中文摘要：

矿物中元素的浓度不仅受平衡分配的制约,还与元素的扩散特性有关。了解扩散行为的影响对认识幔源岩浆成分及其演化史有着重要的意义。采用球形扩散模型对地幔矿物石榴子石中稀土元素的浓度剖面及轻重稀土元素的分异情况进行了扩散动力学模拟计算,研究了温度、时间、颗粒半径等因素对石榴子石中稀土元素分布的制约。结果表明,温度越高、时间越长,元素扩散丢失的越多,甚至会对颗粒内部元素浓度有较大的影响。扩散造成轻重稀土元素浓度丢失程度的不同也会导致元素之间产生分异。在温度1300℃,压力2GPa,颗粒半径1mm,Mg含量为0.25～0.35,晶体核心到边缘位置最大分异时CLa/CYb约为86%,而中心处仅为96%。此次模拟揭示了元素在矿物中的扩散行为是石榴子石中微量元素分布的一个重要成因,并且影响着稀土元素的配分模式。

英文摘要：

The concentrations of elements in minerals not only depend on equilibrium partitioning but also relate to diffusion behaviors.It is important to understand influence of diffusion behavior on mantle derived magma composition and its evolution.In this paper,REE concentration profiles and fraction between LREE and HREE in the garnet were respectively calculated using spherical diffusion model,and then analyzed constrains of temperature,time,and grain radius on the distribution of REE in garnet.It shows that the elements in garnet has undergone significant diffusion processes,which have effects on its core elemental concentrations,at higher temperature and longer timescale.The maximum fractional value of CLa/CYb reaches approximately 86% from its core to rim,whereas its core is only 96% at the conditions of 1300℃,2 GPa,1 mm crystal radius and 0.25-0.35 of Mg content.Additionally,it was revealed that diffusion behaviors of elements in minerals are important controlling factors of zoning of trace elements and of constraining REE distribution patterns in garnet.