大兴安岭北段新林战备村地区广泛发育晚中生代火山岩及花岗岩体.LA--ICP--MS锆石U--Pb测得战备村花岗岩体侵位年龄为121.0 ± 0.8 Ma,其周围出露的白音高老组流纹岩喷发年龄为136.9 ± 1.3 Ma,二者均形成于早白垩世.地球化学特征上,二者均属于过铝质高钾钙碱性--钾玄质系列,高SiO2,富K2O、Na2O,低Mg、Ti,微量元素富集大离子亲石元素Rb、K、Ba及LREE,亏损高场强元素Nb、Ta、Ti及HREE,轻重稀土明显分异 ( (La/Yb)N=11 ~23.2),具中等--弱的Eu负异常(δEu=0.35~0.82),二者具同源岩浆演化的特征.结合前人研究结果,新林战备村地区早白垩世火成岩形成于后造山或碰撞后的构造环境,代表了伸展的大地构造背景,这些火成岩产出可能与蒙古—鄂霍茨克洋中侏罗世至早白垩世闭合造山后的伸展作用有关.%Late Mesozoic volcanic rocks and intrusive rocks widely occurred in Xinlin Zhanbeicun area of northern Greater Hinggan Mountain. Zircon U--Pb dating using the LA--ICP--MS method gives the emplacement age of 121.0 ± 0.8 Ma for Zhanbeicun intrusive rocks and 136.9 ± 1.3 Ma for Baiyingaolao Formation rhyolites distrib-uted around the Zhanbeicun intrusive rocks. The results suggested that the intrusive rocks and rhyolites were formed in Early Cretaceous. Moreover the rocks belong to high K calc-alkaline-shoshonite series in geochemistry,and ex-hibit high SiO2,K2O,Na2O and low Mg,Ti. The trace elements generally have a similar variation trend,e.g. en-richment of LILE (Rb,K,Ba) and LREE, and depletion of HFSE (Nb, Ta, Ti) and HREE, with significant fractionation of LREE and HREE ( (La/Yb)N=11 ~23.26) and weak-medium Eu anomalies (δEu=0.35 ~0.82). This indicates that the intrusive rocks and rhyolites have the same sources. Combined with previous stud-ies,it is suggested that the Early Cretaceous igneous rocks in Zhanbeicun area are originated from partial melting of the lower crust and formed in a post-orogenic extensional tectonic setting related to the closure of Mongolia--Okhotsk ocean during Middle Jurassic-Early Cretaceous.
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