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Abstract:From the view of hard-soft acid-base (HSAB) theory, the metallogenic specialization of hydrothermal ore deposits can be regarded as the consequence of the maximum hardness principle (MHP) and the minimum electrophilicity principle (mEP), which govern the reactions among the magma, the ore-forming ions and the anions from magmatic fluid phase. According to the HSAB theory, fluorine is a hard base with high electrophilicity and hardness, it can attract the hard acid such as tungsten (W) and tin (Sn); conversely, sulfur is a soft base with low electrophilicity and hardness, it can attract the soft acid such as copper (Cu) and gold (Au); meanwhile, chlorine exhibits intermediate properties, so it mainly attracts the borderline acid such as iron (Fe), rare earth elements (REE), and gold. As the hardness of the hydrothermal fluids bearing ions such as F, Cl, and/or S is always higher than that of the silicate melts, the magmatic fluid can segregate the ore-forming metals from the melts during the hydrothermal stage of magmatic evolution. The felsic magmas generated in the collisional environment is fluorine-rich, it can attract the hard acid (W and Sn) from the source, and leads to the W and/or Sn metallogensis. However, the arc magma has much higher sulfur content, and these melts will attract the soft acid (Cu, Au) from the source to form the porphyry deposit. The chlorine and/or CO2 are enriched in the alkaline magmas generated in the intraplate extensional environment, which can attract the borderline ions such as Fe, Au, and REE to form the iron-oxides-copper-gold (IOCG) deposit. |