麻地与汉儿庄岩体岩相学及含矿性对比分析

麻地与汉儿庄岩体为冀东马兰峪复式背斜核部西段目前已发现的两个稀有金属矿化花岗岩体,表明该区具有一定寻找稀有金属矿的潜力。通过野外地质调查,初步查明两个岩体均为至少两次侵入活动形成的复式岩体,早期为肉红色碱长花岗岩,晚期为灰白色碱长花岗岩。岩相学和地球化学特征表明:两个岩体的岩石类型均属于碱长花岗岩,主要矿物成分以石英、钠长石、碱性长石为主,含少量(锂)云母,岩石化学成分上高硅、富碱,贫钙、镁,属于过铝质、钙碱性系列。均具Rb、Nb、Ta等稀有金属矿化,其中麻地岩体以Rb矿化为主,地表已出露岩体全部矿化,汉儿庄岩体以Nb、Ta矿化为主,主要富集在晚期的灰白色碱长花岗岩中。源区含矿流体特征及岩体侵位构造环境的不同可能为造成含矿性差异的主要因素。

Contrastive Analysis on Petrographic Features and Metallogenesis of Madi and Hanerzhuang Rocks

The rocks of Madi and Hanerzhuang are two mineralized granitic bodies of rare metals which have been found in the western part of Malanyu complex anticline in eastern Hebei province recently.That indicated area has potential to search for rare metal ore.In field geological survey,it is preliminarily found that the two rock masses are complex rock bodies formed by at least two intrusive activities,including the early pale red alkali feldspar granite and the lately grayish-white alkali feldspar granite.The petrographic and geochemical characteristics show that the rock types of the two rock masses belong to alkali feldspar granite.The chemical composition of rock is characterized by high silicon,enriching in alkali,poor in calcium and magnesium,as belongs to peraluminous calc-alkaline series.The main minerals are quartz,aldolite and alkaline feldspar,with a small amount of(lithium)mica.All of them are mineralized with Rb,Nb,Ta and other rare metals.Among them,the Madi rock body is dominated by Rb mineralization,all the exposed rock bodies on the surface are mineralized,and the Han’erzhuang rock body is dominated by Nb-Ta mineralization,which is mainly enriched in the late grayish-white alkali-feldspar granite.The characteristics of ore-bearing fluid in the source area and the different emplaced tectonic environment of the rock body may be the main factors causing the differences in mineralization.