The Jiaodong Peninsula is a globally significant gold province, hosting ~6,000 t of identified gold resources. The deposits are typical hydrothermal vein-type orebodies strictly controlled by fault structures. A step-wise mineralization model was previously proposed based on structural controls, but it has lacked systematic deep observational data and has not adequately explained the formation of thick, gently dipping orebodies. A research team led by Song Mingchun at Hebei GEO University integrated extensive deep drilling, high-precision geophysical surveys, and detailed 3D geological modeling from Jiaodong. They revealed how fault-dip inflections and gently dipping faults control the spatial distribution of gold orebodies, clarified the ore-controlling mechanism of gently dipping faults, and refined the step-wise mineralization model for hydrothermal vein-type gold deposits. This work provides important theoretical support for deep gold exploration.
Based on nearly 1,500 boreholes from the giant and supergiant Sanshandao, Jiaojia, and Shuiwangzhuang gold deposits, the team extracted 359 dip measurements from orebodies at various depths and systematically analyzed dip variations from shallow to deep levels. The data reveal an overall spatial pattern of "steep at shallow depths, gentle at depth, with alternating steep and gentle segments." The dip differences between deep and shallow orebodies are 17°, 10°, and 7° for the three deposits (Fig. 1). Gently dipping orebodies host significantly more gold than steeply dipping ones; at Sanshandao, the gold resource in deep gently dipping orebodies is >3.5 times that in shallower, steeper orebodies, indicating that gently dipping orebodies dominate the enormous Jiaodong gold endowment.
Exploration cross-sections show that the ore-controlling fault dips alternate between steep and gentle in a step-like pattern. Within a 2000 m vertical depth, there are typically 2–3 marked dip inflection points, forming two relatively gently dipping steps. High-precision geophysical surveys further reveal that the Jiaojia and Sanshandao fault zones extend continuously to 4000 m depth, with wide damage zones. The fault-plane dip is generally steep at shallow levels and gentle at depth, with a gently undulating surface and alternating steep-gentle segments. Additionally, a 3D resistivity model of the Zhaoping fault derived from wide-field electromagnetic (WFEM) profile inversion displays a listric (shovel-like) geometry, with the dip gradually decreasing downward and similarly alternating between steep and gentle (Fig. 2).
Based on detailed 3D geological models of typical gold deposits, the 3D spatial information of ore-controlling fault surfaces and gold orebodies was extracted and a coupling analysis performed. The results show that orebodies distribution closely matches fault geometry. Thick, high-grade orebodies are predominantly localized at the steep-to-gentle dip transitions and within the gently dipping segments of the faults, defining a step-like mineralization spatial pattern.
This study identifies three types of step-like mineralization (Fig. 3). (1) Single-fault step control: orebodies are enriched at multiple levels along the gentle segments and bend zones of a single fault, representing the dominant mineralization style in Jiaodong. (2) Master-subsidiary fault combination: steep master faults act as fluid conduits, while adjacent subsidiary gently dipping faults provide ore-hosting space. (3) Interlayer structure control: orebodies occur in gently dipping interlayer detachment zones bounded by multiple steeply dipping faults. Similar mineralization structures have been observed in gold deposits in Henan, Guangxi, Guizhou, Gansu, and elsewhere, confirming the wide applicability of this model.
This study further elucidates the intrinsic mechanism of step-like mineralization. Variations in fault dip angle alter the rock's resistance to shear fracturing, fault sealing properties, and the local stress field, leading to marked changes in ore-forming physicochemical conditions. These are the key controls on step mineralization. Mohr circle analysis shows that as the Mohr circle for an initial normal fault shifts to the right, the fault dip (θ) decreases and the shear fracture strength of the rock weakens, favoring the formation of wide fracture zones. Simultaneously, gently dipping fault segments experience higher normal stress, promoting stress concentration and fluid sealing. Dip-angle inflections also destabilize the fluid system, triggering unloading and precipitation of ore-forming materials. The dip angles (25°–35°) of thick, deep orebodies in typical Jiaodong deposits closely match the 30° plane of weakness where rock strength is lowest, indicating that fault dips around 30° are most conducive to forming large-scale ore-hosting space.
As shallow gold resources in China become increasingly depleted, deep exploration is essential for sustaining reserves and production. The step-like mineralization model effectively resolves the uncertainty in deep targeting once shallow orebodies pinch out. It can predict deep ore-hosting steps, optimize drilling layouts, and avoid barren zones. In Jiaodong, research and exploration teams moved beyond the traditional anomaly-delineation approach and established a deep stepwise exploration technology system centered on the "step-like mineralization model + refined geophysical model," targeting gently dipping fault segments as key exploration targets. This strategy has led to a major breakthrough in deep gold exploration in Jiaodong.
Song M, Yang Z, Li J, Li J, Wang R, He C, Yang Z, Zhang J, Xie T. 2026. A step metallogenic model and mechanism for hydrothermal vein-type gold deposits: A case study from the Jiaodong gold province. Science China Earth Sciences, 69(5): 1822–1838, https://doi.org/10.1007/s11430-025-1876-0
Science China Earth Sciences
Case study