内蒙古阿鲁科尔沁地区晚侏罗世侵入岩年代学、地球化学特征及成矿潜力
Geochronological, Geochemical Characteristics and Mineralization Potentiality of Late Jurassic Intrusive Rocks in Ar Horqin Banner Area, Inner Mongolia

摘要： 摘要：阿鲁科尔沁地区位于兴蒙造山带东段，中生代岩浆岩分布广泛。对该地区晚侏罗世侵入岩进行了年代学、岩石地球化学及其成矿潜力研究。阿鲁科尔沁地区晚侏罗世侵入岩主要由石英二长闪长岩、石英二长岩、黑云母花岗闪长岩组成，主岩体黑云母花岗闪长岩的LAICPMS锆石UPb加权平均年龄为(14379±084) Ma(MSWD=33)，属晚侏罗世，在区域MoAuCu成矿峰期内。岩体属准铝质高钾钙碱性-钾玄岩系列，相对富碱，稀土元素总量较低，轻重稀土分馏明显，具有中等Eu负异常，富集强不相容元素Rb、Th、U、LREE，亏损高场强元素P、Ti、Y及HREE，相对亏损Nb和Ta，相对亏损大离子亲石元素Ba，属I型花岗岩。岩体主体来源于壳源基性岩组分的部分熔融，形成于晚侏罗世的后碰撞伸展环境，为有利成矿构造演化阶段。K/Rb和Rb/Sr比值较小，DI值较大，SI值较小，Fe2O3/FeO比值较大，属中等-强演化中等分异程度的氧化型或磁铁矿系列花岗岩，地球化学含矿性参数显示其Cu、Au、Mo金属成矿潜力依次降低，与研究区已发现的矿化特征相一致。
Abstract: Ar Horqin Banner area is located in the eastern XinganMongolian orogenic belt, and the Mesozoic magmatic rocks are widely distributed. In this paper, zircon UPb geochronological and element geochemical studies were carried out for the Late Jurassic intrusive rocks in Ar Horqin Banner area. The study of petrology indicates that the granitoids are mainly composed of quartz monzobiorite, quartz diorite and biotite granodiorite. Zircon LAICPMS UPb dating of the biotite granodiorite gives a weighted average age of (14379±084) Ma(MSWD=33), indicating that it belongs to the Late Jurassic, and it is during regional MoAuCu metallogenic peak period. Major elemental geochemistry shows that the rocks are quasialuminous calalkaline granites, which is characterized by relatively rich alkali. Trace elements have a similar variation trend of low REE contents and obvious fractionation of light and heavy rare earth, significant negative anomaly of Eu, the enrichment of strong incompatible elements (Rb, Th, U, LREE), depletion of high fieldstrength element (P, Ti, Y and HREE), relative depletion in Nb, Ta and Ba. Main body of the granites belongs to calcalkaline I genetic type. The magmas were the product of partial melting of the basite in the crust, formed in an extensional setting after the collision, which is a favorable metallogenic tectonic evolution stage. SI, K/Rb and Rb/Sr ratios are relatively small, DI values and Fe2O3/FeO ratios are relatively large, which shows that the granites belong to mediumstrong evolution, medium fractionated, oxidation type or magnetiteseries. Their geochemical ore parameters indicate that Cu, Au, Mo mineralization potentiality decreases systematically, consistent with the other mineralization characteristics in the study area