青海南山新生代隆升与黄河龙羊峡下切时间的低温热年代学研究

The Indian plate collided with the Eurasia took place in early Cenozoic, however, when the tectonic deformations propagating to the northeastern margin of the Tibetan Plateau remains controversial. To better understand this process, we choose the "Cenozoic tectonic deformation and evolution" as the breakthrough point, selecting the Qinghai Nan Shan as the studying area located in the northeastern Tibetan Plateau, using the apatite fission track (AFT) and apatite (U-Th)/He coupled with the AFT thermal history simulation to rebuild the spatiotemporal evolution of Qinghai Nan Shan during the Cenozoic era, and also make clear the uplift time of the ranges around the Longyang Gorges from the upper reaches of the Yellow River, constraining the time ceiling of the Yellow River incision. Based on the new results, combined with the previously results, especially low temperature thermochronology and the formation time of the upper reaches of Yellow River, we can provide new information about the far-field effect and outgrowth model for the northeastern Tibetan Plateau, and then better understand the interaction between the uplift, tectonic deformation, climatic changing and the big river system.

新生代以来，印度板块与欧亚大陆发生碰撞，构造应力何时传递到青藏高原东北缘一直处于争论之中。本申请以“新生代构造变形与演化”为切入点，选择青藏高原东北缘的青海南山为对象，运用基岩磷灰石裂变径迹 (FT) 和磷灰石 (U-Th)/He 低温热年代学方法结合磷灰石 FT 热历史模拟，重点研究青海南山东南端新生代构造活动的时空演化，厘定黄河上游龙羊峡河谷两侧山体的隆升时间，提供河流下切的时间上限。在此基础上，结合前人在青藏高原东北缘的研究结果，探讨青藏高原东北缘的隆升和黄河形成的时间，为理解高原东北缘的远程效应的传递和生长模式提供新材料，重塑青藏高原东北缘变形和隆升历史，探讨构造变形、气候变化与大河演化之间的相互作用。

新生代以来，印度板块与欧亚大陆发生碰撞，构造应力何时传递到青藏高原东北缘一直处于争论之中。本申请以“新生代构造变形与演化”为切入点，选择青藏高原东北缘的青海南山为对象，运用基岩磷灰石裂变径迹 (FT) 和磷灰石 (U-Th)/He 低温热年代学方法结合磷灰石FT 热历史模拟，重点研究青海南山东南端新生代构造活动的时空演化。在此基础上，结合前人在青藏高原东北缘的研究结果，探讨青藏高原东北缘的隆升和黄河形成的时间，为理解高原东北缘的远程效应的传递和生长模式提供新材料，重塑青藏高原东北缘变形和隆升历史，探讨构造变形、气候变化与大河演化之间的相互作用。磷灰石FT年龄显示峡谷底部早白垩世(114 ~ 122 Ma)至顶部早中侏罗世(165 ~180 Ma)年龄具有明显的随海拔升高而增加的趋势。平均(U-Th)/He年龄以早白垩世(97~128 Ma)为主，同时存在始新世(42 Ma)为一个异常值。结合裂变径迹长度、Dpar值和热模拟结果表明，早白垩世和新生代早期，由于拉萨板块和印度板块与亚洲大陆南缘的碰撞作用，导致青海南山东南端发生隆升。尽管如此，从那时起这一隆升高度被限制在不到几公里的范围内。结合区域地质研究，热年代学分析表明，自中生代以来，祁连山北缘和南缘同时发生了强烈的隆升活动。因此，我们认为青藏高原东北缘的地貌格局是在早白垩世-早新生代形成的。