磷灰石低温热年代学技术及在塔里木盆地演化研究中的应用

摘要

随着磷灰石低温热年代学技术理论研究的不断完善和发展,它已被广泛用于地质体定年、构造-热演化、地形地貌演化等研究领域.该文首先对磷灰石裂变径迹和(U-Th)/He热定年技术近几年的研究进展进行了综述,在此基础上阐述了低温热年代学方法在塔里木盆地构造-热历史和物源分析领域的应用效果.多组分动力学退火模型的建立、激光剥蚀ICP-MS方法的提出及裂变径迹自动测试仪的开发极大地推动了磷灰石裂变径迹技术的发展.对于磷灰石(U-Th)/He热定年技术,FT-等效圆校正模型极大地降低了He年龄校正过程中产生的误差;辐射损伤捕获扩散模型首次揭示了晶格缺陷对4He扩散的影响模式;辐射损伤积累和退火模型有效地解释了克拉通盆地部分磷灰石样品裂变径迹年龄小于He年龄的现象.塔里木盆地巴楚隆起的低温热年代学数据和热史模拟结果揭示出巴楚隆起自中生代以来曾经历过185～140 Ma、140～100 Ma、75～50 Ma等三期快速隆升事件,主要是由羌塘地体、拉萨地体、印度板块与欧亚板块南缘碰撞引起的.塔北隆起钻孔内浅部样品的磷灰石裂变径迹年龄和(U-Th)/He年龄都大于相应的地层年龄,记录的是物源区南天山的热信息;其热史模拟结果揭示出南天山曾经历过晚中新世早上新世(15～5 Ma)一期快速隆升事件,并以此构建了塔里木盆地北部与南天山晚中新世上新世构造-沉积耦合演化模式.%Apatite low temperature thermochronometry,as its theory and applications are continuously evolving,has been widely used to study the absolute age of volcanic deposits,tectono-thermal evolution of mountains arnd basins,landscape evolution,etc.In this paper,we first summarized the research advancement of the apatite fission track and (U-Th)/He dating techniques,and then introduced thermochronometry applications to the tectono-thermal history and provenance analysis of the Tarim Basin.In recent years,new theories and techniques for the apatite fission track,including the multi-kinetic annealing model,Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP MS) testing,and fully automated counting of fission tracks in natural minerals,have been developed.Using apatite (U-Th)/He dating,the new FT-equivalent sphere correction model greatly reduced errors in the corrected He ages;the trapping model for the first time revealed how radiation damage impeded 4He diffusion in apatite;and the radiation damage accumulation and annealing model effectively explained cases in the cratonic basins where ages of the apatite fission track were younger than that of the corresponding He The measured low-temperature thermochronometry data and thermal modeling results indicated that the Bachu Uplift in the Tarim Basin experienced three cooling events related to the collisions of the Qiangtang Terrane,Lhasa Block and India Plate with the southern margin of the Eurasia continent at 185-140 Ma,140-100 Ma and 75-50 Ma,respectively.The measured (U-Th)/He and fission track ages of the apatite from the boreholes' samples in the Tabei Uplift were older than the corresponding stratigraphic age,indicating that these ages had recorded the thermal information of the provenance-South Tianshan.The thermal modeling results revealed that the South Tianshan experienced the Late Miocene-Early Pliocene (15-5 Ma) rapid uplifting event.Finally,we rebuilt the tectonics-sedimentation coupling relationship between the northern Tarim Basin and South Tianshan.