Zircon U–Pb Age and Geochemistry of Ore-Hosting Rocks from the Liuhe Orefield of the Jiapigou Gold Ore Belt, NE China: Magmatism and Tectonic Implications

Abstract

Liuhe gold orefield is being newly explored in the southeast part of the Jiapigou gold ore belt, and occurs in the Neoarchean basement composed of trondhjemite–tonalite–granodiorite (TTG). Zircon U–Pb data suggest that the ore-hosting magma emplacement in the Liuhe orefield mainly took place in two epochs: late Neoarchean to early Paleoproterozoic (ca. 2500 Ma) and early Jurassic of the Mesozoic era (ca. 170 Ma). The TTG rocks show higher A12O3 (12.58 to 15.71%) and Na2O/K2O ratios (1.16 to 2.9), and lower MgO (0.93 to 2.73%) and Mg# values, with positive Eu anomaly and low Y and Yb content, and high Sr/Y (22.3–79.6), and the plot in the adakite field in the Sr/Y-Y discriminant diagram belongs to the modern island-arc adakite rocks. Samples in this study are plotted in the pre-plate collision area in the R1-R2 discrimination diagram, and fall into the VAG and VAG + Syn-COLG field in the Rb-Y + Nb and Nb-Y diagram, respectively, indicating that the magmatism is related to plate subduction. The ore-bearing TTGs of the late Neoarchean to early Paleoproterozoic deposits were derived from the partial melting of mafic lower crustal caused by the underplating of basaltic magma on the island-arc or active continental margin before plate collision. The magmatism of the Dajiagou deposit occurred in active continental margin setting associated with the westward subduction of the paleo-Pacific plate beneath Eurasian Plate during the early Jurassic of Mesozoic period.