The partial equilibration of garnet porphyroblasts in pelitic schists and its control on prograde metamorphism, Glen Roy, Scotland
The partial equilibration of garnet porphyroblasts in pelitic schists and its control on prograde metamorphism, Glen Roy, Scotland
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泥质片岩中石榴石成斑细胞的部分平衡及其对前变质作用的控制，格伦罗伊，苏格兰
DOI：
10.1111/jmg.12467
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发表时间：
2019
影响因子：
3.4
通讯作者：
P. Chung
中科院分区：
文献类型：
--
作者：
T. Dempster;M. I. Gilmour;P. Chung
含硅线石泥质片岩中的石榴石变斑晶具有复杂的结构和成分分带，在相邻样品内部和样品之间都有相当大的变化。含硅线石的片岩局部出现在区域性Barrovian石榴石带组合中，表明在俯冲变质作用期间持续缺乏平衡。这些来自苏格兰高地的Dalradian岩石中的石榴石保存了一系列变质反应的证据，包括初始生长和斑片状耦合溶解-再沉淀，然后部分溶解。单个的成斑晶对榴辉岩变质作用具有独特的和可变的响应，并且具有主要平坦成分剖面的石榴石与含有基本上未改变的特征钟形Mn剖面的石榴石共存。这突出表明，在应用传统的有效体积扩散解释消除成分变化时需要谨慎。在初始成斑晶的不完全改性过程中产生了具有丰富流体包裹体的混浊石榴石，并且这些多孔石榴石随后特别容易在硅线石生成反应中被部分置换。通过溶解-再沉淀过程对石榴石进行改性，将Ca释放到有效的全岩成分中，从而取代后续等梯度反应的压力-温度位置。这是首次报道的内部交代控制反应途径。石榴石的行为突出了动力学因素的重要性，特别是变形和流体，在控制反应进程，以及如何产生的可变性影响随后的沉积历史。缺乏一致的变质反应，内部和相邻的片岩之间，这表明，在当地和区域尺度上，这些岩石在很大程度上没有平衡在高峰变质条件。
Garnet porphyroblasts in sillimanite‐bearing pelitic schists contain complex textural and compositional zoning, with considerable variation both within and between adjacent samples. The sillimanite‐bearing schists locally occur in regional Barrovian garnet zone assemblages and are indicative of a persistent lack of equilibrium during prograde metamorphism. Garnet in these Dalradian rocks from the Scottish Highlands preserves evidence of a range of metamorphic responses including initial growth and patchy coupled dissolution–reprecipitation followed by partial dissolution. Individual porphyroblasts each have a unique and variable response to prograde metamorphism and garnet with mainly flat compositional profiles co‐exists with those containing largely unmodified characteristic bell‐shaped Mn profiles. This highlights the need for caution in applying traditional interpretations of effective volume diffusion eliminating compositional variation. Cloudy garnet with abundant fluid inclusions is produced during incomplete modification of the initial porphyroblasts and these porous garnet are then particularly prone to partial replacement in sillimanite‐producing reactions. The modification of garnet via a dissolution–reprecipitation process releases Ca into the effective whole‐rock composition, displacing the pressure–temperature positions of subsequent isograd reactions. This represents the first report of internal metasomatism controlling reaction pathways. The behaviour of garnet highlights the importance of kinetic factors, especially deformation and fluids, in controlling reaction progress and how the resulting variability influences subsequent prograde history. The lack of a consistent metamorphic response, within and between adjacent schists, suggests that on both local and regional scales these rocks have largely not equilibrated at peak metamorphic conditions.
石榴石生长过程中有效整体成分（EBC）的评估
影响因子：
3.9
作者：
Spear, Frank S.;Wolfe, Oliver M.
通讯作者：
Wolfe, Oliver M.
影响因子：
5
作者：
Jonas, Laura;Mueller, Thomas;Putlitz, Benita
通讯作者：
Putlitz, Benita