松辽盆地青山口组橄榄组安岩:^(40)Ar/^(39)Ar年龄、地球化学及其成盆、成烃和成藏意义  

^(40)Ar/^(39)Ar age and geochemical features of mugearite from the Qingshankou Formation:Significances for basin formation, hydrocarbon generation and petroleum accumulation of the Songliao Basin in Cretaceous

作　　者：王璞珺[1] 高有峰[1] 任延广[2] 刘万洙[1] 张建光[1] 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]大庆油田有限责任公司勘探开发研究院,大庆163712

出　　处：《岩石学报》2009年第5期1178-1190,共13页Acta Petrologica Sinica

基　　金：国家重点基础研究发展计划项目(2006CB701403和2009CB219303)资助

摘　　要：在松辽盆地上白垩统青山口组二段湖相泥岩中识别出橄榄粗安岩夹层,高精度^(40)Ar/^(39)Ar坪年龄t_p=88.0±0.3Ma,属晚白垩世Coniacian阶。岩石具玻基少斑斑状结构,斑晶为橄榄石、辉石和斜长石。岩石富钠、富铝、富轻稀土(∑LREE/∑HREE=8.0～9.7)和U、Th、Pb、Rb、Sr、Ba等不相容的大离子亲石元素,Rb/Sr比高、Sm/Nd比低,δEu=0.95～1.36,高镁(Mg~#=0.61～0.64),高氧化度(Ox°=0.62～0.68),低分异指数(MDI=3.4～5.3)。MgO/Al_2O_3和标准矿物压力计算得到岩浆源区深度大于60km。岩浆源于富集型地幔,属板内火山岩,是成盆过程中裂谷作用发育到最大深切割期的产物。火山活动热效应及其高区域地温场有利于成烃,造成局部类礁相环境形成的大量生物灰岩沉积是重要烃源岩,火山岩之下的牵引构造、之上的差异压实局部高部位以及其周围的浊积体是成藏有利部位。Interlayers of mugearite are recognized within lacustrine mudstone of the Upper Cretaceous Qingshankou Formation ( K_2qn ) in the Songliao basin ( SB) of Northeast China. Precise ^(40) Ar /^(39) Ar plateau age of 88.0 ±0.3 Ma is obtained for the mugearite, interpreted as a Late Cretaceous, Coniacian stage. The volcanic rocks are characterized by glassy matrix and porphyritic texture. Phenocrysts are olivine, augite and plagioclase. The rocks are rich in Na, Al, LREE (∑LREE/∑HREE =8.0～9.7) and LILE (e. g. U, Th, Pb, Rb, Sr and Ba) , with high Rb/Sr ratios, low Sm/Nd ratios and the δEu value ranges from 0.95 to 1.36. The volcanics have also high Mg~# values (0.61～0.64) , high Ox^0 values (0.62～0.68) , and low MDI values (3.4 ～5.3). Standard mineral pressure plot coupled with MgO/Al_2O_3 ratios indicate a depth of >60km for the magma chamber. Hereby, the magma originates from enriched mantle, turns to be intraplate rift volcanism as a result of maximal transtension cutting through the crust. The volcanic activities have two effects on oil & gas, accelerating hydrocarbon generation owing to the rising regional heat flow, and resulting in biolithite sediments of important source rocks owing to the local reef-building environment. Three factors involved in the volcanism are favorable for petroleum accumulation, including drag structures beneath, topographic highs above and turbidites around the volcanic rocks.

关 键 词：松辽盆地 白垩系青山口组 橄榄粗安岩 年代学和地球化学 成烃成藏作用 

分 类 号：P588.144[天文地球—岩石学] P597.3[天文地球—地质学]