北黄海盆地前中生代-中生代火山岩磁化率、地球化学特征及构造意义  

Susceptibility,Geochemical Characteristics and Tectonic Significance of Volcanics of North Yellow Sea Basin from Pre-Mesozoic to Mesozoic

作　　者：许中杰[1] 王嘹亮[2] 孔媛[1] 程日辉[1] 

机构地区：[1]吉林大学地球科学学院,吉林长春130061 [2]广州海洋地质调查局,广东广州510075

出　　处：《地球科学（中国地质大学学报）》2017年第2期191-206,共16页Earth Science-Journal of China University of Geosciences

基　　金：国家青年科学基金项目(No.41402087);中国地质调查局国家专项项目(No.GZH200700405);中国博士后科学基金面上项目(No.2013M530976)

摘　　要：北黄海盆地内多口钻井钻遇到前中生代和中生代火成岩,证实了盆地中生代经历的多期构造活动伴随着多期次火成岩的发育.对北黄海盆地X1和X2井火山岩进行了岩石学鉴定、磁化率和密度测试、主量元素、ICP-MS微量和稀土元素测试,研究表明:X1井前中生代碱玄岩和粗面玄武岩属于弱磁性((131.5~138.5)(4π×10^(-6)))、中密度岩石,X2井中生代英安岩(下层)和含角砾英安岩(上层)属于微弱磁性((27.5~82.5)(4π×10^(-6)))、中密度岩石;X1井碱玄岩属于高钾钙碱性系列,粗面玄武岩属于钙碱性系列,2种火山岩表现为ΣREE较高(108.11×10^(-6)~208.02×10^(-6))、轻稀土富集(LREE/HREE=4.04~6.91)、δEu有微弱异常(0.99~1.18);X^2井2层火山岩属于钙碱性系列,均表现为ΣREE较低、轻稀土富集、δEu有微弱异常,微量元素具有Ba、U、Sr富集和Nb、Ta亏损的特征,而且(Rb/Sr)_N、(La/Nb)_N和(Ba/Nb)_N的比值均高于原始地幔值,反映岩浆源于地壳熔融.北黄海盆地前中生代火山岩形成于板内构造背景,中生代火山岩可能形成于板块俯冲的弧后伸展环境.The multiple Mesozoic and Mesozoic igneous rocks in the well drilling in the North Yellow Sea basin confirm the multi-stage tectonic activity experienced by the Mesozoic has been accompanied by the development of multi-stage igneous rocks.A petrology study is carried out on magnetic susceptibility,density,main elements,ICP-MS trace elements and rare earth elements of the volcanics of X1 and X2 well of North Yellow Sea basin in this paper.Results show that tephrite and trachy basalt of Pre-Mesozoic in X1 well of North Yellow Sea basin is weaker magnetic（（131.5-138.5）（4π×10^-6）.Dacite in the lower part of X2 and dacite containing breccia in the upper part is weak magnetic（（27.5-82.5）（4π×10^-6））and rocks of medium density.The tephrite of X1 belongs to the high potassium calcalkaline series and the trachy basalt is the calcalkaline series.These two kinds of volcanics are characterized by higherΣREE（108.11×10^-6 to 208.02×10^-6）,enriched LREE（LREE/HREE=4.04-6.91）and weak anomalies withδEu（0.99-1.18）.And the two layers of volcanic in X2 are both characterized by lowerΣREE,enriched LREE and weak anomalies withδEu.The rare elements are characterized by enriched Ba,U and Sr and depleted Nb and Ta.The ratios of（Rb/Sr）N,（La/Nb）N and （Ba/Nb）N are all higher than those of the original mantle,which indicates that the magma derived from the crust melting.It is concluded that the volcan-ics of North Yellow Sea basin in Pre-Mesozoic formed in the plate tectonic setting the ones in Mesozoic probably formed in the back-arc extension of plate subduction.

关 键 词：北黄海 前中生代 中生代 火山岩 磁化率 构造背景 地球化学 

分 类 号：P595[天文地球—地球化学]