^40Ar／^39Ar测年中的冷却年龄和变形年龄

^40Ar／^39Ar法年龄数据的解释与Ar同位素在矿物中的封闭温度有关。冷却年龄只能限制变质——变形事件发生的时间区间,不能真正代表地质事件的发生时间。因此,必须想办法得到变形年龄。本文从封闭温度概念出发,探讨了压力、冷却速率、有效扩散范围和几何形态、颗粒大小、动力学参数等对矿物封闭温度的影响,介绍了新近提出的“封闭窗”概念,并讨论了在什么情况下可以获得变形年龄。

Cooling and deformation ages in 40Ar/39Ar dating

Interpretation of 40Ar/39Ar ages depends on the closure temperatures of Ar in minerals. Cooling ages are only restricted within the time range of occurrence of an event of metamorphism-deformation and cannot represent the real time of occurrence of a geological event. Therefore we must get the deformation ages. Proceeding from the concept of closure temperatures, this paper discusses the influences of such parameters as pressure, cooling rate, effective diffusion dimensions and geometry, grain sizes and dynamics on the closure temperatures of minerals, and introduces the new concept of "closure window". Based on these influences, the paper also discusses how to get deformation ages.