Compositional zoning patterns of the major elements and REEs in prograde‐zoned garnets whose Mg/(Mg + Fe) atomic ratios increase rimward have been widely used to understand the metamorphic P–T–t trajectories, and the diffusion‐limited REE‐uptake model is a promising way to interpret their growth rates and the REE diffusion kinetics in the low‐temperature eclogite. In order to elucidate their growth kinetics with Skora et al.'s (2006) diffusion‐limited REE uptake model for prograde‐zoned garnets, we examine the trace‐element zoning patterns of two prograde‐zoned porphyroblastic garnets (~6 mm in size) in low‐temperature eclogites from two different localities. Core‐to‐rim trace‐element profiles in a garnet (prp_5–9alm_61–67sps_1–3grs_24–30) of a glaucophane‐bearing epidote eclogite of Syros (Cyclades, Greece) are characterized by the presence of Y + HREE peaks in the mantle, which might be attributed to a continuous breakdown of the titanite to form rutile during the garnet growth. In contrast, those in a garnet (prp_4–7alm_61–68sps_3–10grs_23–24) extracted from a lawsonite‐eclogite of the South Motagua Mélange (SMM) (Guatemala) have prominent central peaks of Y + HREEs. Although the REE profiles of both the garnets can be explained by the diffusion‐limited uptake, their Mn profiles suggest that their growth‐rate laws are different: i.e., diffusion‐controlled (Syros) and interface‐controlled (SMM). Prior to the model application, we optimize the number of the parameters as the garnet grows with the interface‐controlled processes based on the growth Péclet number. In particular, we propose the ratio of the REE diffusivity in the eclogitic matrix to the garnet growth rate as the new parameter. Visualizing the values of the new parameters allows to readily understand the relationship between the REE profiles and the REE‐diffusion/garnet‐growth kinetics in low‐T eclogite. Our model refinement leads to the simple quantitative characterization of core‐to‐rim REE profiles in garnet in low‐temperature eclogites.

中文翻译：

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低T榴辉岩中卟啉榴石石榴石中痕量元素的分区模式：扩散受限的REE吸收模型的参数优化

Mg /（Mg + Fe）原子比增加边沿的渐进带石榴石中主要元素和REE的组成区划模式已广泛用于理解变质的P – T–t轨迹和扩散受限的REE吸收模型是解释它们在低温榴辉岩中的生长速率和REE扩散动力学的一种有前途的方法。为了用Skora等人（2006）的扩散限制的REE吸收模型阐明渐进带石榴石的生长动力学，我们研究了两种渐进分区的卟啉核石榴石（〜6 mm大小）的痕量元素分区模式。 ）来自两个不同地方的低温榴辉岩中。石榴石中的核心到边缘痕量元素分布图（prp _5–9 alm _61–67 spsSyros（希腊基克拉泽斯）含葡聚糖的榴辉岩榴辉岩的_1-3 grs _24-30）的特征是地幔中存在Y + HREE峰，这可能归因于钛矿的连续分解形成金红石在石榴石生长期间。相比之下，石榴石（prp _4–7 alm _61–68 sps _3–10 grs _23–24）从南莫塔瓜梅朗日（SMM）（危地马拉）的钠钙榴辉榴岩中提取，有明显的Y + HREEs中心峰。尽管两种石榴石的REE分布都可以通过扩散限制的吸收来解释，但是它们的Mn分布表明它们的生长速率规律是不同的：即扩散控制（Syros）和界面控制（SMM）。在进行模型应用之前，随着石榴石随着界面控制过程的增长，石榴石会根据增长Péclet数来优化参数的数量。特别地，我们提出了渐近矩阵中的稀土元素扩散率与石榴石生长速率的比值作为新参数。可视化新参数的值可轻松了解REE分布与低T下REE扩散/石榴石生长动力学之间的关系榴辉岩。通过对模型的改进，可以对低温榴辉岩中石榴石的核心到边缘REE剖面进行简单的定量表征。