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大兴安岭中段扎兰屯地区晚古生代埃达克岩主要岩石类型为安山岩、粗面安山岩、英安岩和粗面英安岩,取得一个安山岩样品的LA-ICP-MS锆石U-Pb年龄为(316.9±2.4)Ma,代表火山岩喷发的年龄.岩石具有较高Si(Si O2=54.97%~63.80%),富碱并相对略富Na(Na2O/K2O>1),富Al(Al_2O_3=14.97%~17.69%),高Sr(715.98×10~(-6)~2100×10~(-6)),低Y(12×10~(-6)~18.41×10~(-6))和Yb(1.02×10~(-6)~1.91×10~(-6))的特点.在原始地幔标准化蛛网图中,富集LREE,亏损HREE,Eu呈微弱正异常(δEu=0.97~1.30).同时Mg值介于0.35~0.57,平均0.46.总体特征属于高钾钙碱性埃达克岩(为C型埃达克岩的一种),来源于增厚的玄武质下地壳的部分熔融.扎兰屯地区晚古生代高钾钙碱性埃达克岩的发现,为兴安地块与松嫩地块的拼贴作用提供了新的线索,对正确认识区域地壳演化有着重要的构造意义,为本区寻找与埃达克岩有关的矿产提供了线索.
The main Paleozoic adakites in the Zhalantun area in the middle section of the Daxinganling are mainly andesite, andesite, dacite and rough dacite. LA-ICP-MS zircon U-Pb dating of an andesite sample is ( 316.9 ± 2.4 Ma, representing age of eruption of volcanic rocks with high Si (Si O2 = 54.97% -63.80%), alkali-rich and relatively Na + / K2O> 1, Al 2 O 3 = 14.97% ~ 17.69%), high Sr (715.98 × 10 -6 ~ 2100 × 10 -6), low Y (12 × 10 -6 ~ 18.41 × 10 -6) and Yb (1.02 × 10 -6 ~ 1.91 × 10 -6) .In the original mantle normalized arachnoid map, enrichment of LREE, loss of HREE, Eu showed a weak positive anomaly (δEu = 0.97 ~ 1.30). At the same time, the value of Mg is between 0.35 and 0.57 with an average of 0.46.The general characteristics belong to the high-K calc-alkaline adakite (a type of C-type adakite) derived from the partial melting of thickened basaltic lower crust. The discovery of the late Paleozoic high-K calc-alkaline adakites in the Zalantun area provided new clues for the collapsing effect between the Xing’an block and the Songnen block and is of important structural significance for correctly understanding the regional crustal evolution. This area provides clues as to the search for minerals associated with the adakite.