Empirical studies of zircon in migmatites document features compatible with growth during heating at suprasolidus conditions. However, numerical modelling of zircon behaviour suggests that suprasolidus zircon is expected to grow only during cooling and melt crystallization. Here, phase equilibrium modelling coupled with mineral–melt Zr partitioning is used in an attempt to reconcile the observations from migmatites with the predictions of previous numerical models of zircon behaviour in anatectic systems. In general, an equilibrium-based model that includes Zr partitioning does not allow prograde suprasolidus zircon growth. However, melting of metapelites at temperatures just above the wet solidus may allow limited zircon growth because of the low solubility of zircon in melt coupled with a source of Zr from minor garnet and ilmenite breakdown. Preservation of this zircon requires entrapment in growing peritectic minerals during subsequent heating and further melting. Heating above muscovite exhaustion in metapelites is unlikely to grow zircon because of the progressive increase in zircon solubility as well as an increasing compatibility of Zr in the residual mineral assemblage. The modelled compatibility of Zr in the residue of a metabasite decreases during heating, but an increase in zircon solubility in melt counteracts this; prograde suprasolidus zircon growth in metabasites is unlikely. Infiltration of Zr-rich melt into a migmatite during open-system anatexis provides an additional potential mechanism for prograde suprasolidus zircon growth during high-temperature metamorphism.

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混合岩中锆石的顺生生长

混合岩中锆石的实证研究记录了在超固相线条件下加热过程中与生长相容的特征。然而，锆石行为的数值模型表明，预计超固体锆石仅在冷却和熔化结晶过程中生长。在这里，相平衡模型与矿物-熔体 Zr 分配相结合，试图将混合岩的观察结果与先前在深熔系统中锆石行为的数值模型的预测相协调。一般来说，包括 Zr 分配的基于平衡的模型不允许进行超固体锆石生长。然而，在刚好高于湿固相线的温度下熔化变泥质岩可能允许有限的锆石生长，因为锆石在熔体中的溶解度低，再加上来自少量石榴石和钛铁矿分解的 Zr 来源。这种锆石的保存需要在随后的加热和进一步熔化过程中包裹在生长的包晶矿物中。由于锆石溶解度的逐渐增加以及残余矿物组合中 Zr 的相容性增加，变泥质岩中的白云母耗尽以上的加热不太可能生长锆石。Zr 在变碱矿残渣中的模拟相容性在加热过程中会降低，但熔体中锆石溶解度的增加会抵消这一点；变基岩中超固相锆石的渐进生长是不可能的。在开放系统深熔过程中富锆熔体渗入混合岩​​为高温变质过程中超固相锆石的生长提供了额外的潜在机制。