Porphyry copper ore-forming magmas worldwide are chemically distinguished from ordinary arc granitoids by lower Zr and by higher Sr/Zr ratios at equivalent SiO₂ contents. Low ppm Zr in zircon-saturated melts and high whole-rock Sr/Zr in granitoid samples retaining igneous plagioclase are useful discriminants of Cu-fertile intrusive complexes. These and other chemical discriminants of porphyry-copper-forming melts of tonalite-granodiorite-adamellite composition cannot develop during crystallisation-differentiation at upper-crustal pressures. They indicate unusually high dissolved H₂O (≥ 9 wt%) in residual melts at depths near the base of the crust. We compare Zr behaviour during mafic-to-felsic magmatic differentiation in orogenically deforming, copper-mineralised arc segments with behaviour during differentiation in non-orogenic, unmineralised arc segments laterally adjacent along the same subduction zones. In orogenically deforming segments, horizontal compressive stress provides resistance to opening of tensile dyke fractures and promotes entrapment of mantle-derived basaltic melts in magma chambers embedded in hot country rock at Moho-vicinity depths, where magmas cool slowly and residual melts tend to last long enough to experience intermittent chamber replenishment by basaltic melts from the deeper mantle. Over several cycles of replenishment and fractional crystallisation, residual melts acquire high concentrations of inherited chemical components that were largely excluded from cumulus minerals—H₂O, Cl, CO₂, SO₃, etc. Accumulating H₂O re-orders the high-pressure crystallisation sequence of igneous minerals in successive cycles and leads to early and prolific production of hornblende and early zircon saturation in mafic melts (< 60 wt% SiO₂) of later cycles and leads to low Zr contents of zircon-saturated intermediate-composition residual melts.

世界范围内的斑岩铜矿形成岩浆在化学上与普通弧花岗岩的区别在于较低的 Zr 和较高的 Sr/Zr 比（在相同的 SiO ₂含量下）。锆石饱和熔体中的低 ppm Zr 和保留火成斜长石的花岗岩样品中的高全岩 Sr/Zr 是富铜侵入杂岩的有用判别因素。这些和其他形成斑岩铜的英闪长石-花岗闪长岩-二金刚砂组合物熔体的化学判别因素在上地壳压力下的结晶分异过程中不能形成。它们表明溶解的 H _2异常高O (≥ 9 wt%) 存在于地壳底部附近深处的残余熔体中。我们比较了造山变形、铜矿化弧段中镁铁质到长英质岩浆分异期间的 Zr 行为与沿相同俯冲带横向相邻的非造山、未矿化弧段分异期间的行为。在造山变形段，水平压应力提供了对张开岩脉裂缝的抵抗力，并促进了地幔来源的玄武岩熔体被困在莫霍面附近深处热乡村岩石中的岩浆房中，其中岩浆冷却缓慢，残余熔体往往持续很长时间足以经历来自更深地幔的玄武岩熔体的间歇性充填。经过几个补充和分级结晶循环，₂ O、Cl、CO ₂、SO _{3等。H 2} O的积累会在连续的循环中重新排序火成矿物的高压结晶顺序，并导致角闪石的早期和大量生产以及镁铁质熔体中的早期锆石饱和（< 60 wt% SiO ₂ )的后续循环导致锆石饱和的中间组合物残余熔体的低Zr含量。