Within subvolcanic plumbing systems, along volcanic conduits and post-eruptive emplacement, mineral textures and compositions are governed by complex kinetic (undercooling) and dynamic (convective) processes that deviate from theoretical models and equilibrium criteria. In this perspective, we have investigated the partitioning of major and trace cations between clinopyroxene and phonotephritic melt under convective stirring conditions at high degrees of undercooling (−ΔT_nominal = 30–60 °C) and atmospheric pressure. We have integrated this novel data set with conventional static (no physical perturbation) clinopyroxene-melt compositions obtained under interface- and diffusion-controlled growth regimes. Results show that clinopyroxene growth kinetics and diffusion boundary layers caused by melt supersaturation are partly mitigated by the homogenizing effects of stirring. Because of continuous supply of fresh melt to the advancing crystal surface, the partitioning of major and trace cations is governed by local equilibrium effects, which are interpreted as the extension of equilibrium thermodynamic principles to non-equilibrium bulk systems. Major cations are incorporated into the clinopyroxene structure via the coupled substitution [^M1Mg, ^TSi] ↔ [^M1Ti, ^TAl] and in conformity with the thermodynamic mixing properties of CaMgSiO₂, CaAl₂SiO₆, and CaTiAl₂O₆ components. The complementary relationship between lattice strain (ΔG_strain) and electrostatic (ΔG_{electrostatic}) energies of heterovalent substitutions is the most appropriate thermodynamic description for the accommodation of trace cations in the clinopyroxene lattice site (i.e., ΔG_partitioning = ΔG_strain + ΔG_{electrostatic}). The excess energy of partitioning ΔG_partitioning changes principally with Al in tetrahedral coordination and determines the type and number of charge-balanced and -imbalanced configurations taking place in the structural sites of clinopyroxene. An important outcome from dynamic stirring experiments is that superimposition of convective mass transfer on melt supersaturation phenomena causes the formation of Cr-rich concentric zones under closed system crystallization conditions. However, these Cr-rich zones do not correlate with enrichment in other compatible elements and depletion in incompatible elements, as would be expected in natural open systems characterized by input of more primitive magmas. While the convective transport acts to reduce the diffusive length scale of chemical species in the experimental melt, fresh Cr cations are more easily incorporated into the concentric zones due to crystal field effects. Together, our findings reveal that during magma ascent and emplacement, convective stirring may promote clinopyroxene crystallization and minimize kinetic effects on clinopyroxene zoning.

在火山下的管道系统中，沿着火山管道和喷发后的侵位，矿物结构和成分受复杂的动力学（过冷）和动力学（对流）过程的控制，这些过程偏离了理论模型和平衡标准。从这个角度来看，我们研究了在高过冷度（-ΔT_标称 = 30–60 °C) 和大气压。我们已经将这个新的数据集与在界面和扩散控制的生长机制下获得的传统静态（无物理扰动）单斜辉石熔体组合物相结合。结果表明，搅拌的均质效应部分减轻了由熔体过饱和引起的单斜辉石生长动力学和扩散边界层。由于不断向前进的晶体表面供应新鲜熔体，主要和痕量阳离子的分配受局部平衡效应的控制，这被解释为平衡热力学原理对非平衡体系统的扩展。主要阳离子通过耦合取代 [ ^M1 Mg, ^T Si] ↔ [^M1 Ti, ^T Al] 并符合CaMgSiO ₂、CaAl ₂ SiO ₆和CaTiAl ₂ O ₆组分的热力学混合特性。晶格应变（ΔG_应变）和异价取代的静电（ΔG_静电）能量之间的互补关系是在单斜辉石晶格位中容纳痕量阳离子的最合适的热力学描述（即，ΔG_分配 =  ΔG_应变 +  ΔG_静电）。分割的多余能量ΔG_分配主要随着四面体配位中的铝而变化，并决定了单斜辉石结构位点中发生的电荷平衡和不平衡构型的类型和数量。动态搅拌实验的一个重要结果是对流传质与熔体过饱和现象的叠加导致在封闭系统结晶条件下形成富铬同心区。然而，这些富含 Cr 的区域与其他相容元素的富集和不相容元素的枯竭并不相关，正如在以更原始岩浆输入为特征的自然开放系统中所预期的那样。虽然对流传输的作用是减少实验熔体中化学物质的扩散长度尺度，由于晶体场效应，新鲜的 Cr 阳离子更容易结合到同心区域中。总之，我们的研究结果表明，在岩浆上升和侵位期间，对流搅拌可能会促进单斜辉石结晶并使对单斜辉石分带的动力学影响最小化。