内蒙古达里诺尔含金云母辉石岩的发现及其地质意义  

Discovery of phlogopite-bearing pyroxenites from Darinoor in Inner Mongolia and its geological implication

作　　者：张珺杰 郭鹏远[1,2] 孙普[1,2] 陈懋卿 肖媛媛[1,2] ZHANG Jun-jie;GUO Peng-yuan;SUN Pu;CHEN Mao-qing;XIAO Yuan-yuan(Institute of Oceanology,Chinese Academy of Science,Qingdao 266071,Shandong,China;Key Laboratory of Marine Geology and Environment(Chinese Academy of Science),Qingdao 266071,Shandong,China;University of Chinese Academy of Science,Beijing 100049,China;Institute of SurfaceEarth System Science,Tianjin University,Tianjin 300072,China)

机构地区：[1]中国科学院海洋研究所,山东青岛266071 [2]海洋地质与环境重点实验室(中国科学院),山东青岛266071 [3]中国科学院大学,北京100049 [4]天津大学表层地球系统科学研究院,天津300072

出　　处：《世界地质》2020年第1期30-44,共15页World Geology

基　　金：国家自然科学基金(41776067)。

摘　　要：对华北克拉通北缘达里诺尔地区鸽子山附近玄武岩中的含金云母辉石岩捕虏体进行了岩石学、矿物学的研究,并对其中的单斜辉石、斜方辉石、金云母和粒间熔体进行了原位微区主、微量元素分析。结果显示,单斜辉石和斜方辉石具有低的Mg^#、Cr 2O 3和高的Al2O3含量,斜方辉石还具有高的MnO含量,这些特征表明辉石岩代表了交代熔体在地幔中冷却固结堆晶形成的岩脉。辉石岩中金云母、粒间熔体的出现及其不平衡的地球化学特征说明辉石岩形成以后又遭受到了多期次的硅酸盐熔体地幔交代作用。结晶出单斜辉石的母岩浆在蛛网图上具有K、Pb元素的弱负异常但不具有Nb、Ta、Ti元素的负异常,推测形成辉石岩的熔体可能来自软流圈地幔。粒间熔体的低SiO2,高MgO和FeO的特征指示其形成于地幔超基性岩的部分熔融,蛛网图上明显的K、Pb正异常以及Nb、Ta负异常说明其源区也存在俯冲沉积物的贡献。基于此,认为中国东部新生代岩石圈地幔经历了多期次地幔交代作用。This study reports the petrology and mineralogy characteristics of the phlogopite-bearing pyroxenites from the basalt near Gezishan in Darinoor in the northern margin of North China Craton,and in-situ major and trace element compositions of clinopyroxenes,orthopyroxenes,phlogopites and intergranular melts in the pyroxenites.The results show that clinopyroxenes and orthopyroxenes are characterized by low Mg^# and Cr2O3 content and high Al 2O 3 content,and the orthopyroxenes also show high MnO content,which indicates that these pyroxenites were segregated from metasomatic melts in upper mantle.The appearance of phlogopites and intergranular melts in pyroxenite,and their unbalanced geochemical characteristics indicate that the pyroxenite was metasomatized by silicate melt after its formation.The geochemical characteristics of the calculated parental magma of clinopyroxenes,such as the weakly negative anomalies of K,Pb and lacking negative anomalies of Nb,Ta,Ti in the spider diagram,indicate that their mantle source was asthenosphere mantle.The geochemical characteristics of intergranular melts,such as the lower SiO2 concentration and higher content of MgO and FeO,indicate their source was the partial melting of ultrabasic rocks from mantle.And the positive anomalies of K,Pb and negative anomalies of Nb,Ta in spider-gram of intergranular melts indicate the contribution of subducted terrigenous sediments in their mantle source.Therefore,it is concluded that there were multi-stage metasomatisms in the Cenozoic lithosphere mantle in eastern China.

关 键 词：金云母 辉石岩 地幔交代作用 华北克拉通 硅酸盐熔体 

分 类 号：P575[天文地球—矿物学] P588.12[天文地球—地质学]