青藏高原腹地羌塘盆地白垩纪快速隆升的锆石裂变径迹测年证据  

CRETACEOUS RAPID UPLIFT OF THE QIANGTANG BASIN IN THE CENTRAL TIBET:EVIDENC FROM THE ZIRCON FISSION TRACK DATING

作　　者：宋春彦[1,2] 王剑[1,2] 谭富文[1,2] 付修根[1,2] 陈文彬[1,2] 何利[1,2] 

机构地区：[1]成都地质矿产研究所,四川成都610081 [2]国土资源部沉积盆地与油气资源重点实验室,四川成都610081

出　　处：《矿物岩石》2014年第2期77-84,共8页Mineralogy and Petrology

基　　金：国家自然科学基金(40972087);国家油气专项(选区[2009]01)

摘　　要：青藏高原的成因与形成过程一直是全球地质学家争议的焦点。为了约束青藏高原腹地晚中生代的构造隆升运动。本文在青藏高原中部的羌塘盆地内三个地区采集了14件锆石裂变径迹测年样品,并进行了系统测年分析。结果显示,羌塘盆地在早白垩世(148Ma^94Ma)发生了强烈的构造运动。由于新特提斯洋向拉萨地块之下不断消减挤压,羌资盆地与拉萨地块之间发生了重要的板块碰撞,从而使羌塘盆地在28Ma^48Ma的时间间隔内发生了快速的隆升运动,岩石迅速从~300℃冷却到~180℃以下,降温幅度达120℃。快速的构造隆升使得羌塘盆地的古海拔迅速增大,进而可能形成一个以南羌塘为核部,地貌向南、北逐渐降低的原始高原。原始高原的出现使得南羌塘地区成为剥蚀区,为拉萨地块内的萎缩海盆提供物源供给。羌塘盆地晚白垩世(89Ma^73Ma)的构造隆升很有限,但此次构造隆升可能在拉萨地块内比较显著,从而导致了拉萨地块内海相沉积的结束和大量陆相粗碎屑沉积的开始,并且可能使原始高原的范围不断扩大,甚至延伸到整个拉萨地块。In order to constrain the tectonic uplift of the central Tibet during the late Mesozoic period,14 zircon fission track samples were selected and measured from three different areas in the Qiangtang basin. The data reveal that an intensive tectonic uplift occurred during the Early Cretaceous （148 Ma-94 Ma）. This uplift is the result of the subcluction under the Lhasa block of the Neotethys and the collision between the Qiangtang basin and Lhasa block. The crust of the Qiangtang basin uplifted rapidly and cooled from -300 ℃ to -180 ℃ during 28 Ma-48 Ma with the cooling amplitude up to 12.0 ℃. The rapid uplift leads to a quick increase of the ancient eleva- tion of the Qiangtang basin, and formed the proto-Tibetan Plateau. The South Qiangtang maybe is the centre of the proto-Tibetan Plateau,and its elevation was higher than other adjacent areas in the Tibetan Plateau. So the South Qiangtang Became an eroded area,and provided the source for the Shrinking sea basin in the Lhasa block. The late Cretaceous uplift of the Qiangtang basin is fairly weak between 89 Ma and 73 Ma. However,the late Cretaceous uplift is relatively intense in the Lhasa block. This uplift leads to the missing of the marine sediments and the starting of the continental coarse clastic sedimentation. The area of the proto-Tibetan Plateau may be increased even extended to the all Lhasa block.

关 键 词：青藏高原 羌塘盆地 白垩纪 快速隆升 锆石裂变径迹 

分 类 号：P597.3[天文地球—地球化学]