甘肃北山地区北部上石炭统火山岩LA—ICP—MS锆石U—Pb年龄及其构造意义

北山地区处于华北板块、塔里木板块和哈萨克斯坦板块的交会带，其晚古生代洋陆转化备受关注，但久有争议。该区晚古生代地层学研究不足，制约了对构造演化的深入讨论。通过LA—ICP—MS锆石U—Pb测年获得北山北部黑鹰山地区原定为下石炭统白山组火山岩的年龄分别为308．6Ma±1．0Ma和299．1Ma±2．4Ma，时代为晚石炭世。研究区内白山组时代的修订可以为该区构造演化提供一定的依据。

LA-ICP-MS zircon U-Pb dating of the Upper Carboniferous volcanic rocks from northern Beishan region in Gansu Province and its tectonic significance.

Much information remains to be discovered concerning the Late Paleozoic ocean-land transition in Beishan region. The Late Paleozoic strata can provide important evidence for this subject. However, the research on the age of the upper Carboniferous volcanic rocks from northern Beishan region is insufficient. This paper shows that the LA-ICP-MS zircon U-Pb ages of the ＂Early Carboniferous Baishan Formation＂ from Heiyinghsan area are 308.6Ma＋l.0Ma and 299.1Ma＋2.4Ma, which belong to the Late Carboniferous Ganquan Formation. The Ganquan l：ormation is widely distributed and unconformably overlies the Lower or Middle Devonian strata in northern Beishan region, which implies the closure of the Paleoasian Ocean before Late Carboniferous. The age revision of the Baishan Formation in some sense provides evidence to the tectonic evolution of the Beishan region.