大兴安岭北部±130Ma火山岩的地质意义  

The Geological Implications of ±130 Ma Volcanic Rocks in the Northern Da Hinggan Mountains

作　　者：张兴洲[1] 刘洋[1] 曾振[1] 张宏涛[1] 崔维龙 Zhang Xingzhou Liu Yang Zeng Zhen Zhang Hongtao Cui Weilong(College of Earth Sciences, J ilin University, Changchun 130061, China)

机构地区：[1]吉林大学地球科学学院,长春130061

出　　处：《吉林大学学报（地球科学版）》2017年第1期1-13,共13页Journal of Jilin University：Earth Science Edition

基　　金：科技部公益性行业基金专项(201311018-02)~~

摘　　要：大兴安岭地区北部广泛发育一套早白垩世中酸性火山岩组合,这套组合下部以粗面岩-粗安岩为主,上部以流纹岩为主,二者的形成时代完全一致,锆石年龄均为130Ma,对应的地质时代为早白垩世欧特里夫期。岩石地球化学资料表明,火山岩以富硅、碱及贫镁为特征,且轻重稀土分馏明显,都具有明显的Eu负异常,反映其同源演化的特点。火山岩时代与相邻正常沉积地层中化石组合时代的对比结果表明,这套火山岩与其上下正常沉积地层的沉积时代是连续演化的。火山岩之下南屯组的化石组合时代为早白垩世凡兰吟期,对应的数值年龄为139~132 Ma,之上大磨拐河组—伊敏组的化石组合时代为早白垩世欧特里夫期晚期—芭蕾姆期,对应的数值年龄为129~125 Ma。这一证据揭示,大兴安岭北部在139~125Ma的早白垩世期间经历了连续的沉积—火山—沉积作用演化过程,反映了该区当时伸展盆地的演化特点。其中,约130 Ma的火山岩是该区一次重要的区域性火山岩喷发事件。The Early Cretaceous intermediate and acid volcanic rocks are widely distributed in the north of the Da Hinggan Mountains.The lower part of this combination is composed mainly of trachytetrachyandesite,while the upper part is composed mainly of rhyolite.They have the same forming time.LA-ICP-MS ziron U-Pb age of these rocks are 130 Ma,corresponding to the Hauterivian period of the Early Cretaceous in age.The geochemical study suggests that volcanic rocks are rich in silicon,alkalis and poor in magnesium.All samples have similar characteristics of REE patterns which are charecterized by significant fractionation of HREE and LREE and strong negative Eu anoalies.These evidence indicates that the volcanic rocks have the characteristics of homologous evolution.Comparing the agewith the fossil ages in the surrounding sedimentary stratas reveals that the volcanic rocks are continuously evolved in the depositional age of the upper and lower normal sedimentary stratas.The fossil age of the Nantun Formation under the volcanic rocks is the Valanginian period of the Early Cretaceous,corresponding to the numerical age of 139-132 Ma and that of the Damoguaihe-Yimin Formation above it is the late Hauterivian-Barremian period of the Early Cretaceous,corresponding to the numerical age of 129-125 Ma.These evidence reveals that the north part of the Da Hinggan Mountains suffered a successive evolution from sedimentation to volcanism to sedimentation during the Early Cretaceous（139-125 Ma）,reflecting the evolution characteristics of the extensional basins.The volcanic rocks with the age of 130 Ma represents a regional eruption event and also it has an important significance for dividing stratigraphic sequence in Early Cretaceous.

关 键 词：大兴安岭北部 火山岩 130 MA 早白垩世 地球化学 

分 类 号：P544.4[天文地球—构造地质学] P588.1[天文地球—地质学]