大兴安岭中南段梅勒图组层型剖面锆石U-Pb年龄、地球化学特征及其地质意义  

Zircon U-Pb age and geochemistry of the stratotype section of the Meiletu Formation in middle southern Da Hinggan Mountains and its geological significance

作　　者：杨海星 高利东 高玉石 隋海涛 赵志飞 吕晶 张维宇 赵胜金 柳志辉[1] 周颖帅 YANG Haixing;GAO Lidong;GAO Yushi;SUI Haitao;ZHAO Zhifei;Lü Jing;ZHANG Weiyu;ZHAO Shengjin;LIU Zhihui;ZHOU Yingshuai(Inner Mongolia tenth geological mineral exploration and development Co.,Ltd.,Chifeng 024005,Innner Mongolia,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China)

机构地区：[1]内蒙古第十地质矿产勘查开发有限责任公司,内蒙古赤峰024005 [2]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地质通报》2019年第5期845-857,共13页Geological Bulletin of China

基　　金：中国地质调查局项目《内蒙古1:5万包尔呼吉尔塔拉等八幅区域地质调查》(编号:DD20160048-11)、《内蒙古1:5万吐卜钦等五幅区域地质调查》(编号:DD20160048-15)和《大兴安岭成矿带突泉—翁牛特地区地质矿产调查》(编号:DD20160048)

摘　　要：梅勒图组为大兴安岭中南段中生代层位最高的火山岩地层,其层型剖面的研究对于大兴安岭中南段梅勒图组的时代划分及区域对比具有重要意义。对梅勒图组层型剖面火山岩进行了年代学及地球化学研究,测试了4件安山岩LA-ICP-MS锆石U-Pb年龄,结果介于127.7±1.4~133.4±1.5Ma之间,时代归属早白垩世。梅勒图组火山岩与中国同类火山岩相比,SiO2(57.95%~64.25%)、TiO2(0.69%~1.25%)及K2O(0.55%~4.97%)含量偏高;Fe2O3(2.03%~4.32%)、FeO(1.05%~3.77%)、MgO(0.52%~2.44%)及CaO(2.22%~6.07%)含量略偏低,MnO(0.05%~1.00%),Al2O( 3 14.97%~17.61%),Na2O(2.61%~4.16%)含量相当;为一套准铝质-过铝质高钾钙碱性系列岩石。稀土元素总量较低,介于133.43×10^-6~181.7×10^-6之间,轻、重稀土元素分异明显(LREE/HREE=7.51~8.14,(La/Yb)N=7.75~8.78);轻稀土元素分馏较强,重稀土元素分馏较弱,具较弱负Eu异常(δEu=0.78~0.95)。微量元素富集大离子亲石元素(Rb、Ba、K、Pb、Sr)和轻稀土元素,亏损高场强元素(Nb、Ta、Ti、P)和重稀土元素。岩浆来源于过渡型地幔,形成环境为大陆边缘弧,可能与太平洋板块俯冲后的陆内伸展作用有关。The Meiletu Formation is the highest strata volcanic rocks in Mesozoic in the southern central part of the Da Hinggan Mountains. The study of the layer section is of great significance for the division and regional correlation. In this paper, the authors carried out the study of the chronology and geochemistry of the Meiletu Formation layer section volcanic rocks, analyzed zircon UPb isotope dating for 4 pieces of andesite samples by using LA- ICP- MS technique, and yielded the ages of 127.7 ± 1.4~133.4 ± 1.5Ma, suggesting Early Cretaceous. A comparison with the similar volcanic rocks in China shows that the Meiletu Formation volcanic rocks have high content of SiO2(57.95%~64.25%), TiO2(0.69%~1.25%)and K2O(0.55%~4.97%), low content of Fe2O3 (2.03%~4.32%), FeO(1.05%~3.77%), MgO(0.52%~2.44%)and CaO(2.22%~6.07%), and consistent MnO(0.05%~1.00%), Al2O3 (14.97%~17.61%)and Na2O(2.61%~4.16%)content, suggesting aluminous- over- aluminous rock of high potassium Ca- alkali series. Lower rare earth (ΣREE) values are between 133.43×10^-6 and 181.7×10^-6 , and there exists obvious regional difference in light and heavy rare earth elements(LREE/HREE=7.51~8.14,(La/Yb)N=7.75~8.78), showing strong fractionation between the light rare earth and the heavy rare earth, with negative EU anomaly(δEu=0.78~0.95). The rocks are enriched in large ion lithophile elements (Rb, Ba, K, Pb, Sr)and LREE and depleted in high field-strength elements (Nb. Ta, Ti and P) and HREE. Magma came for the transitional mantle. The rocks were formed in a continental edge arc environment, and were related to the continental extension after the Pacific Plate subduction.

关 键 词：梅勒图组 火山岩 锆石U-PB年龄 岩石地球化学 层型剖面 

分 类 号：P597.3[天文地球—地球化学] P588.14[天文地球—地质学]