拉萨地块北缘中晚侏罗世周缘前陆盆地的厘定  

Definition of Mid-Late Jurassic Peripheral Foreland Basin in the Northern Margin of Lhasa Block

作　　者：李奋其[1] 张士贞 李俊[1] 刘函[1] 秦雅东[1] Li Fenqi;Zhang Shizhen;Li Jun;Liu Han;Qin Yadong(Chengdu Center of China Geological Survey,Chengdu 610081,China)

机构地区：[1]中国地质调查局成都地质调查中心,四川成都610081

出　　处：《地球科学》2022年第2期387-404,共18页Earth Science

基　　金：国家自然科学基金项目(Nos.41972113,42002032)。

摘　　要：研究拉萨地块北缘中晚侏罗世盆地类型、演化对重塑班公湖-怒江结合带及邻区构造-古地理和含油气盆地评价具有重要的意义.通过对那曲县城北部的中上侏罗统拉贡塘组进行了沉积特征分析和碎屑锆石U-Pb测年.结果表明,该组一段为陡坡型三角洲沉积,下部的碎屑流显示出向南东流动的特点;二段主要为潮坪-混积陆棚沉积;一段下部的石英杂砂岩、二段下部的石英细砂岩的碎屑锆石年龄范围分别为2611~216 Ma和2800~152 Ma.综合研究表明,该区中晚侏罗世盆地为受班公湖―怒江结合带控制的周缘前陆盆地,具有双物源的特征;152 Ma±,该区经历了由复理石盆地向磨拉石盆地的转换;同时,结合带内部逆冲推覆活动较强,形成以莎木罗组为标志的新的前陆盆地.To identify its types and evolution features of the Mid-Late Jurassic basin located in northern margin of Lhasa block is of great significance for reconstructing its tectonic-paleogeography and assessing the petroliferous basins in Bangonghu-Nujiang junction zone and its adjacent area.In this paper,the sedimetary features and provenance area of Mid-Late Jurassic Lagongtang Fm which is exposed in north of Nagqu county,was studied.The results shows that the Member 1 of Lagongtang Fm belongs to steep-slope delta deposition,and debris flow deposits located in its lower part has the characterisitics of southward flow,and Member 2 of the Fm was deposted in tidal flats and mixed shelf,and the detrital zircon ages of greywackes in the lower part of Member 1 and quartz fine sandstone in the lower part of Member 2 range from 2611 Ma to 216 Ma and from 2800 Ma to 152 Ma respectively.Comprehensive research results shows that the basin located in northern marigin of Lhasa block is a peripheral foreland one controlled by Bangonghu-Nujiang junction zone,and had dual source supply,and experienced the conversion from flysch basin to molasses one at 152 Ma or so.Meanwhile,the overthrust which took place in Bangonghu-Nujiang junction zone become stronger than before since that time,and caused a new foreland basin marked by the Shamuluo Formation form in it.

关 键 词：拉贡塘组 班公湖―怒江结合带 周缘前陆盆地 物源区 中晚侏罗世 莎木罗组 构造地质 

分 类 号：P548[天文地球—构造地质学]