A comparative study on the apatite and zircon from the ore-related and -barren magmatic rocks of the Shatanjiao region, Lower Yangtze River Belt: Controlling effects for petrogenesis and Cu-Au mineralization

The links between the adakitic rocks and Cu-Au mineralization have long been argued. This study investigates petrogenesis and its link to mineralization potential by a series of in-situ geochronological and geochemical signatures of apatite and zircon in three ore-related intrusions and one-barren intrusion in the Middle-Lower Yangtze River Metallogenic Belt (MLYRB). Zircon U-Pb dating yield ages of 139–143 Ma and 121 Ma for the ore-related and ore-barren intrusions, respectively. The ore-related rocks have higher apatite Sr/Y (1.57–9.69), (La/Yb)N (16.7–159.5), and δEu (0.45–0.74) than the ore-barren rocks of 0.57–1.02, 19.3–24.1 and 0.40–0.45, respectively, indicating the former has an adakitic affinity, while the latter has a non-adakitic affinity. The ore-related rocks have enriched zircon Hf isotopes with εHf(t) values of −15.9 to −5.5 and TDMC ages of 2408–1655 Ma and apatite Sr-Nd isotopes, indicating that the ore-related magmas were mainly originated from partial melting of subducted oceanic crust. The ore-barren rocks have higher εHf(t) values of −6.6 to −4.6 and lower TDMC ages of 1598–1469 Ma and apatite Sr-Nd isotopes, indicating a lithospheric mantle source. The ore-related rocks have higher oxygen fugacity of mean ∆FMQ+2.00 and XF/XOH of 8.36–175 than the ore-barren rocks of mean ∆FMQ+1.43 and 3.72–4.96. It was inferred that magma source, water content, and oxygen fugacity emerge as critical factors governing the regional Cu-Au mineralization potential.