大兴安岭北部塔河县十八站—呼玛县韩家园地区发育早古生代中酸性侵入岩.文章选取二长闪长岩和二长花岗岩开展岩石年代学与地球化学研究.二长闪长岩LA-ICP-MS锆石U-Pb年龄为512.4±3.5 Ma,为早—中寒武世岩浆作用的产物.岩石地球化学分析表明,中酸性侵入岩归属于准铝质—弱过铝质(A/CNK=0.77~1.04)钙碱性—高钾钙碱性系列.岩石稀土总量∑REE=69.51×10-6~275.83×10-6,轻重稀土分异明显(La/Yb)N=9.11~26.64.在稀土元素配分图上,显示为LREE富集、HREE相对平缓的右倾型,Eu异常不显著(δEu =0.90~1.35).微量元素组成具明显富集大离子亲石元素Ba、Sr,显著亏损高场强元素Nb、Ta、Ti的特征.结合区域资料和本文研究,初步分析认为早古生代侵入体形成于活动大陆边缘或岛弧环境,为前古亚洲洋闭合背景下萨拉伊尔造山作用的产物.%Objectives:There are a set of intermediate—acidic intrusions in Shibazhan—Hanjiayuan area,Great Hinggan Mountains. This article focus on the chronology of monzodiorite, geochemical characteristics of monzodiorite and monzonitic granite,and their geological significance. Methods: Detailed geological survey, LA-ICP-MS zircon U-Pb dating of monzodiorite, and whole rock geochemical analysis of monzodiorite and monzonitic granite. Results:LA-ICP-MS zircon U-Pb dating of monzodiorite yielded a weighted mean age of 512.4 ± 3.5 Ma,revealing that it was a product of the early Paleozoic magmatism. Intermediate—acidic intrusions belong to metaluminous(A/CNK=0.77~1.04), calc-alkaline to high-K calc-alkaline series based on the geochemical analysis results. ∑REE change between 69.51×10-6and 275.83×10-6with(La/Yb)Nranging from 9.11 to 26.64. REE patterns are characterized by enriched in LREE and relatively depleted HREE with a moderate Eu anomaly (δEu =0.90~1.35). Trace elements characteristics show that the early Paleozoic intrusions distinctly enriched in LILE(Ba,Sr)and prominently depleted in HFSE(Nb,Ta,Ti). Conclusions:Combining achievements of predecessors with this study,we concluded that intermediate—acidic intrusions generated from an active continental margin or island arc environment, and it was a product of Salair orogeny,which related to Paleo-Asian ocean closing.
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