云南省丽江-宾川地区二叠纪玄武岩地球化学特征及其构造背景研究  

THE GEOCHEMICAL CHARACTERISTICS AND TECTONIC SETTING OF THE PERMIAN BASALTS IN THE BINCHUAN-LIJIANG AREA IN YUNNAN PROVINCE

作　　者：朱士飞[1] 秦勇[1] 钱壮志[2] 高艳青[3] 

机构地区：[1]中国矿业大学资源与地球科学学院,江苏徐州221008 [2]长安大学地球科学与国土资源学院,陕西西安710054 [3]徐州空军学院机场工程系,江苏徐州221000

出　　处：《矿物岩石》2008年第1期64-71,共8页Mineralogy and Petrology

基　　金：云南省自然科学基金(2003D0016Z);中国地质调查局地质大调查综合研究项目(200110200058)

摘　　要：在峨眉山大火成岩省中，宾川-丽江地区的溢流玄武岩厚度最大，发育较为完整。该区岩石ω（SiO2）（36．72％～51．44％），微量元素中不相容元素如大离子亲石元素K，Rb,Cs,Ba,Th富集；高场强元素Ta，Nd，Hf，Zr以及LREE含量低。它们的岩石地球化学性质呈现递变性，富集轻稀土和大离子亲石元素。具有与洋岛玄武岩相似的地球化学特征。为板内拉张玄武岩。通过对其进行岩石学和地球化学研究，系统分析该区玄武岩岩石地球化学及其岩浆活动特征。认为研究区玄武岩可划分为3个系列：高铗（ωMgO=12．3％～14．3％）、低镁（ωMgO=2．48％～7．53％）和过渡系列（ωMgO=10．4％～11．3％）火山岩。高镁系列玄武岩岩石接近原始岩浆的组成，岩浆源区可能为下地幔，形成深度大，源区地幔部分熔融比例小；低镁系列玄武岩受到较强的地壳混染作用的影响。显示出富集岩石圈地幔或地壳物质的参与，形成深度浅，熔融比例较大，可能有地壳物质混染；过渡系列介于前两者之间。根据玄武岩大地构造环境判别图解，确定玄武岩形成于大陆拉张环境，与地幔柱活动有关。The trace and major elements of the Emeishan basalts occurred in the Binchuan and Lijiang area were studied. The basalts with a Permian age in the area were of the largest thickness of over 5000m and had a series of rock types. In this paper,the petrologic and geochemical characteristics and magma activation of the Emeishan basalts were described systemically. The research showed that the basalts with ω（SiO2） composition of 36.72%-51.44% can be compositionally subdivided into three types, the high-Mg （ωMgO=12. 3%-14.3%）, the low-Mg （ωMgO=2. 48%- 7.53% ） and transitional-Mg （ωMgO = 10. 4 %-11. 3% ） basalt. All three groups showed continuous shift and trace elements,enriched LREE and LILE,while the high field-strength elements such as Ta,Nd,Zr and Hf were notably depleted. The basalts exhibited similar geochemical features to the Oceanic Island Basalts and belonged to the intra-plate tholeiitic basalts. It was considered that the Emeishan basalts represented a major magmatic event triggered by deep-seated plumes. The magma, raised from the mantle plume interacted with lithosphere materials,underwent different degrees of mixing of lithosphere mantle and crustal components and developed a variety of basalts.

关 键 词：宾川-丽江 大陆溢流玄武岩 岩石地球化学 地幔柱 构造背景 

分 类 号：P597.2[天文地球—地球化学]