The garnet megacrysts of Gore Mountain (Adirondacks, US) are world-renown crystals due to their size, up to 1 m in historical record, which makes them the largest known garnets on the planet. We show here that they are also host to the first primary inclusions of trondhjemitic melt found in natural mafic rocks. The petrological and experimental investigation of the inclusions, coupled with phase equilibrium modelling, shows that this melt is the result of H₂O-fluxed partial melting at $T>900$ °C of a lower crustal gabbro. The compositional similarity between the trondhjemitic melt inclusions and tonalitic–trondhjemitic–granodioritic (TTGs) melts makes these inclusions a direct natural evidence that melting of mafic rocks generates TTG-like melts, and provides us with the possibility to clarify processes responsible for the formation of the early continental crust. These TTG embryos represent the trondhjemitic end-member of the melts whose emplacement at upper crustal levels, after being modified by mixing and crystallization-related processes, leads to the formation of the TTG terranes. Moreover, our study shows how the melt from H₂O-fluxed melting of mafic lower crust has mismatched major and trace element signatures, previously interpreted as evidence of melting at very different pressures. This poses serious limitations to the established use of some chemical features to identify the geodynamic settings (e.g. subduction versus thickened crust) responsible for TTGs generation and the growth of early crust.

戈尔山（美国阿迪朗达克）的石榴石巨晶因其大小而闻名于世，历史记录高达 1 m，是地球上已知最大的石榴石。我们在此表明​​，它们也是天然镁铁质岩石中发现的第一个长闪长岩熔体的主要包裹体的宿主。包裹体的岩石学和实验研究，加上相平衡模型，表明这种熔体是 H ₂ O-fluxed 部分熔化的结果$吨>900$ °C 的下地壳辉长岩。长闪长岩熔体包裹体与方长岩-长闪长岩-花岗闪长岩 (TTG) 熔体之间的成分相似性使这些包裹体成为基性岩熔化生成类 TTG 熔体的直接自然证据，并为我们提供了澄清导致形成的过程的可能性早期大陆地壳。这些 TTG 胚胎代表了熔体的 trondhjemite 末端成员，其在上地壳水平的侵位，经过混合和结晶相关过程的修改，导致 TTG 地体的形成。此外，我们的研究表明 H ₂的熔体如何镁铁质下地壳的 O-fluxed 熔化具有不匹配的主要和微量元素特征，以前被解释为在非常不同的压力下熔化的证据。这严重限制了已建立的使用某些化学特征来确定导致 TTG 生成和早期地壳生长的地球动力学环境（例如俯冲与增厚地壳）的限制。