Metallogenic Age and Genetic Type of the Donggou Pb-Zn Deposit in the Qimantagh Region, East Kunlun: Constraints from Zircon U-Pb Dating, Sulfur Isotopes, and Trace Element Compositions of Ore Minerals

Abstract

The Donggou Pb-Zn deposit in the Qimantagh region is stratabound, with ore bodies occurring as stratoid and lenticular forms within clastic rocks and andesites of the Qimantagh Group. To constrain the mineralization age, ore genesis, and ore-forming conditions, this study conducted zircon U-Pb dating, sulfur isotope analysis, and LA-ICP-MS trace element analysis of sphalerite. Zircon U-Pb dating of the overlying andesite yields an age of 437.1 ± 1.9 Ma, which provides an upper age constraint for mineralization. Sulfur isotope values (δ³⁴S range from −5.98‰ to +12.01‰) suggest a mixed sulfur source, dominated by magmatic sulfur with a minor seawater contribution. Trace element analysis of sphalerite (Sp1) shows enrichment in Fe, Mn, Co, Cd, and In, and depletion in Ni, Ga, and Ge. The estimated mineralization temperature, based on the sphalerite geothermometer, is approximately 327–344 °C. Volcanic rocks in the deposit are mainly andesite with minor dacite and rhyolite, indicating an island arc setting, and the clastic rocks point to a continental arc provenance and a shallow marine environment. Collectively, these features suggest that the Donggou Pb-Zn deposit is a VMS-type deposit formed during the late subduction stage of the Qimantagh Ocean. This study provides new constraints on the Early Silurian Pb-Zn mineralization in the Qimantagh region and has implications for exploration targeting in similar volcanic-hosted settings.

1. Introduction

The Qimantagh region, located in the western part of the East Kunlun Orogenic Belt, is a well-known polymetallic metallogenic belt situated between the Qaidam Basin to the north and the East Kunlun magmatic arc to the south (Figure 1). This region hosts a variety of deposit types, including skarn, porphyry, magmatic segregation, and hydrothermal vein types, with iron, copper, lead–zinc, nickel, gold, and molybdenum as the main economic metals [1].

Previous studies on Pb-Zn mineralization in the Qimantagh region have focused mainly on Triassic deposits associated with the evolution of the Paleo-Tethys Ocean. Representative examples include the Hutouya, Galinge, Jingren-Yingqinggou [2], and Yemaquan Pb-Zn deposits [3,4], which are generally considered to be skarn or hydrothermal vein-type deposits. In contrast, Silurian–Devonian Pb-Zn mineralization has been only locally reported; e.g., as overprints in the Hutouya and Niukutou districts [5,6]. Consequently, the Pb-Zn metallogenic potential of the Early Paleozoic magmatic rocks in this region remains poorly understood.

The Donggou Pb-Zn deposit is a medium-sized deposit recently discovered by the Qinghai Fifth Geological Exploration Institute in the Qimantagh region. The ore bodies are stratoid and lenticular, hosted in the clastic and volcanic rocks of the Ordovician Qimantagh Group. Medium-fine-grained diorite and Late Devonian monzogranite are exposed in the mining area, suggesting a Proto-Tethyan tectonic setting. However, the precise mineralization age of the Donggou deposit has not been directly constrained. Furthermore, the genesis of stratabound Pb-Zn deposits in this region remains controversial, with competing models including volcanogenic massive sulfide (VMS), sedimentary exhalative (SEDEX), and skarn types. For example, the Kendekeke iron–lead–zinc deposit has been variously interpreted as a skarn-type [7] or SEDEX-type [8,9,10] deposit. Although the stratoid ore bodies of the Donggou deposit exhibit syngenetic features, its exact genetic type remains to be determined.

To address these issues, this study integrates zircon U-Pb dating, whole-rock major and trace element geochemistry, and LA-ICP-MS in situ trace element analysis based on systematic field geological investigations. The aims are to constrain the maximum age of mineralization, determine the source of sulfur and metals, estimate the ore-forming temperature, and propose a genetic model for the Donggou deposit. The results provide new insights into Early Paleozoic Pb-Zn metallogeny in the Qimantagh region and have practical implications for exploration targeting.

2. Regional Geological Background

The East Kunlun Orogenic Belt, trending east–west on the northeastern margin of the Qinghai–Tibet Plateau, is bounded by the Bayan Har Block to the south and the Qaidam Block to the north. Three nearly east–west-trending ophiolitic mélange belts—the Qimantagh–Xiangride, the Aqikekule Lake–Kunzhong, and the Muztag–Buqingshan–A’nyêmaqên—divide the orogen from north to south into three tectonic units: the Northern Qimantagh Belt, the Central Kunlun Belt and the Southern Kunlun Belt [11]. Since the Early Paleozoic, the region has experienced multi-stage ocean–continent transition, arc–arc collision, and arc–continent collision related to the Proto-Tethys and Paleo-Tethys oceans, producing diverse and distinctive large-scale metallogenesis, forming the Qimantagh–Dulan Variscan Fe-Co-Cu-Pb-Zn-Sn (Sb-Bi) metallogenic belt [12].

The study area is situated at the western extremity of the East Kunlun Orogenic Belt; the Lower Paleozoic Ordovician Qimantagh Group, Upper Paleozoic Devonian and Carboniferous strata, and Triassic strata are widely exposed in the area, with the Mesoproterozoic Jinshuikou Rock Group distributed in the southern part (Figure 1). The Jinshuikou Rock Group is the oldest exposed stratigraphic unit in the area, consisting of a suite of medium- to high-grade metamorphic rocks, which can be divided into marble, gneiss, and schist formations.

The Qimantagh Group represents a back-arc basin hydrothermal sedimentary and marine volcanic rock assemblage. From bottom to top, it comprises the clastic rock formation, volcanic rock formation, and carbonate rock formation. The Devonian strata consist of the Haerzha Formation and Heishangou Formation, representing a set of extensional rift-related molasse deposits formed in an intraplate rift setting [13]. The Early Carboniferous continued the sedimentary characteristics of the Late Devonian, with the marine area gradually expanding and carbonate sedimentation intensifying on the basis of Late Devonian marine or transitional facies. This resulted in the Shiguaizi Formation, characterized by purplish-red and variegated clastic rocks and high-energy sandy conglomerates at the base [14], which is overlain by the Dagangou Formation and Di’aosu Formation, consisting of littoral to neritic carbonate rocks intercalated with clastic sedimentary sequences.

The Upper Triassic Elashan Formation is mainly distributed in the central–southern part of the Qimantagh region, consisting predominantly of continental volcanic rocks and volcaniclastic rocks. Intrusive rocks in the area range from ultramafic to felsic compositions. Ultramafic rocks are sporadically exposed in the Xiarihamu, Shizigou, and Akechukesai areas. Intermediate to felsic intrusive rocks are widely distributed, with their orientations generally consistent with the regional tectonic line. The main rock types include diorite, quartz diorite, granite, and alkali-feldspar granite [15,16,17].

The study area is characterized by well-developed faults, predominantly NWW–trending, with subordinate NW- and nearly E–W-trending faults. Regional-scale faults include the Northern Qimantagh concealed fault, the Adatan fault, and the Lianhuashi–Xiaolangyashan fault. Regional folds are dominated by NWW-trending composite anticlines and synclines.

3. Geological Characteristics of the Mining Area

The strata exposed in the mining area are predominantly the clastic rock formation and volcanic rock formation of the Ordovician Qimantagh Group, with minor outcrops of the Lower Carboniferous Shiguaizi Formation and Dagangou Formation in the southern part. The Qimantagh Group is the main ore-hosting stratigraphic unit in the mining area (Figure 2a) and is characterized by clastic sedimentary rocks intercalated with intermediate–basic volcanic rocks that occur as thin layers or lenses. The clastic sedimentary rocks consist of biotite–chlorite–sericite phyllitic slate (Figure 3a,b), sericite quartz phyllite (Figure 3c,d), meta-fine-grained quartz greywacke, lithic arkose, argillaceous carbonaceous silty slate, andesitic crystal tuff (Figure 3e,f), and strongly schistose marble (Figure 3g,h). Among these, andesitic crystal tuff is only identified in small amounts in drill cores (Figure 2b). Volcanic rocks are dominated by basaltic andesite, andesite, and rhyolite and are interbedded with clastic rocks in the mining area.

Faults are well-developed in the mining area, with the predominant structural trend being NW–NWW, subordinate in near N–S, NE, and nearly E–W directions. Most faults are reverse faults. Magmatic activity was intense, with rocks ranging from intermediate–felsic to mafic and ultramafic compositions. Mafic rocks are mainly gabbro and pyroxenite exposed in the southern part of the mining area, occurring as lenses. Acidic rocks, consisting of Late Devonian monzogranite and Early Jurassic syenogranite, are mainly distributed on the eastern and western sides of the mining area. Additionally, minor lens-shaped medium-fine-grained diorite (425.1 ± 3.3 Ma, unpublished data) occurs in the central part of the mining area, representing Late Silurian magmatic rocks.

4. Ore Body Characteristics

Through drilling exploration, six lead–zinc polymetallic blind ore bodies (M1–M6) have been delineated in the deep part of the mining area (

Table 1. Summary of ore body characteristics in the Donggou deposit.

Ore Body	Host Rock	Ore Type	Length (m)	Thickness (m)	Oblique Depth (m)	Grade (wt%)	Drill Holes
M1	Andesite	Disseminated	200	1.46	35	Cu: 0.47%	ZK802, ZK804, ZK002
M2	Andesite	Disseminated	400	12.68	255	Zn: 2.04%	ZK001, ZK002, ZK003, ZK804, ZK801
M3	Feldspar-quartz sandstone, andesit	Disseminated, Vein	800	5.47	610	Zn: 1.76%	OZ001, ZK001, ZK002, ZK003, ZK804, ZK801, ZK701, ZK702
M4	Andesite	Massive	400	4.39	600	Zn: 5.96%; Pb: 0.56%; Cu: 0.32%	OZ001, ZK001, ZK002; ZK003, ZK004 ZK804, ZK801
M5	Andesite	Disseminated	400	2.9	370	Cu: 0.36%	ZK001, ZK002, ZK003
M6	Andesite	Disseminated	400	2.44	155	Cu: 0.36%; Zn: 2.12%	ZK003

). Among them, M4 is the main ore body. These ore bodies are significantly controlled by stratigraphic horizons and can be classified into massive (M4), disseminated (M1, M2, M5, M6), and veinlet-disseminated (M3) types. Among them, the massive ore bodies are mainly hosted by andesite. The ore bodies are generally stratoid in morphology, with relatively stable extension along the dip direction (Figure 4). The main ore bodies are described below.

M4 (Zn + Pb + Cu): This ore body is hosted in layered andesite. The andesite is overlain and underlain by clastic rocks. The ore body is located in the lower part of the andesite, occurring as a stratoid body, with a length of 400 m, a thickness of 4.39 m, and a controlled oblique depth of 550 m. The average grade of Zn is 5.96% (maximum 21.25%), Pb averages 0.56%, and Cu averages 0.32%, with associated Au averaging 0.41 g/t and Ag averaging 25.71 g/t. The ore body strikes NW–SE and dips to the south at angles ranging from 40° to 56°. The ore type is massive (Figure 5a,b). The metallic minerals occur as massive aggregates, predominantly pyrite, pyrrhotite, sphalerite, chalcopyrite, and galena, with minor amounts of arsenopyrite. The total content of metallic minerals ranges from 90% to 95%.

M1 (Cu): This lens-shaped ore body is hosted in andesite and intersected in drill holes ZK802, ZK804, and ZK002. It strikes NW–SE and dips ~40° south, with a length of 200 m, a true thickness of 1.46 m, an oblique depth of 35 m, and an average Cu grade of 0.47%. Pyrite is the dominant metallic mineral, occurring as anhedral granular aggregates with disseminated texture. M2 (Zn): This ore body is hosted in sericite quartz phyllite of the clastic rock formation. The ore body is 400 m in length, with a controlled oblique depth of 610 m, an average true thickness of 12.68 m, and an average Zn grade of 2.04%. It strikes NW–SE and dips to the south at an angle of approximately 40°. The ore type is mainly veinlet or disseminated (Figure 5g). The metallic minerals are dominated by pyrite, sphalerite, and minor galena, occurring as anhedral granular aggregates with disseminated textures, mostly developed along bedding.

M3 (Zn): This ore body is 800 m in length, with a controlled oblique depth of 610 m, an average true thickness of 5.47 m, and an average Zn grade of 1.76%. It strikes NW–SE and dips to the south at an angle of approximately 40°. The ore body occurs mainly as veinlet and disseminated forms (Figure 5c–e). The metallic minerals are predominantly pyrrhotite, pyrite, and sphalerite, occurring as veinlets and disseminated forms.

M5 and M6: Based on the table, M5 (Cu 0.36%, 400 m length, 2.9 m thickness, 370 m oblique depth) and M6 (Cu 0.36% + Zn 2.12%, 400 m length, 2.44 m thickness, 155 m oblique depth) are both disseminated and hosted in andesite.

5. Ore and Mineral Characteristics

The metallic minerals in the M4 ore body are mainly composed of pyrrhotite, sphalerite, galena, and chalcopyrite, occurring as massive and laminated forms, with the ore predominantly exhibiting massive texture. In the lower ore bodies (M2 and M3), metallic minerals are mainly distributed as sparse disseminated and stockwork forms, with sphalerite and galena being relatively scarce and unevenly distributed. The ores are dominated by disseminated and banded textures, with relatively lower metal grades.

Based on the occurrence of metallic minerals, these ore types can be broadly classified into massive ores (Figure 5a,b), laminated-like ores (Figure 5c–e), vein-type ores (Figure 5f–h), and disseminated ores (Figure 5i). In Figure 5h, metallic minerals are hosted within fractures of cryptoexplosive breccias.

The metallic minerals mainly consist of sphalerite, pyrrhotite, pyrite, chalcopyrite, galena, arsenopyrite, and bismuthinite. Arsenopyrite represents the latest hydrothermal overprinting mineral. Gangue minerals are mainly composed of feldspar, sericite, chlorite, and quartz, with minor calcite and clay minerals.

Pyrite can be divided into three generations. The first-generation pyrite (Py1) occurs as euhedral crystals, predominantly euhedral to subhedral granular crystals, with mostly straight edges. The cross-sections are commonly regular triangular, square, and polygonal shapes, with grain sizes continuously ranging from 0.03 mm to 1.5 mm. Py1 is mostly distributed as single crystals, with some crystals interlocking to form irregular aggregates or graded bands. Locally, Py1 is replaced by pyrrhotite (Figure 6a,b,d,e). The second-generation pyrite (Py2) occurs as irregular grains (0.02–0.15 mm) and micro-veinlet aggregates (<0.02 mm wide) and disseminated forms, mainly distributed around the margins of some non-metallic minerals. In high-concentration areas, Py2 interconnects to form stockwork textures (Figure 6c,e). The third-generation pyrite (Py3) occurs as fine veinlets that cut across the first-generation euhedral pyrite (Figure 6f).

Sphalerite occurs in two generations. The first-generation sphalerite (Sp1) is anhedral and granular, gray with a slight brownish tint, isotropic, and occurs as interlocking aggregates with grain sizes too fine to measure. Locally, Sph1 and pyrrhotite form alternating laminae (Figure 6e), and Sph1 is commonly associated with pyrrhotite and chalcopyrite. The second-generation sphalerite (Sp2) occurs as fine veinlets cutting across chalcopyrite and pyrrhotite (Figure 6h).

Pyrrhotite occurs as anhedral granular aggregates, with a creamy yellow to slightly pinkish brown color and strong anisotropy, displaying light bluish gray–brownish yellow gray–slightly reddish brown colors. Pyrrhotite forms extensive aggregates as interlocking crystals, with chalcopyrite grains associated along the margins. Locally, galena and sphalerite replace pyrrhotite (Figure 6l).

Based on the SEM-BSE images, it is also evident that the first-generation sphalerite is mostly intergrown with pyrrhotite, and galena is mainly distributed on the surfaces of sphalerite and pyrrhotite or at the contacts between sphalerite and pyrrhotite. Chalcopyrite is intergrown with arsenopyrite (Figure 7a–c). The first-generation euhedral pyrite is intergrown with pyrrhotite and quartz (Figure 7d). Arsenopyrite is mainly distributed on the surfaces of pyrrhotite and sphalerite or on quartz surfaces (Figure 7e,f). Bismuthinite occurs within fractures of pyrrhotite, and fine-grained chalcopyrite is also observed on the surface of pyrrhotite (Figure 7g). Cassiterite is distributed in the interstices between pyrrhotite and sphalerite (Figure 7h).

Based on the detailed petrographic observations and crosscutting relationships described above, a paragenetic sequence of mineralization has been established. As summarized in

Table 2. Paragenetic sequence of mineralization in the Donggou mining area.

Ore-Forming Stage		Mineral Assemblage	Main Minerals and Occurrence	Texture/Structure
Diagenetic/Sedimentary stage		Pyrite (Py1)	Euhedral–subhedral granular, cubic	Star-shaped, sparsely disseminated
Hydrothermal stage	Stage I: Massive sulfide stage	Pyrrhotite + sphalerite (Sp1) + chalcopyrite + pyrite (Py2)+ galena	Anhedral granular aggregates; Sp1 and pyrrhotite form alternating laminae; chalcopyrite associated	Massive, banded, stockwork
	Stage II: Veinlet-disseminated sulfide stage	Sphalerite (Sp2) + pyrite (Py3) + galena	Fine veinlets cutting across chalcopyrite and pyrrhotite; Py3 veinlets crosscut Py1	Veinlet, sparsely disseminated, crosscutting veins
	Stage III: Late overprint stage	Arsenopyrite + bismuthinite + cassiterite	Apy fine grains along margins/surfaces of Pyh; Bmt within fractures of Pyh; Cst in interstices between Pyh and Sp1	Replacement, interstitial
Supergene/Alteration stage		Calcite, chlorite, sericite, clay minerals	Veinlets or fillings	Vein, filling

, the mineralization can be divided into four main stages: the diagenetic/sedimentary stage (Py1), the hydrothermal stage (subdivided into the massive sulfide stage (Stage I), the veinlet-disseminated sulfide stage (Stage II), and the late overprinting stage (Stage III)), and the supergene/alteration stage.

6. Sample Collection and Analysis Methods

Fresh and representative samples from drill cores of the Donggou lead–zinc deposit were collected to systematically constrain its magmatic and metallogenic ages, sources of ore-forming materials, and genetic mechanisms. A total of 24 geochemical samples (clastic and volcanic rocks) were obtained from drill holes ZK001, QZ001, ZK002, ZK003, and ZK004. Seven samples from ore-bearing horizons in drill holes ZK001 (2), ZK002 (1), ZK003 (3), and ZK004 (1) were analyzed for sulfur isotopes and by electron probe microanalysis (EPMA), representing different ore types. Samples for zircon U–Pb dating were obtained from the andesite overlying the M4 ore body (

Table 3. Sample collection information.

Number	Sample	Drill Hole Number	Depth (m)	Lithology	Ore Body Number	Ore Type	Analytical Method
1	DG-N1	ZK003	292.0	Andesite			U-Pb zircon
2	QZ001-HX1	QZ001	92.4	Silty slate/Andesite			whole-rock geochemistry
3	QZ001-HX2	QZ001	110.0	sericite quartz phyllite			whole-rock geochemistry
4	ZK002-HX2	ZK002	99.0	sericite quartz phyllite			whole-rock geochemistry
5	ZK002-HX4	ZK002	246.8	sericite quartz phyllite			whole-rock geochemistry
6	ZK002-HX6	ZK002	288.5	feldspathic quartz sandstone			whole-rock geochemistry
7	ZK002-HX7	ZK002	311.5	sericite quartz phyllite			whole-rock geochemistry
8	ZK002-HX8	ZK002	327.0	feldspathic quartz sandstone			whole-rock geochemistry
9	ZK004-HX7	ZK004	446.9	sericite quartz phyllite			whole-rock geochemistry
10	ZK004-HX8	ZK004	449.3	tuff			whole-rock geochemistry
11	ZK004-HX9	ZK004	454.0	rhyolite/sericite quartz phyllite			whole-rock geochemistry
12	ZK004-HX13	ZK004	524.6	chalcopyritized and pyritized rhyolite			whole-rock geochemistry
13	ZK001-HX1	ZK001	62.9	sericite quartz phyllite			whole-rock geochemistry
14	ZK001-HX3	ZK001	98.8	sericite quartz phyllite			whole-rock geochemistry
15	ZK001-HX4	ZK001	130.1	arkose			whole-rock geochemistry
16	ZK001-HX6	ZK001	153.8	sericite quartz phyllite			whole-rock geochemistry
17	ZK003-HX1	ZK003	409.7	sericite quartz phyllite			whole-rock geochemistry
18	QZ001-HX3	QZ001	120.5	rhyolite			whole-rock geochemistry
19	ZK002-HX1	.ZK002	81.0	andesite			whole-rock geochemistry
20	ZK002-HX3	.ZK002	184.5	andesite			whole-rock geochemistry
21	ZK002-HX9	.ZK002	369.7	andesite			whole-rock geochemistry
22	ZK004-HX3	ZK004	223.5	andesite			whole-rock geochemistry
23	ZK004-HX4	ZK004	257.7	andesite			whole-rock geochemistry
24	ZK004-HX15	ZK004	574.6	andesite			whole-rock geochemistry
25	ZK001-HX5	ZK004	135.3	andesite			whole-rock geochemistry
26	ZK004-S1	ZK004	457.0	ore	M4	massive ore	in situ S isoplot, rare elements
27	ZK001-S1	ZK001	59.2	ore	M4	disseminated ore	in situ S isoplot, rare elements
28	ZK001-S2	ZK001	172.0	ore	M4	disseminated ore	in situ S isoplot, rare elements
29	ZK002-S1	ZK002	252.0	ore	M4	massive ore	in situ S isoplot, rare elements
30	ZK003-S1	ZK003	292.0	ore	M4	massive ore	in situ S isoplot, rare elements
31	ZK003-S2	ZK003	312.0	ore	M4	massive ore	in situ S isoplot
32	ZK003-S3	ZK003	407.7	ore	M3	disseminated ore	in situ S isoplot

). The various analytical methods are described as follows.

6.1. Zircon U-Th-Pb Dating

Zircon U–Pb isotopic analysis, including sample preparation, cathodoluminescence (CL) imaging, and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS), was carried out at Wuhan SampleSolution Analytical Technology Co., Ltd. (Wuhan, China). The LA-ICP-MS system consisted of an Agilent 7900 ICP-MS coupled with a Geolas 200M laser ablation unit (Agilent Technologies, Santa Clara, CA, USA), operated at a spot size of 32 μm and an ablation depth of 20–40 μm. NIST SRM610 served as the external calibrant, and ²⁹Si was used for internal normalization. The analytical primary data were processed using the ICPMSDatacal V8.3 software. A common Pb correction and ages of the analyzed samples were calculated using the ComPbCorrection program [19]. Weighted average and concordia plots were drawn using Isoplot 4.5 embedded in Microsoft Excel. Individual analyses and concordia plots are presented with 1σ uncertainty. U-Pb age uncertainty is quoted at the 95% confidence level. The analytical results are summarized in

Table A1. LA-ICP-MS zircon U-Pb dating results for samples from the Donggou Pb-Zn deposit.

Spot No.	Th (ppm)	U (ppm)	207Pb/206Pb	1σ	207Pb/235U	1σ	206Pb/238U	1σ	207Pb/206Pb (age)	1σ	207Pb/235U (age)	1σ	206Pb/238U (age)	1σ
ZK003-WT1-01	233	378	0.05582	0.00125	0.53964	0.01215	0.07009	0.00086	445	29	438	8	437	5
ZK003-WT1-02	215	377	0.05654	0.00118	0.54068	0.01145	0.06933	0.00084	474	26	439	8	432	5
ZK003-WT1-03	200	322	0.05589	0.00093	0.54071	0.00928	0.07014	0.00082	448	19	439	6	437	5
ZK003-WT1-04	357	496	0.05513	0.00086	0.53518	0.00877	0.07038	0.00082	417	18	435	6	438	5
ZK003-WT1-05	208	328	0.05583	0.00097	0.54057	0.0097	0.07021	0.00083	446	20	439	6	437	5
ZK003-WT1-06	174	317	0.05824	0.00157	0.56211	0.01511	0.06997	0.0009	539	36	453	10	436	5
ZK003-WT1-07	249	377	0.05621	0.00103	0.5434	0.01026	0.07009	0.00084	461	22	441	7	437	5
ZK003-WT1-08	325	463	0.05455	0.00086	0.52813	0.00869	0.0702	0.00083	394	18	431	6	437	5
ZK003-WT1-09	331	480	0.0575	0.00109	0.55144	0.01072	0.06954	0.00084	511	23	446	7	433	5
ZK003-WT1-10	264	400	0.05466	0.00096	0.53172	0.00967	0.07053	0.00084	398	21	433	6	439	5
ZK003-WT1-11	221	346	0.05668	0.00113	0.54639	0.0111	0.06989	0.00085	479	24	443	7	435	5
ZK003-WT1-12	194	326	0.05547	0.00111	0.53897	0.01102	0.07045	0.00086	431	25	438	7	439	5
ZK003-WT1-13	152	288	0.05474	0.00114	0.53147	0.01132	0.0704	0.00087	402	26	433	8	439	5
ZK003-WT1-14	483	580	0.05688	0.00136	0.54804	0.01322	0.06987	0.00088	487	31	444	9	435	5
ZK003-WT1-15	217	328	0.05555	0.00114	0.54014	0.0113	0.0705	0.00087	434	26	439	7	439	5
ZK003-WT1-16	190	302	0.05754	0.00122	0.55666	0.01205	0.07016	0.00087	512	27	449	8	437	5
ZK003-WT1-17	181	282	0.05544	0.00152	0.53765	0.01478	0.07033	0.00092	430	38	437	10	438	6
ZK003-WT1-18	301	461	0.05787	0.00125	0.55425	0.01219	0.06946	0.00087	525	27	448	8	433	5
ZK003-WT1-19	381	504	0.05622	0.00102	0.54635	0.01028	0.07048	0.00086	461	21	443	7	439	5
ZK003-WT1-20	269	432	0.05765	0.00099	0.55836	0.00998	0.07024	0.00085	516	20	450	7	438	5
ZK003-WT1-21	353	472	0.05963	0.00119	0.57406	0.01174	0.06983	0.00087	590	24	461	8	435	5
ZK003-WT1-22	337	483	0.05596	0.00121	0.54347	0.01194	0.07044	0.00088	451	27	441	8	439	5
ZK003-WT1-23	236	394	0.05677	0.00112	0.54995	0.01115	0.07026	0.00087	483	24	445	7	438	5
ZK003-WT1-26	206	568	0.05488	0.00108	0.53486	0.01081	0.07069	0.00088	407	24	435	7	440	5
ZK003-WT1-27	294	430	0.05349	0.00092	0.51892	0.00938	0.07037	0.00086	350	20	424	6	438	5
ZK003-WT1-28	412	538	0.05565	0.00102	0.53755	0.01021	0.07007	0.00086	438	22	437	7	437	5
ZK003-WT1-29	335	477	0.05584	0.00092	0.54196	0.00941	0.0704	0.00086	446	19	440	6	439	5
ZK003-WT1-30	210	351	0.05364	0.00127	0.52166	0.01252	0.07055	0.0009	356	32	426	8	439	5

.

6.2. Whole-Rock Geochemical Analysis

Sample preparation and geochemical analysis were performed at the Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Natural Resources (Jilin University). Rock samples were crushed to 2–4 cm, ultrasonically cleaned with 3%–5% dilute hydrochloric acid to remove surface contaminants, and then powdered to 200 mesh. Whole-rock major elements were measured by X-ray fluorescence spectrometry (XRF). Trace and rare earth elements (REEs) were analyzed using an Agilent 7500a ICP-MS (Agilent Technologies, Santa Clara, CA, USA). Powder samples with a grain size of 200 mesh were weighed and moved to a PTFE crucible, followed by addition of 1.5 mL HNO₃ and 1.0 mL HF. Strict standard digestion protocols, including repeated reagent supplementation and heating and cooling cycles, were implemented. The final solution was then moved to a polyethylene bottle and diluted to 50 mL using 2% HNO₃ for ICP-MS measurements. The analytical precision and accuracy are better than 10% for trace elements and 5% for major elements. The analytical results are presented in

Table A2. Whole-rock geochemical compositions of clastic sedimentary rocks from the Donggou Pb–Zn deposit.

Sample	QZ001-HX1	QZ001-HX2	ZK002-HX2	ZK002-HX4	ZK002-HX6	ZK002-HX7	ZK002-HX8	ZK004-HX7	ZK004-HX8	ZK004-HX9	ZK004-HX13	ZK004-HX15	ZK001-HX1	ZK001-HX3	ZK001-HX4	ZK001-HX6	ZK003-HX1
SiO2	70.85	65.68	79.01	66.04	66.68	65.14	68.96	71.88	59.58	70.26	62.20	67.38	66.67	65.20	65.44	75.58	65.61
Al2O3	12.61	13.56	10.14	7.81	11.68	13.17	10.95	11.66	16.01	11.55	13.42	12.37	14.70	13.38	11.58	10.39	14.89
Fe2O3	1.57	2.07	0.76	4.56	1.89	1.02	2.20	2.27	1.00	0.95	1.86	0.71	1.02	1.00	0.70	2.91	3.49
FeO	4.55	6.87	1.46	11.80	8.94	9.46	8.03	2.87	7.57	8.28	12.14	4.47	4.54	4.86	4.07	1.35	3.58
CaO	0.26	0.26	0.54	0.08	0.23	0.25	0.22	1.10	0.27	0.08	0.34	2.36	0.26	4.03	3.95	0.28	0.45
MgO	1.09	1.89	0.58	1.80	0.82	0.62	0.70	1.42	5.60	0.61	1.61	3.57	3.97	0.50	3.87	0.67	1.28
K2O	4.19	3.91	1.81	1.74	3.79	4.06	3.51	3.72	3.06	3.33	2.08	3.64	3.61	6.03	3.03	5.07	2.14
Na2O	0.11	0.21	3.31	0.16	0.31	0.27	0.32	0.07	0.14	0.25	0.52	0.35	0.09	1.49	0.91	0.09	3.94
TiO2	0.65	0.70	0.25	0.36	0.61	0.69	0.57	0.61	0.84	0.26	0.54	0.66	0.73	0.41	0.28	0.26	0.61
P2O5	0.14	0.16	0.04	0.03	0.14	0.17	0.15	0.15	0.18	0.02	0.08	0.16	0.15	0.06	0.03	0.02	0.09
MnO	0.13	0.14	0.05	0.07	0.06	0.04	0.04	0.14	0.28	0.04	0.20	0.07	0.08	0.15	0.24	0.07	0.08
LOI	3.57	4.35	1.56	5.56	4.82	4.81	4.21	3.96	5.07	4.04	4.92	3.92	4.13	2.83	5.66	2.86	3.65
Total	99.72	99.79	99.50	100.02	99.97	99.71	99.87	99.85	99.58	99.68	99.90	99.66	99.96	99.94	99.76	99.54	99.81
K2O+Na2O	4.30	4.12	5.12	1.91	4.10	4.34	3.84	3.79	3.20	3.58	2.60	3.99	3.70	7.52	3.94	5.16	6.08
Al2O3/SiO2	0.18	0.21	0.13	0.12	0.18	0.18	0.20	0.16	0.16	0.27	0.16	0.22	0.18	0.22	0.21	0.18	0.14
K20/Na2O	0.03	0.05	1.83	0.09	0.08	0.08	0.07	0.09	0.02	0.04	0.07	0.25	0.10	0.03	0.25	0.30	0.02
CIA	73.44	75.62	64.17	79.72	72.94	72.94	74.15	73.00	70.49	82.23	75.94	82.03	66.08	78.78	53.67	59.46	65.62
Li	8.778	23.86	5.482	16.26	8.567	2.845	6.279	13.9	39.19	4.735	9.923	23.1	22.81	8.82	28.85	15.45	13.93
Be	2.544	1.823	1.887	0.5583	1.544	1.479	1.458	1.86	2.158	1.782	1.984	2.304	3.338	2.248	3.217	1.711	2.279
B	4.653	5.053	5.627	5.87	5.893	6.037	6.03	6.367	5.867	6.383	6.547	6.273	7.297	6.147	5.82	5.75	5.937
Sc	9.896	13.72	6.353	7.024	8.993	6.849	5.866	10.84	11.79	4.3	7.104	9.462	14.08	13.37	5.222	6.125	19.14
V	134.4	164.8	9.201	60.38	103.8	148.6	105.7	93.93	178.8	12.75	20.44	122.9	141.7	4.511	3.98	2.38	2.723
Cr	145.4	139.4	16.09	123.6	134.7	139.5	248.5	199.6	119.8	11.83	26.89	150.6	145	14.8	7.327	20.31	15.14
Co	17.31	28.49	6.23	8.213	9.968	13.14	19.08	13.1	20.29	2.901	17.25	16.18	15.05	3.146	2.022	1.494	6.787
Ni	83.95	97.31	10.58	31.19	62.47	87.28	124.2	66.02	101.9	6.021	15.62	99.27	86.07	6.076	8.058	7.725	4.955
Cu	141.9	346.6	62.67	3552	395.9	288.2	274.7	56.52	74.05	439.7	261.7	57.23	33.25	25.54	77.94	35.04	446.4
Zn	1149	4191	21.44	3872	7467	5166	8191	39.26	1333	2213	93.37	42.56	67.57	75.57	253.4	70.22	33.44
Ga	16.97	18.49	16.23	15.11	14.93	16.25	13.32	14.8	21.07	21.19	30.57	14.46	23.4	22.02	21.3	19.73	33.5
Ge	3.979	5.152	2.72	7.124	5.51	5.143	5.132	3.677	5.105	4.86	6.984	3.426	5.066	4.682	3.317	2.839	4.074
As	2.155	2.622	1.885	2.084	2.077	2.286	3.691	2.302	2.039	2.485	1.762	1.924	2.292	2.112	1.832	3.674	2.375
Se	1.235	1.745	1.801	8.881	1.236	1.277	1.221	1.15	1.402	3.801	2.452	1.161	1.344	1.878	2.293	2.132	3.485
Rb	107.8	82.24	47.13	57.48	122.5	127.6	116.7	117.9	66.85	89.97	33.13	40.29	59.39	103.9	63.73	109.1	17.85
Sr	12.47	18.27	81.82	9.278	14.09	15.07	12.48	25.91	12.64	15.69	16.36	58.82	13.09	219.9	73.56	32.48	29.94
Y	18.7	23.28	47.34	14.17	20.49	12.51	16.77	21.07	27.72	66.32	49.37	23.85	33.65	58.17	73.51	62.46	61.8
Zr	154	147.2	282.1	133.3	167.5	150	185.8	220.4	173.8	385.3	362.4	157.6	208.5	289.3	375.5	343.4	390.6
Nb	11.28	12.73	9.431	6.693	10.46	13.07	9.707	10.52	14.96	13.67	13.52	10.44	14.29	11.73	13.35	12.42	14.33
Mo	0.9016	1.408	1.091	1.476	1.095	2.211	2.038	1.061	1.15	1.575	2.345	1.764	3.951	1.107	4.398	2.128	2.456
Ag	2.102	1.954	0.266	1.144	1.297	1.546	0.5444	0.2364	1.126	0.4079	0.435	0.1907	0.2302	0.2585	0.3733	0.4793	0.5663
Cd	2.32	20.79	1.422	25.72	30.97	5.932	23.69	1.088	4.68	10.35	1.781	0.8214	1.069	1.631	2.687	1.799	2.041
Sn	24.55	27.59	3.421	9.789	13.53	52.41	27.23	8.472	30.71	9.105	9.104	2.357	3.891	4.5	4.921	6.013	8.195
Sb	0.5206	0.6447	0.1916	0.2626	0.3717	0.4057	0.939	0.5454	0.3807	0.2581	0.317	0.3021	0.3624	0.3216	0.2501	0.8689	0.1723
Te	1.398	3.092	0.7188	1.685	1.031	1.248	1.764	0.8996	1.02	1.1	1.088	1.109	1.099	0.577	0.3351	0.5654	0.8776
Cs	3.341	4.07	1.304	1.618	3.58	3.813	2.688	2.563	2.111	1.985	1.103	3.224	2.442	1.822	3.419	2.907	1.154
Ba	537.7	522.6	292.2	260.4	264.7	504.2	373.5	592.1	534.2	941.1	925.7	157.9	463.8	1366	660.8	1205	999
La	22.36	24.29	11.71	14.12	22.16	24.19	21.68	28.2	29.73	30.06	29.09	24.25	36.63	22.44	25.35	24.52	17.14
Ce	47.37	52.07	26.21	29.52	46.87	53.4	45.57	57.36	63.95	68.44	67.66	54.13	78.78	49.28	64.52	52.38	44.52
Pr	5.505	6.243	3.383	3.479	5.486	5.653	5.189	6.627	7.352	8.656	8.313	6.269	9.285	6.262	7.728	7.165	5.936
Nd	21.16	24.27	14.28	13.09	20.85	21.47	19.68	25.08	28.03	37.07	35.68	24.27	36.68	26.19	34.4	31.27	26.62
Sm	4.154	4.828	3.603	2.453	4.028	3.898	3.791	4.864	5.623	9.114	8.308	4.809	7.588	6.514	8.999	7.889	7.192
Eu	1.096	1.054	0.7542	0.5503	1.641	0.9856	0.9109	1.103	1.309	1.15	1.816	0.9993	1.48	1.995	2.374	2.614	1.62
Gd	4.157	4.883	5.451	2.563	3.977	3.63	3.754	4.766	5.653	10.84	9.547	4.77	7.408	8.411	11.33	9.749	9.294
Tb	0.6225	0.7457	1.092	0.4247	0.6126	0.4947	0.5717	0.6972	0.8728	1.887	1.58	0.7225	1.075	1.449	1.968	1.714	1.78
Dy	3.612	4.449	7.776	2.617	3.757	2.69	3.357	3.968	5.204	12.34	9.978	4.259	6.381	9.65	12.82	11.58	12.5
Ho	0.7441	0.9241	1.818	0.5534	0.7953	0.53	0.6817	0.8086	1.068	2.694	2.117	0.8838	1.316	2.17	2.786	2.545	2.802
Er	2.132	2.73	5.655	1.634	2.3	1.474	1.976	2.362	3.107	8.043	6.108	2.491	3.845	6.601	8.362	7.642	8.505
Tm	0.3289	0.41	0.8955	0.2508	0.3549	0.2151	0.2986	0.354	0.4619	1.234	0.8799	0.3768	0.5736	0.9835	1.27	1.173	1.287
Yb	2.125	2.638	5.803	1.615	2.246	1.343	1.871	2.367	3.038	8.003	5.498	2.369	3.706	6.461	8.363	7.706	8.565
Lu	0.3282	0.3967	0.8973	0.2461	0.352	0.2048	0.2785	0.3661	0.4573	1.194	0.8164	0.3521	0.5649	0.9911	1.275	1.181	1.316
Hf	3.973	3.902	7.14	3.06	4.417	4.036	4.78	5.471	4.614	9.705	9.356	4.009	5.335	7.432	9.318	8.606	9.97
Ta	0.769	0.8602	0.6017	0.4624	0.7111	0.8593	0.6559	0.6809	0.9398	0.8002	0.8059	0.6763	0.9041	0.6751	0.7567	0.6968	0.7882
W	4.441	3.98	1.749	2.7	3.91	4.201	2.667	3.04	5.367	2.911	4.768	2.19	2.79	1.229	1.046	4.484	3.875
Au	5.494	7.2	5.096	10.78	12.31	6.187	10.63	5.721	5.474	9.662	10.78	33.93	6.017	5.904	6.278	8.534	8.225
Hg	0.7186	0.8364	0.2796	0.8642	1.896	1.098	0.987	0.4286	0.5945	0.7264	0.5652	0.4906	0.504	0.2573	0.5212	0.3521	0.3269
Tl	0.7557	0.8072	0.3267	0.3884	1.209	0.8931	0.6599	0.7997	0.6019	0.7696	0.2946	0.531	1.309	0.6851	1.296	1.233	0.3913
Pb	1363	87.8	5.899	11.97	24.15	3220	28.49	31.28	615.2	9.312	2.708	7.911	11.47	11.96	19.05	77.74	3.511
Bi	0.5643	2.74	1.105	18.85	2.57	0.3204	2.947	0.4203	2.618	3.332	0.9403	0.4585	0.272	0.3706	0.8241	0.1217	1.126
Th	9.829	10.79	7.931	6.977	9.69	11.52	10.26	10.97	13.4	10.54	8.806	10.16	12.29	8.781	9.269	8.58	6.885
U	2.875	3.572	2.604	2.19	3.278	3.612	3.063	3.353	4.047	3.196	2.861	3.159	3.68	2.696	3.043	2.755	2.852
∑REE	115.69	129.93	89.33	73.12	115.43	120.18	109.61	138.92	155.86	200.73	187.39	130.95	195.31	149.40	191.55	169.13	149.08
Cu/Zn	0.12	0.08	2.92	0.92	0.05	0.06	0.03	1.44	0.06	0.20	2.80	1.34	0.49	0.34	0.31	0.50	13.35
Rb/Zr	0.70	0.56	0.17	0.43	0.73	0.85	0.63	0.53	0.38	0.23	0.09	0.26	0.28	0.36	0.17	0.32	0.05
Rb/Sr	8.64	4.50	0.58	6.20	8.69	8.47	9.35	4.55	5.29	5.73	2.03	0.68	4.54	0.47	0.87	3.36	0.60
Ce/La	2.12	2.14	2.24	2.09	2.12	2.21	2.10	2.03	2.15	2.28	2.33	2.23	2.15	2.20	2.55	2.14	2.60
Ni/Co	4.85	3.42	1.70	3.80	6.27	6.64	6.51	5.04	5.02	2.08	0.91	6.14	5.72	1.93	3.99	5.17	0.73
U/Th	0.29	0.33	0.33	0.31	0.34	0.31	0.30	0.31	0.30	0.30	0.32	0.31	0.30	0.31	0.33	0.32	0.41
V/Cr	0.92	1.18	0.57	0.49	0.77	1.07	0.43	0.47	1.49	1.08	0.76	0.82	0.98	0.30	0.54	0.12	0.18

Notes: LOI = loss on ignition; Mg^# = [MgO/(MgO + FeO × 100]; A/CNK = molecular Al₂O₃/(CaO + Na₂O + K₂O). Major oxides are in wt%; trace elements and REE are in ppm.

and

Table A3. Whole-rock geochemical compositions of volcanic rocks from the Donggou Pb–Zn deposit.

Sample	QZ001-HX3	ZK002-HX1	ZK002-HX3	ZK002-HX9	ZK004-HX3	ZK004-HX4	ZK004-HX15	ZK001-HX5
SiO2	67.95	54.00	51.69	67.40	73.31	62.30	67.38	70.82
Al2O3	15.41	13.81	15.78	12.53	12.92	13.19	12.37	11.58
Fe2O3	1.15	2.45	1.08	1.72	0.46	1.37	0.71	1.15
FeO	3.00	4.17	6.76	6.13	3.72	8.31	4.47	3.06
CaO	0.28	6.01	6.32	2.10	0.41	3.77	2.36	2.05
MgO	2.51	7.62	6.37	0.52	0.87	2.08	3.57	2.84
K2O	5.74	1.21	2.65	0.90	4.16	1.35	3.64	1.38
Na2O	0.11	4.64	2.27	5.01	0.61	3.13	0.35	3.21
TiO2	0.35	1.00	1.02	0.51	0.32	1.12	0.66	0.27
P2O5	0.03	0.44	0.14	0.07	0.03	0.42	0.16	0.03
MnO	0.15	0.12	0.19	0.23	0.09	0.17	0.07	0.16
LOI	3.32	4.18	5.50	2.45	3.03	2.44	3.92	3.19
Total	100.01	99.65	99.76	99.57	99.93	99.67	99.66	99.73
Li	32.2	14.69	28.23	7.883	7.558	12.46	23.1	20.76
Be	2.964	1.897	1.347	1.643	2.383	1.131	2.304	2.174
B	5.343	5.697	5.993	6.033	6.107	5.93	6.273	5.923
Sc	4.204	4.662	17	10.72	6.115	12.81	9.462	5.197
V	19.2	152.2	206.2	15.42	4.416	48.42	122.9	1.632
Cr	94.73	339.8	100.7	34.16	24.16	90.99	150.6	8.875
Co	2.883	31.61	33.6	1.78	1.899	12.34	16.18	1.246
Ni	45.32	178.4	36.87	8.358	9.675	19.63	99.27	5.926
Cu	47.67	27.82	51.06	10.18	14.9	11.43	57.23	19.73
Zn	102.1	57.07	83.46	96.63	39.52	92.87	42.56	134.9
Ga	29.23	20.64	18.73	23.88	26.87	18.83	14.46	18.26
Ge	2.849	5.191	4.67	5.349	3.269	5.872	3.426	3.51
As	1.951	2.161	1.984	2.187	2.193	1.94	1.924	1.892
Se	2.236	1.191	1.326	1.93	2.319	1.378	1.161	2.11
Rb	57.33	55.33	100.2	12.48	148.6	22.81	40.29	39.49
Sr	24.68	1282	295.5	62.3	21.92	128.7	58.82	158.5
Y	67.98	21.19	34.1	61.06	75.03	35.98	23.85	70.75
Zr	535.9	189.2	166.8	326.8	444.4	153.5	157.6	364.3
Nb	19.25	8.26	6.267	11.89	15.97	7.884	10.44	13.06
Mo	3.02	0.7321	1.164	2.281	4.352	1.019	1.764	2.252
Ag	0.5652	0.1685	0.1868	0.2904	0.3682	0.1522	0.1907	0.3167
Cd	2.511	0.873	0.9268	1.708	2.33	0.9337	0.8214	2.255
Sn	14.13	1.616	2.165	3.596	5.468	4.329	2.357	3.272
Sb	0.3123	0.3821	0.2927	0.2536	0.2693	0.2126	0.3021	0.1729
Te	0.5175	0.5595	0.3471	0.3014	0.7958	0.5009	1.109	0.6697
Cs	4.628	7.995	2.279	2.482	3.057	4.476	3.224	2.107
Ba	776.6	857.7	487.9	272.1	357.9	292.8	157.9	434.6
La	30.62	69.74	13.3	20.87	26.35	14.84	24.25	26.54
Ce	75.06	145.9	31.62	42.48	60.06	37.44	54.13	62.49
Pr	10.17	17.39	4.08	6.677	7.765	4.47	6.269	7.972
Nd	43.94	67.62	18.11	29.85	33.61	20.05	24.27	34.67
Sm	11.27	10.65	4.601	7.766	8.285	5.098	4.809	8.952
Eu	2.048	2.741	1.515	2.299	1.411	1.677	0.9993	2.086
Gd	13.39	8.219	5.665	9.532	10.81	6.353	4.77	10.94
Tb	2.339	0.9455	0.9674	1.68	1.973	1.045	0.7225	1.866
Dy	14.67	4.564	6.132	10.99	13.43	6.513	4.259	12.21
Ho	3.026	0.848	1.312	2.403	2.991	1.391	0.8838	2.683
Er	8.707	2.22	3.79	7.339	9.139	3.97	2.491	8.052
Tm	1.282	0.3175	0.5697	1.143	1.365	0.5862	0.3768	1.236
Yb	8.397	1.903	3.595	7.648	9.048	3.776	2.369	8.202
Lu	1.336	0.2897	0.5398	1.211	1.376	0.5721	0.3521	1.252
Hf	13.89	4.384	3.992	8.386	11.19	3.94	4.009	8.955
Ta	1.067	0.4911	0.3778	0.6998	0.8935	0.4863	0.6763	0.7394
W	2.713	1.165	0.8287	1.869	3.377	1.451	2.19	1.067
Au	9.376	4.509	3.004	6.42	7.022	3.928	33.93	5.856
Hg	0.4948	0.2663	0.2224	0.3389	0.346	0.266	0.4906	0.3865
Tl	1.095	0.5048	0.6727	0.2223	1.382	0.343	0.531	0.752
Pb	36.16	7.761	9.836	8.062	6.118	6.912	7.911	6.862
Bi	0.0962	0.0809	0.1072	0.1875	0.5738	0.1307	0.4585	0.3432
Th	11.52	9.182	3.033	7.652	11.16	4.591	10.16	9.363
U	4.25	3.045	1.112	2.555	3.59	1.431	3.159	2.939
A/CNK	2.51	1.16	1.40	1.57	2.49	1.60	1.95	1.74
Mg#	50	59	52	14	29	30	49	51
∑REE	226	333	96	152	188	108	131	189
Nb/Ta	18.04	16.82	16.59	16.99	17.87	16.21	15.44	17.66
Th/La	0.38	0.13	0.23	0.37	0.42	0.31	0.42	0.35
Th/Nb	0.60	1.11	0.48	0.64	0.70	0.58	0.97	0.72
Th/Ta	10.80	18.70	8.03	10.93	12.49	9.44	15.02	12.66
Sm/Nd	0.26	0.16	0.25	0.26	0.25	0.25	0.20	0.26
Lu/Hf	0.10	0.07	0.14	0.14	0.12	0.15	0.09	0.14
Rb/Sr	2.32	0.04	0.34	0.20	6.78	0.18	0.68	0.25
Th/Ce	0.15	0.06	0.10	0.18	0.19	0.12	0.19	0.15

Notes: LOI = loss on ignition. Major oxides are in wt%; trace elements and REE are in ppm.

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6.3. In Situ Trace Element, SEM–EDS and Sulfur Isotope Analysis

In situ sulfide trace element analyses were conducted at the State Key Laboratory for Critical Mineral Research and Exploration (Institute of Geochemistry, Chinese Academy of Sciences) using a GeoLasPro 193 nm ArF excimer laser ablation system (Coherent Corp., Saxonburg, PA, USA) coupled with an Agilent 7700× ICP-MS. NIST SRM 610 Agilent Technologies, Santa Clara, CA, USA) was used as the external standard for trace element calibration, and NIST SRM 612 was used as a quality control monitor. Matrix matching was achieved using silicate glass standards with ²⁹Si as the internal standard for signal normalization. The laser was operated at a spot size of 26 μm, a repetition rate of 5 Hz, and an energy density of 3 J/cm², with helium as the carrier gas at a flow rate of 350 mL/min. Prior to analysis, the ICP-MS was tuned with SRM610 to achieve optimal sensitivity (U/Th ≈ 1) and a low oxide production rate (ThO/Th < 0.3%). Instrument drift was corrected by analyzing NIST SRM 610 every 10–15 sample analyses using linear interpolation. Offline data reduction was performed using ICPMSDataCal v. 8.6 software. The analytical precision for trace elements in sulfides was better than 10%, with detection limits in the range of 10⁻⁹. The results are presented in

Table A4. Trace element compositions (ppm) of ore minerals from the Donggou Pb–Zn deposit.

Mineral		Ti	Cr	Mn	Fe	Co	Ni	Cu	Zn	Ga	Ge	As
Sp1 (n = 52)	Min	3.15	1.27	170.29	47,308.55	0.14	0.67	46.11	212,344.72	0.37	0.44	3.07
	Max	1882.82	2.43	5811.27	431,509.08	238.16	58.30	15,086.09	617,250.06	31.39	7.21	38,298.58
	Average	86.76	1.83	1924.30	78,355.93	7.10	3.65	1866.65	575,643.24	8.36	1.30	3331.99
	Median	4.53	1.78	1593.59	59,959.22	0.54	0.71	237.21	596,685.46	3.27	0.83	6.61
Py (n = 46)	Min	4.10	1.71	0.70	200,223.90	0.05	0.56	0.26	0.55	0.02	0.42	1.62
	Max	353.67	24.17	1953.16	465,421.92	918.09	918.10	238,507.38	278,210.46	177.50	39.08	382,691.87
	Average	17.47	6.65	175.65	377,179.64	42.72	62.79	68,824.47	19,555.96	4.47	3.05	20,609.39
	Median	9.37	2.45	5.89	432,103.71	2.80	25.55	35.34	383.02	0.42	1.35	246.20
Ccp (n = 45)	Min	6.13	1.28	2.67	271,567.99	0.05	0.73	10,798.73	347.67	0.17	0.47	1.90
	Max	14.05	4.82	328.45	514,129.50	2.51	21.48	346,924.78	83,844.32	1.59	3.87	2.72
	Average	9.43	2.74	41.37	326,279.69	0.57	3.42	305,554.38	10,020.05	0.60	2.12	2.31
	Median	8.94	2.56	4.83	318,601.34	0.07	1.23	328,880.02	522.53	0.48	2.14	2.31
Mineral		Se	Mo	Ag	Cd	In	Sn	Sb	Au	Tl	Pb	Bi
Sp1 (n = 52)	Min	5.25	0.04	0.95	592.36	15.34	0.55	1.86	0.04	0.15	1.76	0.28
	Max	59.00	54.53	736.38	1795.06	115.57	43.14	131.20	5.55	3.54	236,778.06	867.65
	Average	12.14	3.87	36.71	1452.52	53.16	6.52	14.63	0.50	0.90	5573.95	24.95
	Median	9.00	0.25	15.83	1482.86	59.41	2.94	8.11	0.07	0.59	15.98	2.22
py (n = 46)	Min	6.31	0.06	0.07	0.23	0.00	0.11	0.43	0.07	0.12	0.17	0.29
	Max	54.90	73.89	181.01	601.16	44.95	592.23	281.31	1.97	1.20	66,553.92	317.92
	Average	15.06	8.48	47.14	71.77	9.02	155.46	15.14	0.34	0.42	2080.61	15.99
	Median	12.32	0.33	1.18	3.24	3.84	0.75	4.48	0.20	0.32	12.61	4.11
Ccp (n = 45)	Min	10.45	0.09	154.76	1.17	8.00	66.19	5.24	0.09	0.11	5.55	0.59
	Max	26.87	0.09	235.49	211.33	57.01	767.93	47.48	2.66	1.56	84,291.46	400.53
	Average	14.50	0.09	181.33	27.42	22.90	593.39	17.02	0.54	0.72	7864.75	40.97
	Median	11.33	0.09	175.05	3.24	15.31	652.08	13.58	0.27	0.61	15.21	2.61

Notes: Sp1 = first-generation sphalerite; Py = pyrite; Ccp = chalcopyrite; n = number of analyses; Min = minimum; Max = maximum; Average = arithmetic mean; Median = median value. All values are in ppm. Analyses were performed by LA-ICP-MS.

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Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) were performed in the same laboratory using a thermal field emission scanning electron microscope (JEOL JSM-7800F, JEOL, Tokyo, Japan) equipped with MonoCL4 cathodoluminescence spectrometer (Gatan, Pleasanton, CA, USA) and a TEAM Apex XL energy dispersive spectrometer (EDAX, Mahwah, NJ, USA). The operating conditions included an accelerating voltage of 25 kV, a beam current of 10 nA, and a spot diameter of 10 μm. Prior to analysis, samples were cleaned with anhydrous ethanol and carbon-coated. Semi-quantitative spectral analysis, including signal curve selection and background subtraction, was carried out using the instrument’s built-in software.

Sulfur isotope compositions of pyrite, chalcopyrite, and sphalerite were also determined at the same laboratory using LA-MC-ICP-MS. The system comprised an ASI laser ablation unit coupled with a Nu Plasma 1700 MC-ICP-MS (Nu Instruments, Wrexham, UK). Analyses were performed in single-spot ablation mode. The laser spot size was set to 26 μm in diameter, and the analytical frequency was 3 Hz. The energy of the laser beam was 36 J/cm². Argon (300 mL/min) and helium (1000 mL/min) were used as carrier gases and mixed with the ablated aerosol prior to ICP introduction. Each measurement cycle included approximately 30 s of background acquisition and 50 s of signal collection for ³⁴S and ³²S isotopes. A pyrite pressed-powder tablet (PPP-1, δ³⁴S = −0.1 ± 0.2‰) was used as the in-house reference material for drift correction and reproducibility monitoring for all analyzed sulfide minerals (pyrite, chalcopyrite, and sphalerite). Although PPP-1 is pyrite matrix, matrix effects among different sulfides in LA-MC-ICP-MS analysis are considered limited, supporting its use as a common internal standard. A standard-sample bracketing protocol was adopted, with NBS-123 (δ³⁴S = +17.1‰) and IAEA-S-1 (δ³⁴S = −0.3‰) as international reference materials to anchor the V-CDT scale. The δ³⁴S values were calculated as δ³⁴S = [(³⁴S/³²S)Sample/(³⁴S/³²S)V-CDT − 1] × 1000, where (³⁴S/³²S)V-CDT is taken as 0.044163. Data reduction was performed using the Nu Instruments software package. The detection limit for ³²S was calculated as three times the standard deviation of the background signal (3σ). Reproducibility was monitored by repeated analyses of PPP-1, yielding an external precision better than ±0.2‰, and the measured values of NBS-123 and IAEA-S-1 agreed with their recommended values within ±0.2‰. All δ³⁴S values are reported relative to the V-CDT scale, and the results are presented in

Table A5. Sulfur isotope compositions (δ³⁴S) of ore minerals from the Donggou Pb–Zn deposit.

Sample No	Mineralization Type	Mineral	δ34 SV-CDT (‰)	Sample No	Mineralization Type	Mineral	δ34 SV-CDT (‰)	Sample No	Mineralization Type	Mineral	δ34 SV-CDT (‰)
z00K4-S1-1	Brecciated	Sphalerite	1.94	zk003-S3-1	Veinlet	Pyrite	4.54	zk002-s1-1	Massive	Chalcopyrite	3.56
z00K4-S1-2	Brecciated	Sphalerite	2.42	zk003-S3-2	Veinlet	Pyrite	3.23	zk002-s1-2	Massive	Chalcopyrite	3.65
z00K4-S1-3	Brecciated	Sphalerite	2.31	zk003-S3-3	Veinlet	Pyrite	3.95	zk002-s1-3	Massive	Chalcopyrite	3.86
z00K4-S1-4	Brecciated	Sphalerite	1.58	zk003-S3-4	Veinlet	Pyrite	6.57	zk002-s1-4	Massive	Chalcopyrite	3.33
z00K4-S1-5	Brecciated	Sphalerite	1.98	zk003-S3-5	Veinlet	Pyrite	6.00	zk002-s1-5	Massive	Chalcopyrite	3.53
z00K4-S1-6	Brecciated	Sphalerite	1.56	zk003-S3-6	Veinlet	Pyrite	4.71	zk002-s1-6	Massive	Chalcopyrite	2.78
z00K4-S1-7	Brecciated	Sphalerite	1.95	zk003-S3-7	Veinlet	Pyrite	5.50	zk002-s1-7	Massive	Chalcopyrite	2.86
z00K4-S1-8	Brecciated	Sphalerite	1.51	zk003-S3-8	Veinlet	Pyrite	12.01	zk002-s1-8	Massive	Chalcopyrite	2.66
zk001-S1-1	Massive	Sphalerite	2.26	zk003-S3-9	Veinlet	Pyrite	8.00	zk002-s1-9	Massive	Chalcopyrite	3.04
zk001-S1-2	Massive	Sphalerite	2.08	zk003-S1-1	Massive	Pyrite	1.99	zk003-s1-1	Massive	Chalcopyrite	1.13
zk001-S1-3	Massive	Sphalerite	1.63	zk003-S1-2	Massive	Pyrite	2.36	zk003-s1-2	Massive	Chalcopyrite	1.26
zk001-S1-4	Massive	Sphalerite	1.85	zk003-S1-3	Massive	Pyrite	1.67	zk003-s1-3	Massive	Chalcopyrite	1.50
zk001-S1-5	Massive	Sphalerite	1.77	zk003-S1-4	Massive	Pyrite	2.80	zk003-s1-4	Massive	Chalcopyrite	1.77
zk001-S1-6	Massive	Sphalerite	1.72	zk003-S1-5	Massive	Pyrite	2.60	zk001-s2-1	Veinlet	Pyrrhotite	2.79
zk001-S1-7	Massive	Sphalerite	1.95	zk003-S1-6	Massive	Pyrite	2.49	zk001-s2-2	Veinlet	Pyrrhotite	1.99
zk001-S1-8	Massive	Sphalerite	1.83	zk003-S1-7	Massive	Pyrite	2.89	zk001-s2-3	Veinlet	Pyrrhotite	3.25
zk002-S1-1	Massive	Sphalerite	2.95	zk004-s1-1	Brecciated	Chalcopyrite	1.61	zk001-s2-4	Veinlet	Pyrrhotite	2.36
zk002-S1-2	Massive	Sphalerite	3.47	zk004-s1-2	Brecciated	Chalcopyrite	3.11	zk001-s2-5	Veinlet	Pyrrhotite	2.72
zk002-S1-3	Massive	Sphalerite	3.18	zk004-s1-3	Brecciated	Chalcopyrite	2.10	zk003-s2-1	Brecciated	Pyrrhotite	2.90
zk002-S1-4	Massive	Sphalerite	3.24	zk004-s1-4	Brecciated	Chalcopyrite	1.81	zk003-s2-2	Brecciated	Pyrrhotite	2.02
zk002-S1-5	Massive	Sphalerite	3.50	zk004-s1-5	Brecciated	Chalcopyrite	2.63	zk003-s2-3	Brecciated	Pyrrhotite	2.16
zk002-S1-6	Massive	Sphalerite	2.59	zk004-s1-6	Brecciated	Chalcopyrite	2.67	zk003-s2-4	Brecciated	Pyrrhotite	1.70
zk002-S1-7	Massive	Sphalerite	2.36	zk004-s1-7	Brecciated	Chalcopyrite	4.03	zk003-s2-5	Brecciated	Pyrrhotite	2.71
zk002-S1-8	Massive	Sphalerite	2.63	zk004-s1-8	Brecciated	Chalcopyrite	1.23	zk003-s2-6	Brecciated	Pyrrhotite	2.96
zk003-S1-1	Massive	Sphalerite	1.54	zk001-s1-1	Massive	Chalcopyrite	2.56	zk003-s2-7	Brecciated	Pyrrhotite	1.93
zk003-S1-2	Massive	Sphalerite	1.84	zk001-s2-1	Veinlet	Chalcopyrite	2.68	zk003-s3-1	Veinlet	Pyrrhotite	2.94
zk003-S1-3	Massive	Sphalerite	2.02	zk001-s2-2	Veinlet	Chalcopyrite	3.47	zk003-s3-2	Veinlet	Pyrrhotite	3.33
zk003-S1-4	Massive	Sphalerite	7.51	zk001-s2-3	Veinlet	Chalcopyrite	2.27	zk003-s3-3	Veinlet	Pyrrhotite	2.29
zk003-S1-5	Massive	Sphalerite	1.96	zk003-s2-1	Brecciated	Chalcopyrite	3.53	zk002-s1-1	Massive	Pyrrhotite	−4.69
zk002-S2-1	Massive	Pyrite	3.99	zk003-s2-2	Brecciated	Chalcopyrite	3.77	zk002-s1-2	Massive	Pyrrhotite	−3.55
zk002-S2-2	Massive	Pyrite	4.40	zk003-s2-3	Brecciated	Chalcopyrite	3.64	zk002-s1-3	Massive	Pyrrhotite	−3.94
zk002-S2-3	Massive	Pyrite	4.81	zk003-s2-4	Brecciated	Chalcopyrite	3.60	zk002-s1-4	Massive	Pyrrhotite	−4.17
zk002-S2-4	Massive	Pyrite	4.56	zk003-s2-5	Brecciated	Chalcopyrite	4.34	zk002-s1-5	Massive	Pyrrhotite	−4.36
zk002-S2-5	Massive	Pyrite	4.97	zk003-s2-6	Brecciated	Chalcopyrite	3.56	zk002-s1-6	Massive	Pyrrhotite	−3.90
zk002-S2-6	Massive	Pyrite	4.54	zk003-s2-7	Brecciated	Chalcopyrite	4.11	zk002-s1-7	Massive	Pyrrhotite	−4.56
zk002-S2-7	Massive	Pyrite	5.58	zk003-s3-1	Veinlet	Chalcopyrite	3.90	zk002-s1-8	Massive	Pyrrhotite	−4.78
zk002-S2-8	Massive	Pyrite	5.06	zk003-s3-2	Veinlet	Chalcopyrite	4.80	zk003-s1-1	Massive	Pyrrhotite	−5.98
zk002-S2-9	Massive	Pyrite	5.14	zk003-s3-3	Veinlet	Chalcopyrite	3.38
zk002-S2-10	Massive	Pyrite	5.16	zk003-s3-4	Veinlet	Chalcopyrite	4.13
zk002-S2-11	Massive	Pyrite	4.48	zk003-s3-5	Veinlet	Chalcopyrite	8.50

Notes: δ³⁴S values are reported relative to V-CDT (Vienna-Canyon Diablo Troilite). Mineralization types: Massive = massive sulfide ore; Veinlet = veinlet-disseminated ore; Brecciated = brecciated ore.

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7. Results

7.1. Zircon U-Pb Geochronology

Zircon U-Pb dating was performed on the host rock (andesite) overlying the ore body. The zircons are transparent, light yellow to colorless, and appear as euhedral, long prismatic crystals with clear oscillatory zoning in CL images (Figure 8a), with Th/U ratios ranging from 0.4 to 0.8, indicating a magmatic origin. Based on CL imaging, analytical spots were selected on oscillatory-zoned domains free of inclusions and fractures. A total of 30 spots were analyzed. Two spots (No. 2 and No. 4) were rejected due to low concordance (<90%). The remaining 28 spots yielded a concordia age of 437.1 ± 1.9 Ma (MSWD = 0.17, n = 28) (Figure 8b, Table A1). Common Pb correction was applied using the ²⁰⁴Pb method with initial Pb isotopic ratios from [20]. The age results indicate that the andesite immediately adjacent to the ore body was formed in the Early Silurian.

7.2. Whole-Rock Geochemistry

Major and trace element analyses were conducted on strata from drill holes in the mining area, classified by lithology (mainly two types: the first type is clastic sedimentary rocks, and the second type is volcanic rocks) (Table A2 and Table A3). The results show that the volcanic rocks have SiO₂ contents ranging from 51.69% to 73.31%, with an average of 64.36%; Al₂O₃ contents range from 11.58% to 15.78%, averaging 13.45%; total alkali (K₂O + Na₂O) contents range from 3.99% to 5.90%, averaging 5.05%, with Na₂O contents ranging from 0.11% to 5.01% (averaging of 2.42%) and K₂O contents varying widely from 0.90% to 5.74% (averaging 2.63%). P₂O₅ contents range from 0.03% to 0.44% (averaging 0.17%), MgO contents range from 0.52% to 7.62% (averaging 3.30%), and Mg^# values range from 10.82 to 68.07 (averaging 44.63). In the Nb/Y–Zr/TiO₂ diagram (Figure 9), the samples partially plot in the andesite field and partially in the dacite and rhyolite fields. The A/CNK values of the samples range from 0.69 to 2.23, with an average of 1.29. Comprehensive major element analysis shows that the volcanic rocks in the Donggou mining area are metaluminous to weakly peraluminous rocks.

The SiO₂ content of the siliciclastic rocks ranges from 59.58% to 79.01%, with an average of 67.77%. The Al₂O₃ content varies between 7.81% and 16.01%, averaging 12.35%. The total alkali (K₂O + Na₂O) content ranges from 1.91% to 7.52%, with an average of 4.19%, within which the Na₂O content ranges from 0.07% to 3.94%, averaging 0.74%, and the K₂O content shows a wide range from 1.74% to 6.03%, averaging 3.45%. The P₂O₅ content ranges from 0.02% to 0.18%, averaging 0.10%, and the MgO content ranges from 0.50% to 5.60%, averaging 1.80%. The FeO^T content ranges from 2.25% to 13.04%, averaging 7.07%. The CaO content is generally low, ranging from 0.08% to 4.03%, with an average of 0.88%.

Both siliciclastic sedimentary rocks and volcanic rocks are enriched in large ion lithophile elements (LILEs) and depleted in Nb, P, Sr, and Ti. Ba enrichment or depletion varies among some samples, with mineralized samples generally showing Ba enrichment (Figure 10a). The chondrite-normalized rare earth element (REE) patterns (Figure 10b) display consistent distribution curves for all samples, indicating that the volcanic rocks and siliciclastic sedimentary rocks share a common provenance.

7.3. Sulfur Isotopic Composition of Minerals

The LA-MC-ICP-MS sulfur isotopic compositions of ore sulfides are presented in Table A4. The δ³⁴S values of all analyzed sulfides exhibit a wide range from −5.98‰ to +12.01‰, with negative values mainly occurring in pyrrhotite from sample ZK002-S1. Excluding the sulfur isotopic data of pyrrhotite from this sample, the δ³⁴S values of the remaining minerals range from 1.13‰ to 12.01‰. The δ³⁴S values increase progressively from pyrrhotite to sphalerite, chalcopyrite, and pyrite (Figure 11a), with ranges and averages of −5.98‰ to 3.33‰ (avg. −0.08‰) for pyrrhotite, 1.50‰ to 7.51‰ (avg. 2.38‰) for sphalerite, 1.13‰ to 8.50‰ (avg. 3.14‰) for chalcopyrite, and 1.67‰ to 12.01‰ (avg. 4.59‰) for pyrite. Different ore types show certain variations in sulfur isotopic compositions; for instance, the δ³⁴S values of sphalerite, chalcopyrite, and pyrite in massive ores are significantly lower than those in the corresponding minerals from disseminated ores (Figure 11b).

7.4. Trace Element Compositions of Minerals

7.4.1. Sphalerite

The LA-ICP-MS analytical results for sphalerite (Sp1, 52 spots) are presented in Table A5 and Figure 12. The trace element composition is characterized by enrichment in Fe, Mn, Co, Cu, Se, Ag, Cd, In, and Sn and depletion in Ni, Ga, Ge, As, Mo, Sb, Au, Ti, Pb, and Bi. Concentrations of Ge, Ni, As, Mo, Te, Au, and Ti are mostly below detection limits. The Fe and Zn contents are high, ranging from 4.73% to 43.15% (avg. 7.83%) and 21.23% to 61.70% (avg. 57.56%), respectively. Elevated contents of minor elements Mn (avg. 0.19%), Cd (avg. 0.14%), Cu (avg. 0.19%), and Pb (avg. 0.55%) were also detected. The Co content ranges from 0.13 × 10⁻⁶ to 238.15 × 10⁻⁶, (avg. 7.09 × 10⁻⁶); the Ag content ranges from 0.35 × 10⁻⁶ to 372.85 × 10⁻⁶ (avg. 18.28 × 10⁻⁶); the In content ranges from 15.34 × 10⁻⁶ to 115.57 × 10⁻⁶ (avg. 53.16 × 10⁻⁶); the Sn content ranges from 0.54 × 10⁻⁶ to 43.14 × 10⁻⁶ (avg. 6.52 × 10⁻⁶); and the Ga content ranges from 0.36 × 10⁻⁶ to 31.39 × 10⁻⁶ (avg. 8.36 × 10⁻⁶). Other elements such as Ni, Ge, Au, Mo, Sb, As, Ti, and Bi are present at relatively low levels, with Ni averaging 3.65 × 10⁻⁶ and Ge ranging from 0.43 × 10⁻⁶ to 7.20 × 10⁻⁶ (avg. 1.30 × 10⁻⁶).

7.4.2. Pyrite

The LA-ICP-MS analytical results for pyrite (Py1 and Py2, 46 spots) are presented in Table A5 and Figure 13. Because the two generations are petrographically similar and were not systematically distinguished during the LA-ICP-MS analysis, their data are reported together. Overall, the trace elements are characterized by enrichment in Fe, Mn, Co, Cu, Se, Ag, Cd, In, Sn, Ni, and Pb and depletion in Cr, Ga, Ge, As, Mo, Sb, Au, Tl, and Bi. The concentrations of elements such as Cr, Se, Sn, Ge, As, Mo, Sb, Au, Ti, and Te are mostly below the detection limit.

The Fe and Zn contents are high, ranging from 20.02% to 46.48% (avg. 41.97%) and from 0.0001% to 2.78% (avg. 2.36%), respectively. Elevated contents of minor elements were also detected: Mn (0.70–1953.16 × 10⁻⁶, avg. 187.84 × 10⁻⁶), Cd (0.069–181.92 × 10⁻⁶, avg. 71.77 × 10⁻⁶), Cu (0.0046–1.5%, avg. 0.19%), and Pb (0.0001–6.65%, avg. 0.21%). The Co content ranges from 0.053 × 10⁻⁶ to 918.09 × 10⁻⁶ (avg. 42.72 × 10⁻⁶); Ag from 0.071 × 10⁻⁶ to 181.00 × 10⁻⁶ (avg. 47.13 × 10⁻⁶); In from 0.0049 × 10⁻⁶ to 44.95 × 10⁻⁶ (avg. 9.01 × 10⁻⁶); Sn from 0.113 × 10⁻⁶ to 592.22 × 10⁻⁶ (avg. 115.45 × 10⁻⁶), with pyrite from sample ZK004 showing notably higher Sn concentrations (avg. 468.90 × 10⁻⁶); and Ga from 0.021 × 10⁻⁶ to 177.5 × 10⁻⁶ (avg. 4.46 × 10⁻⁶).

Other elements such as Ni, Ge, Se, Au, Mo, Sb, As, Ti, and Bi are present at relatively low levels: Ni ranges from 0.56 × 10⁻⁶ to 918.10 × 10⁻⁶ (avg. 61.35 × 10⁻⁶), Ge from 0.085 × 10⁻⁶ to 39.07 × 10⁻⁶ (avg. 2.56 × 10⁻⁶), and Se from 6.30 × 10⁻⁶ to 54.90 × 10⁻⁶ (avg. 15.06 × 10⁻⁶).

7.4.3. Chalcopyrite

The LA-ICP-MS analytical results for chalcopyrite (samples collected from drill hole ZK004) are presented in Table A5 and Figure 14. The trace element composition is characterized by enrichment in Fe, Mn, Cu, Se, Ag, Cd, In, Sn, and Pb and depletion in Ga, Ge, As, Mo, Sb, Co, Au, Ni, Tl, and Bi. Concentrations of most elements such as Cr, Sc, Se, As, Te, Ta, and Ti are below detection limits.

The Fe and Cu contents are high, ranging from 27.15% to 51.41% (avg. 32.62%) and 1.07% to 34.69% (avg. 30.55%), respectively. The Zn content varies considerably, ranging from 0.034% to 8.38% (avg. 1.00%). The Mn content ranges from 2.67 × 10⁻⁶ to 328.44 × 10⁻⁶ (avg. 41.37 × 10⁻⁶).

Good data validity was obtained for Bi, Sn, Cd, Ag, In, Ge, and Ga: Cd ranges from 1.16 × 10⁻⁶ to 211.33 × 10⁻⁶ (avg. 27.41 × 10⁻⁶), Ag from 155.88 × 10⁻⁶ to 230.31 × 10⁻⁶ (avg. 180.16 × 10⁻⁶), In from 8.00 × 10⁻⁶ to 57.00 × 10⁻⁶ (avg. 22.89 × 10⁻⁶), Sn from 66.18 × 10⁻⁶ to 767.93 × 10⁻⁶ (avg. 593.38 × 10⁻⁶), Ge from 0.46 × 10⁻⁶ to 3.86 × 10⁻⁶ (avg. 2.12 × 10⁻⁶), and Ga from 0.17 × 10⁻⁶ to 1.59 × 10⁻⁶ (avg. 0.60 × 10⁻⁶).

Other elements such as Co, Ni, and Se are present at relatively low levels. Among 15 analytical spots, Co is below detection in 10 spots, Ni in six spots, and Se in nine spots. The Co content ranges from 0.049 × 10⁻⁶ to 2.50 × 10⁻⁶ (avg. 0.29 × 10⁻⁶); Se from 4.08 × 10⁻⁶ to 30.49 × 10⁻⁶ (avg. 9.73 × 10⁻⁶); and Ni from 0.54 × 10⁻⁶ to 21.47 × 10⁻⁶ (avg. 2.41 × 10⁻⁶).

8. Discussion

8.1. Age Constraint

The precise determination of the mineralization age is a critical aspect of ore deposit research, as it is essential for elucidating ore genesis, identifying ore-controlling factors, synthesizing metallogenic regularities, and guiding exploration and prospecting [26]. To indirectly constrain the mineralization age of the Donggou Pb–Zn deposit, this study conducted zircon U–Pb dating on the overlying wall rock (andesite) immediately adjacent to the massive ore body, yielding a diagenetic age of 437.1 ± 1.9 Ma. Given that the ore body occurs as stratoid lenses at the base of the andesite, this age provides a maximum age constraint (i.e., the mineralization must have occurred no later than 437.1 ± 1.9 Ma). No direct ore mineral geochronology was obtained; thus, the andesite age serves only as an indirect upper bound. This age not only fills a gap in geochronological data for Pb–Zn mineralization associated with the evolution of the Proto-Tethys Ocean in the Qimantagh region, but also provides important constraints on further exploration of regional metallogenic regularities during this period.

Regional geochronological data indicate that Pb–Zn polymetallic mineralization in the Qimantagh region is predominantly concentrated in the Triassic (250–220 Ma), closely associated with magmatic activity during the evolution of the Paleo-Tethys Ocean [1,16], whereas records of Early Paleozoic mineralization events are sparse. Recent regional geochronological studies suggest that granitoids in the East Kunlun–Qimantagh region are mainly distributed in two periods: 435–370 Ma and 245–96 Ma, formed during the post-collisional stages following the closure of the Proto-Tethys and Paleo-Tethys oceans, respectively [14]. The age of 437.1 ± 1.9 Ma for the Donggou deposit coincides with the late-stage northward subduction (450–425 Ma) of the Qimantagh back-arc basin, indicating a spatiotemporal genetic link with the continental arc setting indicated by the andesite. This suggests that the late-stage Proto-Tethys subduction represents an important Pb–Zn metallogenic epoch in this region. This finding challenges the traditional view that Pb–Zn mineralization in the area was primarily confined to the Triassic and offers significant theoretical implications and exploration insights for expanding regional prospecting strategies [5].

8.2. Sources of Sulfur and Metal

The ore minerals of the Donggou deposit are dominated by sulfides such as sphalerite, pyrite, galena, pyrrhotite, chalcopyrite, and arsenopyrite, with no sulfate minerals observed. Therefore, the sulfur isotopic compositions of sulfides can effectively represent the total sulfur characteristics of the ore-forming fluid [27,28].

Sulfur sources in hydrothermal deposits generally fall into three categories [29,30,31,32]: mantle or deep-crustal sulfur (δ³⁴S ≈ 0 ± 3‰), sulfur derived from bacterial sulfate reduction (characterized by strongly negative δ³⁴S values), and sulfur from marine evaporites or seawater sulfate (δ³⁴S ≈ 20‰). The in situ δ³⁴S values of sulfides obtained in this study range from −5.98‰ to +12.01‰, with an average of 3.07‰, which is generally similar to the range of magmatic sulfur and significantly lower than that of seawater sulfate. The δ³⁴S values of pyrrhotite from sample ZK002-S1 (−5.98‰ to −3.55‰) are distinctly different from typical seawater sulfur and mantle-derived magmatic sulfur and also differ from purely bacteriogenic sulfur, indicating a non-uniform sulfur source.

The δ³⁴S values increase progressively from pyrrhotite to sphalerite, chalcopyrite, and pyrite (Figure 11a), and the δ³⁴S values of corresponding minerals in massive ores are lower than those in disseminated ores (Figure 11b), suggesting differences in formation conditions between the two ore types. The observed sulfur isotope variations between massive and disseminated ores may result from multiple factors (e.g., temperature, oxygen fugacity, sulfur fugacity, fluid composition), and further work is required to identify the dominant controls. The δ³⁴S values of sulfides do not exhibit the equilibrium sequence of δ³⁴Spyrite > δ³⁴Spyrrhotite > δ³⁴Ssphalerite > δ³⁴Schalcopyrite [33], indicating that sulfur isotopes did not reach complete equilibrium, which is consistent with a dominantly magmatic source with possible fluid mixing.

The host rocks of the Qimantagh Group include marine carbonate sequences that could have provided seawater sulfate. During the ascent of magmatic–hydrothermal fluids, mixing with seawater-derived fluids may have occurred. The moderately negative δ³⁴S values (down to −5.98‰) are consistent with possible thermochemical sulfate reduction (TSR) of seawater sulfate, which can produce reduced sulfur with δ³⁴S values lower than magmatic sulfur. However, direct petrographic evidence for TSR (e.g., sulfate minerals such as anhydrite or gypsum, or bitumen) has not been observed in the Donggou deposit, and further work is needed to evaluate the role of TSR.

In summary, the sulfur isotopic data indicate that the sulfur in the Donggou deposit was predominantly derived from a magmatic source, with possible minor contributions from seawater sulfate via fluid mixing and/or TSR. The sources of metals (e.g., Zn, Pb, Cu) are primarily constrained by the sulfur source and the magmatic–hydrothermal system.

8.3. Ore Genesis

Sphalerite trace element compositions vary considerably among different deposit types. For example, magmatic–hydrothermal skarn-type deposits are enriched in Fe, Mn, In, Sn, and Co but depleted in Cd, Ge, and Ga; VMS-type deposits exhibit relatively high Fe, Mn, and In but are depleted in Cd, Ge, and Ga; whereas MVT-type deposits show a wide range of variations, characterized by enrichment in Ge, Cd, Ga, and Ti but depletion in Fe, Mn, In, Sn, and Co [34,35,36]. Sphalerite from the Donggou deposit is enriched in Fe, Mn, and In, depleted in Ga and Ge, and relatively depleted in Cd (Figure 15), which is similar to a characteristic of VMS-type deposits [37].

In magmatic-related Pb–Zn deposits, sphalerite typically has Cd/Fe and Ge/In ratios < 0.1, Ga/In < 1, Cd/Mn < 5, and Zn/Cd < 250. In contrast, sedimentary or stratabound Pb–Zn deposits show Cd/Fe > 1, Zn/Cd > 400, and Cd/Mn, Ga/In, and Ge/In all > 10 [35,38]. For the Donggou deposit, sphalerite Fe contents range from 4.73% to 43.15% (avg. 7.83%), Cd from 592.4 × 10⁻⁶ to 1795 × 10⁻⁶ (avg. 1452 × 10⁻⁶), and Mn from 170.3 × 10⁻⁶ to 5811 × 10⁻⁶ (avg. 1924 × 10⁻⁶). The calculated Cd/Fe = 0.001–0.03, Cd/Mn = 0.20–3.48 (avg. 1.12), Zn/Cd = 337–452 (avg. 398), Ga/In = 0.006–1.71 (avg. 0.33), and Ge/In = 0.005–0.103 (avg. 0.024). These ratios are consistent with a magmatic-related origin, which is compatible with a VMS interpretation.

On various discrimination diagrams (Mn–Ag, Mn–(In + Sn), Fe–Mn, Mn–In/Cd, In/Ge–Mn, In–Mn/Fe, and Ga–In; [39]), Donggou sphalerite compositions predominantly fall within or near the SEDEX and VMS fields (Figure 16a–f). Furthermore, on the Cd/Fe–Co and Cu–Sn diagrams (Figure 16g,h), they plot within or near the VMS field. Collectively, these features demonstrate that the trace element composition of sphalerite from the Donggou deposit reflects a magmatic–hydrothermal origin and shows affinities with VMS-type deposits. This geochemical overlap with the SEDEX field can be attributed to late hydrothermal overprint, contamination by early syngenetic sedimentary components, and the inherent multi-interpretation nature of conventional discriminant diagrams when applied to multi-stage ore systems [33,40,41].

The Co/Ni ratio of pyrite is an effective indicator of its genesis: syndepositional sedimentary pyrite typically has Co/Ni < 1 [44,45]; hydrothermal pyrite generally exhibits Co/Ni ratios between 1 and 5 [40,46]; and volcanic-related pyrite often shows Co/Ni ratios ranging from 5 to 100. Pyrite from the Donggou deposit has Co/Ni ratios ranging from 0.002 to 0.65, with an average of 0.16, indicating the influence of both syndepositional sedimentation and volcanic activity. Three analytical spots with high Co/Ni ratios (6.42–97.32) are located in the pyrite cores, similar to magmatic pyrite [47], suggesting multi-stage mineralization and involvement of magmatic–hydrothermal fluids.

Sedimentary pyrite typically has Zn/Ni and Cu/Ni ratios ranging from 0.01 to 10 and 0.01 to 2, respectively. In contrast, pyrite from the Donggou deposit exhibits extremely high Zn/Ni (avg. 2119) and Cu/Ni (avg. 86,132) ratios, indicating a non-sedimentary origin. To ensure that these elevated ratios reflect lattice-bound elements rather than micro-inclusions (e.g., sphalerite or chalcopyrite), all LA-ICP-MS signals were carefully inspected. Time-resolved signal profiles were examined for each analytical spot (representative examples shown in Figure 17), the spots with extremely high Zn/Ni and Cu/Ni ratios are interpreted as representing lattice-bound elements (or nanoscale inclusions) in pyrite, rather than artifacts of polymineralic micro-inclusions. On the Co–Ni discrimination diagram, the samples predominantly fall within the fields of VMS and SEDEX deposits. Notably, all samples from the massive ores plot exclusively within the VMS field, whereas the samples from other ore types show more scattered distributions, with some samples falling within the SEDEX field (Figure 16h–i).

The Se content and S/Se ratio can also serve as genetic indicators: sedimentary pyrite has Se contents of 0.5 × 10⁻⁶ to 2 × 10⁻⁶ and S/Se ratios up to tens of thousands to hundreds of thousands, whereas magmatic–hydrothermal pyrite has Se > 20 × 10⁻⁶ and S/Se < 15,000 [48,49]. Pyrite from the Donggou deposit has Se contents ranging from 6.30 × 10⁻⁶ to 54.90 × 10⁻⁶ (avg. 15.06 × 10⁻⁶) and S/Se ratios ranging from 4597 to 84,737 (avg. 42,323), indicating a polygenetic origin for pyrite, but with a dominant magmatic–hydrothermal signature, consistent with the petrographic observation of multi-stage pyrite.

In summary, based on the stratoid occurrence of ore bodies, the syn-metamorphic deformation shared by ores and host rocks, the systematic trace element discrimination of sulfides, and the spatial distribution (i.e., massive ores representing the main mineralization event are located at shallow levels and hosted by rhyolite, whereas deeper banded and veined ores are partially hosted by clastic rocks), we interpret the Donggou Pb–Zn deposit as showing features consistent with a VMS-type deposit. The scattered geochemical signatures overlapping with the SEDEX field are more likely attributable to late-stage hydrothermal overprint or distal sedimentation along permeable layers, rather than evidence for an independent SEDEX event.

8.4. Temperature Estimation

The types and concentrations of trace elements in metal sulfides (e.g., pyrite, sphalerite) are primarily controlled by temperature; higher temperatures generally result in greater diversity and higher concentrations of trace elements [46,50,51,52,53].

In pyrite, Co and Ni substitute for Fe via isomorphism, with higher temperatures facilitating more extensive substitution and thus higher Co and Ni contents [54]. High-temperature pyrite is characterized by ω (Co) > 1000 × 10⁻⁶, medium-temperature pyrite by ω (Co) between 100 × 10⁻⁶ and 1000 × 10⁻⁶, and low-temperature pyrite by ω (Co) < 100 × 10⁻⁶ [55,56,57]. Pyrite analyzed in this study (Py1 and Py2) from the Donggou deposit shows highly variable Co contents ranging from 0.053 × 10⁻⁶ to 918.09 × 10⁻⁶, with an average of 61.34 × 10⁻⁶. The average Co content falls within the medium- to low-temperature range (<100 × 10⁻⁶), whereas the maximum value (918.09 × 10⁻⁶) approaches the high-temperature field, indicating that pyrite predominantly formed under medium- to low-temperature conditions, with contributions from a high-temperature stage. The Cd/Zn ratio of chalcopyrite increases with crystallization temperature, with high temperatures (>400 °C) producing higher ratios [58]. The Donggou chalcopyrite yields ratios of 0.002–0.05 (avg. 0.006), suggesting formation under non-high-temperature conditions.

The trace element contents and ratios in sphalerite are temperature-sensitive [31,32,33,34,59,60]. Specifically, high-temperature sphalerite is characterized by elevated Fe (generally >10%), Mn, In, Se, and Te, whereas low-temperature sphalerite is characterized by enrichment in Cd, Ga, and Ge. The Zn/Cd ratio is positively correlated with temperature, while the Zn/Fe and Ga/In ratios are negatively correlated with temperature (low temperature: Zn/Fe > 100, Zn/Cd < 100, and Ga/In = 1–100; medium to high temperature: Zn/Fe = 10–100, Zn/Cd ≈ 250, and Ga/In = 0.01–5 (avg. 0.1); high temperature: Zn/Fe < 10, Zn/Cd > 500, and Ga/In = 0.001–0.05 (avg. 0.015)) [36,61,62,63,64]. Sphalerite (Sp1) from the Donggou deposit has Fe contents ranging from 4.73% to 43.15% (avg. 7.83%), In contents ranging from 15.34 × 10⁻⁶ to 115.57 × 10⁻⁶ (avg. 53.16 × 10⁻⁶), Zn/Fe ratios ranging from 0.49 to 13.04 (avg. 9.18), Zn/Cd ratios ranging from 337.35 to 452.48 (avg. 398.04), and Ga/In ratios ranging from 0.006 to 1.72 (avg. 0.33). These ratios consistently indicate medium-temperature ore-forming conditions for Sp1.

Using the sphalerite (Sp1) trace element geothermometer based on Fe, Ga, Ge, In, and Mn [59]:

T (°C) = (54.4 ± 7.3)·PC1* + (208 ± 10)

(1)

$$\mathrm{PC}1*=\ln ({\displaystyle \frac{C_{Ga}^{0.22}·C_{Ge}^{0.22}}{C_{Fe}^{0.37}·C_{Mn}^{0.20}·C_{In}^{0.11}}})$$

(2)

where ln is the natural logarithm, and C represents the mass fractions of trace elements in sphalerite (Ga, Ge, In, and Mn in ×10⁻⁶, Fe in wt%).

For all 52 Sp1 analysis spots, the contents of Fe, Ga, Ge, In, and Mn were measured by LA-ICP-MS. All elements in each spot were significantly above the detection limit, and no data was excluded. PC1* was calculated according to Equation (2) and then substituted into Equation (1) to obtain the temperature. The resulting ore-forming temperature range is 285–385 °C, with an average of 327 °C. The coefficients in Equation (1) include standard errors (±7.3, ±10).

The Sp1 sphalerite generation is suitable for this geothermometer, primarily because it coexists with chalcopyrite, pyrite, and pyrrhotite, shows no replacement, dissolution, or exsolution textures, and its element contents (Fe: 4.7–43.2 wt%; Ga: 0.37–31.4 ppm; Ge: 0.52–6.6 ppm; In: 15.3–115.6 ppm; Mn: 170–5811 ppm) all fall within the calibration range of the geothermometer [58]. In summary, the calculated temperatures from the Sp1 sphalerite generation represent the main mineralization stage conditions. Furthermore, this temperature range is highly consistent with the typical ore-forming temperatures of chalcopyrite-rich VMS-type deposits [64], providing further support for the VMS-type genesis of the deposit.

8.5. Tectonic Setting

Volcanogenic massive sulfide (VMS) deposits are typical stratabound deposits formed syngenetically with submarine volcanic–hydrothermal activity, and their formation is strictly controlled by specific submarine volcanic-sedimentary basin environments [65,66,67,68]. In the Donggou mining area, the ore bodies are hosted in andesite and siliciclastic rocks, and the study of these rocks can effectively constrain the metallogenic tectonic setting.

Although the Donggou andesite has undergone alteration (LOI values ranging from 2.44 to 5.50, with an average of 3.51), the rare earth elements (REEs) and high-field-strength elements (HFSEs) remain relatively immobile [69] and can be used to infer the magma source characteristics. The Mg^# values of the samples range from 10.82 to 68.07, with an average of 44.63, which lies between values for lower crust-derived partial melts (Mg^# < 40; [70]) and mantle values (Mg^# between 68 and 75; [71]). The samples exhibit pronounced negative Eu anomalies, relatively low Cr and Ni contents, and low Sm/Nd (0.24) and Lu/Hf (0.12) ratios, which may argue against direct partial melting of hydrous mantle peridotite or lower crust [23,69,72,73]. The high Th and U contents (8.33 × 10⁻⁶ and 2.76 × 10⁻⁶, respectively) and low Sm/Nd and Lu/Hf ratios (0.24 and 0.12, respectively) also do not appear to support a genetic model involving interaction between delaminated lower crust and the mantle.

Continental crust is typically characterized by low Nb and Ta contents, low Nb/Ta ratios (8.33–13.33), and high Th contents [74]. Crustal contamination generally results in decreased Nb/Ta ratios and elevated Th/La, Th/Nb (>5), and Th/Ta (>10) ratios [70]. The Donggou volcanic rocks exhibit Nb/Ta ratios ranging from 15.43 to 18.04 (averaging 16.95), which are slightly lower than those of mantle melts (18.27; [74]) but significantly higher than the crustal average (7.9). Their Th/Ta ratios vary from 9.44 to 15.02 (averaging 12.26), exceeding values for both the primitive mantle (~2) and the upper (~6.9) and lower (~7.9) crust [17,75,76]. Furthermore, the lack of correlation between Nb/Ta and Th/La ratios versus Mg^# suggests that the significant crustal contamination is not a major factor.

The samples display obvious enrichment in large ion lithophile elements (LILEs; K, Ba, Th, U) and depletion in high-field-strength elements (HFSEs; Nb, P, Ti, Sr), exhibiting typical arc magmatic characteristics [77]. The observed depletion in Nb and Ta is consistent with derivation from a mantle source metasomatized by subduction-related fluids. The Zr contents range from 153.5 × 10⁻⁶ to 535.90 × 10⁻⁶, with an average of 292.31 × 10⁻⁶, and the Hf contents range from 3.94 × 10⁻⁶ to 13.89 × 10⁻⁶, with an average of 7.34 × 10⁻⁶, which are significantly higher than those of volcanic arc tholeiitic basalts (40 × 10⁻⁶ and 1.17 × 10⁻⁶, respectively). The TiO₂ contents range from 0.27% to 1.12%, consistent with the TiO₂ contents of island arc and active continental margin volcanic rocks (less than 1.25%; [78]). On the Nb/Yb–Th/Yb diagram (Figure 18a), all samples deviate significantly from the MORB-OIB trend and plot within the continental arc field, displaying characteristics similar to volcanic arcs and suggesting that their formation was influenced by subduction processes [79]. All Donggou samples plot within the island arc basalt field on the Hf/3–Th–Ta diagram (Figure 18b), which is consistent with derivation of the andesitic magma from a mantle wedge metasomatized by subduction-related fluids. Collectively, these features suggest that the tectonic setting of the Donggou deposit is best interpreted as a continental island arc (or back-arc basin) related to subduction.

The geochemical characteristics of siliciclastic rocks provide constraints on tectonic setting and provenance [81,82]. Siliciclastic rocks from the Donggou deposit exhibit Al₂O₃/SiO₂ ratios of 0.12–0.27 (avg. 0.18) and generally low K₂O/Na₂O ratios of 0.02–1.84 (avg. 0.30), indicating relatively high maturity. In the Th/Sc–Zr/Sc diagram (Figure 19a), samples predominantly plot within the field of felsic source rocks and display a sedimentary recycling trend. The Hf–La/Th diagram (Figure 19b) suggests an affinity with acidic arc provenance and passive continental margin settings. On the Th–Co–Zr/10 diagram (Figure 19c), most samples fall into the continental island arc field, with minor projections into the passive continental margin and oceanic island arc fields. This is consistent with the interpretation that the South Qimantagh Belt developed in an early oceanic island arc setting prior to the Silurian [15]. Similarly, the Th–Cs–Zr/10 diagram (Figure 19d) shows most samples plotting within the continental island arc and passive continental margin fields. The pre-Ordovician strata in the region are dominated by the Paleoproterozoic Jinshuikou Rock Group, which is interpreted as a passive continental margin siliciclastic–carbonate succession [83,84]. Collectively, these observations suggest that the provenance of the siliciclastic rocks in the Donggou mining area was likely derived primarily from the Jinshuikou Rock Group and Early Paleozoic continental margin arcs. The Y/Ho ratios of the samples range from 22.05 to 26.98, with an average of 25.04, which falls within the range typical of igneous rocks and terrigenous siliciclastic sediments (26–28), consistent with the above interpretation of provenance.

In terms of paleo-water depth and redox condition discrimination, the Rb/Zr ratio is positively correlated with water depth and negatively correlated with hydrodynamic intensity [85]. The Sr/Ba ratio can be used to distinguish marine facies (>1), brackish water facies (0.6–1), and slightly brackish water facies (<0.6) [86]. The Donggou samples have Rb/Zr ratios ranging from 0.04 to 0.85 (avg. 0.38) and Sr/Ba ratios ranging from 0.01 to 0.37 (avg. 0.07), reflecting a sedimentary environment characterized by shallow, slightly brackish water. The Ni/Co ratios range from 0.37 to 6.64 (avg. 3.90), U/Th ratios from 0.29 to 0.42 (avg. 0.32), V/Cr ratios from 0.12 to 1.49 (avg. 0.74), and V/(V + Ni) ratios from 0.08 to 0.68 (avg. 0.50), all indicating an oxic environment [87].

Although the siliciclastic rocks in the Donggou mining area record a shallow, oxic shelf environment, the spatial morphological characteristics of the VMS ore body (M4)—limited strike and dip extents with a lenticular shape—suggest that mineralization was likely strictly controlled by a local volcanic depression. This depression provided a relatively closed, reduced microenvironment for hydrothermal fluids, increased hydrostatic pressure, prevented fluid boiling, and thus promoted efficient local sulfide precipitation. Therefore, there is no contradiction between the regional shallow-water background and localized reduced mineralization. This interpretation is consistent with the typical geological characteristics of shallow-water volcanic-hosted VMS deposits.

Integrating the provenance characteristics of the siliciclastic rocks and the sedimentary water environment, the Qimantagh Ocean was likely in a late-stage subduction setting during the depositional period of the siliciclastic rocks in the Donggou area, characterized by shallow-water depths, which is consistent with geological observations such as the presence of lithic feldspar sandstone within the siliciclastic succession in the mining area.

Figure 19. Discrimination diagrams for the provenance and sedimentary environment of clastic rocks in the Donggou mining area. (a) From [88]; (b) from [89]; (c,d) from [90].

Figure 19. Discrimination diagrams for the provenance and sedimentary environment of clastic rocks in the Donggou mining area. (a) From [88]; (b) from [89]; (c,d) from [90].

8.6. Genetic Model

Regionally, the Qimantagh Ocean, represented by the Shizigou ophiolite, is considered to be a back-arc basin formed by localized extension in the Qimantagh region during the Late Ordovician to Early Silurian (480–460 Ma) as a result of the subduction of the Central Kunlun Ocean [11,91,92,93]. This back-arc basin subducted northward during ca. 450–425 Ma and underwent closure and collision during ca. 425–420 Ma [11]. Regionally, syn-collisional granites at ca. 422 Ma [94] and eclogite metamorphic ages of 430–410 Ma further constrain the timing of ocean closure [95,96]. The age of the andesite in the Donggou deposit (437.1 ± 1.9 Ma) falls precisely within the late stage of the back-arc basin subduction, indicating its formation in a continental arc setting.

Based on the above studies, this paper proposes the following genetic model for the Donggou lead–zinc deposit (Figure 19): during the late stage of the Qimantagh Ocean subduction, the mantle wedge metasomatized by subduction-related fluids underwent partial melting to form primary magma. After a certain degree of fractional crystallization, the magma ascended and erupted onto the seafloor, carrying ore-forming materials. In a shallow submarine environment, magmatic sulfur mixed with seawater sulfur, and the ore-forming fluids (medium temperature, approximately 285–385 °C) formed stratoid and laminated ore bodies through exhalative sedimentation, ultimately resulting in a VMS-type lead–zinc deposit (Figure 20).

The establishment of this genetic model not only precisely determines the mineralization age (Early Silurian) and genetic type (VMS-type) of the Donggou lead–zinc deposit but also reveals that the late stage of the Proto-Tethys Ocean subduction (Early Silurian) represents an important lead–zinc metallogenic epoch in the Qimantagh region. Briefly, the Donggou Pb-Zn deposit (Early Silurian, 437.1 ± 1.9 Ma; hosted by Ordovician clastic–volcanic rocks; VMS-type) differs from the regional Triassic Hutouya, Niukutou, and Kendekeke deposits, which are predominantly skarn-type deposits and hosted in different lithologies (

Table 4. Comparison of the Donggou deposit with other major Pb-Zn polymetallic deposits in the Qimantagh region.

Deposit	Age	Host Rock	Ore Type	δ34S (‰)	Genetic Type	Data Source
Donggou	Early Silurian (ca. 437 Ma)	Qimantagh Group	Pb-Zn	−5.98 to +12.01	VMS-type	This study
Hutouya	Triassic	Carbonate rocks	Fe-Pb-Zn-Cu	Not reported	Skarn-type	[97,98,99,100]
Niukutou	Triassic	Carbonate rocks	Pb-Zn-Fe-(Co)	+3.7 to +7.0	Skarn-type	[101,102]
Kendekeke	Triassic (ca. 225 Ma)	Qimantagh Group	Fe-Pb-Zn-Co-Au	Not reported	Skarn-type/SEDEX-type (debated)	[103,104]
Galinge	Triassic (ca. 237 Ma)	Carbonate rocks	Pb-Zn-Fe-(Co)	Not reported	Skarn-type	[105]

). This finding challenges the traditional understanding that lead–zinc mineralization in this region was mainly concentrated in the Triassic, adding a critical data point to the regional metallogenic geochronological framework. It holds significant theoretical importance and exploration implications for reassessing the metallogenic potential during the Proto-Tethys evolution and broadening regional exploration strategies.

9. Conclusions

The andesite immediately overlying the ore body in the Donggou mining area yields a zircon U-Pb age of 437.1 ± 1.9 Ma, providing a maximum age constraint for mineralization (i.e., the Donggou Pb-Zn deposit formed no later than 437.1 ± 1.9 Ma). Sulfide δ³⁴S values range from −5.98‰ to +12.01‰ (mean 3.07‰), indicating a mixed sulfur source dominated by magmatic sulfur with minor seawater input and formation in an open environment. The deposit is interpreted as a VMS-type Pb-Zn system formed in a shallow submarine setting during the late stage of Qimantagh Ocean subduction. Primary magmas were derived from partial melting of a mantle wedge metasomatized by subduction-related fluids, followed by fractional crystallization and ascent to the seafloor. Mineralization occurred at approximately 327 °C, corresponding to a medium-temperature environment.