The northern margin of the West Tianshan in Xinjiang is well endowed with epithermal gold deposits. These deposits are primarily hosted in the continental volcanic rocks of the Late Devonian-Early Carboniferous Dahalajunshan Formation and are concentrated in the Tulasu and Yelimodun volcanic fault-depression basins and the Wusunshan area. Based on a systematic review of the geological and geochemical characteristics of typical gold deposits such as Axi, Jingxi-Yermand, and Tawuerbieke in the region, this paper analyzes the relationship between gold mineralization and regional tectonic-magmatic evolution, and discusses the post-mineralization modification and preservation processes as well as their implications for mineral exploration. The epithermal gold deposits in the northern margin of the West Tianshan include various types such as low-sulfidation, high-sulfidation, and porphyry-epithermal transitional types, which exhibit significant differences in ore body occurrence, ore texture, mineral assemblages, and alteration characteristics. The ore-forming materials are mainly derived from the host volcanic-subvolcanic rocks, and the ore-forming fluids consist primarily of magmatic hydrothermal fluids (high-sulfidation type), meteoric water (low-sulfidation type), or a mixture of these two fluids (porphyry-epithermal transitional type). Gold precipitation mechanisms include fluid boiling, water-rock interaction, and fluid mixing. The mineralization age is mainly concentrated in the Late Devonian-Early Carboniferous, formed in a back-arc extensional environment during the peak subduction of the North Tianshan and South Tianshan oceans. After their formation, the deposits underwent a complex modification and preservation history. The epithermal gold deposits in the Tulasu and Yelimodun basins have been preserved due to relatively weak erosion, and their deep sections hold potential for the discovery of porphyry-skarn-type Cu-Au polymetallic deposits. In contrast, the peripheral areas of the basins have experienced higher degrees of erosion, leading to the destruction of most epithermal deposits, but the prospects for porphyry- and skarn-type deposits remain favorable.

The Qinling metallogenic belt is one of China’s most important Au–polymetallic metallogenic belts and the country’s second-largest Au-metallogenic belt after Jiaodong. In recent years, new breakthroughs have been achieved in many deposits such as Zaozigou, creating an urgent need for in-depth research on its Au-metallogenic regularities and resource potential. Based on a systematic review of strata, structures, magmatism, geophysical–geochemical characteristics, and the metallogenic setting, mineralization features, and ore-controlling factors of 613 Au deposits (or occurrences) within the belt, this study reveals that Au deposits in the Qinling metallogenic belt display a spatial pattern of "NW-trending belts and NE-trending clusters". Large Au deposits commonly occur at the intersections of NW- and NE-trending structures and in areas with intense magmatic activity. The Au metallogenesis of the eastern and western Qinling exhibits significant differences. In western Qinling, most Au deposits are hosted in the Devonian, Permian, and Triassic strata, with mineralization ages concentrated at 250～230 Ma and 225～210 Ma, closely related to contemporaneous magmatism. Metallogenic types include hydrothermal type hosted in metamorphosed clastic rocks and magmatic-hydrothermal type. In eastern Qinling, Au deposits are mainly hosted in the Archean Taihua Group, the Cambrian, and the Devonian strata, with mineralization ages primarily between 145 and 110 Ma. Their metallogenic type is mainly magmatic-hydrothermal type. For crustal structure, western Qinling shows crustal decoupling influenced by the expansion of the Tibetan Plateau, with deep magmatic channels controlling the distribution of Au deposit districts. In contrast, eastern Qinling exhibits high-conductivity crust–mantle penetrating structures influenced by the Paleo-Pacific Plate, contributing to the Yanshanian metallogenesis. Through comprehensive comparison, this study delineates 25 fourth-order Au metallogenic sub-belts and 10 Au metallogenic series within the Qinling metallogenic belt. Among these, the two most important series are the Indosinian series related to intermediate–felsic magmatic intrusions and the Yanshanian series associated with magmatic–hydrothermal activity. Integrating geological, geophysical, and geochemical information, 73 prospective Au exploration targets are identified within the Qinling metallogenic belt (28 Class I, 34 Class II, and 11 Class III). Based on the metallogenic regularities and resource-potential assessment, It is suggested that exploration in western Qinling should focus on the Xiahe–Hezuo and Zhaishang–Liba ore districts, targeting the deep and peripheral zones of existing deposits. In addition, exploration should also be strengthened in Huayagou–Jiutiaogou, FengTai, and other prospective areas, and particular attention should be given to concealed orebodies related to magmatic-hydrothermal activity in the Wenxian–Kangxian ore district. In eastern Qinling, the application of integrated geophysical techniques should be enhanced for deep-level exploration. Deep exploration should be prioritized in the Xiaoqinling ore district, with special attention to deep and peripheral zones of known deposits such as Xiajiadian, Liujiaxia, and Sulinggou.

The Zaozigou gold deposit is located in the Triassic intracontinental rift basin at the western part of the West Qinling orogenic belt, between the Zacalebu-Zaozigou fault and the Sangqu-Diluotang fault. The Zaozigou gold deposit has been divided into two periods and four stages, the electron probe analysis is focused on the sulfide in the pyrite - arsenopyrite - quartz (II) stage during the hydrothermal mineralization stage in this paper. There are mainly four groups of structures in the mine, such as NE, NW, near EW and near SN trending, among which NE and NW trending are the main ones. There were two types of sulfide assemblage in stage II, one is porous hemidiomorphic pyrite (II₁), the other is flat idiomorphic pyrite (II₂). In situ sulfur and LA-ICP-MS trace element experiments were carried out for the two subclasses in stage II. The results showed that the pyrite is arsenic-containing pyrite with poor iron and sulfur. The δ³⁴S_V-CDT of pyrite in II₁ stage is −9.92‰～−14.00‰, the δ³⁴S_V-CDT of pyrite in II₂ stage is −15.58‰～−23.46‰, and the δ³⁴S_V-CDT value of pyrite in II₂ stage is larger. The ore-forming materials may be mainly sedimentary and magmatic sources at first, with a small amount of metamorphic sources added later. The trace data of pyrite show that the occurrence form of Au shows a gradual transition trend from Au⁺ to Au⁰, the changes of Co, Ni and As elements in iron and copper elements show a downward trend, and the changes of Cu, Pb, Zn and Ag elements in metallogenic elements show an upward trend. The Co-Ni binary discriminant map indicates that the proportion of hydrothermal deposits increased in the later ore-forming period, and the Co-Ni-As map shows that the two subpyrites are located in the combination area of Carlin type, epithermal type and magmatic hydrothermal type, indicating that the Zaozigou gold deposit has multi-stage genesis. Based on the geological and geochemical characteristics of the deposit, it is considered that the Zaozigou gold deposit belongs to the post-magmatic hydrothermal type.

The Liba gold deposit is located 2 km outside the Zhongchuan pluton in the West Qinling Orogen. Based on the latest exploration results of the Liba gold deposit, the geological characteristics are analyzed in detail, and the fluid inclusion and zircon U-Pb dating in the gold bearing quartz vein are studied. The mineralized alteration types of Liba gold deposit are pyritization, sericitization and silicification, which are obviously different with the metamorphic characteristics of the Zhongchuan pluton contact zone. Mineralized alteration, ore body and vein rock are strictly controlled by faults, but the scale and mineralization degree of vein rocks are lower than ore body, indicating that magmatic activity may not provide main fluid and material for metallogenesis. The study of fluid inclusions indicate that the ores were deposited from medium-high temperature (220～360 ℃), low salinity (5% NaCl_eq～10% NaCl_eq) NaCl-H₂O-CO₂-(CH₄) fluids, similar to metamorphic fluid. The zircons in the gold bearing quartz veins are mostly sub rounded, indicating that they may undergone the process of transportation and rounding sedimentation. Zircon U-Pb ages can be divided into four spectral segments: 397～585 Ma, 673～1023 Ma, 1097～1868 Ma, and 1963～2575 Ma, which are very close to the age characteristics of detrital zircons in the host rock Liba Group, indicating that they were captured from the stratum during the activation and migration of ore-forming fluid. The Liba gold deposit can be grouped with other orogenic gold deposits that have similar characteristics, which is formed under the transition tectonic background from collision to extension. During the emplacement of Zhongchuan pluton, faults were developed along its margin, providing favorable spaces for the precipitation of ore-forming fluid and the emplacement of vein rocks. This caused the granitic pluton, vein rocks and gold bodies are together with space and time, but it may not have an inherent genetic relationship.

Arsenopyrite (Apy) and chlorite (Chl) are abundant sulfide or altered minerals in hydrothermal gold deposits, which been widely used in the inversion of the physical chemical conditions of gold mineralization. The Jinshan gold deposit in Gansu Province is located in the Xiahe-Xihe-Fengxian-Huangbaiyuan metallogenic sub-belt in the eastern section of the West Qinling metallogenic belt, with superior mineralization conditions, characterized by the development of multiple generations of arsenopyrite and chlorite. In this study, we take the various types of arsenopyrite and chlorite in ore samples from the Jinshan gold deposit as the research object. Based on the division of the three mineralization stages in Jinshan Gold deposit, using electron probes to determine the major elemental composition of Apy (Apy-Ⅱ～Apy-Ⅲ) and Chl (Chl-Ⅰ～Chl-Ⅲ) at each stage, dividing the chemical types of Chl-Ⅰ～Chl-Ⅲ, calculating the formation temperature, oxygen fugacity (lgfO₂), sulfur fugacity (lgfS₂), and pH value of Chl-Ⅰ～Chl-Ⅲ and Apy-Ⅱ～Apy-Ⅲ. Furthermore, analyzing the formation environment and physicochemical conditions of Apy and Chl at each stage, and exploring the gold mineralization mechanism of the Jinshan gold deposit. The results indicate that the diagenetic shallow metamorphic stage of Chl-I exhibits characteristics of low temperature, low lgfO₂, and low lgfS₂. During the hydrothermal mineralization stage, the temperature, lgfO₂, lgfS₂, and pH values of Chl-Ⅱ and Apy-Ⅱ significantly increased compared to stage I, indicating the loss of a large amounts of acidic components such as CO₂ in Stage II, it is speculated that there was strong fluid mixing and boiling during the hydrothermal mineralization stage. Subsequently, during the hydrothermal mineralization stages Ⅱ～Ⅲ, boiling causes a significant decrease in temperature, pressure, and S content in the fluid, promoting large-scale precipitation of Au in the form of natural gold, thereby promoting the large-scale precipitation of Au in the form of natural gold. Meanwhile, under low sulfur fugacity and neutral pH value conditions, a large amount of invisible gold was formed in arsenopyrite as Au-As like substances.

The Zhen’an-Xunyang basin, an Early Paleozoic rifted basin situated in the central part of the South Qinling tectonic belt, has seen the discovery of several disseminated gold deposits, like Xiaohe, Huijiagou, and Wangzhuang in recent years. Understanding the occurrence state of gold in these deposits is crucial for uncovering the regional gold mineralization enrichment mechanism. This study focuses on two fine-disseminated gold deposits, Wangzhuang and Laojunmiao, by carrying out the systematic microscopic identification and EPMA analysis. These gold deposits exhibit low-grade and metallic sulfide-hosted mineralization. Three types of pyrite closely associated with gold mineralization are identified in the region: arsenic-free pyrite (Py1, Py2), arsenic-bearing pyrite (arsenopyrite) (Py3, Apy), and arsenic-poor pyrite (Py4), with gold enrichment mainly observed after Py2. The Co/Ni ratios of the ore-forming pyrite during the mineralization period typically fall between 1 to 10, indicating a hydrothermal origin linked to the influx of arsenic-bearing hydrothermal fluids. Furthermore, based on the Au-As relationship, it is tentatively suggested that gold elements in the fine-disseminated gold deposits in the area are primarily present in lattice gold form within pyrite and arsenopyrite.

The Laojunmiao gold deposit, located between the Gongguan and Qingtongou super-large Hg-Sb deposits, is a medium-size gold deposit recently discovered in the South Qinling Orogenic Belt. The gold mineralization mainly hosted in the clastic-carbonate rocks of the Upper Devonian Xichahe Formation. Controlled by stratigraphy and structure, the orebodies are distributed along the EW-trending structural fracture zone, and the mineralization is relatively concentrated at the intersection of faults. However, there is still a lack of systematic research on the distribution pattern of gold in minerals and the types of deposits. Based on field investigations, mineralogy observations, backscattered electron (BSE) imaging, and electron probe micro probe analysis (EPMA), the compositions of the gold-bearing minerals and the occurrence state of Au in the Laojunmiao gold deposit are determined, and the deposit's genesis was discussed. The results show that the mineralization process of the Laojunmiao gold deposit can be divided into three stages: sedimentary-diagenetic stage, hydrothermal mineralization stage, and supergene oxidation stage. The gold mineralization during the hydrothermal stage is predominantly fine-grained disseminated type, which can be subdivided into three substages: Quartz + Arsenic-bearing pyrite stage (Ⅰ), Quartz + Arsenic-bearing pyrite + Arsenopyrite + Sphalerite stage (Ⅱ), and Quartz + Calcite stage (Ⅲ). Arsenic-bearing pyrite and arsenopyrite are both gold-bearing minerals, but pyrite is the primary gold-bearing mineral. Both sedimentary-stage pyrites (Py1 and Py2) and hydrothermal-stage pyrites (Py3 and Py4) contain gold. The gold content of hydrothermal-stage pyrites is significantly higher than that of sedimentary-stage pyrites, and there is a positive correlation between Au and As. Gold primarily exists as invisible gold. Au in sedimentary-stage pyrites (Py1 and Py2) occurs primarily as gold nanoparticles (Au⁰); while gold in hydrothermal-stage pyrites (Py3 and Py4) and arsenopyrite (Apy) occurs as lattice gold (Au⁺). The results indicate that the Laojunmiao gold deposit show similargeological characteristics, metallogenic conditions, and gold occurrence modes with typical Carlin-type gold deposits. Compared with the δFe-δS, δFe/δS-As, and (Fe+S)-As systems of various genetic types of gold deposits in China, the pyrite mineralization during the mineralization period all falls within the Carlin-type gold deposit region. Therefore, the Laojunmiao gold deposit could be classified as a Carlin-type gold deposit.

The Saibagou gold deposit, located in the Wulan area, eastern part of the northern Qaidam metallogenic belt, is one of the representative gold deposits in the northern Qaidam metallogenic belt. Recently, new breakthroughs have been made in prospecting at the deep and peripheral areas, but the genetic mechanism of the deposit is still controversial. Fluid inclusions and H-O-S-Pb isotopes of gold-bearing quartz veins from the Saibagou deposit are examined in this study. The results show that the fluid inclusions in the Saibagou gold deposit are mainly characterized by gas-liquid two-phase inclusions and CO₂-bearing three-phase inclusions. The homogenization temperature of the inclusions ranges from 200 ℃ to 320 ℃, the salinity ranges from 0.18% NaCl_eqv to 14.67% NaCl_eqv, and the fluid density ranges from 0.67 g/cm³ to 1.13g/cm³. These lines of evidence support an ore-forming fluid characterized by medium temperature, medium-low salinity and low density, and belonging to the H₂O-NaCl-CO₂ system. The δD_V-SMOW values are between −75.1‰ and −65.2‰, and δ¹⁸O_H2O values are between 2.3‰ and 3.3‰, suggesting that the ore-forming fluid is mainly derived from magmatic water with a small amount of metamorphic fluid. S isotope studies show that δ³⁴S of pyrite is between −2.52‰ and 2.61‰, which is within the composition range of meteorite S, reflecting that the sulfur in the deposit mainly comes from deep mantle, which may be related to magmatic activity. The pyrite ²⁰⁶Pb/²⁰⁴Pb ranges from 18.0314 to 18.2503, the ²⁰⁷Pb/²⁰⁴Pb ranges from 15.5907 to 15.7308, and the ²⁰⁸Pb/²⁰⁴Pb ranges from 38.1726 to 38.4326, indicating that Pb is mainly derived from magmas, and to a lesser extent, the Cambrian-Ordovician strata. Combined with the geological characteristics, fluid inclusions and H-O-S-Pb isotope research results, as well as the regional tectonic evolution background, it can be concluded that the Saibagou gold deposit is an orogenic gold deposit formed by continental collision between the Qaidam Block and Olongbuk Block and its genesis is closely related to the dike activities in the mining area.

The northern Qaidam metallogenic belt is one of the most important gold and polymetallic metallogenic belts in Qinghai Province. The gold mineralization of the Xitieshan lead-zinc deposit, Qinglonggou gold deposit and Jinlonggou gold deposit, which have been discovered so far, is mainly produced in the ductile/brittle fault zone in the western Saishiteng area. In recent years, a new Sanjiaodingbei gold deposit has been discovered in the west part of Saishiteng tectonic belt. The detailed anatomical fracture characteristics and their relationship with gold enrichment are of great significance for prospecting and deployment in Saishiteng area. Based on the detailed field investigation, structural analysis and microscopic characteristics of the Sanjiaodingbei fault zone, it is concluded that the ore-bearing fault zone has ductile deformation in the early stage and brittle deformation in the later stage. Among them, mylonitization and curved neck developed in the fault zone indicate that the early left-lateral ductile shear deformation was the main deformation. Later, brittle deformation was superimposed and fault cataclastic rocks developed, showing the characteristics of thrust faults.By means of quartz fabric analysis (EBSD) in mylonite belt, the results show that the preferred orientation of quartz C-axis lattice is dominated by bottom <a> slip, the formation temperature is medium and low temperature, and the extremely dense characteristics indicate that the deformation pattern is left-lateral shear. According to the comprehensive regional data, the mylonitization in the early stage and the superimposed brittle fracture in the late stage are the key factors of gold enrichment and mineralization, which can be used as a marker for further gold prospecting.

The Pianyanzi gold deposit, situated on the western margin of the Yangtze Craton within the Daduhe gold belt in western Sichuan Province, represents a rare sellaite-bearing orogenic gold deposit.However, key aspects of its ore-forming processes, particularly regarding the nature of ore-forming fluids and the mechanisms governing gold enrichment and precipitation, remain poorly constrained. This study integrates field observations with microthermometric analysis of fluid inclusions, electron probe microanalysis (EPMA) of individual minerals, and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in-situ microanalysis of individual fluid inclusions. Based on these experimental results, thermodynamic simulations were conducted to comprehensively investigate the conditions conducive to gold enrichment and its precipitation mechanisms. Based on the ore vein cross-cutting relationships and mineral assemblages, the mineralization process can be divided into four distinct stages: the pyrite-quartz stage (I), the pyrite- sellaite-gold-quartz-dolomite stage (II), the quartz-polymetallic sulfide stage (III), and the hematite- limonite-gold stage (IV). EPMA analyses reveal that the gold fineness values in Stage II and Stage IV range from 976.4 to 986.9 and from 960.9 to 992.9, respectively, indicating a consistently high gold content. Fluid inclusions are predominantly CO₂-bearing and H₂O-bearing, with homogenization temperatures ranging from 135 to 357.1 ℃, peaking between 220 and 300 ℃, and salinities varying from 0.4% NaCl_eqv to 14.4% NaCl_eqv, with a peak concentration between 6% NaCl_eqv and 12%NaCl_eqv. LA-ICP-MS analyses of individual fluid inclusions reveal that during the evolution from the early to late stages of mineralization, both the total elemental content and the concentrations of trace elements such as Na and K exhibit a progressively decreasing trend. Moreover, the Rb/Na, Cs/Na, Sr/Na, and K/Na ratios observed in these fluid inclusions are consistent with the geochemical signatures of fluids associated with orogenic gold deposit. Thermodynamic simulations and integrated studies indicate that gold is primarily transported in the form of AuHS⁰ complexes. The decrease in temperature during stages II, along with an increase in oxygen fugacity specifically in stage IV, may serve as the primary factors contributing to gold precipitation and variations in gold fineness.