内蒙古乌兰敖包地区流纹质凝灰熔岩锆石U——Pb年龄及其地质意义

Zircon U-Pb Dating and Geolpgical Significance of Rhyolitic Tuff Lava in Wulanaobao Area in Inner Mongolia

摘要:

运用LAICPMS技术，对内蒙古乌兰敖包地区原“阿木山组”之上所采集的流纹质凝灰熔岩样品进行锆石UPb测年，获得19个有效数据，年龄范围分布为（248±5）~（277±5）Ma，主要峰值263~248Ma(17个数据)，另有2个数据为273Ma、277Ma与其他17个数据不协调，这可能是岩浆从外部带入的早期结晶锆石。根据样品岩石学特征及UPb年代学特征，结合区域构造演化等，分析认为研究区在晚二叠世早期(255.2±2.4）Ma有一定规模的熔岩喷发，该套海相火山碎屑岩层位与银额盆地北部地区哈尔苏海组地层相当，可归入哈尔苏海组。

Abstract:

By using La ICP MS technology, zircon U Pb dating of rhyolitic tuff lava samples collected on the original "Amushan formation" in Wulanaobao area in Inner Mongolia, 19 effective data have been obtained. The age range is (248±5) ~ (277±5) Ma, the main peak is 263~248Ma (17 data), and the other two data are 273~277Ma. They are inconsistent with the other 17 datas, which may be the early crystalline zircon brought in by magma from the outside. According to the petrological characteristics of the samples and U Pb chronological characteristics, combined with the analysis of regional tectonic evolution, it is considered that there is a certain scale of lava eruption in the study area in the early late Permian period(255.2±2.4 Ma). The horizon of this set of marine volcaniclastic rocks is equivalent to that of halsuhai formation in the northern part of yine basin and can be classified into Halsuhai formation.