渤海湾盆地南堡凹陷火山岩锆石年代学及形成模式  

Zircon U-Pb age and formation model of volcanic rocks from Nanpu Sag of Bohai Bay Basin

作　　者：杜景霞[1] 石文武[1] 周贺[1] 王全利[1] 夏秋君[1] 刘君荣[1] 

机构地区：[1]中国石油冀东油田分公司勘探开发研究院,河北唐山063004

出　　处：《石油与天然气地质》2014年第5期742-748,共7页Oil & Gas Geology

基　　金：国家科技重大专项(2011ZX05006-006)

摘　　要：南堡凹陷古近系火山岩经历了两个裂陷旋回、4个喷发幕。对火山岩锆石形貌、SHRIMP和LA-ICPMS U-Pb年龄测定及LuHf同位素研究结果表明,岩浆旋回早期的锆石95%以上为变质重结晶形成,U-Pb年龄变化大,主要来自1 800 Ma前碰撞花岗岩地壳,它是中、新太古代（2 900~2 600 Ma）新生地壳与古洋壳碰撞引起的重熔和再循环过程而形成的。岩浆旋回中、晚期锆石为幔源原岩浆溢出结晶而成,含岩浆锆石和较丰富的俘虏晶,有利于进行锆石年代学和同位素研究。通过这些锆石年龄,建立了南堡凹陷和华北克拉通相对应的构造热事件的垂向序列,同时准确标定了幔源岩浆溢出和相关地层的绝对年龄。南堡凹陷的馆陶组属于新近系中新统,东营组属于古近系渐新统,而沙河街组跨越古近系的古新统和始新统。Nanpu Sag underwent two magmatic cycles and four episodic eruptions. Zircons of volcanic rocks from Nanpu Sag are dated by U-Pb SHRIMP,LA-ICPMS and Lu-Hf isotope method. The results indicate that more than 95% of zircons in the early magmatic cycle are formed by metamorphic recrystallization,with a big range of U-Pb age. It is explained that they are formed by collision granite crust in 1 800 Ma,which is caused by remelt and recycling process induced by collision between new crust of Middle and Neo-Archean（ 2 900 ~ 2 600 Ma） with palaeo-oceanic crust. In the middle to late magmatic cycle,zircons are formed by crystallization of mantle-derived magma overflow,and they contain magmatic zircon and rich captive crystal,which are helpful for chronology and isotope studies. Through those zircon ages,a vertical sequence of correspondent tectono-thermal events of the North China craton and Nanpu Sag is established. Moreover,the absolute ages of mantle-derived magma overflow and the related strata are calibrated accurately. The result shows that Guantao Formation belongs to Miocene,Dongying Formation belongs to the Oligocene and Shahejie Formation crosses Paleocene and Eocene.

关 键 词：新生代玄武岩 SHRIMP锆石年龄 火山岩 南堡凹陷 渤海湾盆地 

分 类 号：TE135[石油与天然气工程—油气勘探]