The development of thermodynamic models for tonalitic melt and the updated clinopyroxene and amphibole models now allow the use of phase equilibrium modelling to estimate P–T conditions and melt production for anatectic mafic and intermediate rock types at high‐temperature conditions. The Permian mid‐lower crustal section of the Ivrea Zone preserves a metamorphic field gradient from mid amphibolite facies to granulite facies, and thus records the onset of partial melting in metabasic rocks. Interlayered metabasic and metapelitic rocks allows the direct comparison of P–T estimates and partial melting between both rock types with the same metamorphic evolution. Pseudosections for metabasic compositions calculated in the Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–O (NCKFMASHTO) system are presented and compared with those of metapelitic rocks calculated with consistent endmember data and a–x models. The results presented in this study show that P–T conditions obtained by phase equilibria modelling of both metabasic and metapelitic rocks give consistent results within uncertainties, allowing integration of results obtained for both rock types. In combination, the calculations for both metabasic and metapelitic rocks allows an updated and more precisely constrained metamorphic field gradient for Val Strona di Omegna to be defined. The new field gradient has a slightly lower dP/dT which is in better agreement with the onset of crustal thinning of the Adriatic margin during the Permian inferred in recent studies.

中文翻译：

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变基性岩中角闪岩到麻粒岩相转变的相平衡模型（Ivrea Zone，NW Italy）

色调岩熔体热力学模型的开发以及更新的斜辉石和角闪石模型现在允许使用相平衡模型来估计高温条件下深熔基性岩和中间岩类型的 P-T 条件和熔体产量。伊夫雷亚带二叠纪中下地壳剖面保留了从中角闪岩相到麻粒岩相的变质场梯度，从而记录了变基岩部分熔融的开始。层间变质岩和变泥质岩允许直接比较具有相同变质演化的两种岩石类型之间的 P-T 估计和部分熔化。介绍了在 Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-O (NCKFMASHTO) 系统中计算的变基性成分的假剖面，并与使用一致的端元数据和 a-x 模型计算的变质岩的剖面进行比较。本研究中提出的结果表明，通过变基性和变泥质岩的相平衡建模获得的 P-T 条件在不确定性范围内给出了一致的结果，允许整合两种岩石类型获得的结果。结合对变基性和变泥质岩的计算，可以为 Val Strona di Omegna 定义更新和更精确约束的变质场梯度。