松辽盆地南部中生代火山岩: 锆石U-Pb年代学及其对基底性质的制约

为了确定松辽盆地南部中生代火山岩的形成时代, 本文对位于盆地南部7个钻遇中生代火山岩的岩芯样品进行了锆石LA~ICP-MSU-Pb定年.松辽盆地南部中生代含火山岩地层主要包括火石岭组和营城组, 其中火石岭组火山岩由玄武安山岩-粗安岩-粗面英安岩组成, 营城组火山岩由玄武质粗面安山岩-粗面安山岩-流纹岩组成.锆石阴极发光(CL)图像和Th/U比值显示, 所测锆石均具有岩浆成因的特点, 锆石的LA-ICP-MSU-Pb定年结果表明, 松辽盆地南部中生代火山岩形成时代介于110b133Ma, 其中火石岭组火山岩形成于129-133Ma, 即早白垩世早期, 营城组火山岩形成于110~119/Via, 即早白垩世晚期.捕获锆石的定年结果显示, 本区基底中存在中晚侏罗世(155~169Ma)、印支期(218~236Ma)、海西期(254/Via、294Ma)、加里东期(413Ma)和前寒武纪(1823/Via和2542Ma)岩浆事件, 这与基底岩石中锆石U—Pb的定年结果相吻合. 

Mesozoic Volcanic Rocks in the Southern Songliao Basin:Zircon U-Pb Ages and Their Constraints on the Nature of Basin Basement

LA-ICP-MS zircon U-Pb dating results are reported for the Mesozoic volcanic rocks from seven wells in the southern Songliao basin in order to constraint their formation time. The Mesozoic volcanic rocks are mainly located in Huoshiling Formation and Yingcheng Formation. The former consists of basaltic andesite, trachyandesite and dacite, the latter is composed of basaltic trachyandesite, trachyandesite and rhyolite. The cathodoluminesence (CL) images and high Th/U ratios of the zircons suggest their magmatic origin. LA-ICP-MS zircon U-Pb dating results indicate that the Mesozoic volcanic rocks in the southern Songliao Basin formed between 110Ma and 133Ma. The volcanic rocks in the Huoshiling Formation were erupted during 129-133Ma, namely early period of the Early Cretaceous, while those in the Yingcheng Formation formed between 110Ma and 119Ma, namely late period of the Early Cretaceous. The dating results of captured zircons show that the Middle-Late Jurassic (155-169Ma), Indosinian (218-236Ma), Hercynian (254Ma, 294Ma), Caledonian (413Ma), and Precambrian (1823Ma and 2542Ma) magmatic events had taken place in the basin basement, which is consistent with the zircon U-Pb dating results from the basin basement rocks.