Most primary magmas evolve compositionally as either tholeiitic or calc-alkaline lava series. The most voluminous magmas are generated through decompression melting of the upper mantle beneath diverging tectonic plates and differentiate as tholeiitic lavas. Calc-alkaline lavas, on the other hand, consist mainly of the bulk of differentiating arc magmas generated through H₂O-fluxed melting of the upper mantle beneath converging plates. The exact origin of the calc-alkaline lava series is one of the earliest but still unresolved controversies in petrology. Here I propose that the calc-alkaline lava series acquires its distinct compositional features mainly because of the Cl content of subducted seawater. The long-held view that the low FeO* differentiation trend of calc-alkaline lava series is primarily due to the early fractionation of its Fe-Ti oxides may be inaccurate. Instead, the calc-alkaline lava series is characteristically depleted in FeO* and oxidized because some of its Fe are sequestered early from its mantle source and parental arc magma by Cl-rich slab-derived fluids as Fe-chlorides, transit upward as part of a separate fluid phase in the upwelling magma and, then, precipitate eventually in the crust as Fe, ore metal-sulphides.

大多数初级岩浆在成分上演化为生高岩浆或钙碱性熔岩系列。数量最多的岩浆是通过对发散的构造板块下方的上地幔进行减压融化而产生的，并分化为可塑熔岩。另一方面，钙碱性熔岩主要由通过H ₂产生的大量微分弧状岩浆组成。O融化会聚板下的上地幔融化。钙碱性熔岩系列的确切起源是岩石学中最早但仍未解决的争议之一。在这里，我提议钙碱性熔岩系列获得其独特的组成特征，主要是因为俯冲海水中的Cl含量高。长期以来一直认为钙碱性熔岩系列的FeO *分化趋势低的主要原因是其Fe-Ti氧化物的早期分馏可能是不准确的。取而代之的是，钙碱性熔岩系列的特征是FeO *贫化并被氧化，因为其中的某些Fe被富含Cl的板状衍生流体（如Fe-氯化物）从地幔源和母弧岩浆中早期螯合，然后作为Fe的一部分向上迁移。上升岩浆中的一个单独的流体相，然后