Problems of modern 40Ar/39Ar geochronology: Reviews

As an important tool in geochronology, 40Ar/39Ar method plays a role in both precise dating and thermochronology. Compared with U-Pb method, 40Ar/39Ar geochronology is more widely applied in thermal history and geodynamic process of the crust. Because of the high potassium content in nature and only isotopic ratios to be analyzed during experiment, 40Ar/39Ar method has a high analytical precision, therefore, it can be used to date very young (e. g., thousands of years) samples. Moreover, based on the nature of chemical inertia and describable behavior, 40Ar/39Ar technique is widely used to quantitatively calculate thermal history of uplift, denudation and metamorphism of deep crustal material, which are important in understanding orogeny and crust-mantle reaction. Nevertheless, how well has 40Ar/39Ar technique developed at present? How exactly can it date natural geological sample? Why seldom was excess argon recognized within yang samples and those from high-pressure belt? Does pressure affect the closure temperature of argon isotope system? Can the age spectrum of K-feldspar reflect the thermohistory truly? What should we be ware when using 40Ar/39Ar and U-Pb method? These problems are discussed carefully in this paper in order to stimulate a broader discussion on 40Ar/39Ar geochronology.