Metallogenic Mechanism of Carlin-Type Gold Deposit in Zhen’an-Xunyang Basin, in the South Qinling of China: Constraints of In Situ Trace Elements and S Isotopes from Newly Discovered Wangzhuang Gold Deposit

: The Zhen’an-Xunyang Basin is a late Paleozoic rifted basin with a series of Au-Hg-Sb deposits that have been found, mostly along the Nanyangshan fault. Recently discovered large-and medium-sized gold deposits such as the Xiaohe and Wangzhuang deposits exhibit typical characteristics of Carlin-type gold deposits. Therefore, it is imperative to select a typical deposit for an in-depth study of its metallogenic mechanism to support future prospecting efforts targeting the Carlin-type gold deposits within the area. Based on detailed ﬁeld investigation and micropho-tographic observation, four ore-forming stages are identiﬁed: I, low-sulﬁde quartz stage, characterized by euhedral, subhedral pyrite, and ﬁne veins of quartz injected parallel to the strata; II, arsenopyrite–arsenian pyrite–quartz stage, the main mineralization stage characterized by strongly siliciﬁed zones of reticulated quartz, disseminated arsenopyrite, ﬁne-grained pyrite; III, low-sulﬁde quartz stage, characterized by large quartz veins cutting through the ore body or ﬁne veins of quartz; IV, carbonate–quartz stage, characterized by the appearance of a large number of calcite veins. In situ analysis of trace elements and S isotopes of typical metal sulﬁdes was carried out. The results show signiﬁcant variations in the trace element compositions of metal sulﬁdes in different stages, among which the main mineralization stage differs notably from those of the Au-and As-low surrounding strata. In situ S isotope analysis reveals δ 34 S values ranging from 15.78‰ to 28.71‰ for stage I metal sulﬁdes, 5.52‰ to 11.22‰ for stage II, and 0.3‰ to 5.25‰ for stage III, respectively, revealing a gradual decrease in S isotopic values from the pre-mineralization stage to post-mineralization stage, similar to those observed in the Xiaohe gold deposit. These features indicate a distinct injection of relatively low 34 S hydrothermal ﬂuids during the mineralization process. The element anomalies of the 1:50,000 stream sediment in the region revealed ore-forming element zonation changing in W → Au (W) → Hg, Sb (Au) anomalies from west to east, manifested by the discovery of tungsten, gold, and mercury–antimony deposits in the area. Moreover, conspicuous Cr-Ni-Ti-Co-Mo anomalies were observed on the western side of the Wangzhuang and Xiaohe gold deposits, indicating a potential concealed pluton related to these deposits. These lines of evidence point to a magmatic–hydrothermal origin for the Carlin-type gold deposits in this area. Furthermore, hydrothermal tungsten deposits, Carlin-type gold deposits, and low-temperature hydrothermal mercury–antimony deposits in this region are probably controlled by the same magma–hydrothermal system.


Introduction
The Carlin-type gold deposits (CTDs), one of the most significant hydrothermal gold deposits, have attracted considerable attention due to their extensive metallogenic scale and promising exploration potential [1,2].In recent years, many studies have revealed that some geological and geochemical characteristics of these gold deposits in China differ from those of the most typical Carlin-type gold deposits in Nevada, USA.Consequently, some scholars named them as Carlin-like gold deposits [3][4][5][6].Taking China as an example, there are hundreds of Carlin-type gold deposits with accumulated industrial reserves totaling approximately 2000 tons [7], primarily concentrated in the Shaanxi, Gansu, and Sichuan regions (Qinling Mountains), as well as Yunnan, Guizhou, and Guangxi regions [5, [8][9][10].Among them, the Qinling orogenic belt hosts two world-class Carlin-type gold deposits, the Jinlongshan and Zhaishang gold deposits, which are regarded as two of the most important Carlin-type gold metallogenic belts in China.
Many Carlin-like, Carlin-type gold deposits have been discovered in the Qinling metallogenic belt, mainly distributed in the west and south of the Qinling metallogenic belt (Figure 1).Since the ore-forming fluid characteristics of some gold deposits in west Qinling are between orogenic gold deposits and Carlin-type gold deposits [3,4,[7][8][9]11], the classification of their ore-forming types has long been debated.It is acknowledged that the fluids and metal sources of orogenic gold deposits are mainly from regional-scale metamorphism instead of magmatic activity, and thus there is no large area of element zonation around these deposits [11][12][13].In contrast, Carlin-type gold deposits generally show a close relationship with magmatic activity, which is represented by the inconsistency of fluid sources in multiple stages and different stages of mineralization [14][15][16][17].As far as the present research is concerned, the origin of gold deposits in south Qinling has a unified understanding, and there are Carlin-type gold deposits represented by Jinlongshan [18][19][20].However, the research on the source of ore-forming materials and the metallogenic mechanism of a series of Carlin-type gold deposits in the central part of the Zhen'an-Xunyang Basin (ZXB) is relatively weak, which restricts the study of the metallogenic system theory of Carlin-type gold deposits and low-temperature hydrothermal Hg-Sb deposits in the area.This lack of research may hinder our understanding of the geological processes that led to the formation of these deposits and their potential for further exploration and development.
The ZXB is an early Paleozoic sedimentary basin located in the south Qinling orogenic belt (SQB).It comprises a series of carbonate and fine clastic sedimentary formations.The distribution of deposits in this area is mainly controlled by the Nanyangshan fault situated in the middle of the basin [22].The basin is renowned for its polymetallic mineralization, including gold, mercury, antimony, lead, and zinc [23][24][25][26].In particular, it hosts the Jinlongshan super-large Carlin-type gold deposit in its northern region [20,26] and a series of sedimentary exhalative (Sedex) lead-zinc deposits in its southern region [22].Additionally, the central part of this basin lies on the Gongguan and Qingtonggou Figure 1.Tectonic divisions and gold distribution in the Qinling orogenic belt (tectonic framework modified after Dong and Santosh [21]; gold distribution and classification compiled after Chen, Liu, and Ma [4,8,20]).
The ZXB is an early Paleozoic sedimentary basin located in the south Qinling orogenic belt (SQB).It comprises a series of carbonate and fine clastic sedimentary formations.The distribution of deposits in this area is mainly controlled by the Nanyangshan fault situated in the middle of the basin [22].The basin is renowned for its polymetallic mineralization, including gold, mercury, antimony, lead, and zinc [23][24][25][26].In particular, it hosts the Jinlongshan super-large Carlin-type gold deposit in its northern region [20,26] and a series of sedimentary exhalative (Sedex) lead-zinc deposits in its southern region [22].Additionally, the central part of this basin lies on the Gongguan and Qingtonggou super-large mercury-antimony deposits, which have become significant metallogenic belts for mercury (antimony) mineralization in China [27][28][29].Several gold deposits, such as Xiaohe (>20 t, by Zijin Mining, Xiamen, China), Laojunmiao (>18 t, by Shaanxi Geology and Mining First Geological Team Co., LTD, Xi'an, China), Huijiagou (>5 t, by Shaanxi Geology and Mining First Geological Team Co., LTD, Xi'an, China), and Wangzhuang (>2.5 t, by Xi'an Center of Mineral Resources Survey, China Geological Survey, Xi'an, China), have been discovered within this Hg-Sb metallogenic belt, forming a gold-dominated Hg-Sb-Pb-Zn polymetallic metallogenic belt (Figure 2).The previous research primarily focused on the fundamental geological characteristics of the deposits; however, the properties and sources of ore-forming fluids have not been well constrained.In this study, we selected the Wangzhuang gold deposit, which is situated at the transition of the entire tungsten and mercury-antimony metallogenic belt, as the research object.Based on comprehensive field investigations, multi-stage alteration characteristics of the Wangzhuang gold deposit are identified.Combining detailed min- The previous research primarily focused on the fundamental geological characteristics of the deposits; however, the properties and sources of ore-forming fluids have not been well constrained.In this study, we selected the Wangzhuang gold deposit, which is situated at the transition of the entire tungsten and mercury-antimony metallogenic belt, as the research object.Based on comprehensive field investigations, multi-stage alteration characteristics of the Wangzhuang gold deposit are identified.Combining detailed mineralogical, mineral geochemical, and in situ S isotopic studies on metal sulfides from each stage, we further constrained the fluid characteristics and ore-forming materials sources, and discuss the genetic mechanism of Carlin-type gold deposits in this region.

Regional Geology
The Qinling orogenic belt (QOB) is located at the junction of the collision between the North China Block and the South China Block.It is an important part of the Central Asian Orogenic Belt (CAOB) and a compound continental orogenic belt with long-term development and evolution [21,30,31].From north to south, the QOB can be divided into four units, namely the southern margin of the North China Block (S-NCB), the North Qinling Block (NQB), the South Qinling Block (SQB) and the northern margin of the South China Block (N-SCB) by the Lingbao-Lushan-Wuyang fault (LWF), Shangdan suture (SDS), and Mianluo-Bashan-Xiangguang fault (MBXF) (Figure 1) [21,31,32].The QOB represents a significant metallogenic belt for non-ferrous metals and precious metals in China [14,33].Over the past three decades, numerous large and super-large gold deposits have been discovered, e.g., the Zhaishang, Yangshan, Dashui, Jinlongshan, and Baguamiao deposits.More than 90% of the gold deposits in the Qinling area are hosted by Devonian strata [3,14], which mainly consist of epimetamorphic rock or sedimentary rock.Notably, most of these deposits have been found to have a close spatial and temporal relationship with magmatic activities [14,20,34].
The Zhen'an-Xunyang Basin is a late Paleozoic rifted basin located in the middle of south Qinling's secondary tectonic belt, bounded by the Ankang fault to the south and the Zhen'an-Banyanzhen fault to the north (Figures 1 and 2A).The tectonic framework in this area is primarily influenced by the Indosinian collision orogeny and Yanshanian intracontinental orogeny.From north to south, the ZXB can be divided into three structural units: Jinjiling synclinorium, Gongguan-Huilong anticlinorium, and Nanyangshan synclinorium.These structures also control the distribution of metal minerals in this region, with the predominance of Au-Sb-Hg deposits in the north, Hg-Sb-Au deposits in the middle, and Pb-Zn deposits in the south [35].This research focuses on the Wangzhuang Carlin-type gold deposit located within the central part of the ZXB.

Ore Geology
The Wangzhuang gold deposit is located in the middle of the late Paleozoic Zhen'an-Xunyang sedimentary basin.The gold deposits surrounding the Nanyangshan fault primarily occur within Devonian formations, including the Xinghongpu Formation (D 3 x), Gudaoling Formation (D 2-3 g), Dafenggou Formation (D 2 d), and Xichahe Formation (D 2 x).In contrast, the Wangzhuang gold deposit was found within the Upper Devonian-Lower Carboniferous Tieshan Formation (D 3 C 1 t), which used to be considered a barren formation in this region (Figure 2A).The predominant lithologies hosting mineralization include calcareous (carbonaceous) phyllite and quartz sandstone, and the wall rock is mainly carbonate rock, forming an interstratified rock of carbonate rock and fine clastic rock, which plays a crucial role as a physicochemical interface in ore formation [36,37].
The Wangzhuang gold deposit is located at the northwest end of the Shadonggou anticline of the Nanyangshan synclinorium, while the other NW-trending Songjiayuan fault (F1) and Gangoutai-Qinggou fault (F12) cut through the fold hinge of Shadonggou, and can extend to the mining area in the northwest direction (Figures 2 and 3).The combination of fold and fault constitutes a promising tectonic pattern for ore formation.
Additionally, the Au-Hg-Sb-W anomaly zone in the area is controlled by the Nanyangshan fault, which intersects with the arc-shaped tectonic belt composed of Wangzhuang and Xiaohe gold deposits.The lithology and structure of these ore-bearing strata exhibit certain similarities, thus creating favorable conditions for mineralization.Gold mineralization in this area is closely associated with fault structures, and most of the faults related to mineralization exhibit the characteristics of multi-stage activity following extension and compression.The distribution of gold deposits is controlled by NE-trending main faults and interlayer fracture zones (Figure 2).Gold ore bodies are predominantly found near east-west secondary structural fracture zones, where expansion, contraction, and pinch-out phenomena have been frequently observed.compression.The distribution of gold deposits is controlled by NE-trending main faults and interlayer fracture zones (Figure 2).Gold ore bodies are predominantly found near east-west secondary structural fracture zones, where expansion, contraction, and pinchout phenomena have been frequently observed.The main stratum outcrops in the mining area are the Upper Devonian-Lower Carboniferous Tieshan Formation (D3C1t) and Upper Devonian Xinghongpu Formation (D3x).The orebodies are predominantly hosted in the Tieshan formation along the western axis of the Shadonggou anticline (Figure 3).Stream sediment survey revealed significant and superimposed Au and As anomalies, indicating promising prospects for Au.The Wangzhuang gold deposit is divided into two ore-forming sections.In the eastern oreforming section, the mineralized bodies primarily occur within the interlayer fracture zone, which is controlled by the interface between limestone and phyllite.Based on current exploration engineering controls, two ore bodies have been found: K1 as an exposed surface ore body and M1 as a blind ore body.K1 extends about 480 m on the surface (Figure 3), with an average grade of 1.41 g/t and an average thickness of 1.3 m.M1 has an average grade of 1.51 g/t and an average thickness of 5.45 m.The two ore bodies show gently undulating waves along the stratiform fracture zone.
1:50,000 stream sediment surveys within the central ZXB show Cr-Ni-Ti-Co-Mo and W anomalies in the western region, W-Au anomalies in the central region, and Hg-Sb-Au anomalies in the eastern region (Figure 2B).Notably, the presence of the Cr-Ni-Ti-Co-Mo anomaly suggests potential concealed plutons under the area, which are probably genetically related to the Au-Hg-Sb deposit.The main stratum outcrops in the mining area are the Upper Devonian-Lower Carboniferous Tieshan Formation (D 3 C 1 t) and Upper Devonian Xinghongpu Formation (D 3 x).The orebodies are predominantly hosted in the Tieshan formation along the western axis of the Shadonggou anticline (Figure 3).Stream sediment survey revealed significant and superimposed Au and As anomalies, indicating promising prospects for Au.The Wangzhuang gold deposit is divided into two ore-forming sections.In the eastern oreforming section, the mineralized bodies primarily occur within the interlayer fracture zone, which is controlled by the interface between limestone and phyllite.Based on current exploration engineering controls, two ore bodies have been found: K1 as an exposed surface ore body and M1 as a blind ore body.K1 extends about 480 m on the surface (Figure 3), with an average grade of 1.41 g/t and an average thickness of 1.3 m.M1 has an average grade of 1.51 g/t and an average thickness of 5.45 m.The two ore bodies show gently undulating waves along the stratiform fracture zone.
1:50,000 stream sediment surveys within the central ZXB show Cr-Ni-Ti-Co-Mo and W anomalies in the western region, W-Au anomalies in the central region, and Hg-Sb-Au anomalies in the eastern region (Figure 2B).Notably, the presence of the Cr-Ni-Ti-Co-Mo anomaly suggests potential concealed plutons under the area, which are probably genetically related to the Au-Hg-Sb deposit.

Ore Texture and Structure
According to the degree of oxidation, the ores in the Wangzhuang gold deposit can be classified into primary and oxidized ores.The oxidized ore typically exhibits a yellowishbrown color and is found within a depth range of 0-30 m from the surface.It commonly contains limonite and iron carbonates as dominant minerals (Figure 4A,C,D).On the other hand, the primary ore comprises cataclastic calcareous (carbonaceous) phyllite-type ore with arsenopyrite (Figure 4B,E), quartz-sulfide-type ore (Figure 4E,F,H,I), and pyritesericite-quartzite-type ore (Figure 4E,G), cataclastic calcareous (carbonaceous) phyllite-type ore is the main type.

Ore Texture and Structure
According to the degree of oxidation, the ores in the Wangzhuang gold deposit can be classified into primary and oxidized ores.The oxidized ore typically exhibits a yellowish-brown color and is found within a depth range of 0-30 m from the surface.It commonly contains limonite and iron carbonates as dominant minerals (Figure 4A,C,D).On the other hand, the primary ore comprises cataclastic calcareous (carbonaceous) phyllitetype ore with arsenopyrite (Figure 4B,E), quartz-sulfide-type ore (Figure 4E,F,H,I), and pyrite-sericite-quartzite-type ore (Figure 4E,G), cataclastic calcareous (carbonaceous) phyllite-type ore is the main type.

Mineral Textures
The main sulfides in the Wangzhuang gold deposit are pyrite and arsenopyrite.The microstructure analysis reveals that both pyrite and arsenopyrite display multi-stage

Mineral Textures
The main sulfides in the Wangzhuang gold deposit are pyrite and arsenopyrite.The microstructure analysis reveals that both pyrite and arsenopyrite display multi-stage growth characteristics with textural and morphological differences and can be divided into the following generations: Py1, Py2: the formation of Py1 primarily occurred particularly in arenaceous limestone and calcareous (carbonaceous) sedimentary rocks during their formation.It generally occurs as strawberry or colloidal aggregates, exhibiting an irregular shape with small particles less than 5 µm (Figure 5A,I).Additionally, many organic-containing pyrite aggregates are observed within this stage.During regional epimetamorphism, pyrite underwent recrystallization and was transformed into cube-like Py2 (Figure 5I).
Apy1a, apy1b: at this stage, a significant influx of hydrothermal solution containing arsenic led to the formation of abundant Apy1a as elongated columns, needles, and large particles (Figure 5C-E,H).Under reflected light, it exhibits a yellow-white gloss.Due to subsequent tectonic processes, the arsenopyrite shows curved or fractured characteristics (Figure 5D,H).It was replaced or filled by later arsenopyrite or pyrite (Figure 5C,D,G).Apy1b occurs mainly as short columns with occasional needle-like structures interspersed among earlier-formed Apy1a crystals.It is comparatively whiter than that observed for Apy1a under reflection microscopy (Figure 5D,E).Notably, fine-grained arsenopyrite with small particles is observed growing around Py2 (Figure 5L).
Py3: the pyrite at this stage exhibits a complex structure, characterized by the presence of arsenian pyrite.It is primarily colloidal, with star-shaped and ring-shaped textures (Figure 5C,D,F-H,J-L).It can be observed that Py3 has replaced the early-formed arsenopyrite (Figure 5C,J), with Py3 being enveloped in a ring shape around Py2 (Figure 5J-L).Similarly, the early arsenopyrite was surrounded by py3 (Figure 5L).Additionally, a small amount of galena and chalcopyrite formed simultaneously with py3, mainly located around the rims of the pyrite and arsenopyrite (Figure 5F,H).
Py4: in the late stage, anhedral pyrite (Py4) replaced early arsenopyrite and formed a ring-shaped structure around arsenic-bearing pyrite (Figure 5J,K).At this stage, the brightness of Py4 under BSE is lower than that of Py3, indicating that the contents of arsenic in Py4 are significantly reduced.The predominant structure observed in Py4 is characterized by anhedral grains arranged in a ring shape (Figure 5J,K).

Periods and Stages of Mineralization
According to the macro and micro characteristics of the minerals, the ore-forming process of the Wangzhuang gold deposit can be divided into three periods: (1) sedimentary diagenesis; (2) metamorphic period, which is characterized by low-sulfide quartz and is characterized by euhedral, subhedral pyrite, and fine veins of quartz injected parallel to the strata (Figure 4E,G).In this period, the pyrite is arsenic-free (Figure 5I-K); (3) Syn-gold hydrothermal mineralization; (4) post-gold supergene.Based on the variations of the mineralized body, mineral association, and intergrowth relationship, the hydrothermal mineralization period can be further divided into three distinct stages (Figure 6).

1.
Stage I is marked by arsenopyrite-arsenian pyrite-quartz assemblage and is characterized by strongly silicified zones of reticulated quartz, disseminated or fine veins arsenopyrite, stellate, and colloidal pyrite (Figure 4B,E,I).Arsenopyrite occurs as needles and columns, and accumulates at broken calcareous slate or the edge of quartz veins (Figure 5D,H).Arsenian pyrite and arsenopyrite show paragenesis, and little galena and chalcopyrite are observed (Figure 5F).Arsenopyrite and arsenian pyrite are the main carriers of gold.This stage shows the most intense mineralization alteration with the highest ore grades.

2.
Stage II is marked by low-sulfide quartz assemblage and is characterized by large quartz veins cutting through the ore body or fine veins of quartz (Figure 4A,D).Metal sulfides are enriched at the edge of the quartz vein, while the interior is relatively pure.At this stage, pyrite has a low arsenic content, and the ores have low gold grades.

3.
Stage III is marked by calcite-quartz assemblage, and is characterized by a large number of calcite veins.These veins cut through the formation and earlier veins, and are relatively pure, without metal sulfides (Figure 4I).
Minerals 2023, 13, x FOR PEER REVIEW 8 of 26 growth characteristics with textural and morphological differences and can be divided into the following generations: Py1, Py2: the formation of Py1 primarily occurred particularly in arenaceous limestone and calcareous (carbonaceous) sedimentary rocks during their formation.It generally occurs as strawberry or colloidal aggregates, exhibiting an irregular shape with small particles less than 5 µm (Figure 5A,I).Additionally, many organic-containing pyrite aggregates are observed within this stage.During regional epimetamorphism, pyrite underwent recrystallization and was transformed into cube-like Py2 (Figure 5I).

Samples and Analytical Methods
More than 30 samples from each stage of mineralization were collected and identified under the microscope.Compositions of pyrite and arsenopyrite with different characteristics at each stage were determined using electron probe microanalysis (EPMA).Their trace elements and S isotopic compositions were further constrained using LA-(MC) ICP-MS.

Electron Probe Microanalysis
The EPMA of metal sulfides was carried out at the Key Laboratory of Western China's Mineral Resources and Geological Engineering, Chang'an University.The instrument was a JEOL JXA-8100 electron probe (JEOL, Tokyo, Japan) operated at 20 KV, beam spot current 1 × 10 −8 A, beam spot diameter 1 µm, peak counting time 20 s, and background counting time 10 s.Laboratory standard samples of pyrite, chalcopyrite, galena, sphalerite, bismuth selenide, antimony telluride, and elementary gold, nickel, cobalt, and chromium were used during the analysis.The lower limit of detection of all elements is 0.01%, the relative error of analysis is within ±2%, and the test accuracy is 0.01%.All data are ZAF basic corrections.

In Situ Trace Elements Analysis of Pyrite and Arsenopyrite
In situ trace element analysis of pyrite and arsenopyrite was completed at the State Key Laboratory of Continental Dynamics, Northwest University, Xi'an, China.The analytical instrument was a New wave (esi) dual-wavelength femtosecond LA system (206 and 257 nm) attached to an ICP-MS (Jena PQ-MS Elite).The laser energy was 1 J/cm 2 and the denudation frequency was 10 Hz.The laser single-point strip etching diameter was 53 µm, the ablation time was 50 s, the background collection time was 30 s, and the sample collection time was 50 s.Helium gas was used as carrier gas and was mixed with argon gas before entering ICP.The helium gas flow rate was 0.5 L/min, and the argon gas flow rate was about 1 L/min.USGS synthetic sulfide standard MASS-1 was used as the external standard, Fe element was used as the internal standard, and SRM 610 was used as the The mineralized bodies, Au grades are strongly positively correlated with the contents of arsenopyrite and arsenian pyrite, as evidenced by the comprehensive analysis of drill samples.

Samples and Analytical Methods
More than 30 samples from each stage of mineralization were collected and identified under the microscope.Compositions of pyrite and arsenopyrite with different characteristics at each stage were determined using electron probe microanalysis (EPMA).Their trace elements and S isotopic compositions were further constrained using LA-(MC) ICP-MS.

Electron Probe Microanalysis
The EPMA of metal sulfides was carried out at the Key Laboratory of Western China's Mineral Resources and Geological Engineering, Chang'an University.The instrument was a JEOL JXA-8100 electron probe (JEOL, Tokyo, Japan) operated at 20 KV, beam spot current 1 × 10 −8 A, beam spot diameter 1 µm, peak counting time 20 s, and background counting time 10 s.Laboratory standard samples of pyrite, chalcopyrite, galena, sphalerite, bismuth selenide, antimony telluride, and elementary gold, nickel, cobalt, and chromium were used during the analysis.The lower limit of detection of all elements is 0.01%, the relative error of analysis is within ±2%, and the test accuracy is 0.01%.All data are ZAF basic corrections.

In Situ Trace Elements Analysis of Pyrite and Arsenopyrite
In situ trace element analysis of pyrite and arsenopyrite was completed at the State Key Laboratory of Continental Dynamics, Northwest University, Xi'an, China.The analytical instrument was a New wave (esi) dual-wavelength femtosecond LA system (206 and 257 nm) attached to an ICP-MS (Jena PQ-MS Elite).The laser energy was 1 J/cm 2 and the denudation frequency was 10 Hz.The laser single-point strip etching diameter was 53 µm, the ablation time was 50 s, the background collection time was 30 s, and the sample collection time was 50 s.Helium gas was used as carrier gas and was mixed with argon gas before entering ICP.The helium gas flow rate was 0.5 L/min, and the argon gas flow rate was about 1 L/min.USGS synthetic sulfide standard MASS-1 was used as the external standard, Fe element was used as the internal standard, and SRM 610 was used as the monitoring standard [38,39].The offline data were calculated by ICPMSData Cal software (10.8) [39].

In Situ S Isotope Analysis of Sulfides
In situ S isotopic composition analysis of pyrite and arsenopyrite was completed at the State Key Laboratory of Continental Dynamics, Northwest University, Xi'an, China.The nanoscale excimer laser ablation system (RESOlution M-50, asi) consists of a 193 nm Ar F excimer laser, an X-Y sample moving table, a positioning system, and a two-compartment sample chamber.The energy density of the laser was 3.7 J/cm 2 , the diameter of the spot beam was 37 µm, the laser frequency was 3 Hz, and its carrier gas was high-purity helium with a flow rate of 280 mL/min.A Nu Plasma 1700 Plasma Mass spectrometer, which mainly consists of a Faraday cup and an ion counter, was applied.Faraday cup H5, Ax, and L4 receive 34 S, 33 S, and 32 S respectively.To monitor the accuracy of data, a pair of laboratory standards were inserted in every 3 samples.An in-house pyrite standard (NWU-Py-4) was used as an external standard and a pair of sphalerite grains (NBS123/PSPT-3) were used as quality control standards.The mean δ 34 S V-CDT value of PSPT-3 measured during the analysis was 26.7 ± 0.2‰ (2 S.D., n = 11), which is within the error of the reference values reported by Bao [40] and Chen [41] (δ 34 S V-CDT = 26.4 ± 0.2‰, 2 S.D.).

Textures and Compositions of Pyrite and Arsenopyrite
As mentioned above, the Wangzhuang gold deposit underwent four hydrothermal stages during its formation, with five sub-stages of sulfides.The Py1 and Py2 contain negligible levels of As (0.03% to 0.11%) and no Au, but showed relatively high contents of S (53.41% to 54.69%).The Apy showed obvious enrichment of Au via EPMA mapping (Figure 7), with Au contents ranging from 0.02% to 0.25%.The Py3 is relatively rich in As (1.35% to 10.38%) and Au (0.05% to 0.20%).Py4 has low As contents, ranging from 0.04% to 0.58%, which is higher than Py1 and Py2 but lower than Py3.Additionally, Py4 can detect Au with lesser contents than 0.07% (Tables 1 and S1).In summary, the highest Au contents were found in Apy, followed by Py3 and Py4.Note: bdl-below the detection limit.

In Situ Trace Element Compositions of the Sulfides by LA-ICP-MS
Due to Py1's aggregation with more internal impurities, the reliability of trace elements is compromised, and Py4 exhibits a small ring band, rendering it unsuitable for LA-ICP-MS testing (Figure 5A,I-K).Therefore, the focus of this study is primarily on Py2, Py3, and Apy, with Py2 occurring in the pre-mineralization period and Py3, Apy occurring in the main mineralization period.The results indicate that Py2 has low a gold content (ranging from 0.18 to 7.22 ppm), while both Py3 and Apy stages exhibit higher gold contents (ranging from 120 to 915 ppm).The transitional stage Py3-1 has an intermediate gold content, with a range of 22.9 to 60.0 ppm (Figure 8 and Table 2).Furthermore, the contents of Au, W, Pb, Zn, and Sb in Py2 are relatively low, while the contents of Apy, Py3-1, and Py3-2 are relatively high.These results suggest a close relationship between the trace elements Au, W, Pb, Zn, and Sb.In contrast, Co, Cu, and Bi have relatively high contents in Py2, with a sudden decrease in the Apy stage and a gradual rise in Py3-1 and Py3-2 stages, indicating a weak correlation between Au and Co, Cu, and Bi (Figure 9 and Table 2).Note: bdl-below the detection limit.(ranging from 120 to 915 ppm).The transitional stage Py3-1 has an intermediate gold content, with a range of 22.9 to 60.0 ppm (Figure 8 and Table 2).Furthermore, the contents of Au, W, Pb, Zn, and Sb in Py2 are relatively low, while the contents of Apy, Py3-1, and Py3-2 are relatively high.These results suggest a close relationship between the trace elements Au, W, Pb, Zn, and Sb.In contrast, Co, Cu, and Bi have relatively high contents in Py2, with a sudden decrease in the Apy stage and a gradual rise in Py3-1 and Py3-2 stages, indicating a weak correlation between Au and Co, Cu, and Bi (Figure 9 and Table 2).

S Isotopic Compositions
To investigate the S isotopic compositions of metal sulfides (pyrite and arsenopyrite) at different stages, an LA-MC-ICP-MS in situ S isotope analysis of sulfides from orebodies, alteration zones, and wall rocks was conducted.The δ 34 S values reveal significant variations among metal sulfides at different stages: the δ 34 S values range from 15.3 to 31.2 for Py1 and Py2 during the pre-mineralization stage, 8.4 to 10.9 for Py3 and Apy during the main mineralization stage, and 0.3 to 5.3 for Py4 during the post-mineralization stage (Figure 10, Tables 3 and S2).The results of the in situ S isotopic analysis indicate that there is a significant decrease in δ 34 S values from the pre-mineralization stage to the postmineralization stage.In particular, there was a sudden change in δ 34 S values from the pre-mineralization to the main mineralization stages, which suggests that the hydrothermal conditions during the main mineralization period were different from those during the premineralization stage.These findings provide important information on the metallogenic processes of pyrite and arsenopyrite in the study area.
ure 10 and Table 3).The results of the in situ S isotopic analysis indicate that there is a significant decrease in δ 34 S values from the pre-mineralization stage to the post-mineralization stage.In particular, there was a sudden change in δ 34 S values from the pre-mineralization to the main mineralization stages, which suggests that the hydrothermal conditions during the main mineralization period were different from those during the premineralization stage.These findings provide important information on the metallogenic processes of pyrite and arsenopyrite in the study area.The sequence of metal sulfide formation in the Wangzhuang gold deposit can be determined as Py1→Py2→Apy→Py3 (including Apy, PbS)→Py4 based on the optical microscope and EPMA analysis of ore-forming material fabric (Figure 11).After Py2, a distinct alteration in hydrothermal characteristics is observed, characterized by the introduction of ore-bearing hydrothermal fluids enriched with As, W, Pb, Sb, Au, etc.During this stage, a significant abundance of arsenic-containing minerals, predominantly arsenopyrite, is formed.Subsequently, with the crystallization of arsenopyrite, a mineralrich in arsenic, Py3 containing arsenic began to form.As the consumption of arsenic continued, late-stage Py4 with lower levels of arsenic was produced (Figure 11).According to the girth structure of pyrite and variations in Au, single-particle pyrite can be categorized into three stages: the core (Py1 and Py2), the arsenic-rich growth belt (Apy and Py3), and the arsenic-poor outer growth belt (Py4) (Figure 11).These stages correspond to three phases of hydrothermal activity before, during, and after mineralization.
rite, is formed.Subsequently, with the crystallization of arsenopyrite, a mineral-rich in arsenic, Py3 containing arsenic began to form.As the consumption of arsenic continued, late-stage Py4 with lower levels of arsenic was produced (Figure 11).According to the girth structure of pyrite and variations in Au, single-particle pyrite can be categorized into three stages: the core (Py1 and Py2), the arsenic-rich growth belt (Apy and Py3), and the arsenic-poor outer growth belt (Py4) (Figure 11).These stages correspond to three phases of hydrothermal activity before, during, and after mineralization.The Co/Ni ratio reflects the genesis of pyrite and arsenopyrite [42][43][44][45].In the studied samples, Co/Ni varied over a narrow range (0.1-4.5), and in 80% of analyses, 10.0 > Co/Ni > 0.1, which is typical for hydrothermal pyrite (Figure 12A) [46].High concentrations of Ni in metallogenetic sulfides (Py3 and Apy) may indicate the participation of basic and ultrabasic components supplied into hydrothermal fluids and involved in the deposition of sulfides [44,47], which is consistent with the regional element anomaly (Figure 2B).Additionally, there is a negative correlation between Co/Ni and Au (Figure 12B).Gold is predominantly isomorphic in pyrite with conductivity (Ni/Co > 1), and Co-rich pyrite is not gold-bearing (Figure 11).The Co/Ni ratio reflects the genesis of pyrite and arsenopyrite [42][43][44][45].In the studied samples, Co/Ni varied over a narrow range (0.1-4.5), and in 80% of analyses, 10.0 > Co/Ni > 0.1, which is typical for hydrothermal pyrite (Figure 12A) [46].High concentrations of Ni in metallogenetic sulfides (Py3 and Apy) may indicate the participation of basic and ultrabasic components supplied into hydrothermal fluids and involved in the deposition of sulfides [44,47], which is consistent with the regional element anomaly (Figure 2B).Additionally, there is a negative correlation between Co/Ni and Au (Figure 12B).Gold is predominantly isomorphic in pyrite with conductivity (Ni/Co > 1), and Co-rich pyrite is not gold-bearing (Figure 11).

The Occurrence States of Gold Elements of Pyrite and Arsenopyrite
Previous studies have established a strong correlation between gold (Au) and arsenic (As) in arsenian pyrite [16,48,49], wherein an increase in As substitution within the pyrite structure leads to a higher defect density.This rise in As concentration, attributed to stacking faults or dislocations, serves as the primary mechanism for gold accumulation [50].Atom probe tomography (APT) has been employed by researchers to investigate arsenian

The Occurrence States of Gold Elements of Pyrite and Arsenopyrite
Previous studies have established a strong correlation between gold (Au) and arsenic (As) in arsenian pyrite [16,48,49], wherein an increase in As substitution within the pyrite structure leads to a higher defect density.This rise in As concentration, attributed to stacking faults or dislocations, serves as the primary mechanism for gold accumulation [50].Atom probe tomography (APT) has been employed by researchers to investigate arsenian pyrite in Carlin-type gold deposits, revealing the absence of gold nanoclusters and the binding of Au atoms to As atoms in the form of solid solutions [49][50][51].While the presence of gold nanoparticles cannot be completely ruled out in previous studies, it can be demonstrated that lattice gold predominates when gold elements are relatively uniformly distributed.The EPMA analysis of the Wangzhuang gold deposit reveals a homogeneous distribution of gold elements, while the LA-ICP-MAS analysis demonstrates relatively consistent Au contents within the arsenian ring belt (Figure 8 and Table 2).Additionally, the As/Au ratio boundary graph (Figure 13) shows that the gold in the pyrite (Py3) during the main mineralization period of Wangzhuang gold deposit is in the state of lattice gold occurrence.Therefore, it can be inferred that the occurrence state of lattice gold predominates in the Wangzhuang gold deposit.Based on the close correlation between Au and As in pyrite, it is an effective means of studying the activity characteristics of Au by analyzing the substitution of As [53,54].Previous studies have found that the entry of As into arsenian pyrite may exist in the following forms: As -replaces S -in pyrite [55][56][57]; As 3+ or As 2+ instead of Fe 2+ [53,57,58]; or As mixed in in the form of nanoparticles As 0 [54].A ternary plot of the arsenian pyrite Fe-S-As (at %) can prove whether As replaces S or Fe [49,53], a trend line parallel to the As-S contents distribution as defined in the Fe-S-As (at%) ternary diagram of Wangzhuang gold deposit, indicating that As replaced S in arsenian pyrite (Figure 14A), and the As and S also showed a strong negative correlation (R 2 = 0.923), measured by EPMA, further corroborating this result (Figure 14B).Based on the close correlation between Au and As in pyrite, it is an effective means of studying the activity characteristics of Au by analyzing the substitution of As [53,54].Previous studies have found that the entry of As into arsenian pyrite may exist in the following forms: As -replaces S -in pyrite [55][56][57]; As 3+ or As 2+ instead of Fe 2+ [53,57,58]; or As mixed in in the form of nanoparticles As 0 [54].A ternary plot of the arsenian pyrite Fe-S-As (at %) can prove whether As replaces S or Fe [49,53], a trend line parallel to the As-S contents distribution as defined in the Fe-S-As (at%) ternary diagram of Wangzhuang gold deposit, indicating that As replaced S in arsenian pyrite (Figure 14A), and the As and S also showed a strong negative correlation (R 2 = 0.923), measured by EPMA, further corroborating this result (Figure 14B).
following forms: As -replaces S -in pyrite [55][56][57]; As 3+ or As 2+ instead of Fe 2+ [53,57,58]; or As mixed in in the form of nanoparticles As 0 [54].A ternary plot of the arsenian pyrite Fe-S-As (at %) can prove whether As replaces S or Fe [49,53], a trend line parallel to the As-S contents distribution as defined in the Fe-S-As (at%) ternary diagram of Wangzhuang gold deposit, indicating that As replaced S in arsenian pyrite (Figure 14A), and the As and S also showed a strong negative correlation (R 2 = 0.923), measured by EPMA, further corroborating this result (Figure 14B).S1 (A) and As vs. S for pyrite from Wangzhuang gold deposit (B).

The Source of Ore-Forming Materials Revealed by Trace Elements
It can be seen that the formation of the Wangzhuang gold deposit is closely related to the addition of ore-bearing hydrothermal fluids with different properties.This process resulted in the generation of a significant number of arsenic-containing minerals, where As atoms replaced S atoms within the pyrite lattice, leading to layer faults or dislocations in the crystal structure and facilitating the incorporation of Au into the pyrite lattice.The variations in pyrite composition at different stages indicate significant changes in hydrothermal properties during the mineralization process.The low concentrations of As and Au in stage I (Py1 and Py2) suggest that Au was not significantly enriched during early deformation and metamorphism processes.Stage II (Apy and Py3) exhibits hydrothermal activities characterized by abundant As, Sb, Pb, W, Au, etc. (Figure 9), indicating distinct ore-bearing hydrothermal properties compared to those observed in stage I.These findings imply that the ore-bearing hydrothermal fluid did not originate from the sedimentary strata but from depth.

Source of Ore-Forming Fluid Revealed by Sulfur Isotope
The S isotopic compositions of the Wangzhuang gold deposit exhibit significant variations from the pre-mineralization to the post-mineralization period.In the premineralization period, the δ 34 S value was predominantly greater than 15‰, with an average δ 34 S value exceeding 20‰.However, during the mineralization period, there is a sudden decline in the δ 34 S value to less than 10‰, gradually decreasing to nearly 0 in post-mineralization stages (Figures 10 and 15A).This evolution can be characterized by two gradient processes (Py1 to Py2 and Py3 (Apy) to Py4), as well as a mutation process from Py2 to Py3.The Xiaohe gold deposit, situated approximately 3 km north of the Wangzhuang Gold deposit (Figure 2A), exhibits similar characteristics in terms of S isotopic variation.Specifically, the δ 34 S values exceed 20 during the pre-mineralization and fall below 20 during mineralization.Furthermore, a decreasing trend in δ 34 S values can be observed in metal sulfides, as per their crystallization sequence.These findings suggest a continuous influx of hydrothermal fluids with low δ 34 S values during mineralization; however, the final δ 34 S values consistently remain above 0‰ [59].This phenomenon aligns with the decrease in δ 34 S from pre-mineralization to post-mineralization stages in the Wangzhuang gold deposit.Additionally, the Wangzhuang gold deposit exhibits δ 34 S values in the mineralization period that align closely with those of the Jinlongshan Carlin-type gold deposit (Figure 15B).Given that the above gold deposits are controlled by the Nanyangshan fault at a spatial scale, their ore-hosting structures represent fractured zones influenced by sequence stratigraphic boundaries, while exhibiting comparable similarities in wall rocks.These findings suggest that fluid characteristics within this area's gold deposits remain consistent on a smaller scale, potentially influenced by a shared hydrothermal system.The δ 34 S values of the Py2 stage during pre-mineralization range from 15.8‰ to 28.7‰, while the δ 34 S values without arsenic core range from 21.8 to 28.7 (Table 3), exhibiting significantly large positive value, which can be attributed to thermochemical sulfate reduction (TSR) occurring within a closed system [60,61].Since Py1 was found to be completely modified and exhibited a similar S isotopic composition to Py2, the latter was chosen as the primary focus for investigating the pre-mineralization stage.The pyrite formed during the pre-mineralization transformation of the Jinlongshan gold deposit in the same region also displayed a significantly positive value [20], which is consistent with Wangzhuang and Xiaohe gold deposits in the Zhen'an-Xunyang Basin in terms of regional tectonic evolution, indicating that all these deposits were formed within an enclosed basin environment through regional thermal metamorphism.
The δ 34 S values of the Apy stage during the main mineralization period range from 8.4‰ to 10.9‰, with a more concentrated dataset.As one of the primary gold-bearing minerals, Apy is an important mineral formed in the thermochemical stage of the main mineralization period and occurs earlier than Py3.In combination with its thermochemical properties, it is distinguishable from trace element compositions during pre-mineralization.The δ 34 S values of Py3 during the main mineralization period range from 5.5‰ to 11.2‰ (Table 3), exhibiting significant differences compared to pre-mineralization Py1 and Py2 (Figure 15A) and relatively smaller variations when compared to those observed in Apy.These findings suggest that the sulfur present in the hydrothermal solution associated with the ore did not originate from pyrite or organic sulfur decomposition within the wall rocks, nor was it formed through thermochemical sulfate reduction (TSR).Previous studies on gold deposits have demonstrated that fluid-derived sulfur can be attributed to three potential sources: (1) magmatic origin [16]; (2) homogeneous deep crustal metamorphic origin [11,20,62]; and (3) sedimentary origin [63].The S isotopic characteristics of metal sulfides (Apy and Py3) in the Wangzhuang gold deposit during the metallogenic period differ from those of metal sulfides (Py1 and Py2) in the sedimentary metamorphic stage; thus, it can be excluded as a potential cause for sedimentary transformation.
The δ 34 S values of pyrite during the post-mineralization stage Py4 range from 0.3‰ to 5.3‰, which are relatively smaller compared to those observed during the main mineralization period.This observation suggests that Py4 is a result of the gradual  3 and S2), exhibiting significantly large positive value, which can be attributed to thermochemical sulfate reduction (TSR) occurring within a closed system [60,61].Since Py1 was found to be completely modified and exhibited a similar S isotopic composition to Py2, the latter was chosen as the primary focus for investigating the pre-mineralization stage.The pyrite formed during the pre-mineralization transformation of the Jinlongshan gold deposit in the same region also displayed a significantly positive value [20], which is consistent with Wangzhuang and Xiaohe gold deposits in the Zhen'an-Xunyang Basin in terms of regional tectonic evolution, indicating that all these deposits were formed within an enclosed basin environment through regional thermal metamorphism.
The δ 34 S values of the Apy stage during the main mineralization period range from 8.4‰ to 10.9‰, with a more concentrated dataset.As one of the primary gold-bearing minerals, Apy is an important mineral formed in the thermochemical stage of the main mineralization period and occurs earlier than Py3.In combination with its thermochemical properties, it is distinguishable from trace element compositions during pre-mineralization.The δ 34 S values of Py3 during the main mineralization period range from 5.5‰ to 11.2‰ (Tables 3 and S2), exhibiting significant differences compared to pre-mineralization Py1 and Py2 (Figure 15A) and relatively smaller variations when compared to those observed in Apy.These findings suggest that the sulfur present in the hydrothermal solution associated with the ore did not originate from pyrite or organic sulfur decomposition within the wall rocks, nor was it formed through thermochemical sulfate reduction (TSR).Previous studies on gold deposits have demonstrated that fluid-derived sulfur can be attributed to three potential sources: (1) magmatic origin [16]; (2) homogeneous deep crustal metamorphic origin [11,20,62]; and (3) sedimentary origin [63].The S isotopic characteristics of metal sulfides (Apy and Py3) in the Wangzhuang gold deposit during the metallogenic period differ from those of metal sulfides (Py1 and Py2) in the sedimentary metamorphic stage; thus, it can be excluded as a potential cause for sedimentary transformation.
The δ 34 S values of pyrite during the post-mineralization stage Py4 range from 0.3‰ to 5.3‰, which are relatively smaller compared to those observed during the main mineralization period.This observation suggests that Py4 is a result of the gradual homogenization of hydrothermal reactions in the early stages and subsequent precipitation of metal sulfides leading to progressive decline in 34 S.
The δ 34 S value of pyrite in the Wangzhuang gold deposit exhibits a decreasing trend from the early stage to the late stage throughout the entire mineralization process.Moreover, there is an abrupt change in thermochemical properties, suggesting that this characteristic of thermochemical fluid represents the primary ore-forming fluid, distinct from the metamorphic exudation of ore-bearing strata.Therefore, the origin of this fluid could be either magmatic or deep basement metamorphic.In the Zhen'an-Xunyang Basin, the gold deposits are closely associated with tectonic deformation and metamorphism, with the majority of deposits hosted within secondary structural formations or ore-conducting structures.Hence, it is difficult to determine whether the fluid is of metamorphic or magmatic origin based on its ore-forming materials.Goldfarb [11] concluded that fluid-rock metasomatic reactions occur during the migration process of metamorphic fluids and at the ore-forming site, resulting in overlapping isotopic values from different source areas.However, due to the formation of fluids along fault channels, which dominate the hydrothermal system, significant changes along the fluid path are unlikely.Based on this, the gradual change following fluid mutation is attributed to fluid-rock metasomatic reactions; however, this effect diminishes with fluid migration, aligning more closely with the characteristics of the ore-forming fluid itself.Therefore, δ 34 S values in the middle and late stages of this period are considered to better reflect the true nature of the fluid, and δ 34 S values within this range (0.3‰~5.3‰) may more likely represent magmatic-hydrothermal fluids.Furthermore, combined with the regional element anomaly, which show the anomaly zoning of W→Au (W)→Hg, Sb (Au) from the west to the east, as well as the deposits' distributions, which change from high temperature to low temperature (Figure 2B).Additionally, there is a comprehensive anomaly of Cr-Ni-Ti-Co-Mo located to the west of Wangzhuang and Xiaohe Gold deposits (Figure 2B), indicating that there is a concealed pluton on the west side of the deposits.The metamorphic fluids tend to homogenize fluid properties and are less likely to generate such extensive elemental zones [11][12][13].Conversely, the behavior of magmatic fluids is more influenced by the spatial distribution of intrusions, which aligns better with the occurrence of large-scale elemental zones [64][65][66][67].Consequently, it is inferred that the metallogenic hydrothermal fluid in the middle zone of Zhen'an-Xunyang Basin is predominantly derived from magmatic sources.

Ore-Forming Process
In recent years, a series of early-to-late Mesozoic plutons have been discovered in the Zhen'an-Xunyang Basin and its surrounding areas.The diagenesis dates primarily range from 150 to 125 Ma [68][69][70][71][72], which align closely with the formation ages of several gold deposits in the region (e.g., Jinlongshan's metallogenic age is 142 Ma and Xiajiadian's metallogenic age is 139 Ma or 141 Ma) [19,73,74].Previous studies suggested that Carlin-type gold deposits are predominantly found in tectonic settings characterized by extension or the transition from compression to extension [8,10,20,26,75,76], which is consistent with the extensional tectonic stress field dominant in the Zhen'an-Xunyang Basin and the regional tectonic background of the Yanshanian stage [31].Meng [77] and Zhang [31] highlighted the connection between the evolution of ZXB during the Late Devonian to Early Carboniferous era and the southern collision of the North Qinling Mountains.This collision led to a shift in ZXB's geological features: from a shallow-water carbonate platform in the Devonian period, it transformed into a rifted basin during the Late Devonian and Early Carboniferous periods due to fault subsidence in the uplifted regions [77].In addition, Yin [78,79] provided evidence from lithofacies' paleogeography that the south Qinling region was primarily characterized by a rifted sedimentation.Based on the above conclusions, the formation of the Zhen'an-Xunyang Basin was mainly restricted by the extensional tectonic stress field, and the regional stress was in a state of decompression.During the intrusion of magmatic rocks, ore-forming elements were extracted from the deep basement through gas, water, and hydrothermal fluids.Subsequently, these fluids migrated along the regional deep fault (Nanyangshan fault) under decompressive conditions, and precipitated ore-forming materials within upper secondary tectonic fracture zones.Through thermal convection within the rock mass, ore-bearing hydrothermal fluids continuously interacted with wall rocks to replace and assimilate them, resulting in the gradual homogenization of fluid channels.Later on, due to the differential unloading temperatures of ore-forming materials, varying migration distances led to vertical and horizontal zoning patterns observed in tungsten, gold, and mercury-antimony deposits (Figure 16).Therefore, it is plausible that the hydrothermal tungsten deposits, Carlin-type gold deposits, and medium-low-temperature hydrothermal mercury-antimony deposits are all products of a shared hydrothermal metallogenic system.deep basement through gas, water, and hydrothermal fluids.Subsequently, these fluids migrated along the regional deep fault (Nanyangshan fault) under decompressive conditions, and precipitated ore-forming materials within upper secondary tectonic fracture zones.Through thermal convection within the rock mass, ore-bearing hydrothermal fluids continuously interacted with wall rocks to replace and assimilate them, resulting in the gradual homogenization of fluid channels.Later on, due to the differential unloading temperatures of ore-forming materials, varying migration distances led to vertical and horizontal zoning patterns observed in tungsten, gold, and mercury-antimony deposits (Figure 16).Therefore, it is plausible that the hydrothermal tungsten deposits, Carlin-type gold deposits, and medium-low-temperature hydrothermal mercury-antimony deposits are all products of a shared hydrothermal metallogenic system.The δ 34 S values of the metal sulfides in the Wangzhuang gold deposit during premineralization, mineralization, and post-mineralization periods range from 15.8‰ to 31.2‰, 5.5‰ to 11.2‰, and 0.3‰ to 5.3‰, respectively.These results suggest that there was a significant hydrothermal interaction between fluids and rocks in the

Minerals 2023 , 26 Figure 2 .
Figure 2. (A) Geologic map of the Zhen'an-Xunyang Basin (geologic framework modified after Zhang [27]); (B) simplified geological map with geochemical anomalies of stream sediments and the locations of related deposits.

Figure 2 .
Figure 2. (A) Geologic map of the Zhen'an-Xunyang Basin (geologic framework modified after Zhang [27]); (B) simplified geological map with geochemical anomalies of stream sediments and the locations of related deposits.

Figure 3 .
Figure 3. (A) Simplified geologic map of the Wangzhuang gold deposit; (B) eastern exploration area.

Figure 3 .
Figure 3. (A) Simplified geologic map of the Wangzhuang gold deposit; (B) eastern exploration area.

Figure 4 .
Figure 4. Field photographs showing alteration characteristics of the surface ore body (A-D) and drill core (E-I) in the Wangzhuang deposit.(A) calcareous (carbonaceous) phyllite and calcarenite with interbedded ore bodies are cut through by late quartz veins; (B) acicular arsenopyrite in calcareous (carbonaceous) phyllite ore bodies; (C) the calcareous (carbonaceous) phyllite ore body develops along the bedding hydrothermal quartz veins, and the arsenopyrite mineralization and enrichment can be seen at the edge of the quartz veins; (D) the multi-layer mineralized body and sandclastic limestone are interbedded, and the mineralized quartz veins are enriched in the later period and cut through the earlier mineralized alteration zone; (E) two kinds of ore bodies are developed, one is arsenopyrite-phyllite-type, the second is hydrothermal quartz-vein-modified-type; (F-H) the pyrite sericite was altered and developed, and a small amount of arsenopyrite was observed; (I) late quartz calcite veins cut through early ore bodies.Qtz-Quartz; Cal-Calcite; Py-Pyrite; Apy-Arsenopyrite.

Figure 4 .
Figure 4. Field photographs showing alteration characteristics of the surface ore body (A-D) and drill core (E-I) in the Wangzhuang deposit.(A) calcareous (carbonaceous) phyllite and calcarenite with interbedded ore bodies are cut through by late quartz veins; (B) acicular arsenopyrite in calcareous (carbonaceous) phyllite ore bodies; (C) the calcareous (carbonaceous) phyllite ore body develops along the bedding hydrothermal quartz veins, and the arsenopyrite mineralization and enrichment can be seen at the edge of the quartz veins; (D) the multi-layer mineralized body and sand-clastic limestone are interbedded, and the mineralized quartz veins are enriched in the later period and cut through the earlier mineralized alteration zone; (E) two kinds of ore bodies are developed, one is arsenopyrite-phyllite-type, the second is hydrothermal quartz-vein-modified-type; (F-H) the pyrite sericite was altered and developed, and a small amount of arsenopyrite was observed; (I) late quartz calcite veins cut through early ore bodies.Qtz-Quartz; Cal-Calcite; Py-Pyrite; Apy-Arsenopyrite.

Figure 6 .
Figure 6.Paragenetic sequence of main minerals from the periods and stages of mineralization.The width of the lines corresponds to the relative abundance of minerals in each stage.

Figure 6 .
Figure 6.Paragenetic sequence of main minerals from the periods and stages of mineralization.The width of the lines corresponds to the relative abundance of minerals in each stage.

Figure 8 .
Figure 8. (A-C) Py2 (BSE) is rimmed by Py3, which has similar morphology and relief.(D) Dislocation of arsenopyrite by tectonic event.Yellow dots indicate locations of LA-ICP-MS analysis, and analysis numbers and Au concentration in ppm are shown.Py2 = pre-mineralization pyrite 2; Py3 = main mineralization 3, which contains more As than Py2; Apy= arsenopyrite; Py3-1= earlier-stage pyrite in Py3 with growth zonation.

Figure 8 .
Figure 8. (A-C) Py2 (BSE) is rimmed by Py3, which has similar morphology and relief.(D) Dislocation of arsenopyrite by tectonic event.Yellow dots indicate locations of LA-ICP-MS analysis, and analysis numbers and Au concentration in ppm are shown.Py2 = pre-mineralization pyrite 2; Py3 = main mineralization 3, which contains more As than Py2; Apy= arsenopyrite; Py3-1= earlier-stage pyrite in Py3 with growth zonation.

Figure 11 .
Figure 11.Stages of sulfidic paragenesis.(A) Backscatter electron image of multistage pyrite; (B-E) schematic diagram showing the sequence of formation of the four types of sulfides.

Figure 11 .
Figure 11.Stages of sulfidic paragenesis.(A) Backscatter electron image of multistage pyrite; (B-E) schematic diagram showing the sequence of formation of the four types of sulfides.

Minerals 2023 , 26 Figure 12 .
Figure 12.Ratio diagram of Co/Ni (A) and relational diagram of Co/Ni and Au (B).

Figure 12 .
Figure 12.Ratio diagram of Co/Ni (A) and relational diagram of Co/Ni and Au (B).

26 Figure 13 .
Figure 13.Simplified As/Au ratio boundary graph of Wangzhuang gold deposit.The broken line represents the limit above which Au nanoparticles are meant to form [52], Carlin-type region from Reid [52].

Figure 13 .
Figure 13.Simplified As/Au ratio boundary graph of Wangzhuang gold deposit.The broken line represents the limit above which Au nanoparticles are meant to form [52], Carlin-type region from Reid [52].

Figure 14 .
Figure 14.Composition of pyrite on As-Fe-S ternary from analyses in Table 1 (A) and As vs. S for pyrite from Wangzhuang gold deposit (B).Figure 14.Composition of pyrite on As-Fe-S ternary from analyses in Table S1 (A) and As vs. S for pyrite from Wangzhuang gold deposit (B).

Figure 14 .
Figure 14.Composition of pyrite on As-Fe-S ternary from analyses in Table 1 (A) and As vs. S for pyrite from Wangzhuang gold deposit (B).Figure 14.Composition of pyrite on As-Fe-S ternary from analyses in Table S1 (A) and As vs. S for pyrite from Wangzhuang gold deposit (B).

Minerals 2023 , 26 Figure 15 .
Figure 15.Boxplot diagrams δ 34 S date of pyrite and arsenopyrite in each stage of Wangzhuang gold deposit (A) and histogram of δ 34 S date in ore pyrite from the Wangzhuang (date from this study) and Jinlongshan (date from Ma [29]) (B).

Figure 15 .
Figure 15.Boxplot diagrams δ 34 S date of pyrite and arsenopyrite in each stage of Wangzhuang gold deposit (A) and histogram of δ 34 S date in ore pyrite from the Wangzhuang (date from this study) and Jinlongshan (date from Ma [29]) (B).The δ 34 S values of the Py2 stage during pre-mineralization range from 15.8‰ to 28.7‰, while the δ 34 S values without arsenic core range from 21.8 to 28.7 (Tables3 and S2), exhibiting significantly large positive value, which can be attributed to thermochemical sulfate reduction (TSR) occurring within a closed system[60,61].Since Py1 was found to be completely modified and exhibited a similar S isotopic composition to Py2, the latter was chosen as the primary focus for investigating the pre-mineralization stage.The pyrite formed during the pre-mineralization transformation of the Jinlongshan gold deposit in the same region also displayed a significantly positive value[20], which is consistent with Wangzhuang and Xiaohe gold deposits in the Zhen'an-Xunyang Basin in terms of regional tectonic evolution, indicating that all these deposits were formed within an enclosed basin environment through regional thermal metamorphism.The δ 34 S values of the Apy stage during the main mineralization period range from 8.4‰ to 10.9‰, with a more concentrated dataset.As one of the primary gold-bearing minerals, Apy is an important mineral formed in the thermochemical stage of the main mineralization period and occurs earlier than Py3.In combination with its thermochemical properties, it is distinguishable from trace element compositions during pre-mineralization.The δ 34 S values of Py3 during the main mineralization period range from 5.5‰ to 11.2‰ (Tables3 and S2), exhibiting significant differences compared to pre-mineralization Py1 and Py2 (Figure15A) and relatively smaller variations when compared to those observed in Apy.These findings suggest that the sulfur present in the hydrothermal solution associated with the ore did not originate from pyrite or organic sulfur decomposition within the wall rocks, nor was it formed through thermochemical sulfate reduction (TSR).Previous studies on gold deposits have demonstrated that fluid-derived sulfur can be attributed to three potential sources: (1) magmatic origin[16]; (2) homogeneous deep crustal metamorphic origin[11,20,62]; and (3) sedimentary origin[63].The S isotopic characteristics of metal sulfides (Apy and Py3) in the Wangzhuang gold deposit during the metallogenic period

7 . Conclusions 1 .
The hydrothermal mineralization period of the Wangzhuang gold deposit can be divided into four mineralization stages: I, low-sulfide quartz early stage; II, main metallogenic stage of arsenopyrite-arsenian pyrite-quartz; III, low-quartz sulfide stage; IV, late stage of calcite-quartz.Stage II serves as the main phase of mineralization, during which significant amounts of arsenopyrite and arsenian pyrite crystallize.The positive correlation between the abundance of arsenic-bearing minerals and gold grades reveals their genetic link.2. The metal sulfide generation sequence of the Wangzhuang gold deposit is Py1→Py2→Apy→Py3 (Apy, PbS)→Py4.After the formation of Py2, there is a significant presence of fluid rich in As, Sb, Pb, W, and Au.The replacement of S by As atoms in the pyrite lattice resulted in layer faults or dislocations in the crystal structure and contributed to the incorporation of Au into pyrite.3. The δ 34 S values of the metal sulfides in the Wangzhuang gold deposit during premineralization, mineralization, and post-mineralization periods range from 15.8‰ to 31.2‰, 5.5‰ to 11.2‰, and 0.3‰ to 5.3‰, respectively.These results suggest that there was a significant hydrothermal interaction between fluids and rocks in the early stage of mineralization.Furthermore, the δ 34 S values ranging from 0.3‰ to 5.3‰ after the mineralization period imply an injection of magmatic fluid into the Wangzhuang gold deposit during its metallogenic process.
hydrothermal mineralization period of the Wangzhuang gold deposit can be divided into four mineralization stages: I, low-sulfide quartz early stage; II, main metallogenic stage of arsenopyrite-arsenian pyrite-quartz; III, low-quartz sulfide stage; IV, late stage of calcite-quartz.Stage II serves as the main phase of mineralization, during which significant amounts of arsenopyrite and arsenian pyrite crystallize.The positive correlation between the abundance of arsenic-bearing minerals and gold grades reveals their genetic link.2.The metal sulfide generation sequence of the Wangzhuang gold deposit is Py1→Py2→ Apy→Py3 (Apy, PbS)→Py4.After the formation of Py2, there is a significant presence of fluid rich in As, Sb, Pb, W, and Au.The replacement of S by As atoms in the pyrite lattice resulted in layer faults or dislocations in the crystal structure and contributed to the incorporation of Au into pyrite.3.

Table 1 .
EPMA compositions of the pyrite and arsenopyrite from the Wangzhuang gold deposit (wt%).

Table 1 .
EPMA compositions of the pyrite and arsenopyrite from the Wangzhuang gold deposit (wt%).

Table 3 .
LA -MC-ICP-MS In situ S isotopic compositions of pyrite and arsenopyrite from the Wangzhaung gold deposit.