4~53.8), Cr(165×10^(-6)~174×10^(-6)) and Ni(31.1×10^(-6)~34.2×10^(-6)) contents as well as higher TiO_(2)(1.34%~1.40%), TFeO/MgO=1.70~2.03, enriched in LREEs and LILEs(Ba, U and K) and depleted in HFSEs(Nb, Ta and Ti). They show the geochemical characteristics similar to arc magma. However, they have slightly negative ε;(t) with a narrow range of-4.48~-4.31. Their T;is from 2509 Ma to 2520 Ma. Besides, they have high Ba/Th and low(La/Sm);, indicating that they were derived from the lithospheric mantle metasomatized by plate subduction fluid resulted from the subduction of oceanic plate in the Neoarchean. Furthermore, the volcanic rocks from the adjacent Xiaoliangling Formation, the Xiong’er Group of southern NCC show geochemical characteristics similar to those of arc magmatism, and their Sr-Nd isotopic composition suggested that they were derived from lithospheric mantle modified by the subduction of oceanic plate in the end of Neoarchean. All these volcanics, together with the coeval mafic dykes, were produced in an extensional setting of within plate, indicating that the NCC has transformed into a continental extensional environment in the early Mesoproterozoic, rather than an arc environment magmatism. They are representative of the first volcanic sedimentary after final solidification of the crystalline basement in the NCC, corresponding to the sedimentary products in the early breakup of Colombia Supercontinent all over the world.

关 键 词：汉高山群 安山岩 伸展背景 大陆岩石圈地幔 吕梁地区 华北克拉通 

分 类 号：P588.14[天文地球—岩石学]