内蒙古狼山西南地区枕状玄武岩LA-ICP-MS锆石U-Pb年龄及意义  

LA-ICP-MS U-Pb ages of pillow lava basalts in southwestern Langshan,Inner Mongolia and their implication

作　　者：张进[1] 李锦轶[1] 刘建峰[1] 李岩峰 曲军峰[1] 张义平[1] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地震搜救中心,北京100049

出　　处：《地质通报》2013年第2期287-296,共10页Geological Bulletin of China

基　　金：中国地质调查局项目<兴蒙造山带基本构造格局综合调查和研究>(编号:1212011085476);<中国主要陆块晚前寒武纪以来裂解重现过程的再造及其对成矿作用的制约>(编号:1212011121064);国家自然科学基金<阿拉善东缘;南缘下古生界物源;变形及构造归属>(批准号:41172198)

摘　　要：报道了新近在华北北缘西段狼山地区发现的枕状玄武岩的初步定年工作。前人将其时代定为早古生代。对选自玄武岩的32颗锆石进行了LA-ICP-MS U-Pb定年结果表明,玄武岩的锆石大量为捕获基底的锆石,其年龄和锆石内部结构复杂多样。根据锆石内部特征将其划分为4类,其中的板状锆石被定为玄武岩的自生锆石,年龄为晚古生代末期—早三叠世早期。其余均为来自阿拉善地块基底的锆石,主要为古元古代—新太古代和古生代锆石。狼山晚古生代末期的玄武岩可能产自古亚洲洋封闭后由于岩石圈拆沉导致的伸展环境,该期伸展贯穿华北北缘直至阿拉善地块,暗示华北板块与阿拉善地块至少在晚古生代之前就已经拼合在一起了。Recent found pillow lava basalts in the southwestern Langshan and its preliminary dating has been reported here. Previous survey had assigned its age at the Early Paleozoic. 32 zircons from pillow lava basalts have been dated using LA-ICP-MS. Most zircons from basalts are captured from the basement, the distribution of ages and internal structures of which are complicated. Four groups of zircons have been distinguished by their internal structures. Among them the tabular zircons have been believed as the autogenetic zir- cons of pillow lava basalts, the ages of these zircons range from the end of Permian to the Early Triassic. The rest zircons in the samples are all from the Alashan basement, among which Paleoproterozoic and Newarchaeozoic zircons and Paleozoic zircons are most. The latest Late Permian Langshan basalts may developed in the extensional tectonics resulting from the delamination of the lithosphere after the closure of the Paleoasian Ocean, the extension of this period occurred along the whole north margin of the North China Plate including the Alashan block, which means that the Alashan block jointed with the North China Plate at least before the Late Paleozoic.

关 键 词：狼山 枕状熔岩 古亚洲洋 锆石LA-ICP—MS 

分 类 号：P588.145[天文地球—岩石学]