The relationship between apparent equilibrium temperature and closure temperature with application to oxygen isotope geospeedometry  

作　　者：NI Huaiwei 

机构地区：[1]CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China [2]Department of Earth and Environmental Sciences, The University of Michigan

出　　处：《Chinese Journal Of Geochemistry》2014年第2期125-130,共6页中国地球化学学报

基　　金：the financial support from the Recruitment Program of Global Experts(Thousand Talents),China;the Natural Science Foundation of China(41322015)

摘　　要：Oxygen isotope fractionation between coexisting minerals in slowly cooled rocks conveys information about their cooling history. By using the fast grain boundary(FGB) model to simulate closed-system diffusive exchange of oxygen isotopes between coexisting minerals, I show that the apparent equilibrium temperatures(Tae) by the mineral pair with the largest isotopic fractionation(PLIF) always lies between the closure temperatures(Tc) of those two minerals. Therefore, when the rate of oxygen diffusion and hence Tc for the PLIF chance to be comparable(such as in the case of quartz and magnetite), Tae will serve as a good approximation of Tc regardless of variation in mineral proportions. The specialty of the PLIF in constraining Tae within their Tc range can be generalized to other stable isotope systems and element partitioning. By approximating Tc with Tae and inverting Dodson's equation, the cooling rate of plutonic or metamorphic rocks can be inferred.Oxygen isotope fractionation between coexisting minerals in slowly cooled rocks conveys information about their cooling history. By using the fast grain boundary （FGB） model to simulate closed-system diffusive ex- change of oxygen isotopes between coexisting minerals, I show that the apparent equilibrium temperatures （Tae） by the mineral pair with the largest isotopic fractionation （PLIF） always lies between the closure temperatures （To） of those two minerals. Therefore, when the rate of oxygen diffusion and hence Tc for the PLIF chance to be comparable （such as in the case of quartz and magnetite）, Tae will serve as a good approximation of To regardless of variation in mineral proportions. The specialty of the PLIF in constraining Tac within their Tc range can be generalized to other stable isotope systems and element partitioning. By approximating Tc with Tac and inverting Dodson＇s equation, the cooling rate of plutonic or metamorphic rocks can be inferred.

关 键 词：氧同位素分馏 封闭温度 平衡温度 表观 共生矿物 冷却速率 应用 PLIF 

分 类 号：P597[天文地球—地球化学] P542.1[天文地球—地质学]