松辽盆地北部火山岩锆石SHRIMP测年与营城组时代探讨

SHRIMP ZIRCON U-Pb GEOCHRONOLOGY OF VOLCANIC ROCKS AND DISCUSSION ON THE GEOLOGICAL TIME OF THE YINGCHENG FORMATION OF THE NORTHERN SONGLIAO BASIN

前人对松辽盆地营城组的时代存在不同认识。利用松辽盆地北部徐家围子断陷区营城组广泛发育的中—酸性火山岩取芯资料,开展了详细的火山岩锆石SHRIMP U-Pb年代学研究,结果表明营城组火山岩年龄集中在113—111Ma之间,属于早白垩世晚期的Aptian与Albian界线附近,从而明确该套火山岩应发育在营城组中上部的新认识,并由此说明营城组的顶界已跨入Albian。因此,认为松辽盆地营城组的时代为Hauterivian到Albian。

The age of the Yingcheng Formation in the Songliao Basin has been disputed. A suite of volcanic intermediate rocks to acidites, mainly acidic eruptive rocks, occurs widely in the Yingcheng Formation in the Xujiaweizi fault-depression in the northern Songliao Basin. SHRIMP zircon U-Pb geochronology gives ages between 111Ma and 113Ma for the volcanic rocks indicating that the volcanic succession formed around Aptian-Albian of the Early Cretaceous. Accordingly it is concluded that this suite of volcanic rocks was emplaced at the middle-upper part of the Yingcheng Formation. Based on available information, the age of the Yingcheng Formation in the northern Songliao Basin is most likely between Hauterivian and Albian.