【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。更多还原

【Abstract】 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 ∑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,ε(Hf)(t)values are-13.4--17.3,and the depleted mantle mode ages(tDM2)are in the range of 1.91-2.11 Ga.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 transitionof syn-collisional to post-collisional tectonic setting.更多还原