Structural Ore-Control Model of the Daliangzi Pb–Zn Deposit, Southwest China

Abstract

The oblique distribution of orebodies is a fundamental characteristic of the spatial arrangement of orebody groups in non-magmatic hydrothermal deposits and is closely related to shearing. The Daliangzi Pb–Zn deposit in the Sichuan–Yunnan–Guizhou Pb–Zn polymetallic metallogenic area is a typical representative of epigenetic hydrothermal deposits controlled by a strike-slip–fault-fold structure. However, the underlying ore-controlling mechanism of this strike-slip–fault-fold structure remains unclear; as a result, achieving breakthroughs in mineral exploration in the deposit’s deep and peripheral zones is directly hindered. This paper focuses on the Daliangzi Pb–Zn deposit. Based on the Theory and Methods of Ore-field Geomechanics, the hierarchical structural ore-controlling pattern of the deposit is clarified, identifying the NE-trending tectonic zone from the Middle-Late Indosinian to Early Yanshanian as the Pb–Zn metallogenic tectonic system. It proposes the spatial oblique distribution patterns of the deposits, ore sections, orebodies, and ore blocks, along with the mechanical mechanisms of multi-scale structural ore control. A compound negative flower structure–fault-fold–diapiric ore-controlling model was constructed for the Daliangzi Pb–Zn deposit. Finally, the locations of concealed orebodies at different scales within the Daliangzi Pb–Zn deposit and its surrounding areas were predicted; moreover, the locations of concealed orebodies at various depths within the deposit area were also predicted.

1. Introduction

The relationship between strike-slip faults and mineralization is highly significant [1,2]. When slip occurs, the surrounding rocks undergo volumetric deformation, thereby altering the orientation of the local maximum compressive stress and changing the kinematic characteristics and mechanical properties of lower-sequence structures within this volume [3,4,5]. Ore-hosting spaces are typically closely associated with specific structures at different positions of anticlines derived from strike-slip faults [6], and their dilatant zones serve as favorable sites for the precipitation and enrichment of metallic minerals [1,7]. During the mineralization process, these structures often regulate the local stress field to control hydrothermal pathways, thereby inducing the formation of dilatant spaces in secondary folds and the precipitation of ore-forming fluids [8]. The tectonic pumping effect generated by their activity acts as a key driving force for fluid migration and mineralization, while the complex lithological variations and abrupt physicochemical changes within the fault zone create ideal barriers for ore precipitation [9,10,11,12,13]. Furthermore, the oblique distribution of orebodies exhibits a genetic relationship with shearing [2].

During the Indosinian period, regional tectonic stress was transmitted into the interior of the Yangtze Block, driven by its collision with the Indochina Block. This led to the formation of an intracontinental strike-slip tectonic system within the Sichuan–Yunnan–Guizhou Pb–Zn polymetallic metallogenic area (SYGA), characterized by widespread spatial distribution and zoned, diverse structural types [2]. The large-scale tectonic deformation of the Neoproterozoic–Paleozoic passive continental margin rift basin drove the large-scale migration of ore-forming fluids. These fluids accumulated within the strike-slip–fault-fold structures of the intracontinental strike-slip system, resulting in the extraordinary enrichment and massive accumulation of germanium-rich Pb–Zn deposits. The spatial distribution of these Pb–Zn deposits correlates closely with the presence of strike-slip–fault-fold structures. The Daliangzi Pb–Zn Deposit is a representative example of an epigenetic hydrothermal deposit within the SYGA that is clearly controlled by such strike-slip–fault-fold structures [14].

Therefore, this study takes the Daliangzi Pb–Zn Deposit as its research object and applies the Theory and Methods of Ore-field Geomechanics [15] to conduct a detailed analysis of the ore-field structures. It aims to clarify the hierarchical structural ore-controlling patterns and the ore-controlling tectonic system of the deposit, and ascertain the spatial oblique distribution patterns of the deposit, ore blocks, orebody groups, and individual orebodies, along with the mechanical mechanisms of multi-scale structural ore control. Subsequently, an ore-controlling structural model for the deposit is constructed, ultimately leading to the proposal of prospecting targets. This research is not only crucial for resolving the issue of resource potential in the deep and peripheral areas of this specific deposit but also holds significant guiding importance for prospecting prediction and the arrangement of exploration engineering in the deep and peripheral regions of hydrothermal deposits in general.

2. Geological Setting

The SYGA is situated on the southwestern margin of the Yangtze Block (Figure 1a–c) [16,17,18,19]. The Daliangzi Pb–Zn deposit is located within the SYGA, and lies on the Ningnan–Qiaojia tectonic–metallogenic belt (Figure 1d) [14]. The deposit is dominated by NWW- to NW-trending faults, followed by NE-trending ones, with minor SN- and EW-trending faults; folds are well developed (Figure 2) [14]. The exposed strata in the area, from oldest to youngest, include the Sinian (Z), Cambrian (Є), Permian (P), Triassic (T), Jurassic (J), and Quaternary (Q). The ore-hosting horizon is the Sinian Dengying Formation (Zbd), which can be subdivided into eight members. Permian Emeishan basalts are distributed in the periphery of the mining area (Figure 2) [14]. The deposit consists of the No. 1 and No. 2 orebodies, with the No. 1 orebody being the principal one, divided into five ore blocks (veins) designated I to V (Figure 2) [14]. The main ore types include massive, brecciated, disseminated, vein-type, and spotted varieties. The mineral assemblage is characterized by sphalerite, galena, and pyrite as the primary ore minerals, accompanied by subordinate quantities of chalcopyrite, cerussite, anglesite, pyromorphite, smithsonite, hemimorphite, hydrozincite, and willemite. The gangue fraction is dominated by calcite, quartz and dolomite, with collophane, sericite, chalcedony, kaolinite, barite, and graphite present in lesser amounts. The main types of wall-rock alteration are calcitization, dolomitization, silicification, and carbonatization. The hydrothermal mineralization period of the Daliangzi Pb–Zn deposit can be divided into five stages (Figure 2 and Figure 3) [20].

3. Materials and Methods

Conducting a detailed analysis of the ore-field structures of the deposit, combined with regional tectonic evolution, reveals the structural hierarchical ore-controlling pattern of the SYGA. Applying the Theory and Methods of Ore-field Geomechanics [15], the geometric, kinematic, mechanical, and material characteristics of structures at different scales within the deposit are analyzed. Integrating these with the spatial distribution characteristics of known orebodies or mineralized bodies allows for the identification of mineralized structures. Based on the principle of structural sequence transformation and using stress units, the mechanical properties of the ore-forming structures and their secondary structural planes are analyzed. This reveals the control exerted by the principal compressive stress on the formation of ore-bearing spaces and summarizes the controlling factors governing the spatial distribution of ore blocks, orebodies, ore sections, deposits, and ore fields. Subsequently, predictions are made for the distribution of ore sections at the deposit scale, the distribution of orebodies at the ore sections scale, and the distribution of ore blocks at the orebodies scale. All images were processed using CorelDRAW (https://www.coreldraw.com/en/?srsltid=AfmBOoosiEDPas24iM77y85DW_fOc_ybkQ39EI-EAouJH6-28Yi7zLnE, accessed on 10 October 2025).

4. Results

4.1. Structural Hierarchal Ore-Controlling Pattern

First-order (SYGA): In the northeastern Yunnan ore concentration area, a NE-trending sinistral oblique thrust strike-slip–fault-fold belt was formed. In the northwestern Guizhou ore concentration area, a NW-trending oblique normal strike-slip–fault-fold belt developed. In the southwestern Sichuan ore concentration area, a nearly N–S trending sinistral strike-slip fault zone and its derived NWW–EW-trending strike-slip–fault-fold zones were generated.

Second-order (the Southwestern Sichuan ore concentration area): The southwestern Sichuan ore concentration area is controlled by multiple nearly N–S trending sinistral strike-slip fault zones.

Third-order (ore field): The nearly N–S trending sinistral shear Puduhe fault, the nearly N–S trending sinistral torsional Xiaojiang deep fault, and the stratigraphic assemblage along the disconformity surface (Si-Ca surface) between the Cambrian Qiongzhusi Formation (Є₁q) and the Sinian Dengying Formation (Zbd) constitute the first-sequence structures of the ore field. These structures control the distribution of the Daliangzi-Huangjiaqing ore field.

Fourth-order (deposit and ore section): The NW–NNW trending sinistral extensional-torsional Daqiaohe fault, the NWW-trending dextral torsional-extensional faults (F₅₅, F₁, F₁₅, F₇₃), the NE-trending sinistral compressional-torsional fault zone that roughly parallels the strata attitude, and the stratigraphic assemblage of the Si-Ca surface composed of the Cambrian Qiongzhusi Formation (Є₁q) and the Sinian Dengying Formation (Zbd) constitute the second-sequence structures of the ore field (which are first-sequence structures at the deposit scale). These structures control the formation and distribution of the Daliangzi deposit, which comprises four ore sections.

Fifth-order (orebody): The NW-trending dextral extensional-torsional faults (F₃, F₅, F₈, F₆, F₁₀₀, etc.), the “black alteration/brecciation zone” diapiric bodies, the NE-axial, SW-plunging anticlines, and the NE-trending sinistral compressional-torsional faults constitute the third-sequence structures of the ore field (which correspond to second-sequence structures at the deposit scale). These structures directly control the morphology and attitude of the approximately E–W trending orebodies, which are composed of a group of ore blocks controlled by a set of NW-trending faults.

Sixth-order (ore block/vein): NW-trending, NE-trending, and SN-trending ore-bearing faults and their associated secondary anticlines, interlayer fault zones in both walls, as well as lower-sequence ore-bearing fault zones, joints, and fractures constitute the fourth-sequence structures of the ore field (corresponding to third-sequence structures at the deposit scale). These structures directly control the morphology and attitude of individual ore blocks.

4.2. Fine Analysis of Ore-Controlling Structures

(1) 

Fourth-order (deposit and ore section)

F₁₅ is one of the largest structures in the mining area (Figure 4), traversing the entire area. It has a general trend of NW35°–72°∠54°–85° SW and exhibits a wavy extension both in plan and profile. The main trend of the structure is NW60–70°, with a dip angle of 70–80°, steeply dipping to the southwest. Locally, it trends nearly E–W and steeply dips to the north. The fault surface appears gently undulating to relatively straight and tight, while the lower fracture surface is wavy. It primarily forms a composite fault structure through overlapping, superimposition, oblique connection, and direct linkage. Characterized as both a fluid-conduit and ore-hosting structure, the Pb–Zn orebodies and the ore-bearing complex breccia zones are both hosted within the F₁₅ fault zone and its hanging wall. The fault mainly exhibits two phases of tectonic activity: an early stage (mineralization period) forming a dextral torsional-extensional fault under NW–SE oriented principal compressive stress, and a late stage forming a sinistral torsional to torsional-compressional fault under NE-SW oriented principal compressive stress.

F₁ shares similar characteristics with F₁₅ and is also classified as a first-order structure within the deposit (Figure 5). Together, they control the distribution of the main ore section of the deposit. The general trend of F₁ is NW60°–70°∠70°–85° SW. The fault zone consists of gray to gray-white fractured dolomite, and the wall rocks on both sides are also gray to gray-white dolomite, exhibiting a series of secondary fractures and joints. The fault surface appears gently undulating to wavy, and is locally relatively straight and tight. This fault also exhibits the characteristics of both a fluid-conduit and ore-hosting structure. Calcitization is observed within the fault zone. The footwall shows pyritization (later oxidized to limonite), Pb–Zn mineralization, silicification, and dolomitization, while the hanging wall exhibits baritization. The fault records evidence of three phases of tectonic activity: an early stage characterized by dextral extensional-torsional to torsional-extensional movement, a second stage marked by sinistral torsional to torsional-compressional movement, and a late stage showing extensional-torsional structural features.

(2) 

Fifth-order (orebody)

The F₆ fault is an important NW-trending dextral extensional-torsional structure within the main mining area (Figure 6). It is divided into F₆(S) and F₆(N) segments, with F₆(N) connecting to F₆(S) south of exploration line 7. The main body of F₆(S) dips steeply to the NE, while the main body of F₆(N) dips to the SW, with local sections dipping to the NE. The F₆ fault primarily exhibits characteristics of two phases of tectonic activity: an early stage of dextral extensional to extensional-torsional movement, and a late stage of sinistral compressional to compressional-torsional movement. The complex breccia zone is distributed mainly along the footwall of F₆(N). Outwards from this breccia zone, it transitions into a hydrothermally brecciated Pb–Zn mineralization and alteration zone. This zoning results sequentially in breccia-type Pb–Zn orebodies, followed by stockwork and brecciated Pb–Zn orebodies, and then veinlet, disseminated, and spotted pyrite–Pb–Zn mineralized bodies. This pattern reflects the genetic relationship between this ore-controlling structure and the breccia zones as well as the mineralization and alteration halos.

The F₅ fault has an overall NW trend, dipping steeply to the NE with local reversals dipping to the SW. The fault surface exhibits gently undulating, slightly undulating, to wavy morphologies. Near the fault surface within the zone, yellowish-brown mortar breccia is present, containing black siliceous dolomite breccia fragments cemented by yellowish-brown ultracataclasite. The wall rocks on both sides consist of gray-white siliceous dolomite, showing well-developed slickensides, phyllonitization, and lensoid structures. The fault primarily records two phases of tectonic activity: an early stage (mineralization period) characterized by dextral extensional-torsional movement, and a late stage (post-mineralization) characterized by sinistral compressional-torsional movement. The main mineralization and alteration include limonitization and Pb–Zn mineralization, with disseminated Pb–Zn ore primarily distributed within the fault zone.

The F₈ fault is another important NW-trending dextral extensional-torsional structure within the main mining area. Its upper fracture surface is wavy, reflecting an early extensional phase followed by a later compressional-torsional phase. The lower fracture surface is relatively straight. The fault surface is gently undulating, with a zone width of 50 cm. The zone contains gray-black to yellowish-brown mortar breccia and shows evidence of phyllonitization and lensoid structures. The wall rocks on both sides consist of gray-black, thin- to medium-bedded, fine-crystalline dolomite, containing bedding-parallel calcite veins. The fault records three phases of tectonic activity, corresponding to the NE-trending tectonic zone → SN-trending tectonic zone → EW-trending tectonic zone.

The F₁₀₀ fault is developed between the F₅ and F₆(S) faults. It has an overall NW trend and dips steeply to the NE. The fault surface appears gently undulating to wavy, and is locally relatively straight. The early-stage fault surface is gently undulating to wavy, while the late-stage fault surface is relatively straight. The fault zone consists of gray-white to white siliceous cataclastic dolomite, exhibiting development of galena, pyrite, limonitization, and malachitization. The eastern wall (hanging wall) is composed of gray-white siliceous dolomite, while the footwall consists of gray-black dolomite. Joints and lensoid structures are well developed. The footwall of the fault often contains mineralized complex breccia, vein-type galena, disseminated galena, pyrite, limonitization, and malachitization. The fault clearly exhibits two phases of activity: an early stage characterized by dextral extensional-torsional movement (mineralization period), and a late stage characterized by sinistral compressional-torsional movement.

The F₃ fault is developed south of the F₁₅ fault. Based on the structural analysis of various levels, it has been determined that the area between F₃ and F₈ (specifically the footwall/south side of F₃) controls the distribution of the No. II-2 and No. II-1 ore blocks. The fault has an overall NW trend and dips steeply to the NE. It exhibits dextral extensional-torsional characteristics during the early stage (mineralization period) and sinistral compressional-torsional characteristics during the late stage. The F₃ fault control the emplacement of the black alteration/brecciation zone and the orebodies within its footwall (south side). Within the footwall of the F₃ fault, from proximal to distal positions relative to the fault, a sequential zonation is observed: the black alteration zone, followed by simple breccia, and then complex breccia. From south to north, a zonation of Pb–Zn mineralization types is observed: disseminated, stockwork, brecciated, and veinlet. The footwall of the F₃ fault hosts numerous subsidiary faults, which control the distribution of the various types of mineralization.

(3) 

Sixth-order (ore block/vein)

NW-trending fault: The upper fracture surface is gently undulating, while the lower fracture surface is wavy; both surfaces are smooth. The fracture zone is 1.0–1.5 m wide and contains complex breccia with Pb–Zn mineralization. The structure is characterized by extensional-torsional properties in its early stage and by sinistral compressional-torsional properties in its late stage. Within the zone, the area near the hanging wall exhibits strong silicification and Pb–Zn mineralization in gray-white dolomite (which is cataclastic). The area near the footwall contains more complex breccia (including black breccia fragments) dominated by gray-white dolomite. The hanging wall consists of silicified gray-white dolomite breccia, which incorporates black dolomite breccia fragments. The footwall is composed of complex breccia with a width ranging from 10 to 80 cm (Figure 7).

SN-trending fault: The fault surface is relatively straight, and the fault zone is 30–40 cm wide. The zone consists of vari-colored ultracataclasite mixed with breccia and exhibits limonitization. The breccia fragments are chaotic and vary greatly in size. The footwall consists of complex breccia with clast diameters ranging from as large as 40 cm down to 5 mm. The clasts include both gray-white and black dolomite, showing poor sorting and subangular to subrounded shapes. The breccia is intersected by black joints and fractures, and is cemented by black dolomite rock fragments, and has been affected by limonitization. The hanging wall also consists of complex breccia, predominantly composed of gray-white dolomite clasts with minor black dolomite clasts. The clast range from 3 mm to 10 cm is diameter, are subangular, and are cemented by yellowish-brown dolomite rock fragments, limonite, and argillaceous material. Based on slickenside observations, it is determined to be a sinistral torsional fault (Figure 7).

NE-trending fault: The fault surface is gently undulating, and the fault zone is approximately 2–10 cm wide. Slickenside indicators determine the fault to be dextral compressional-torsional. The hanging wall exhibits joints and fractures with developed limonitization. Additionally, simple breccia is observed, characterized by poorly sorted, subangular clasts cemented by sphalerite and gray-black dolomite rock fragments (Figure 7).

4.3. Characteristics of the Black Alteration/Brecciation Zone

The black alteration/brecciation zone is a geological body closely associated with mineralization and serves as the main ore-hosting structure. It is divided into the “black zone” and the “brecciated zone,” which exhibit distinct differences in ore potential. The black zone is generally barren or weakly mineralized, whereas the brecciated zone typically shows higher ore mineral content. While a standalone black zone is usually non-mineralized, it acts as a barrier, channeling ore-forming fluids to precipitate within the brecciated zone. Hydrothermal breccias within the brecciated zone play a critical controlling role in Pb–Zn mineralization (Figure 8).

The brecciated zone is further subdivided into complex breccia and simple breccia.

Complex breccia contains subrounded to angular clasts (with >5 types of clast components). The main clast types include: Zbd gray-black dolomite, Zbd bluish-gray siliceous dolomite, Zbd gray dolomite, Zbd gray-white dolomite, Zbd banded dolomite, and Pth intermediate-acidic volcaniclastic rocks. The clasts exhibit characteristics of being contemporaneous, allogeneic, and autochthonous (Figure 8).

Simple breccia contains subangular to angular clasts (consisting of only one clast type) and exhibits a jigsaw-fit texture. The primary clast type is Zbd gray-white dolomite. The clasts exhibit characteristics of being contemporaneous, cognate, and autochthonous (Figure 8).

The black zone consists mainly of Cambrian (Є) black carbonated dolomite (Figure 8).

5. Discussion

5.1. Ore-Controlling Mechanism of Fault-Fold Structure

Integrating regional tectonic evolution characteristics [2,14] with the genetic development process of the structures in the Daliangzi Pb–Zn deposit, the ore-controlling tectonic system and its dynamic evolution process have been clarified (Figure 9). Since the Indosinian period, the deposit has primarily undergone four major tectonic evolutionary stages: the NE-trending tectonic zone from the Middle-Late Indosinian to Early Yanshanian, followed by the NW-trending tectonic zone during the Middle Yanshanian, then the SN-trending tectonic zone during the Late Yanshanian, and finally the EW-trending tectonic zone during the Himalayan period. The metallogenic tectonic system is identified as the NE-trending tectonic zone active from the Middle-Late Indosinian to the Early Yanshanian.

During the mineralization period (Middle-Late Indosinian to Early Yanshanian), influenced by the continued subduction of the Indochina Block towards the Yangtze Block, accompanied by the closure of the Paleo-Tethys Ocean, numerous micro-blocks collided to form part of the western Indosinian orogenic system. This also induced changes in the lithofacies-paleogeographic pattern along the southwestern margin of the Yangtze Block. This orogenic event further triggered the formation of fault-fold structural belts, leading to the development of an intracontinental strike-slip tectonic system within the SYGA, characterized by widespread spatial distribution and zoned, diverse structural types. Simultaneously, a series of Pb–Zn mineralizations related to tectonic-magmatic thermal events formed along the southwestern margin of the Yangtze Plate. This is consistent with the findings of some scholars based on geochronological analysis. For example, by applying Sm-Nd dating to calcite coexisting with sphalerite, an isochron age of 204.4 ± 4.2 Ma was obtained [21].

Under a NW–SE oriented regional tectonic stress field, the sinistral strike-slip movement along the two roughly parallel, nearly N–S trending deep-seated faults—the Xiaojiang Fault and the Puduhe fault—in the southwestern Sichuan ore concentration area generated a series of NW–NNW trending sinistral torsional-extensional faults, such as the Daqiaohe fault, within the ore field. At the deposit scale, NWW-trending dextral torsional-extensional faults (F₅₅, F₁, F₁₅, F₇₃) were formed. The NWW-trending dextral transtensional F₁₅ fault, along with the subordinate NW-trending dextral extensional-torsional faults (F₃, F₅, F₈, F₆, F₁₀₀, etc.) and their associated secondary folds, as well as NE-trending sinistral compressional-torsional fault zones that roughly parallel the strata attitude, collectively formed a principal strike-slip–compound fault-fold structural assemblage style (a negative flower structure). This framework gave rise to a set of structural-mineralization-alteration zoning and the various ore blocks of the No. 1 orebody, characterized by different ore types.

Post-mineralization (Middle Yanshanian): Subduction of the Pacific Plate, southward movement of the Siberian Plate, and the subduction-collision of the Indochina Block with the South China Block occurred. The early closure of the Paleo-Tethyan sea basin along the southern margin of the South China Block led to the collision and convergence of the Indochina Block with the South China Block, reactivating the collision between the Yangtze Block and the Cathaysia Block. This resulted in a compressional regime in the SYGA, with the principal stress direction shifting from the NW–SE trend of the Middle-Late Indosinian to Early Yanshanian to a NE–SW trend. A series of NW-trending tectonic systems formed, wherein the NWW-trending dextral torsional-extensional faults (F₅₅, F₁, F₁₅, F₇₃) were reactivated with sinistral torsional to compressional-torsional characteristics, and NW-trending faults were overprinted by compressional to sinistral compressional-torsional deformation, forming positive flower structures. Concurrently, a small number of NE-trending tensional faults developed, though they are limited in scale.

Post-mineralization (Late Yanshanian): Against the backdrop of the India-Eurasia collision, the nearly N–S trending Chenghai Fault underwent medium- to low-angle thrusting or overthrusting from west to east. During this period, the principal compressive stress direction of the regional tectonic stress field in the Chenghai Fault area was approximately E–W. Within the deposit, this period is characterized by the formation of a small number of small-scale E–W trending extensional faults, NE-trending dextral compressional-torsional faults, and NW-trending sinistral compressional-torsional faults.

Post-mineralization (Himalayan Period): The collision between the Indian and Eurasian plates began approximately 60–40 Ma. By this time, the Indian and Eurasian plates were in full contact. The crust experienced overall slow uplift, manifesting as the final formation of the Asian continent, the uplift of the Tibetan Plateau, the activity of fold and thrust faults, and the intrusion of intermediate-acidic magmas. In this context, the principal compressive stress direction in the Daliangzi Pb–Zn deposit shifted from E–W to N–S, leading to the formation of E–W trending faults dominated by compressional, NW-trending faults dominated by dextral torsional, and NE-trending faults dominated by sinistral torsional, collectively forming an E–W trending tectonic zone.

5.2. Oblique Distribution Patterns and the Underlying Mechanical Model at Different Scales

Several types of hydrothermal mineral deposits exhibit a distinct spatial correlation with faults and crustal tectonic structures across a wide range of scales [22,23,24,25,26]. The en echelon distribution of ore bodies is a fundamental spatial characteristic of orebody clusters in both non-magmatic and magmatic hydrothermal deposit systems, and is genetically linked to shear processes [2,27,28,29]. Within shear systems, the mechanical properties and kinematic characteristics of syn-mineralization faults of different orders primarily control the systematic spatial emplacement of individual orebodies, orebody clusters, and entire deposits, thereby governing the pattern of en echelon distribution [27,30,31,32].

In summary, the oblique distribution patterns and their underlying mechanical mechanisms at four hierarchical levels—deposit, ore section, orebody, and ore block/vein—have been systematically synthesized. These findings can be directly applied to other deposits within the Ge-rich Pb–Zn ore concentration area of southwestern Sichuan. Furthermore, the conclusions are applicable to other non-magmatic hydrothermal deposits and also provide valuable insights for research on magmatic hydrothermal deposits. An ore field consists of multiple deposits; a deposit comprises multiple ore sections; an ore section contains multiple orebodies; and an orebody is made up of multiple ore blocks/veins. The mechanical mechanisms of ore control vary at different structural scales. Under the same principal compressive stress field, the mechanical behavior of ore-controlling structures at different scales results in distinct oblique distribution patterns in both plan and profile views (

Table 1. Underlying mechanical model of ore-controlling structures at different scale.

Plan			Profile			Contact
Scale	Object	Mechanical Properties of Ore-Controlling	Scale	Object	Mechanical Properties of Ore-Controlling
ore field	/	/	ore field	/	/	(1) long axis of ore field = series plane of deposit (2) long axis of deposit = series plane of ore section (3) long axis of ore section = series plane of orebody (4) long axis of orebody = series plane of ore block/vein
	long axis	sinistral compressional-torsional plane		long axis	dextral extensional-torsional plane
deposit	series plane		deposit	series plane
	long axis	sinistral extensional-torsional plane		long axis	sinistral torsional- extensional plane
ore section	series plane		ore section	series plane
	long axis	dextral extensional-torsional plane		long axis	sinistral torsional- extensional plane
orebody	series plane		orebody	series plane
	long axis	sinistral compressional-torsional plane		long axis	sinistral extensional-torsional plane
ore block/vein	series plane		ore block/vein	series plane
	long axis	dextral torsional- extensional plane		long axis	sinistral compressional-torsional plane

and

Table 2. Underlying mechanical model of ore-controlling structures at different scale.

Scale	Sequence of Ore-Controlling Structural	Hierarchy of Ore-Controlling Structure	Plan	Profile
deposits of the field	first sequence	third-order and fourth-order	right echelon	right echelon
ore sections of the deposit	second sequence	fourth-order	left echelon	right echelon
orebodies of ore section	third sequence	fourth-order	right echelon	right echelon
ore blocks/veins of orebody		fifth-order and sixth-order	left echelon	left echelon

, Figure 10 and Figure 11).

The Daliangzi–Huangjiaqing ore field is jointly controlled by the nearly N–S trending sinistral torsional Puduhe fault and the nearly N–S trending sinistral torsional Xiaojiang deep fault, which constitute the long axis of the ore field (i.e., the series connection plane of the deposits). In plan view, it is controlled by a sinistral compressional-torsional plane, while in profile view, it is controlled by a dextral extensional-torsional plane.

The Daliangzi Pb–Zn deposit is jointly controlled by the NW–NNW trending sinistral torsional-extensional Daqiaohe fault and the NWW-trending dextral torsional-extensional faults (F₅₅, F₁, F₁₅, F₇₃), which constitute the long axis of the deposit (i.e., the series connection plane of the ore sections). In plan view, it is controlled by a sinistral extensional-torsional plane, while in profile view, it is controlled by a sinistral torsional-extensional plane. The deposits at the ore field scale exhibit a right echelon arrangement in both plan and profile views.

The individual ore sections are controlled by the NWW-trending dextral torsional-extensional faults (F₅₅, F₁, F₁₅, F₇₃), which constitute the long axis of the ore sections (i.e., the series connection plane of the orebodies). In plan view, they are controlled by a dextral extensional-torsional plane, while in profile view, they are controlled by a sinistral torsional-extensional plane. The ore blocks at the deposit scale exhibit a left echelon arrangement in plan view and a right echelon arrangement in profile view.

The individual orebodies are jointly controlled by the NW-trending dextral extensional-torsional faults (F₃, F₅, F₈, F₆, F₁₀₀, etc.), which constitute the long axis of the orebodies (i.e., the series connection plane of the ore blocks). In plan view, they are controlled by a sinistral compressional-torsional plane, while in profile view, they are controlled by a sinistral extensional-torsional plane. The orebodies at the ore block scale exhibit a right echelon arrangement in both plan and profile views.

The individual ore blocks are controlled by the dilatant “gentle-narrow, steep-wide” opening spaces within the NW-trending dextral extensional-torsional faults (F₃, F₅, F₈, F₆, F₁₀₀, etc.), which define the long axis of the ore blocks. In plan view, they are controlled by a dextral torsional-extensional plane, while in profile view, they are controlled by a sinistral compressional-torsional plane. The ore blocks at the orebody scale exhibit a left echelon arrangement in both plan and profile views.

5.3. Structural Ore-Controlling Model

Shear zones play a critical role in the formation, preservation, and destruction of mineral deposits. Their structural weaknesses and permeability make them ideal pathways for mineralizing fluids, facilitating ore formation in different tectonic settings [33,34]. A negative flower structure is a form of tectonic deformation that exhibits a “flower cluster”-like shape in cross-section, typically developing within strike-slip fault systems. In cross-sectional view, the structure is primarily characterized by a set of fractures dominated by normal faults, which splay outward and upward in a fan-like manner, while in plan view, they often appear as nearly parallel strike-slip shear faults. Both horizontal shearing and vertical displacement influence the structural characteristics, distribution patterns, and evolutionary processes of the formation [35]. In the formation of mineral deposits, negative flower structures play a critical ore-controlling role, regulating the migration and precipitation of ore-forming fluids, as well as the formation and distribution of mineralization spaces [36,37].

Areas of stress transition are often regions where physicochemical conditions undergo significant changes [38,39,40,41]. In hydrothermal lead-zinc deposits, stress transition zones facilitate the destabilization of ore-forming fluids, leading to decompression boiling and continuous CO₂ escape. This process results in pronounced gas-liquid-solid phase separation [42,43], causing further concentration of the ore-forming fluids. When the increasingly enriched deep-sourced fluids mix with reduced sulfur-rich fluids entering dilatant spaces, rapid reactions trigger sulfide precipitation, leading to extraordinary enrichment of lead, zinc, and germanium. For example, mineral deposits controlled by compressional-torsional fault, the dilatant space is controlled by two compressional-torsional structural planes, such as a major fault and an anticline axis (the area towards the core of the anticline is a compressive space, and the area towards the hub of the anticline is a tensile space; the deep part analyzed here is the area towards the core of the anticline is a compressive space). It is interconnected by torsional and torsional-extensional faults, which act as ore-distributing structures governing the mineralization pattern [44,45].

Influenced by the orogenic event, large-scale regional fluid migration occurred. Deep-sourced fluids, carrying high-temperature hydrothermal ore-forming elements such as Mo and Tl associated with deep fluid systems, underwent extensive migration along SN-trending sinistral torsional regional deep fault (Puduhe fault). During migration, these fluids continuously leached and extracted medium- to low-temperature ore-forming and mineralizing elements (e.g., Pb, Zn, Cd, Sb, Hg, Ag, As) related to Pb–Zn mineralization from the Mesoproterozoic basement rocks or sedimentary cover sequences. This process formed ore-forming fluids enriched with Pb²⁺, Zn²⁺, and other components. These fluids, carrying the two sets of element associations, were then injected along the NWW-trending dextral torsional-extensional ore-conducting structures (F₅₅, F₁, F₁₅, F₇₃), NW–NNW trending sinistral torsional-extensional fault (Daqiaohe fault) and migrated into favorable spaces within the anticlines of compound folds located in the footwalls of secondary faults such as F₃, F₈, F₆, F₁₀₀, and F₅ [14]. Simultaneously, meteoric water leached late Triassic-early Jurassic strata and extracted brines from these formations. Driven by tectonic stress, the two types of fluids eventually converged in these favorable structural spaces, where “infiltration”-metasomatism occurred, precipitating abundant sulfides and thus forming the deposit (Figure 12).

Within the deposit area, the shallow Є black carbonated dolomite, after being fragmented by ore-forming structures, migrated along faults such as F₃, F₈, F₆, F₁₀₀, and F₅, forming a continuous black zone distributed along the faults that acts as a barrier layer. Simultaneously, deep ore-forming fluids carrying complex breccia of varying compositions from the deep Pth and Zbd strata migrated upward along the ore-conducting structure (Puduhe fault), through ore blending structures (Daqiaohe fault, F₅₅, F₁, F₁₅, F₇₃). At relatively steep locations in the footwalls of faults such as F₃, F₈, F₆, F₁₀₀, and F₅, diapirism occurred, forming anticlines, and the in situ Zbd gray-white dolomite was subjected to cataclasis. At this stage, both the complex breccia and the ore-forming fluids rich in Pb²⁺, Zn²⁺, and other components entered the dilatant spaces within the anticlines. Due to changes in physicochemical conditions, abundant sulfides precipitated, cementing the breccias and thus forming brecciated Pb–Zn orebodies [14] (Figure 12).

Ultimately, an ore-controlling model of a compound negative flower structure–fault-fold–diapiric structure was constructed for the Daliangzi Pb–Zn deposit (Figure 12).

5.4. Prospecting Prediction

The locations of concealed orebodies at different scales in the periphery of the Daliangzi Pb–Zn deposit were predicted based on oblique distribution patterns and mechanical mechanisms (Figure 10 and Figure 11). Furthermore, the positions of concealed orebodies at different depths within the deposit scale were forecasted according to the ore-controlling model of composite negative flower structure and fault-fold piercing (Figure 12).

Ore sections at the deposit scale: Focus should be placed on concealed ore sections that exhibit a left echelon distribution in plan view relative to known ore sections. These are controlled by NWW-trending dextral torsional-extensional faults (F₅₅, F₁, F₁₅, F₇₃) (Figure 10, Figure 11 and Figure 12).

Orebodies at the ore section scale: Within the same ore section, focus should be placed on concealed orebodies that display a right echelon distribution in plan view relative to known orebodies (e.g., the No. 1 orebody). These are controlled by NW-trending dextral extensional-torsional faults (F₃, F₅, F₈, F₆, F₁₀₀, etc.) (Figure 10, Figure 11 and Figure 12).

Ore blocks at the orebody scale: Within the same orebody, focus should be placed on concealed ore blocks that show a left echelon distribution in both plan and profile views relative to known ore veins. These are controlled by the dilatant “gentle-narrow, steep-wide” opening spaces within the NW-trending dextral extensional-torsional faults (F₃, F₅, F₈, F₆, F₁₀₀, etc.) (Figure 10, Figure 11 and Figure 12).

Focus on areas within the deposit where NW-trending dextral extensional-torsional faults are exposed, particularly those with developed anticlines in their footwalls, along with strong mineralization alteration and well-developed “black fracture zones.” Additionally, attention should be given to regions containing NE-trending sinistral compressional-torsional faults and SN-trending sinistral torsional faults within the deposit scope, especially where these faults exhibit anticlinal structures in their footwalls, accompanied by intense mineralization alteration and prominent “black fracture zones.”

6. Conclusions

This study clarified the hierarchical ore-controlling structural patterns of the Daliangzi Pb–Zn Deposit.

It defined the ore-controlling structural system of the Daliangzi Pb–Zn Deposit. Since the Indosinian period, the deposit has undergone four stages of structural evolution: the NE-trending structural zone (Middle-Late Indosinian to Early Yanshanian) → NW-trending structural zone (Early-Middle Yanshanian) → SN-trending structural zone (Late Yanshanian) → EW-trending structural zone (Himalayan). Among these, the NE-trending structural zone (Middle-Late Indosinian to Early Yanshanian) constitutes the Pb–Zn metallogenic structural system.

It also proposed the spatial en echelon distribution pattern of the deposits, ore sections, ore bodies, and ore blocks, along with the mechanical mechanisms of multi-scale structural ore control.

It further established an ore-controlling model of composite negative flower structure and fault-fold piercing for the Daliangzi Pb–Zn Deposit.

The locations of concealed orebodies at different scales within the Daliangzi Pb–Zn deposit and its surrounding areas were predicted; moreover, the locations of concealed orebodies at various depths within the deposit area were also predicted.