大兴安岭北段龙江盆地中生代火山岩激光全熔^(40)Ar/^(39)Ar测年  

Laser ^(40)Ar/^(39)Ar chronology of the Mesozoic volcanic rocks from Longjiang basin in northern Da Hinggan Mountains

作　　者：李永飞[1] 卞雄飞[1] 郜晓勇[1] 陈树旺[1] 丁秋红[1] 

机构地区：[1]中国地质调查局沈阳地质调查中心,辽宁沈阳110034

出　　处：《地质通报》2013年第8期1212-1223,共12页Geological Bulletin of China

基　　金：中国地质调查局项目(编号:1212010813070;1212011085473;1212011121085)

摘　　要：现龙江组与光华组作为大兴安岭北段龙江盆地中的主要地层单元,二者的时代与含义仍存有争议。通过对二者的建组剖面进行野外调查,采用最新的激光全熔40Ar/39Ar测年对剖面及周边的7件火山岩样品进行了精细的定年研究,结果显示,现龙江组年龄为125.1Ma±1.5Ma～117.0Ma±9.0Ma;光华组为125.4Ma±1.8Ma～121.6Ma±1.4Ma;甘河组为123.1Ma±1.1Ma～82.0Ma±4.0Ma。本区晚白垩世火山岩信息揭示龙江盆地可能发育大兴安岭北段晚白垩世弧山镇期火山岩。野外地质调查结果表明,现龙江组和光华组具有基本相同的火山喷发旋回,结合2个岩组相同的年龄结果,建议合并现龙江组与光华组,恢复为原龙江组,而不再使用从原龙江组上部划分出的光华组。从火山-沉积地层出露特征分析,龙江盆地与其北部的大杨树盆地具有一定的相似性,2个盆地具有相同的地质演化历史,表明龙江盆地可能是潜在的油气调查新区。There has long been controversy concerning the stratigraphic division and the implications of Longjiang and Guanghua Formations,which constitute the main units in Longjiang basin,northern Da Hinggan Mountains.According to field observation of the established profiles of these two formations and neighboring areas,the volcanic rocks of the three Formations（Longjiang Formation,Guanghua Formation,Ganhe Formation） distributed extensively in Longjiang basin in northern Da Hinggan Mountains were studied on the basis of the laser 40Ar/39Ar dating method.The results show that the ages of these three formations are 125.1Ma ±1.5Ma ~ 117.0Ma±9.0Ma,125.4Ma ±1.8Ma^121.6Ma ±1.4Ma,and 123.1Ma ±1.1Ma^82.0Ma ±4.0Ma,respectively.The age of Early Late Cretaceous is most likely to have a good agreement with that of Gushanzheng Formation distributed rarely in northern Da Hinggan Mountains.In combination of the field observation with dating results,the present Longjiang and Guanghua Formations should be treated totally as the originally-named Longjiang Formation on the ground of having experienced simultaneously evolution process under the condition of the same volcanic cycle,and the name of Guanghua Formation previously separated from the upper layer of originally-named Longjiang Formation should be abandoned.An analysis of the characteristics of the volcanic-sedimentary strata shows that Longjiang basin has a good stratigraphic correlation with its northern neighboring Dayangshu basin in the same geological evolution process,indicating that there probably exists an oil-and-gas prospective area in Longjiang basin.

关 键 词：龙江盆地 大杨树盆地 激光全熔40Ar/39Ar年代学 龙江组 光华组 甘河组 

分 类 号：P588.14[天文地球—岩石学] P597.3[天文地球—地质学]