藏北羌塘盆地大规模古风化壳的发现及其意义  

Discovery of the large-scale paleo-weathering crust in the Qiangtang basin,northern Tibet, China and its significance

作　　者：付修根[1] 王剑[1] 吴滔 何江林[1] 

机构地区：[1]中国地质调查局成都地质矿产研究所,四川成都610082 [2]贵州省地质调查院,贵州贵阳550004

出　　处：《地质通报》2009年第6期696-700,共5页Geological Bulletin of China

基　　金：国家油气专项《青藏高原油气资源战略选区调查与评价》(编号:XQ2004-06);国家自然科学基金项目(批准号:40702020)资助

摘　　要：新的野外油气地质调查发现,在羌塘盆地中央隆起带及其两侧的南、北羌塘坳陷中,那底岗日组及其同沉积地层之下广泛发育了一古风化壳,古风化壳覆盖了石炭系、二叠系和前人已确定的三叠系肖茶卡组,具有区域性展布的特点。研究表明,不同地区古风化壳的形成时代不同:在南羌塘及中央隆起带上,风化剥蚀作用可能于晚二叠世就已开始,并经历了早、中三叠世的进一步演化;北羌塘地区的古风化壳形成时代可能为晚三叠世(或中三叠世),至晚三叠世肖茶卡组沉积期,形成了南北羌塘统一的古风化壳,并被那底岗日组及其同沉积地层超覆。这些新发现对于重新认识羌塘盆地的沉积演化、正确评价羌塘盆地的石油地质条件具有重要意义。Recendy, a new paleo-weathering crust occurred at the top of Carboniferous and Permian strata and Xiaochaka Formation, was discovered in the North Qiangtang depression, central uplift and the South Qiangtang depression during field investigation of petroleum geology, indicating a regional distribution. New geologic survey indicates that the era of weathering and erosion are various in different regions. During the Late Permian, most part of the South Qiangtang and central uplift regions was uplifted into a land and subjected to the weathering and erosion, and then a paleo-weathering crust was formed widely at the top of the Longge and Lugu Formation. By the Late Triassic, most part of the North Qiangtang region was also uplifted into a land and subjected to the weathering and erosion, and then a large weathering and erosion region, including the North Qiangtang depression, central uplift and the South Qiangtang depression, was formed. After a short erosion process （especially for the Xiaochaka Formation）, these paleo-weathering crusts were overlapped by the Nadi Kangri volcanic-volcaniclasfic rocks and corresponding sediments. The discovery of large-scale paleo-weathering crust is important for assessing petroleum geological conditions in the Qiangtang basin and the overall significance of basin evolution.

关 键 词：古风化壳 地质地球化学 羌塘盆地 

分 类 号：P542.2[天文地球—构造地质学] P512.2[天文地球—地质学]