新疆尉犁县兴地Ⅲ号岩体铜镍含矿性评价及找矿远景

Cu-Ni Ore-bearing Potential Evaluation and Prospecting Potential of No.3 Xingdi Complex in Yuli County,Xinjiang

兴地Ⅲ号岩体位于兴地大断裂南侧,受其次级断裂控制,属于兴地河基性-超基性杂岩带;岩体岩相分带较丰富,可分为辉长岩相和橄辉岩相2个岩相带,矿化蚀变多位于橄辉岩相带。岩石类型属于拉斑玄武质岩浆系列;稀土总含量较低,轻重稀土分异明显,稀土元素配分模式为轻稀土富集型,无明显的Eu异常;m/f值大于2,有利于形成铜镍矿;在岩体中部取新鲜辉长岩岩石样品,利用LA-ICP MS方法获得其U-Pb同位素年龄为(716.7±2.4)Ma,形成于陆内裂谷环境,可能与Rodinia超大陆裂解事件有关。通过与已发现铜镍矿的Ⅱ号岩体进行对比,发现Ⅲ号岩体也具有相似的岩相学、岩石学、稀土元素配分模式、物化探特征及矿化蚀变特征,并且两者均形成于新元古代。因此,Ⅲ号岩体具有较好铜镍矿找矿前景。

The No. 3 intrusion in Xingdi area belongs to the Xingdi River basic - uhrabasic complex beh on the south of Xingdi fault zone, of which secondary faults control the No. 3 intrusion. It has abundant lithofacies zonation（gabbro facies and olivine - pyroxenite facies）, and the alterna- tions are in the olivine- pyroxenite facies. The rocks belong to tholeiite basalt with features of low total rare earth, obvious fractionation of REE and weak Eu anomaly. The m/f ratio is greater than 2, which is conducive to the formation of Cu - Ni deposit. With the U - Pb isotope age of 716.7＋2.4 Ma, the gabbro selected from the No. 3 intrusion is formed in an intracontinental rift, which is something to do with Rodina supercontinent breakup event. Through comparison with No. 2 intrusion, where a small copper nickel ore was explored, similar features of petrogra- phy, petrology, REE distribution pattern, physic- chemical characteristics and alternation features were identified, in addition, the two intrusions were both formed in Neonrotornzoic Era.So, the No. 3 intrusion has fairly good prospecting potential.