佳木斯地块东缘晚古生代大陆边缘构造演化

The Late Paleozoic continental margin tectonic evolution at the eastern margin of the Jiamusi Block

佳木斯地块位于中国东北微陆块群的最东缘,其东缘地区晚古生代的岩浆和沉积演变进程为欧亚大陆东缘由被动陆缘向活动陆缘构造环境的转化提供了关键证据。年代学和地球化学研究表明,佳木斯地块东缘中泥盆世黑台组砂岩,形成于被动陆缘的构造环境,黑台组上覆的老秃顶子组流纹岩也形成于被动陆缘的构造环境;晚石炭世珍子山组砂岩,形成于活动陆缘的构造环境;早二叠世的二龙山组安山岩以及相邻地区早二叠世的其它火成岩形成于活动陆缘的构造环境。同时,佳木斯地块东缘泥盆-二叠纪的沉积地层也呈现出由浅海相到陆相地层转化的特征。因此,佳木斯地块东缘由被动陆缘向活动陆缘的转化应该发生在中泥盆世到晚石炭世,而该构造环境的转化也为晚古生代时期蒙古-鄂霍茨克洋向欧亚大陆之下俯冲过程的研究提供了关键信息。

The Jiamusi Block,one of the micro-continental blocks in NE China,is located at the eastern margin of the Eurasia.The Late Paleozoic magmatic and sedimentary evolution of the eastern margin of the Jiamusi Block provide the key evidence for understanding the transition from a passive to an active continental margin at the eastern margin of the Eurasia.New geochronological and geochemical studies indicate that the sandstones in the Middle Devonian Heitai Formation formed in a passive continental margin setting.And the rhyolite in the Laotudingzi Formation overlying the Heitai Formation formed in the same tectonic setting to that of the Heitai Formation.The sandstones from the Late Carboniferous Zhenzishan Formation formed in an active continental margin setting.The andesite from the Early Permian Erlongshan Formation and the other kinds of Early Permian igneous rocks from the adjacent areas formed in an active continental margin setting.The Late Paleozoic sedimentary strata also show the characteristic of the transition from shallow marine facies to continental facies.Thus,the transition from a passive to an active continental margin in the Jiamusi Block occurred during Middle Devonian to Late Carboniferous,which provides key information for the process of the Mongol-Okhotsk oceanic subduction-accretion beneath the Eurasia during the Late Paleozoic.