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The study of metallogeny includes origin, development, modification, and preservation of mineralisation. The understanding of temporal evolution, and post-mineralisation modification and preservation of mineralisation are vital for building metallogenic theory and mineral prospecting, but they remain poorly understood and controversial. The Zaozigou deposit is the largest Au deposit in the West Qinling Orogen of central China with a resource of 142 t Au, and offers an excellent opportunity for deciphering the post-mineralisation exhumation and preservation of Au deposit in orogens. Here, we present integrated results from zircon U-Pb (ZUPb), apatite U-Pb (AUPb), apatite fission-track (AFT) and apatite (U-Th-Sm)/He (AHe) dating, thermal history modelling, biotite thermobarometer, and pyrite thermoelectricity of the deposit. The aims of the study are to decipher the temporal history, and post-mineralisation tectonic evolution and exhumation, and to evaluate the degree of exhumation and preservation potential of the deposit. Integrating the newly determined ZUPb (ca. 242–238 and 218–201 Ma), AUPb (ca. 247–235 Ma), AFT (ca. 237–186 Ma), and AHe (ca. 131–52 Ma) ages with multiple geo-thermochronological dates published from the Zaozigou deposit, major magmatic and hydrothermal events are recognised during ca. 250–233 and 230–203 Ma, with two Au mineralisation being deposited at ca. 230 and 211 Ma. The Zaozigou area underwent rapid post-magma cooling during ca. 250–228 Ma, rapid hydrothermal cooling at ca. 219–211 Ma, and episodic post-Triassic cooling pulses. Thermal history modelling indicates rapid cooling at ca. 210–170 Ma, slow reheating at ca. 170–60 Ma, and enhanced cooling during ca. 60–35 and 20–9 Ma at the Zaozigou deposit. In conjunction with the Triassic to Cenozoic tectonic evolution of the West Qinling Orogen, the ca. 250–233 Ma magmatism, ca. 230 Ma Au mineralisation, and ca. 250–228 Ma rapid postmagma cooling are related to the northward subduction of the Mianlue Ocean (Paleo-Tethys Ocean). The ca. 211 Ma Au mineralisation and rapid hydrothermal cooling during ca. 210–170 Ma are correlated with the collision between the South Qinling Belt and South China Block during ca. 220–210 Ma and the post-collisional gravitational collapse during the Jurassic. Prolonged reheating during ca. 170–60 Ma is associated with the unconformable deposition of coeval sedimentary sequences. The ca. 60–35 and 20–9 Ma enhanced cooling relates to the India-Eurasia collision, the northward growth of Tibetan Plateau, and the intensive East Asian summer monsoon during the Cenozoic. ∼28%–68% amounts of the Au orebodies in the Zaozigou deposit have been eroded away. In contrast with the estimated post-mineralisation exhumation depth of ∼4.8 km and reported ore-forming depth of 2–6 km, local portions of the deposit are indicated to be preserved to a depth of over 1 km for Au exploration. Timely supply of post-mineralisation sediments and regional peneplanation during the Jurassic to Cenozoic are important factors for preservation of the deposit. During rapid uplift and exhumation of orogens, sediment-hosted Au mineralisation has highly prospective for prospecting. The study also highlights that multidisciplinary approaches of geo-thermochronology, thermobarometer, and thermoelectricity are effective tools in determining post-mineralisation modification and preservation of orebodies.

The Xiahe-Hezuo district in the West Qinling orogen contains numerous Au-(As-Sb) and Cu-Au-(W) deposits. The district is divided into eastern and western zones by the Xiahe-Hezuo Fault. The western zone is exposed at a shallow level and contains sediment-hosted disseminated Au-(As-Sb) deposits, whereas the eastern zone is exposed at a deeper level and contains Cu-Au-(W) skarn and lode gold deposits within or close to granitic intrusions. The Laodou gold deposit in the eastern zone consists of auriferous quartz-sulfide-tourmaline and minor quartz-stibnite veins that are structurally controlled by fault zones transecting the Laodou quartz diorite porphyry stock and enveloped by potassic and phyllic alteration. Both the veins and alteration halos commonly contain quartz, sericite, tourmaline, pyrite, and arsenopyrite, with minor galena, sphalerite, chalcopyrite, tetrahedrite, and enargite. Gold occurs mainly as invisible gold in pyrite or arsenopyrite and locally as inclusions less than 50 μm in diameter. The zircon U-Pb age of 247.6 ± 1.3 Ma (2 σ ) on the host quartz diorite porphyry and the sericite 40 Ar/ 39 Ar plateau ages of 249.1 ± 1.6 and 249.0 ± 1.5 Ma (2 σ ) on two ore-related hydrothermal sericite samples are within analytical errors of one another. At the formation temperature (275 °C) inferred from microthermometric measurements of fluid inclusion, sericite and tourmaline yield calculated δ D H2O values of −70 to −45‰ and δ 18 O H2O of 5.8 to 9.7‰, while quartz yields calculated δ 18 O H2O values of 5.1∼5.7‰. Hydrothermal tourmaline in quartz-sulfide-tourmaline veins has δ 11 B of −11.2 to −0.9‰ (mean of −6.3‰) that are similar to the values of magmatic tourmaline (−8.9 to −5.5‰ with a mean of −6.8‰) in the host quartz diorite porphyry. The δ 34 S values of sulfide minerals range from −5.9 to +5.8‰ with a mean of −0.6‰ that is typical of magmatic sulfur. Pyrite from hydrothermally altered quartz diorite porphyry and quartz-sulfide-tourmaline veins have relatively homogeneous lead isotopic compositions, compatible with granitic intrusions in the district. The geochronological and isotopic data combined support a magmatic origin for the Laodou gold deposit, most likely formed from fluids exsolved from the Laodou quartz diorite porphyry or associated intrusive phases at deeper levels beneath the stock. Orogenic and Carlin-like gold deposits in the West Qinling orogen have been commonly thought to have formed from metamorphic fluids. This study, however, highlights the role of magmatic-derived fluids in the formation of lode gold deposits. Synthesis of geochronological, geological, and geochemical data on magmatic rocks and ore deposits in and surrounding the Xiahe-Hezuo district indicates that gold mineralization predominantly occurred within a subduction-related magmatic arc prior to collision between the Yangtze and North China cratons that produced the West Qinling orogen.

The West Qinling Orogen is endowed with more than 100 sediment-hosted gold deposits with an estimated resource of > 2000 t Au. Previous radiometric dating results have shown that most deposits formed during a Late Triassic to Early Jurassic period of contractional deformation over the orogen. However, here we show that the newly discovered Daqiao gold deposit (> 105 t at 3–4 g/t) in the southern belt of the West Qinling Orogen formed in latest Jurassic to Early Cretaceous under a different tectonic regime. The Daqiao gold deposit is hosted in weakly metamorphosed Triassic turbidites and is spatially associated with hydrothermally altered granodiorite and diorite porphyry dykes. Six granodiorite dykes have similar zircon U–Pb ages ranging from 215.0 ± 1.1 to 211.5 ± 1.5 Ma (1σ), whereas one diorite porphyry dyke has a zircon U–Pb age of 187.5 ± 2.1 Ma (1σ). The age of gold mineralization is constrained by two types of sericite: sericite aggregates coexisting with disseminated auriferous pyrite in relatively high-grade breccia ores and sericite coexisting with auriferous pyrite in weakly mineralized granodiorite dykes. Sericite aggregates from the breccia ores have 40Ar/39Ar plateau ages ranging from 150.7 ± 3.1 to 142.3 ± 2.5 Ma (2σ), whereas grains from the altered granodiorite dykes and low-grade breccia ores have 40Ar/39Ar plateau ages of 130.8 ± 3.1 to 127.2 ± 0.6 Ma (2σ). The 40Ar/39Ar ages thus suggest two periods of gold mineralization in the latest Jurassic and Early Jurassic that are likely related to repeated brecciation at Daqiao. These Jurassic-Cretaceous mineralization ages coincide with discounted ages from several other gold deposits in the region and suggest that there is an underappreciated gold event in the West Qinling Orogen that may not have been associated with the orogenic deformation but is genetically related to the far-field effects of plate reorganization during Paleo-Pacific subduction beneath the eastern Eurasian continent.

This study tested and compared the mineral potential mapping capabilities of the random forest (RF) and maximum entropy (MaxEnt) algorithms using gold deposit occurrences within the Hezuo–Meiwu district, West Qinling Orogen, China. Eighteen orogenic gold deposits in this district and associated regional exploration datasets were used to construct data-driven predictive models to identify locations prospective for gold mineralization. The 18 orogenic gold deposits used in the modeling can be divided into magmatic-hydrothermal gold deposits and mesothermal gold deposits in terms of metallogenic characteristics and nine evidential maps associated with Au deposit occurrences (i.e., distance to intrusions and faults; Au, As, Ag, Cu, and Sb singularity indices; and principal component scores (PC1 and PC2) based on isometric logratio-transformed geochemical data were selected as inputs to the models). The PC1 represents a primary geochemical signature of tectonic process or their products (i.e., fault system), whereas PC2 represents a secondary geochemical signature. Both RF and MaxEnt models were then used to quantitatively rank the importance and identify the sensitivity of the evidential maps based on their spatial relationships to the known gold deposits in the study area. The two groups of populations in the response curves and marginal effect curves indicate that the mineral potential mapping should be performed by zones in consideration of different metallogenic characteristics of gold deposits. The accuracy of the resulting models was then assessed, and the results of the mineral potential mapping were examined using receiver operating characteristic (ROC) analysis, capture-efficiency curve, and success rate curve. Both mineral potential mapping by zones with RF and MaxEnt models have higher area under the ROC curve (AUC) values than the models performed in the study area and delineate 19% of the study area containing > 88% of the known deposit occurrences. Finally, according to the concentration–area (C-A) thresholds for prospectivity maps, two ternary prospectivity maps were generated for further mineral exploration. The results indicate that the RF and MaxEnt algorithms can be used effectively for mineral potential mapping and represent machine learning algorithms that can be used in areas with a few known mineral occurrences.

The West Qinling orogen in central China, formed from continental collision between the North China and Yangtze cratons in the Late Triassic, hosts numerous gold deposits with a total Au endowment of about 2000 t. Most deposits were emplaced at ca. 250–195 Ma and are genetically associated with the Triassic orogenesis. Here in situ U-Pb titanite dating with laser ablation inductively coupled plasma mass spectrometry indicates the Ma’anqiao gold deposit in the northern portion of this orogen has a distinctive age and under a contrasting tectonic regime. This structurally controlled gold deposit is hosted in Late Ordovician to Early Silurian sub-greenschist facies metasedimentary rocks. The gold mineralization is hosted in quartz-pyrite-pyrrhotite veins and pyrite-pyrrhotite disseminations in hydrothermally altered rocks, which are crosscut by K-feldspar-calcite-chlorite±pyrite veins. Titanite, present both in the disseminated sulfide ores and later veins, was used for in situ U-Pb dating. Titanite from three disseminated sulfide ore samples with Th and U averaging 27.46 and 39.31 ppm (1 ppm=1 µg g −1 ), respectively, yielded lower-intercept ages of 121.1±3.1 to 120.7±3.5 Ma (2 σ ) in the Tera-Wasserburg diagram. Titanite from three later vein samples with much lower Th and U concentrations averaging 2.74 and 16.21 ppm, respectively, yielded overlapping ages of 120.8±3.2 to 120.3±5.8 Ma (2 σ ). These new titanite U-Pb ages tightly constrain the formation of the Ma’anqiao gold deposit at ca. 121–120 Ma and, when combined with independent geological data, indicate it is not related to the Triassic Qinling orogeny. Rather, its formation is attributed to lithospheric thinning and destruction of the North China craton during the Late Jurassic to Early Cretaceous which has generated numerous gold deposits along the southern margin of this craton. This catastrophic event caused extensive magmatism in large areas of the North Qinling terrane and northern edge of the West Qinling orogen immediately to the south of the North China craton. The heat flux and elevated geothermal gradients associated with this magmatism could have induced prograde metamorphism of the Paleozoic sedimentary infrastructure in and beneath these areas with the derived fluids ascending along pre-existing crustal-scale regional structures to form the Ma’anqiao gold deposit. We suggest that areas in the North Qinling terrane that have been affected by the Late Mesozoic magmatism are potential targets for future exploration of the decratonization-related gold deposits. Additionally, this study highlights the use of titanite U-Pb dating as a robust geochronometer for metasedimentary rock-hosted gold deposits in Phanerozoic orogens, which has previously not been utilized.

The North Huicheng Basin strike-slip fault system is on the northeastern frontier of the Tibetan Plateau and separates the West and East Qinling differential orogeny. However, the deformation mechanism of this strike-slip fault system and its exact tectonic significance are unclear. Here, we carried out systematic field structural analysis, physical analog modeling, and multiproxy geochronological dating to address these issues. The field structural analysis indicates that the North Huicheng Basin strike-slip fault system was induced from the plate-like movement of the West and East Qinling Orogens, which underwent multiple left-lateral strike-slip faulting and controlled salient and recessed structures. The scaled physical analog experiment results confirm this hypothesis and reveal the primary spatial-temporal deformational kinematic process. Combined with published works, multiproxy geochronological dating (zircon U-Pb age of 213 Ma, biotite 40Ar/39Ar age of 203 Ma, and apatite fission-track age of 56 Ma) outlines the main thermal history of the hanging wall. Based on the above facts, the integrated research suggests that multistage strike-slip faulting played a significant role in the main tectonic events, that is, Late Triassic magmatic emplacement, Jurassic/Cretaceous local pull-apart, and Cenozoic rapid exhumation driven by Tibetan Plateau growth.

Recent exploration has demonstrated significant prospecting potential at the Huayagou Au deposit in Longnan mineral Field, Gansu Province, West Qinling Orogen, Central China. However, the nature and evolution of the auriferous fluids responsible for gold enrichment remain poorly constrained, hindering effective exploration targeting of high-grade ores. In this study, apatite and tourmaline closely associated with gold mineralization are investigated as mineralogical recorders of fluid composition and evolution. Integrated petrographic observations, TIMA phase mapping, cathodoluminescence imaging, electron probe microanalysis, and in situ trace element analyses were used to distinguish magmatic, metamorphic, and syn-ore hydrothermal generations of apatite and tourmaline, together with in situ Nd isotopic analyses of apatite and B isotopic analyses of tourmaline. Syn-ore hydrothermal apatite is characterized by homogeneous blue cathodoluminescence, fluorapatite compositions, strong LREE depletion, and εNd(t) values overlapping those of Triassic magmatic apatite, whereas Early-Devonian magmatic and metamorphic apatites display more distinct signatures. Tourmaline records a systematic evolution from early dravite to late schorl, accompanied by trace element enrichment and a shift toward heavier δ11B values. These mineralogical and isotopic features, together with published sulfur isotope constraints, indicate that gold mineralization at Huayagou was dominantly controlled by structurally focused metamorphic fluids, with localized Triassic magmatic–hydrothermal overprinting enhancing gold enrichment in high-grade ores. The Huayagou Au deposit is, therefore, best interpreted as an atypical orogenic gold system, highlighting enhanced exploration potential in structurally favorable zones at depth, particularly in the western part of the district where Triassic magmatism is inferred.

The Yawan gold deposit, located in the Western Qinling Orogen, contains gold mineralisation that is predominantly controlled by approximately east-west-trending fault systems. This study integrates field geology, petrography, cathodoluminescence imaging, electron probe microanalysis of gold-bearing minerals (pyrite and arsenopyrite), and in situ laser ablation U-Pb dating of calcite to constrain the timing of mineralisation and to elucidate the mechanisms of gold enrichment. This study reveals that the deposit is significantly structurally controlled and comprises two discrete mineralisation stages: a quartz-pyrite (Py1)-arsenopyrite (Apy1)-chalcopyrite assemblage (Stage 1), and a quartz-calcite-pyrite (Py2)-arsenopyrite (Apy2)-stibnite-sphalerite-galena assemblage (Stage 2). Py1 displays distinct zonation, with rim As contents notably higher than core values, while Co and Ni contents gradually decrease from core to rim. Py2 is characterised by high As (0.00%–4.72%), low Fe/S ratios, and a porous texture, containing gold and arsenopyrite inclusions. Invisible gold occurs in lattice-bound form in both Py1 and Py2. The As-Fe-S ternary diagram of pyrite indicates that Au+ likely entered the crystal lattice as a solid solution. Arsenopyrite geothermometry yields a mineralisation temperature of 389 ± 44 °C, and sulfur fugacity (ƒS2) decreased markedly from Stage 1 to Stage 2. Combined with the S and Fe characteristics of pyrite, these features support a medium-temperature metamorphic hydrothermal environment. U-Pb dating of calcite from Stage 2 yields an age of 215.6 ± 7.1 Ma. In summary, the Yawan gold deposit belongs to the orogenic gold system, with its gold precipitation and enrichment controlled by sulfidation triggered by Late Triassic tectono-fluid activity.

The large Dongtangzi Zn-Pb deposit is located in the southwest of the Fengxian–Taibai (abbreviated as Fengtai) ore cluster in the west Qinling orogen. The origin of the deposit is controversial, positing diverse genesis mechanisms such as sedimentary-exhalative (SEDEX), sedimentary-reformed, and epigenetic-hydrothermal types. This study combines systematic ore geology observations with high-precision Rb-Sr and Sm-Nd ages of 211 Ma and in situ S-Pb isotopes to constrain the timing and origin of mineralization. In situ S-Pb isotopic studies show that the sulfide ores display a narrow range of δ34S values from 1.1‰ to 10.2‰, with 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of 18.07 to 18.27, 15.64 to 15.66, and 38.22 to 38.76, respectively. On the other hand, pyrites of the sedimentary period and the granite porphyry dike have δ34S values ranging from 15.8 to 21.4‰ and from 2.1 to 4.3‰ (with 206Pb/204Pb ratios of 18.09 to 18.10, 207Pb/204Pb ratios of 15.59 to 15.61, and 208Pb/204Pb ratios of 38.17 to 38.24), respectively. The above-mentioned S-Pb isotopic compositions indicate that the metallic materials involved in ore formation originated from a mixture of Triassic magmatic hydrothermal fluid and metamorphic basement. By integrating the regional geology, mineralization ages, and S-Pb isotopic studies, we propose that the Dongtangzi Zn-Pb deposit is the product of epigenetic hydrothermal fluid processes, driven by Late Triassic regional tectono-magmatic processes.

The Qinling Complex is located in the core of the northern Qinling Orogen and plays a key role in understanding the tectonic evolution of the Qinling Orogen, but its metamorphic evolution remains controversial. The combined investigation of petrographic observation, zircon U-Pb dating, and phase equilibria modeling for garnet amphibolites from the Tianshui area in the West Qinling Orogen is reported in this study. The results show that the garnet amphibolites record a clockwise P-T path characterized by a pre-TMax decompression heating stage, a temperature peak at P-T conditions of 0.84–0.99 GPa and 869–886 °C, followed by a decompression cooling stage. Zircon U-Pb dating yields four age populations of ~479 ± 4 Ma, ~451 ± 8 Ma, ~411 ± 4 Ma, and ~377 ± 6 Ma. The 479–450 Ma reflects the timing of the pre-TMax high–medium pressure upper amphibolite-facies metamorphism. The metamorphism at peak temperature condition occurred at c.411 Ma and was followed by decompression cooling to c.377 Ma. The Ordovician high–medium pressure metamorphism is related to the continental collision, which is slightly later than the HP–UHP eclogite-facies metamorphism in the East Qinling Orogen. The HT granulite-facies metamorphism at peak temperature condition took place at reduced pressures, suggesting thinning of the collision-thickened orogenic crust. Therefore, the northern West Qinling Orogen experienced a tectonothermal evolution from initial crust thickening to thinning during the Paleozoic collisional orogeny.