内蒙古北山地区小红山钒钛磁铁矿成岩成矿过程探讨

内蒙古北山地区小红山镁铁质岩体主要由辉长岩、角闪辉长岩和角闪辉石岩组成，其中角闪辉石岩中赋存了中型V-Ti-Fe矿床，角闪辉长岩具有一定程度的矿化，辉长岩中未见到矿化信息。岩体主要受近东西向的红柳河-牛圈子-洗肠井蛇绿岩缝合线深大断裂控制，成岩成矿作用发生在活动大陆边缘俯冲挤压环境下的局部拉张环境，岩体时代为（424.6±6）Ma。通过岩石地球化学研究，发现含矿岩体具有低碱、低铝、低硅、高磷、高钛、高钒的特征；稀土元素总量∑REE较高，富集LREE，亏损HREE，δEu负异常；微量元素具有Rb-Ba、Nb-Ta、Sr、Zr-Hf的负异常特征。成矿过程发生在岩浆演化中晚期，主要经历了岩浆分异，矿浆贯入及富矿热液活动3个阶段。大量钛铁氧化物融离发生在角闪石和磷灰石出现阶段。

The Diagenetic Mineralization Process of the Xiaohongshan Vanadium-bearing Titanometite in the Beishan Area of Inner Mongolia

The Xiaohongshan mafic intrusion, located in Beishan area of Inner Mongolia, was controlled by the nearly east-west deep faults of Hongliuhe-Niuquanzi-Xichangjing suture belt, which is mainly composed of gabbro, bojite and hornblende pyroxenolite.The middle-size V-Ti-Fe deposit was occurred in hornblende pyroxenolite, with a certain degree of mineralization in bojite, without any mineralization information in gabbro.Diagenesis and mineralization were occurred in the local tensile condition under thesubduction and extrusion environment of active continental margin,and the related rocks were formed in (424.6±6) Ma. The geochemical results show that these rocks have low alkali,aluminum and silicon, as well as high phosphorus, titanium and vanadium, which are benenfit for Mineralization. Their rocks have higher ∑REE values, which were enriched in LREE and depleted in HREE, with negative Eu anomalies. Their trace elements have the negative anomalies of Rb-Ba, Nb-Ta, Sr and Zr-Hf.Thus, the mineralization was occurred in the late magmatic evolution,which had experienced three stages, such as magmatic differentiation, ore pulp injection and ore-enriched hydrothermal activity.And then, a large number of Fe-Ti oxides were melted and separated in the stage of forming hornblende and apatite.