华北板块北缘西段东升庙岩体地球化学特征及其构造意义  

Geochemical Characteristics and Tectonic Implications of the Dongshengmiao Intrusion in the West Segment of the Northern Margin of the North China Plate

作　　者：吴亚飞[1] 王小龙[1] 曾键年[1] 曹建劲[2] 陆顺富[1] 孙晓东 

机构地区：[1]中国地质大学(武汉)资源学院,武汉430074 [2]中山大学地球科学系,广州5102751 [3]内蒙古第九地质矿产勘查开发院,内蒙古锡林浩特026000

出　　处：《矿物岩石地球化学通报》2014年第6期820-829,共10页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金重点项目(41030425)

摘　　要：华北板块北缘具有复杂的构造演化历史,沿板块北缘发育有上千千米的近东西向晚古生代—早中生代岩浆岩带,东升庙岩体是该岩浆岩带西段上具有代表性的岩体之一。但对该岩体系统的地球化学研究基本没有开展。为揭示华北板块北缘复杂的构造演化历史,本文对该岩体白云母二长花岗岩进行了系统的岩石地球化学和Lu-Hf同位素研究。结果表明,东升庙岩体富含SiO2(70.70%~76.46%)、Al2O3(12.66%~14.98%)和Na2O(3.60%~5.49%),而贫TiO2(0.02%~0.08%)、MgO(0.07%~0.49%)和Fe2O3(0.02%~2.46%),其A/CNK值为0.90~1.15,为弱过铝质-准铝质高钾钙碱性系列。岩石相对富集Rb、U、K、Hf,亏损Ba、Sr、Nb、Ti;稀土总量很低(18.50×10-6~63.15×10-6),具负Eu异常和M型四组分效应。176 Hf/177 Hf值为0.2821~0.2823,εHf(t)=-13.4^-17.3,tDM2=1.9~2.1Ga。结合其他资料,可以认为东升庙岩体是典型的壳源S型花岗岩,岩浆源区为古老的古元古代陆壳物质,在岩浆演化过程中经历了高度的结晶分异作用,形成于华北—欧亚板块同碰撞末—后碰撞初的转换构造时期。The Dongshengmiao intrusion,which developed in the late Paleozoic to the early Mesozoic,is located in the west segment of the east-west magmatic belt in the northern margin of the North China Plate.This paper reports petrogeochemistry and Lu-Hf isotopes studies of the Dongshengmiao muscovite monzonitic granite.The results indicate that it contains high contens of SiO2 （70.70%-76.46%）,Al2O3 （12.66%-14.98%）,and Na2O （3.60%-5.49%） and low contents of TiO2 （0.02%-0.08%）,MgO （0.07%-0.49%） and Fe2O3 （0.02%-2.46%）,and that its A/CNK ranges from 0.90-1.15,indicating that the Dongshengmiao intrusion belongs to the metaluminous to peraluminous and high-K calc-alkaline series.The trace element normalized spider diagram shows that it riches in Rb,U and K,depletes in Ba,Sr,Nb and Ti.The granite has very low Σ REE values of 18.50～63.15）×10^-6,negative Eu anomaly and M-type REE tetrad effect.Hf isotope analyses in zircons show that initial Hf isotopic compositions are relatively homogeneous,176 Hf/177 Hf ratios are 0.2821-0.2823,e（Hf） （t） values are-13.4--17.3,and the depleted mantle mode ages （tDM2） are in the range of 1.91-2.11Ga.Comprehensive analyses show that the Dongshengmiao intrusion is a typical crust-derived S-type granite,it mainly derived from the old paleoproterozoic crust and experienced strong crystal fractionation processes,and this intrusion was formed at the transition of syn-collisional to post-collisional tectonic setting.

关 键 词：东升庙花岗岩 华北板块 S型花岗岩 地球化学特征 同碰撞 

分 类 号：P588.1[天文地球—岩石学]