Decoupling of Sr-Nd Isotopic Composition Induced by Potassic Alteration in the Shapinggou Porphyry Mo Deposit of the Qinling–Dabie Orogenic Belt, China

In our previous study on petrogenesis of quartz syenite and granite porphyry, the host rocks Late Mesozoic Shapinggou Mo deposit in Qinling–Dabie orogenic belt, we found that initial Sr isotopic composition is strongly affected by degree K-alteration. Here, provide further evidence their minerals to investigate geochemical behaviour trace elements isotopes during alteration explain phenomenon decoupling Sr–Nd composition. The porphyry are altered K-alteration varying degrees have high K2O Rb contents low Na2O, CaO, Sr, Ba contents. Rock samples both variable Rb/Sr ratios 87Sr/86Sr values (even < 0.70) but contain quite homogeneous εNd(t) (−12.8 −14.8). Minerals from moderate intense very −17), while those weakly 87Sr/86Sr(t) 0.7044 0.7084. same can be observed several deposits within eastern belt. This fact suggests similar hydrothermal features a comparable origin for magmatic fluids this A comparison between Cu shows Rb–Sr isotope system different behaviours K-alteration, implying distinct material sources igneous deposits, respectively.