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The large‐scale concentration of Au associated with Mesozoic granitoid intrusions in the North China Craton (NCC) has inspired many investigations to explore the genetic relationship between the magmatism and gold metallogeny. The Xiaoqinling gold province is located in the southern margin of the North China Craton. The Wenyu and Huashan monzonitic granites formed at Early Cretaceous represent two of the important intrusions in this region, and a large number of gold deposits occur around the Wenyu pluton. Here we present results from an integrated study using in situ zircon U–Pb ages, trace elements, and Hf isotope to infer the composition and environmental changes during different evolution stages of the fertile Wenyu pluton and compare with the infertile Huashan pluton. The Huashan pluton was emplaced at 144.0 ± 0.6 Ma, whereas the fertile Wenyu pluton experienced multistage magmatic activity from 141.4 ± 0.6 to 129.6 ± 0.5 Ma. Temperatures computed from Ti‐in‐zircon thermometry indicate that the late‐stage Wenyu magma crystalized at 644°C, the Huashan magma, and early‐stage Wenyu magma crystalized at around 750°C. And the oxygen fugacity (Ce4+/Ce3+ > 200 and Eu/Eu* > 0.7) and the water content of the late‐stage Wenyu magma stay at higher levels. The U/Yb–Hf and U/Yb–Y relationship with εHf(t) (−15.63 to −17.89) of the late‐stage Wenyu magma suggest that the ancient lower crust with subsequent inputted basaltic components make up the source of the fertile and infertile plutons. Combined with previous geochronological data and geodynamics studies, we propose that the late‐stage intrusion of the Wenyu pluton experienced intensive magma mixing. And the formation of Wenyu pluton created conducive heat energy, oxygen fugacity, and water conditions for the formation of high‐grade gold deposits. [ABSTRACT FROM AUTHOR]

The Chen'er gold deposit hosted in the Precambrian Taihua Supergroup metamorphic rocks is one of the typical gold deposits in the Xiaoqinling region along the southern margin of the North China Craton. The metallic mineral assemblage in this deposit includes sulfides, tellurides, native gold, electrum, and native bismuth. The telluride minerals are composed of calaverite, petzite, hessite, altaite, joseite; except for hessite and matildite, the other tellurides and native bismuth are first reported in this study. Fluid inclusion studies in the auriferous quartz reveal three types: aqueous, aqueous–carbonic, and carbonic inclusions. The homogenization temperatures range from 184 to 364°C, and salinities are in the range of 1.74‐ to 11.47‐wt.% NaCl equiv. At temperatures of 275°C, the logfTe2 and logfS2 of the fluid are estimated as −16.13 to −8.19 and −12.74 to −4.80, respectively, and at temperatures of 305°C, the pH and logfO2 of the fluid are estimated as 3.61 to 5.69 and −34.31 to −27.81, respectively. It is inferred that Au(HS)2− and Au(HS)0 are the predominant gold‐bearing complexes, and tellurium was transported as Te22−. Based on thermodynamic models of logfO2(g) versus pH, we suggest that the precipitations of native gold and electrum in the early and main mineralization stages are different, with the oxygen and hydrogen isotope values of auriferous quartz suggesting mixing of magmatic water with meteoric water. [ABSTRACT FROM AUTHOR]

The Bagrote and Dainter valleys in Gilgit Baltistan Pakistan, belonging to the Kohistan island arc and southwestern domain of the Karakorum metamorphic complex, respectively, are a location of regional placer gold mining. However, no in situ hydrothermal gold deposits have been discovered in this region. Here, we report the textural, morphological, and geochemical characteristics of placer gold from the stream sediments of the Bagrote and Dainter valleys with a view to trace the provenance. The morphological features of the studied gold grains indicate proximal source mineralization. The gold grains display a microtexture typical of mechanical abrasion rather than chemical activity. Their chemical composition of most of the grains from each stream falls in a restricted range (minor alloying elements mainly Cu) with high fineness (1,000 Au/(Au + Ag)), suggesting derivation from a homogeneous source or limited number of mineralization types. The high Cu content of the gold grains from the Bagrote stream suggests that the gold here might be associated with previously undiscovered porphyry gold mineralization, whereas the Au–Ag–Hg alloys from the Dainter stream suggest a genetic linkage with undiscovered fault‐controlled auriferous veins of epithermal origin in the southwestern part of the Karakorum metamorphic complex. The chemical composition of both streams placer gold in triangular diagram in terms of Au–Ag–Cu shows all the gold grains from Dainter stream were derived from epithermal type of mineralization, and most of the plots of Bagrote stream fall on the domain of porphyry epithermal type of deposits which are also in consistent with a continental arc setting in the study area. The mechanically developed microtexture, homogeneous chemical composition in individual grains from core to rim, and absence of high fineness rims of the gold grains from both streams, suggest the absence of any supergene regrowth and direct transfer from the primary source through glacier to the fluvial system. The Gilgit Baltistan province, dominated by dry temperate climate and glacial environment having steep geomorphology, precluding any significant supergene processes such as silver leaching and addition of authigenic gold on detrital gold grains. [ABSTRACT FROM AUTHOR]

The North China Craton (NCC) hosts the world's most typical example of "decratonic" gold deposits including lode, porphyry, cryptoexplosive breccia, and skarn subtypes. The lithospheric structure in the ore fields show "triple-junctions" of basement microblocks, zones of lithospheric thinning, and "hotspots" with abnormal crustal heat flow. The basement rocks are dominantly composed of trondhjemite-tonalite-granodiorite (TTG) suite and amphibolites. The intermediate-felsic calc-alkaline plutons with crust-mantle mixed origin and formed under high oxygen fugacity, volatile-rich and moderately fractionated conditions, together with dyke swarms of diverse compositions are indicators for the gold mineralization. The mantle under the gold field shows metasomatic or juvenile "EM2" or "EM2 + EM1" characteristics. The gold deposits are closely associated with craton destruction, heterogenous reactivation, large-scale magmatic intrusion and eruption, and upwelling of voluminous ore-bearing fluids within a transitional tectonic regime. The presence of mantle-derived mafic rocks, mafic microgranular enclaves (MME) and amygdaloidal bodies, minerals rich in Te, Ni, Cr, Mg, C and N, He and stable isotopes with mantle signature, among other features, indicate that the ore-forming metals and fluids have mixed mantle and deep crustal origin. Gold deposits coexisting or closely associated with mafic dykes and crust-mantle-derived stocks indicate that the upwelling of ore-forming fluid and localization of the ore-materials were facilitated at least partly by the intrusion of deep magma. The spatial distributions of altered rocks with alkali-feldspar-hematite zone distal to the orebody (barren) and pyrite-phyllite (sericite) zone proximal to the ore (ore-bearing zone) indicate a marked physico-chemical interface at the final stage of evolution of the ore-forming fluid. The presence of wide alteration zone indicates that the ore-controlling faults were in a compressive stress state, whereas narrow alteration zone is generally associated with a tensile stress state. The cataclastic, poikilitic, interstitial and zonal textures displayed by the various stages of ore minerals are related to the impact of alternating local tectonic stress fields in the faults, as well as fault-valve mechanism. Intense gold mineralization is typically associated with the development of polymetallic sulfide minerals and complex mineral assemblages. The major gold mineralization is also commonly related with pyrite with xenomorphic or complex forms, rich in As, Se, and Te, with large unit cells, wide X-ray diffraction peaks, and high P/(P + N) values corresponding to thermoelectric conductive type. Quartz grains formed in the main gold mineralization stage are generally fine grained and irregular, occasionally occurring as grain clusters, and showing complex thermoluminescence patterns with both high and low temperature peaks. Multiple rhythmic zones in quartz, pyrite or other ore minerals with various impurities in between the different zones indicate the pulses of ore fluid flow toward the upper part of the orebody. In contrast, minerals with few or no zones may indicate an ore-fluid reservoir typically in the middle to lower parts of orebody. • Indicators of decratonic gold mineralization include geodynamic background and mineralizing processes. • Five subcategories of indicators for geodynamic background are discussed. • Mineralizing processes are indicated by six subcategories of evidences. • Indicators are summarized as references for prospecting similar gold deposits elsewhere. [ABSTRACT FROM AUTHOR]

[Display omitted] • Apatite from both the Huashan and Wenyu plutons are fluorapatite of magmaticorigin. • Wenyu apatite formed under a higher oxidation state and incorporated more mantle-derived materials than Huashan apatite. • Wenyu apatite crystallized earlier than feldspar and Huashan apatite was affected byfeldsparcrystallization. • The magma of the Wenyu pluton incorporated more intensive fluid exsolution during crystallization. • Wenyu pluton is more favorable to gold mineralization than the Huashan pluton. The relationship between granitic magmatism and lode gold mineralization has remained as a controversial topic among economic geologists. In this paper, we report in situ elemental and Sr isotopic signature of apatite from the Wenyu and Huashan granitic plutons in the Xiaoqinling goldfield, southern margin of the North China Craton (NCC), intending to provide further constrain the relationship between magmatism and metallogeny. The formation ages of Huashan and Wenyu granitic plutons are coeval with the gold mineralization, but most of the gold deposits are clustered nearing the Wenyu pluton, and only a few small gold deposits are found adjacent to the Huashan pluton. Although apatite from both plutons is all fluorapatite, characterized by negative Eu anomaly and enrichment of LREEs, the apatite from the two plutons shows different signatures. Based on these differences, the apatite from the Huashan pluton is divided as group A (HS-A) and group B (HS-B). The δEu, δCe values and MnO and Ga contents of the Wenyu and HS-A apatite indicate high oxygen fugacity range from MH to NNO for the magma, whereas the HS-B apatite shows low oxygen fugacity range from NNO to FMQ. The 87Sr/86Sr, REE, Th/U, and Ce/Y values of the apatite suggest that the magma for the Wenyu pluton incorporated more mantle-derived materials in contrast to Huashan pluton. Sr/Y ratio and REE content of the apatite indicate that WY apatite crystallized earlier than feldspar and Huashan apatite was affected by feldspar crystallization. The fluid-volatiles exsolution texture and S content of the apatite indicate higher content of volatiles in the Wenyu pluton magma, where the magma experienced more intense fluid exsolution than that of the Huashan pluton during apatite crystallization. The characteristics of many mantle-derived materials, high oxygen fugacity, and higher volatiles as revealed by the apatite data show that the magmatism of Wenyu pluton was more conducive to the mineralization of gold deposits than that of the Huashan pluton and is more closely related to gold deposits. [ABSTRACT FROM AUTHOR]

• Magnetite from fertile intrusion shows magmatic and hydrothermal origin. • Magnetite from barren intrusion is of typical magmatic origin. • The fertile Wenyu pluton formed at higher oxygen fugacity and lower temperature compared to the barren pluton. • Deep sourced was fluid involved in the formation of the Wenyu pluton. The Xiaoqinling district in the southern margin of the North China Craton is the second largest gold enriched area in China. The Huashan and Wenyu plutons represent two typical Mesozoic magmatic intrusions in this region and were coeval with the gold mineralization. Here we report the geochemistry and Mössbauer spectral characteristics of magnetite from the two plutons with a view to explore the role of the granitic magmatism in the gold enrichment. The results of EPMA and Mössbauer spectroscopy suggest that the average values of Fe2+/Fe3+ in the magnetite from the two intrusions are lower than the standard value of 0.50, indicating an oxidizing environment. The estimated oxygen fugacity is higher for the Wenyu pluton than that of the Huashan pluton, which is also supported by the occurrence of hematite in the former, and the distinct δEu-δCe anomalies for magnetite from the two intrusions. The Sn content in magnetite indicates lower formation temperatures of the Wenyu pluton as compared to that of the Huashan pluton. The results of LA-ICP-MS analysis demonstrate similar multi-element variation patterns for the two intrusions. Titanium vs. Ni/Cr relationship suggests that the magnetite from the Huashan pluton is of typical magmatic origin, whereas that from the Wenyu pluton shows both magmatic and hydrothermal signature. The Ni/Co ratio of magnetite from the Wenyu granite is higher than that of the Huashan granite, which indicates a deeper source for the Wenyu pluton. The comparatively more favorable physico-chemical conditions, such as higher oxygen fugacity, lower temperature, as well as the involvement of deep-sourced material are envisaged to have provided better metallogenic environment for generating the gold mineralization around the Wenyu pluton. [ABSTRACT FROM AUTHOR]