东天山阿奇山-雅满苏地区构造热演化历史研究

Tianshan is an important Paleozoic collision orogenic belt, strong compression and uplift-denudation occurred since Cenozoic due to the far field effect of collision between India and Eurasia plate. Tianshan orogenic belt has experienced a complex evolutionary process, in which Eastern Tianshan is an important tectonic part. The tectonic-thermal evolution history research on Eastern Tianshan will help researchers to understand the uplift-exhumaiton process of Tianshan orogenic belt, which was driven by the collision between India and Eurasia plate. However, the thermochronology research in Eastern Tianshan has adopted fission track dating as a main method, and this has limited the thermal evolution temperature scope. Due to these limits, the uplift-exhumation process during Cenozoic in Eastern Tianshan is controversial. This project intends to select Aqishan-yamansu island-arc belt as the research area, where the intermediate-acid intrusive rock are widely exposed, and adopt zircon and apatite (U-Th)/He dating and apatite fission track dating to reveal the tectonic-thermal evolution. By this project, we expect to constrain the thermal evolution history of the southern margin of Eastern Tianshan in shallower surface, and to establish the uplift-denudation-time framework in this area. We also expect to provide new scientific basis for further understanding the impact process to the whole Tianshan orogenic belt induced by the collision. In addition, this project will indirectly reflect uplift and denudation history of the iron ore deposit in the research area, so that we can provide some beneficial reference for searching for the concealed ore deposits in this region.

天山是重要的古生代俯冲碰撞带，新生代以来由于受印度和欧亚板块碰撞产生的远程效应，又发生了强烈挤压和隆升剥蚀的构造变动。东天山是天山造山带重要的构造部位，对其构造热演化历史的研究直接关系着人们准确认识印亚碰撞对天山造山带隆升剥蚀的影响过程。目前对东天山地区的热年代学研究由于技术手段单一，限定的热演化温度范围过窄等原因，导致其新生代时期的隆升剥蚀过程存在较多争议。本项目拟选取东天山广泛出露中酸性侵入岩的阿奇山-雅满苏岛弧带为研究区，运用锆石和磷灰石(U-Th)/He测年及磷灰石裂变径迹测年等低温热年代学技术进行构造热演化历史研究。通过本项目的研究，将限定东天山阿奇山-雅满苏地质体更接近地表时的热演化历史，建立该地区隆升剥蚀作用时间格架，为进一步全面认识印亚碰撞对天山造山带隆升剥蚀的影响过程提供新的科学依据；另外还将间接反映该地区产出铁矿床的隆升剥蚀历史，为该地区进一步寻找隐伏矿床提供有益参考。

东天山是天山造山带重要的构造部位，对其构造热演化历史的研究直接关系着人们准确认识天山造山带隆升剥露过程。目前人们对东天山地区隆升剥露过程的认识存在较多争议。本项目对东天山阿奇山-雅满苏岛弧带及其邻区为研究区，运用锆石和磷灰石(U-Th)/He测年等低温热年代学技术进行热演化历史研究，并构建该地区的隆升剥露作用时间格架。取得了如下成果：（1）阿齐山-雅满苏地区经历了中-晚三叠世和晚白垩世两期快速隆升剥露作用；（2）阿齐山-雅满苏地区两侧的断裂带经历了中-晚三叠世和晚侏罗世-早白垩世两期快速隆升剥露作用；（3）吐哈盆地地区渐新世期间曾发生过快速抬升作用。盆地内部上白垩统地层最大埋藏总体小于2公里；下白垩统地层最大沉积埋藏深度约为2公里，侏罗系地层最大埋藏深度均超过2公里；盆地边缘侏罗系地层埋藏深度小于2公里；（4）识别出研究区部分样品的磷灰石(U-Th)/He年龄异常老的原因是由于晶体内部存在难溶的子矿物。