Timing and origin of multi-stage magmatism and related W–Mo–Pb–Zn–Fe–Cu mineralization in the Huangshaping deposit, South China: An integrated zircon study

Abstract

The Huangshaping deposit (South China) is closely related to hypabyssal granites (e.g., quartz porphyry, granophyre, and granite porphyry), developing massive skarn-type W–Mo–Fe polymetallic mineralization, skarn-type Pb–Zn–Cu mineralization, and vein-type PbZn (Cu) mineralization. To better constrain the geochronology, fluid composition, magma source, metallogenic affinity, and source of ore-forming materials in the Huangshaping deposit, morphological, textural, in situ geochronological, compositional, and LuHf isotopic studies on zircons hosted in granitoids, skarns (ores), and wall rocks have been carried out. Overall, five types of zircons are identified: low-U magmatic (abbreviated as LUMZ), high-U magmatic (HUMZ), hydrothermally-altered metamict (HAZ), inherited, and detrital types. Round-shaped inherited and detrital zircons with low trace element compositions are rarely captured in the granite porphyry and largely hosted in sulfide skarn ores and wall rocks. The HUMZ are mainly observed in the granophyre and are easily distinguished from LUMZ by their much higher U, Th, and Y contents, black CL images, and stronger Eu anomalies. In addition, the crystallization time of HUMZ was later than that of LUMZ. The HAZ uniquely exists in granite porphyry and genetic-related skarns with cracked and porous textures and strong enrichment of many trace elements. These zircons were originally HUMZ that have undergone rapid partial metamictization and subsequent fluid-zircon interaction. This study demonstrates that the granophyre is a two-stage intrusion with ages of 179 ± 0.3 Ma and 163 ± 0.7 Ma, whereas the granite porphyry yields younger ages of 157 ± 0.5 Ma. The discovery of Triassic inherited zircons in the latter leads us to propose the presence of a concealed Triassic pluton (~220 Ma). The zircon populations of W−Mo−Fe mineralized garnet skarns are mainly composed of ~160 and 180 Ma magmatic zircons, whereas magnetite skarn ores contain both magmatic zircons (~50%) and inherited zircons (~50%). In contrast, inherited zircons are the dominant zircon population of the skarn Pb−Zn ores. This may indicate that the granite porphyry (the foremost one) and granophyre mostly contributed to the skarn-type W−Mo−Fe mineralization, whereas the Carboniferous and Devonian carbonate strata significantly contributed to the skarn-type Pb−Zn (Cu) mineralization. Fluids separated from the granite porphyry that modified the zircons are likely the principal ore-forming fluids, which are enriched in F, U, Th, Y, REE, Nb, Ta, Hf, Ca, P, Ti, Pb W, Mo, and Fe. Zircon Hf isotopes suggest that these magmas, at least the granophyre and granite porphyry, were generated by reworking of Mesoproterozoic crustal rocks without significant input of mantle materials. This study highlights the use of different types and generations of zircons from variable rock types to reveal fluid compositions and mineralization potentials in complex metallogenic systems.