Collision-related porphyry Cu deposits (PCDs) are restricted to previous magmatic arcs, in which sulfide-rich lower crust occurred. Fertile adakite-like porphyries associated with PCDs have higher K₂O contents and K₂O/Na₂O ratios than barren porphyries emplaced in the same arc. The elevated K₂O/Na₂O ratios of fertile porphyries reflect substantial inputs of coeval hydrous, oxidized ultrapotassic melts. Input of such melts could increase the water content and oxygen fugacity of the lower-crust-derived melts, which in turn would promote the breakdown of sulphides in the lower crust and increase the contents of Cu and S in the melts, making them favourable for the formation of large PCDs. The relatively low K₂O contents and K₂O/Na₂O ratios of barren porphyries indicate limited input of ultrapotassic melts; these magmas have low potential to form PCDs. Thus, the input of ultrapotassic melts into the sulfide-rich juvenile lower crust drives the formation of collision-related PCDs.

中文翻译：

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超钾熔体注入富硫化物下地壳形成的碰撞相关斑岩铜矿床

与碰撞相关的斑岩铜矿床 (PCD) 仅限于以前的岩浆弧，其中发生了富含硫化物的下地壳。与 PCD 相关的肥沃埃达克岩样斑岩比同一弧内的贫瘠斑岩具有更高的 K ₂ O 含量和 K ₂ O/Na ₂ O 比值。肥沃斑岩的K ₂ O/Na ₂ O 比率升高反映了同时期含水、氧化的超钾熔体的大量输入。这类熔体的输入可以增加下地壳熔体的水含量和氧逸度，进而促进下地壳硫化物的分解，增加熔体中铜和硫的含量，使其有利于大型 PCD 的形成。相对较低的 K贫斑岩的₂ O 含量和 K ₂ O/Na ₂ O 比值表明超钾熔体的输入有限；这些岩浆形成 PCD 的可能性很低。因此，超钾熔体输入富含硫化物的幼年下地壳驱动了碰撞相关 PCD 的形成。