鲁东中生代青山群火山岩锆石U-Pb年代学

Zircon U-Pb Geochronology of the Mesozoic Volcanic Rocks from Qingshan Group in the Eastern Shandong

青山群火山岩是山东境内最具代表性的中生代火山岩,研究其形成时代及其成因对了解华北克拉通东部的地质演化历史具有重要意义.对鲁东万第地区中生代青山群中基性火山岩和中酸性火山岩样品进行LA-ICP-MS锆石U-Pb定年,结果分别为117±2Ma和116±4Ma,表明万第地区中生代青山群火山岩的形成年龄为早白垩世中晚期.结合前人研究结果,可得鲁东青山群火山岩岩浆开始和结束的时间均略晚于鲁西;万第中基性和中酸性火山岩形成过程中均受到过华北克拉通古老地壳物质的影响,且万第中基性火山岩还受到了扬子陆壳深俯冲的影响.

The mesozoic volcanic rocks from the Qingshan Group are the most representative in the Shandong Province,and investigation of its genesis and forming time is very important to reveal the evolution history of the eastern North China Craton.LA-ICP-MS zircon U-Pb ages of meta-basic volcanic rocks and meta-acid volcanic rocks from the Qingshan Group in the eastern Shandong are reported in this paper.The dating results show that the ages of the meta-basic and meta-acidic volcanic rocks are117±2Ma(MSWD=3.2)and 116±4(MSWD=3.5)respectively,which represent the formation time of the volcanic rocks from the Qingshan Group.Based on the synthesis of geochronology,the start and the end age of the volcanic rocks from the Qingshan Group in the eastern Shandong are younger than those in the western Shandong.The meta-basic volcanic rocks might have undergone multiple events induced by continental crustal materials both from the North China Craton and the deep subduction of the Yangtze Craton.