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引用本文:张波,苏尚国,王国栋,司晓博,伍月,蒋校,冯艳芳,刘江涛. 河北武安洪山正长岩杂岩体中单斜辉石矿物成分特征与岩浆演化过程[J]. 中国地质, 2020, 47(3): 782-797.
ZHANG Bo,SU Shangguo,WANG Guodong,SI Xiaobo,WU Yue,JIANG Xiao,FENG Yanfang,LIU Jiangtao. Mineral chemistry of clinopyroxene from the Hongshan syenite complex in Wu'an, Hebei Province: Implications for magma evolution[J]. Geology in China, 2020, 47(3): 782-797(in Chinese with English abstract).
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河北武安洪山正长岩杂岩体中单斜辉石矿物成分特征与岩浆演化过程
张波1, 苏尚国1, 王国栋2, 司晓博1, 伍月3, 蒋校4, 冯艳芳5, 刘江涛5
1.中国地质大学(北京)地球科学与资源学院, 北京 100083;2.山东省水土保持与环境保育重点实验室, 临沂大学资源环境学院, 山东 临沂 276005;3.中国地质调查局沈阳地质调查中心, 辽宁 沈阳 110034;4.中国国土资源航空物探遥感中心, 北京 100083;5.中国地质调查局发展研究中心, 北京 100037
摘要:
洪山正长岩杂岩体发育较多的具有核-边(核-幔-边)结构的单斜辉石,通过研究单斜辉石成分的变化,可以获得岩石成因及演化信息。本文在详细野外地质调查的基础上,采用锆石U-Pb年代学、矿物学研究,获得洪山正长岩杂岩体内黑云辉石正长岩锆石U-Pb年龄为(126.9±1.2)Ma,是华北克拉通岩石圈减薄峰期的产物;洪山正长岩杂岩体内辉石正长岩与黑云辉石正长岩中单斜辉石Mg#值分别在39.4~72.5、55.4~81.7,具有较高FeO、Na2O、CaO含量,较低Al2O3、MgO、TiO2含量的特征;单斜辉石总体具有透辉石→霓石的演化趋势,并与熔体达到平衡状态,单斜辉石在初始演化时具有Fe2+对Mg2+的取代关系,随着演化的进行,岩浆更加富钠、富铁,反映了岩浆体系具有高温、中等氧逸度和富碱的特点。结合单斜辉石核-边(核-幔-边)具有截然的接触关系和不连续的化学组成,表明洪山正长岩杂岩体在形成后还经历了富钠、富铁流体的改造,致使单斜辉石形成了具有富钠、富铁的边部,流体可能是由西向东(或者由洪山正长岩杂岩体中部向外部)对杂岩体进行改造的。
关键词:  正长岩杂岩体  单斜辉石  矿物学  锆石U-Pb年龄  中生代  岩浆演化  富钠流体  地质调查工程  武安  河北
DOI:10.12029/gc20200316
分类号:P578.954
基金项目:国家自然科学基金项目(41272105,41802201)、中国地质调查局项目(12120115069701、DD20190429)、教育部博士学科点基金(20130022140001)和山东省自然科学基金项目(ZR2018BD012)联合资助。
Mineral chemistry of clinopyroxene from the Hongshan syenite complex in Wu'an, Hebei Province: Implications for magma evolution
ZHANG Bo1, SU Shangguo1, WANG Guodong2, SI Xiaobo1, WU Yue3, JIANG Xiao4, FENG Yanfang5, LIU Jiangtao5
1.School of Earth and Resources, China University of Geosciences(Beijing), Beijing 100083, China;2.Shandong Provincial Key Laboratory of Water and Soil Conservation and Environmental Protection, School of Resources and Environment, Linyi University, Linyi 276005, Shandong, China;3.Shenyang Institute of Geology and Mineral Resources, China Geological Survey, Shenyang 110034, Liaoning, China;4.China Aero Geophysical Survey & Remote-Sensing Center for Land Resources, Beijing 100083, China;5.Development and Research Center, China Geological Survey, Beijing 100037, China
Abstract:
Hongshan syenite complex has fairly abundant clinopyroxene with core-rim (core-mantle-rim) structure. By studying the changes in the composition of clinopyroxene, information on the genesis and evolution of rocks can be obtained. Based on detailed field geological survey, the authors used zircon U-Pb chronology and mineralogical studies to obtain the biotite pyroxene syenite zircon U-Pb dating data of Hongshan syentite complex, with the age being(126.9±1.2)Ma, suggesting a product of the thinning peak period of the North China Craton lithosphere. The Mg# values of clinopyroxene from pyroxene syenite and biotite pyroxene syenite in the Hongshan syenite complex are 39.4-72.5 and 55.4-81.7, with characteristics of high FeO, Na2O and CaO content and low Al2O3, MgO and TiO2 content. The clinopyroxene generally had the evolutionary trend of diopside and aegirine, and reached an equilibrium state with the melt. The clinopyroxene had a Fe2+ to Mg2+ substitution relationship during the initial evolution. With the evolution, the magma became richer in sodium and iron, which suggests that the magma system had the characteristics of high temperature, medium oxygen fugacity and richness in alkali. Combined with the clinopyroxene core-rim (core-mantle-rim), the authors hold that there existed a clear contact relationship and discontinuous chemical composition. It is shown that, after the formation of the Hongshan syenite complex, it also underwent the transformation of sodium-rich and iron-rich fluids, causing the clinopyroxene to form a sodium-rich and iron-rich rim. The fluid may have modified the complex from west to east or from the inside of the Hongshan syenite complex to the outside.
Key words:  syenite complex  clinopyroxene  mineralogy  zircon U-Pb chronology  Mesozoic  magma evolution  sodium-rich fluid  geological survey engineering  Wu'an  Hebei Province