龙首山岩带典型镁铁-超镁铁质岩体岩石地球化学特征

通过龙首山岩带中几个典型镁铁-超镁铁质岩体样品的岩石地球化学分析,对金川超镁铁质岩体与其外围镁铁-超镁铁质岩体的形成演化关系进行探讨,结果发现:这些岩体处于相同的构造环境,样品点整体为亚碱性拉斑玄武岩系列,随M g#值的增加,C aO,A l2O3,N a2O,K2O值具有连续减少的趋势,指示了它们存在连续的岩浆演化关系;稀土与微量元素分析,蛛网图整体具有右倾特征,龙首山岩带中段岩体有明显δEu负异常,东、西段岩体样品有δEu正异常或无异常,暗示中段岩体较外围岩体经历了更完全的分离结晶作用;结合前人对金川所做的S r-N d同位素等资料,证明金川岩体的岩浆源区为富集型地幔。

GEOCHEMICAL CHARACTERISTICS OF TYPICAL MAFICULTRAMAFIC ROCKS IN LONGSHOU MOUNTAINS

Collecting rock samples from several mafic-ultramafic intrusions in Longshou Mountains and studying the petrochemical compositions,trace elements,rare earth elements,combining with the Sr-Nd isotopes of Jinchuan ultramafic intrusion,the authors compare the geochemical characteristics of typical mafic-ultramafic rocks in Longshou Mountains.It is demonstrated that various mafic-ultramafic rocks are the same petrochemical series,with a continuous evolution process.The Longshoushan rock belts experienced fractional crystallization,except the intrusions in the east part and the west part,inferring that the peripheral intrusions provided Ni for Jinchuan ore deposit in early stage,intruding to near surface firstly,and contributing to the ore formation of Jinchuan ore deposit.