The Yechangping Mo–W deposit in the East Qinling Orogen is a giant porphyry-skarn system, but the differences in genesis between its barren monzogranitic porphyry and mineralized granitic porphyry remain poorly defined. This study presents new zircon U–Pb ages, Hf isotopes, whole-rock geochemistry, Nd–Pb isotopes, and pyrite sulfur isotopes to elucidate the petrogenesis and key controls on Mo–W mineralization. Zircon U–Pb dating yields indistinguishable emplacement ages of 146.4 ± 2.3 Ma for the barren porphyry and 147.5 ± 2.0 Ma for the mineralized porphyry, indicating synchronous magmatism. Both intrusions are I-type granites, characterized by negative ε Hf (t) (−14.69 to −9.95) and ε Nd (t) (−15.22 to −12.33) values, Paleoproterozoic two-stage model ages (1.83–2.17 Ga), and Pb isotopic compositions similar to the Taihua Group basement, indicating a dominantly ancient crustal source from the Taihua Supergroup with a possible minor contribution from the North Qinling Accretionary Belt. The higher degree of fractional crystallization and moderately oxidized conditions (avg. logƒO 2 = −13.11) of the mineralized porphyry are the key factors controlling Mo–W mineralization. Pyrite grains from both porphyry-type and skarn-type ore bodies yield δ 34 S values ranging from 3.16‰ to 5.35‰, indicating a common magmatic sulfur source. Furthermore, the restriction of scheelite to skarn orebodies highlights the fundamental role of carbonate wall–rock interaction in localizing tungsten mineralization.
Zhao et al. (Tue,) studied this question.