黑龙江省嫩江县三矿沟Cu-Fe-Mo矿床岩浆岩成因研究

A study of the genesis of igneous rocks from the Sankuanggou Cu-Fe-Mo deposit in Heilongjiang Province

三矿沟Cu-Fe-Mo矿床是大兴安岭地区三矿沟—多宝山构造-成矿带中一个比较典型的矽卡岩型矿床。在大量野外地质调查、室内岩矿鉴定的基础上，对与成矿有关的三矿沟复式英云（花岗）闪长岩体的岩石地球化学特征进行了分析，探讨了该岩体的成因类型和构造环境。研究表明，该矿床岩浆岩体属于钙碱性I型花岗岩，具有大陆地壳的特征，形成于与造山花岗岩有关的火山弧环境或相似的构造环境中，主要与造山阶段的火山弧花岗岩关系密切。稀土元素配分图显示向右缓倾斜的轻稀土元素富集型特点，轻、重稀土分馏较为明显，无明显的负铕异常，暗示其具有相同或相近的成因，也反映了同源岩浆的特点。δEu值介于0.81~1.24，δCe值为1.00~1.13，表明岩浆演化过程中发生了微弱的分离结晶作用，同时又受到同化混染作用的一定影响，其成岩环境氧逸度较低，指示了缺氧环境，有利于金属元素的积聚而形成矿床。

Located along the Sankuanggou-Duobaoshan tectonic- metallogenic belt in Da Hinggan Mountains, the Sankuanggouskarn- type Cu- Fe- Mo deposit is a typical skarn- type deposit. On the basis of field geological survey and indoor rock oreidentification, the authors analyzed the lithogeochemical characteristics of Sankuanggou (granite) tonalite related to metallogeny,and discussed the genetical type and tectonic setting of this rock mass. Studies show that the magmatic rocks of this deposit belongto the calc- alkaline I- type granite, with the characteristics of continental crust, and that these magmatic rocks were formed in avolcanic arc tectonic environment or a similar environment, mainly having close relationship with volcanicarc granite orogenic phase. REE distribution patterns show LREE-enriched patterns with gently rightly inclined shape, and strongREE fractionation with no pronounced negative Eu anomaly, suggesting that these magmatic rocks have the same or similar genesisand reflect the characteristics of comagmatic region. δEu values vary from 0.81 to 1.24, δ Ce values range from 1.00 to 1.13,indicating that weak fractional crystallization occurred in the process of magma evolution, with some influence of assimilation andcontamination, and that their low oxygen fugacity of diagenetic environment might imply some anoxic environment.