上扬子盆地新生代差异抬升剥蚀与分异过程
Differential uplift and fragment of the upper Yangtze basin in Cenozoic

中－新生代上扬子陆相盆地不仅是华南大陆的核心构造单元，也是大陆构造和盆地成因演化研究的天然实验室.基于楚雄盆地和四川盆地晚白垩世地层剖面中6件样品LA-ICP-MS磷灰石FT-U/Pb双法定年和热演化史模拟等研究，揭示上扬子盆地新生代差异抬升剥蚀及其分异过程.楚雄盆地大姚宜就剖面江底河组磷灰石裂变径迹(apatite fission track，AFT)年龄和径迹长度分别为43.2～33.9 Ma、10.06～11.30 μm，中新世以来快速抬升冷却速率达约3～5 ℃/Ma；四川盆地宜宾柳嘉剖面三合组－高坎坝组AFT年龄和径迹长度分别为128～95.2 Ma、10.2～11.7 μm，为部分埋深退火样品.宜就剖面和柳嘉剖面上白垩统磷灰石U-Pb年龄峰值特征总体相似，共同揭示物源区古元古代(2 100～1 700 Ma)、新元古代(820～700 Ma)、早古生代(500～400 Ma)和早中生代(250～170 Ma)中高级别变质－岩浆构造热事件，其晚白垩世物源区主要为扬子板块西缘和北缘地区(即松潘－甘孜褶皱带、义敦岛弧、康滇古陆和秦岭造山带).尤其柳嘉剖面磷灰石FT-U/Pb对比年龄揭示三合组－高坎坝组中少量磷灰石矿物为物源区晚三叠世－晚白垩世快速岩浆侵位过程的初始旋回沉积产物.晚新生代上扬子盆地受控于青藏高原东南向扩展生长过程控制影响，最终发生肢解分异形成现今盆地格架.
The Meso-Cenozoic upper Yangtze continental basin is not only the core tectonic unit of the Southern China continent, but also a natural laboratory for the study of continental tectonics and basin genetic evolution. Based on LA-ICP-MS apatite FT-U/Pb double dating and thermal evolution history simulation of 6 samples in the Cretaceous stratigraphic section of Chuxiong basin and Sichuan basin, this paper reveals the differential uplift and denudation and differentiation process of the upper Yangtze basin. The AFT(apatite fission track) ages and track length of Jiangdihe Formation in the Yijiu section of Dayao county in Chuxiong basin are dominated with 43.2-33.9 Ma and 10.06-11.3 μm, respectively. The thermal models suggest a rapid cooling occurred in Miocene with rates of 3-5 ℃/Ma. Whilst the AFT ages and track length in the Liujia section of Yibin county in Sichuan basin are dominated with 128-95.2 Ma and 10.2-11.7 μm, as a result of partial reset. Furthermore, the apatite U-Pb ages are consistent between the Yijiu and Liujia sections, characterized with peak-ages of 2100-1700 Ma, 820-700 Ma , 500-400 Ma, and 250-170 Ma, which indicates the upper Yangtze basin had provenances from the Songpan-Ganzhi flysch, Yidun Arc, Kangdian Paleo-uplift and Qinling Orogen in late Cretaceous. In particular, the contrast of apatite FT-U/Pb reveals that a few of apatite minerals from Sanhe-Gaokanba Formation stemed from a first-cycle deposit of provenance with rapid cooling of granites during late Triassic to Cretaceous. In the end, the upper Yangtze basin has been dispersed and fragmented with a rapid cooling and uplift in Miocene, and then forms the current basin framework, as a result of southeastward growth of Tibetan Plateau