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松辽盆地是我国东北地区一个大型的晚中生代含油气沉积盆地。在盆地发育早期阶段受强烈伸展作用影响形成了大规模的断陷和大量的火山活动。本文以松辽盆地北部徐家围子断陷区火山岩的年代学研究为切入点,通过对徐家围子断陷升深更2井和徐深9-2井营城组(K_1y)火山岩的岩芯样品进行SHRIMP U-Pb定年,获得了营城组火山岩年龄为114～112 Ma,并认为该年龄结果代表了松辽盆地区域晚中生代岩浆作用的上限时间。通过对松辽盆地及邻区的火山年代学的对比发现:中国东北地区晚中生代曾发生过多期的岩浆事件,时间分别为:166～150 Ma;140～130 Ma;130～120 Ma;114～109 Ma。松辽盆地内早白垩世营城组火山岩年龄与我国东北地区中生代最后一期岩浆作用时间一致,指示了东北地区中生代最后一期岩浆事件年龄。松辽盆地营城组火山岩年龄的厘定将为本区中生代岩石圈减薄的上限时间提供进一步可靠的年代学约束。
Songliao Basin is a large Late Mesozoic oil and gas accumulation basin in northeast China. During the early stages of basin development, extensive faulting and massive volcanic activities have been formed due to intense stretching. Based on the chronology of volcanic rocks in the Xujiaweizi fault depression area in northern Songliao Basin, the core of the K_1y volcanic rocks in the Shengcheng Formation (K 2y) and Wushen 2-well SHRIMP U-Pb dating of the samples, the volcanic ages of Yingcheng Formation are obtained from 114 to 112 Ma, and the age results represent the upper limit of the Late Mesozoic magmatism in the Songliao Basin. Comparisons of volcanic geochronology in the Songliao Basin and its adjacent areas show that magmatic events occurred in the late Mesozoic in northeastern China with time intervals of 166-150 Ma, 140-130 Ma, 130-120 Ma, 114 ~ 109 Ma. The volcanic ages of the Early Cretaceous Yingcheng Formation in the Songliao Basin coincide with the Mesozoic last-period magmatism in Northeast China, indicating the age of the last Mesozoic magmatic event in Northeast China. The determination of the volcanic age of the Yingcheng Formation in the Songliao Basin will provide further reliable chronological constraints for the upper limit of lithospheric thinning in the area.