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September 10, 2025Open Access

Controls on Metal Zonation in Porphyry-Skarn Systems: Evidence from the Tonglvshan Cu Polymetallic Deposit, Eastern China

XWXiaolin WuChina University of Geosciences (Beijing)GXGuiqing XieChinese Academy of Geological Sciences JXJing XuNanyang Technological University

Key Points

Distinct metal zonation patterns indicate the influence of both redox and temperature on mineralization in the Tonglvshan deposit.
Trace element and S isotope analyses reveal a genetic control mechanism governing the distribution of metals from porphyry to distal vein types.
The study identifies two pyrite types enriched differently in metals, with significant implications for understanding ore-forming fluids.
Findings suggest that both temporal and spatial controls influence metal zoning, providing crucial insights for future mineral exploration.

Abstract

Abstract Tonglvshan is the largest porphyry-skarn Cu polymetallic deposit in the Edong ore district, Eastern China, which has proven metal reserves of 86.3 Mt @1.78% Cu, 39.4% Fe, 0.94g/t Au, and 0.13% Mo. The ore bodies exhibit distinct sub-lateral metal zonation, from proximal intrusion to distal carbonate, i.e., porphyry-type Cu-Mo, to skarn-type Cu-Fe-Au, carbonate replacement-type Cu-Zn-Pb-(Au), and distal vein-type Cu-Pb-Zn mineralization. However, the genetic factors governing both the temporal and spatial metal zoning remain uncertain. Here, we present trace element and S isotope data for sulfide stage (early stage pyrite and late-stage sphalerite) across various ore types in a well-constrained paragenetic framework. The early-stage contains two distinct types of pyrite, including colloform Py0 and euhedral Py1. Py0, observed in both skarn- and carbonate replacement-type ores, is selectively enriched in Cu, Ag, Au, Pb, and Bi relative to later Py1, reflecting a steep temperature gradient process. By contrast, Py1 exhibits increasing concentrations of Co, Ni, As, and Se with increasing distance from the intrusion, but shows depletion in the most distal vein-type ore. Redox exert the dominant control on this spatial pattern, whereas temperature plays a subordinate role. Values of δ34Spy generally increase from −0.4‰ within the intrusion to 1.5‰ in skarn-type ore, following a decrease to −0.6‰ in carbonate replacement-type ore and −2.15‰ for distal vein-type ore, which is dominantly controlled by temperature. Late-stage sphalerite (Sp2) exhibits systematic spatial trends, with high Fe, Co, and Mn contents in skarn-type ores evolving to elevated Cd, Hg, and Sn concentrations in carbonate replacement- and distal vein-type ores. These trends are controlled by redox and temperature variations, as recorded by Mn/Sn and Fe/Cd ratios. These findings offer valuable insights into the spatial evolution of ore-forming fluids and metallogenic zonation from proximal porphyry to distal vein-type mineralization, providing a potential guide for future mineral exploration.

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