北京门头沟地区棋盘岩铁辉长岩的发现及其地质意义

The First Report of Qipanyan Ferrogabbro of Mentougou,Beijing,and Its Implications

根据北京门头沟地区棋盘岩岩体的主元素分析结果,按Middlemost提出的TAS分类,有4个样品可以归属为橄榄辉长岩(Peridotgabbro)和似长石辉长岩(Foid Gabbro),属于辉长岩类,并且样品具有高铁(w(FeO*)>14%),贫硅(w(SiO2)<45%)的特征,因此属于铁辉长岩类。这是迄今为止燕山造山带存在铁辉长岩类岩石的首次报道。关于铁辉长岩类的成因目前还有争论,棋盘岩岩体在w(SiO2)-w(FeO*)/w(MgO)图解上显示有Fenner趋势,但是具体的成因还有待于进一步研究。铁辉长岩及其成因的研究将对揭示燕山期北京地区的构造环境和动力学背景、深部过程具有重要的启示意义。

Based on the major element analyses of Qipanyan gabbro of the Mentougou area, Beijing and TAb classification diagram proposed by Middlemost, 4 samples can be classified into peridotgabbro and foid gabbro. And the 4 samples are characterized by high Fe（total FeO^＊ 〉 14% ）and low silica contents （SiO2 〈45% ）, esis of Qipanyan ferrogabbro will need to be studied detailedly though the SiO2-FeO ^＊/MgO diagram of Qipanyan ferrogabbro shows the Fenner trend, because there are different opinions about the petrogenesis of ferrogabbro. The study of ferrogabbro and its petrogenesis will play an important role in studying tectonic setting and dynamic background, deep process of the Beijing area during Yanshanian Movement.