基于LA-ICP-MS设备的裂变径迹测年实验方法研究

As one of the most important thermochronology dating methods, fission track (FT) dating is widely used to obtain both cooling ages and thermal history in geological studies. The external detector FT method was always limited by the poor thermalization and long-time irradiation, and environment safety problem. Along with the development of the mass spectrum and laser technology, it becomes possible that the uranium content can be directly measured. Consequently, the FT dating by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) was developed. The LA-ICP-MS-FT method can avoid the error from poor thermalization and unevenly distributed thermal neutrons, and it also greatly improves the test efficiency. Moreover the other attractive advantage is the multi-element measurement, such as REE and chlorine in the samples. This further can promote the annealing mechanism studying and provide parameters for the thermal modeling. The present proposal will aim to establish the LA-ICP-MS-FT dating method by measuring the content of 238U, REE and chlorine simultaneously. We will construct an experiment flow by choosing the standard glasses and standard samples, and further we will testify the experiment processes by samples with the known-age and chlorine content. Establishment of the LA-ICP-MS-FT method will efficiently provide accurate age data and technical support to study the Cenozoic tectonic movement, fault evolution and oil and gas exploration.

裂变径迹（FT）是一种重要的低温热年代方法，由于其较低的封闭温度，被广泛应用于岩体冷却年龄测试及热史研究等领域。传统FT年龄测定的外探测器法一直受限于国内反应堆中子热化不充分、辐照周期长以及辐照带来的环境安全等问题。随着质谱技术和激光的发展，使得磷灰石等低铀矿物铀含量的直接测量成为可能。激光-电感耦合等离子质谱裂变径迹方法（LA-ICP-MS-FT）的建立及应用可避免因中子热化不充分、热中子分布不均带入的误差，提高测年效率及精度，亦可同时获取稀土元素及氯含量，能够为热史模拟提供参数。本项目拟建立基于激光熔蚀样品，电感耦合等离子质谱直接测量238U浓度、稀土元素及氯含量的裂变径迹测年技术。利用标玻及标样建立可靠的测试流程，通过已知年龄及氯含量样品验证测试流程的准确度。该项目将更加高效的为新生代构造运动、断裂活动历史及油气勘探等研究提供有力的年代学支持。

裂变径迹（FT）是一种重要的低温热年代方法，由于其较低的封闭温度，被广泛应用于岩体冷却年龄测试及热史研究等领域。传统FT年龄测定的外探测器法一直受限于国内反应堆中子热化不充分、辐照周期长以及辐照带来的环境安全等问题。随着质谱技术和激光的发展，使得磷灰石等低铀矿物铀含量的直接测量成为可能。激光-电感耦合等离子质谱裂变径迹方法（LA-ICP-MS-FT）的建立及应用可避免因中子热化不充分、热中子分布不均带入的误差，提高测年效率及精度，亦可同时获取稀土元素及氯含量，能够为热史模拟提供参数。本项目通过测试已知238U和稀土元素浓度标准玻璃SRM610和SRM612获得了元素信号和浓度的校准曲线；通过EPMA获取磷灰石标准样品的Cl含量，建立起了Cl元素信号和Cl含量的校准曲线。通过测试标准磷灰石样品的径迹密度和238U含量建立了基于LA-ICPMS设备的磷灰石样品年龄测试流程。最终建立了基于LA-ICPMS设备的磷灰石年龄、稀土元素含量和Cl元素含量的测试流程。该项目的成功完成，提高了测试效率，为新生代构造运动、断裂活动历史及油气勘探等研究提供有力的年代学支持。同时为研究裂变径迹退火的动力学机理提供了更丰富的信息，亦有助于利用裂变径迹法示踪沉积物源区，研究山体隆升及水系变迁。