【摘要】 笔者近期在大兴安岭北端漠河地区早古生代花岗岩的研究中发现了埃达克质岩,岩石类型主要为二长花岗岩及少量花岗闪长岩,岩石富 K 但相对略富钠（Na₂O/K₂O>1）,富 SiO₂;高 Sr 低 Y、Yb,Sr/Y>40;富集 LREE,亏损重稀土元素,La/Yb>20,Eu 呈弱负异常或轻微正异常（δEu=0.71～1.1）。与典型的俯冲板片熔融形成的埃达克岩相比更为富硅和钾,属高钾钙碱性系列,具有低的 Mg^#（31.1～34.9）及不同于Ⅰ型埃达克岩的 Nd、Sr 同位素组成,属Ⅱ型埃达克质岩,推测形成于加厚的中基性下地壳的部分熔融。漠河早古生代埃达克岩的确认表明额尔古纳地块早古生代有过陆壳加厚过程,大陆发生过垂向的增生。同时在德尔布干成矿带中段的本区寻找与埃达克岩有关的斑岩型铜、金矿床是一个新的找矿方向。更多还原

【Abstract】 Early Paleozoic adakitic rocks recently discovered in Mohe area,northern Da Hinggan Mountains,are mainly composed of monzogranite and granodiorite.These rocks have high SiO₂ and Na₂O（Na₂O/K₂O>1）,and low contents of HREE and high Sr/Y ratio（>40）.They are characterized by LREE-enrichment and weak Eu anomaly（δEu=0.71～1.1）.Compared with the adakites generated by subducted slab-melting,the Mohe rocks display higher SiO₂ and K₂O contents,and can be classified as high-K calc- alkaline series rocks.These features make them resemble Type Ⅱ adakites,which may have originated by partial melting of the thickened lower crust.Occurrence of the adakitic rocks in Mohe area suggests that the crust in southeastern Ergun Massif has been thickened by magmatic underplating during the Paleozoic.On the other hand,porphyry copper and gold deposits related to the adakitic rocks in this area can be a new target for ore-prospecting.更多还原