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The Chinese Tianshan experienced large-scale transcurrent tectonics, synkinematic emplacement of ultramafic to felsic intrusions, and the formation of various mineral deposits during late Paleozoic accretionary orogenesis. The relationships among the spatial variation of deformation, the distribution of Permian orogenic Au and magmatic Ni-Cu sulfide deposits, and the kinematic evolution of crustal-scale shear zones, however, remain ambiguous. To address these ambiguities, the spatial variation in the degree of deformation in the Kanggur-Huangshan shear zone in the Chinese Tianshan was characterized using detailed structural measurements and zircon U-Pb and muscovite 40Ar/39Ar age data. The new structural data indicate that a prominent spatial variation exists in the style of deformation throughout the Kanggur-Huangshan shear zone; intense ductile deformation structures are dominant in the east, while brittle structures become progressively more dominant toward to the west. Zircon U-Pb and muscovite 40Ar/39Ar age data for syn- and postkinematic intrusions along the Kanggur-Huangshan shear zone indicate that dextral strike-slip shearing occurred between 279 Ma and 249 Ma. The spatial variation in the degree of deformation and exhumation along the Kanggur-Huangshan shear zone was potentially caused by regional differential uplift induced by the collision of the Tianshan and Beishan regions; this was likely responsible for the predominant occurrence of magmatic Ni-Cu sulfide deposits in the eastern portion of the Kanggur-Huangshan shear zone and orogenic Au deposits in the western portion. The identified spatio-temporal relationship between deformation and distribution of orogenic Au and magmatic Ni-Cu sulfide deposits is crucial to the future success of mineral exploration in the Central Asian orogenic belt.

Mafic intrusions in the Coldwell Complex have previously been interpreted as forming from a metasomatized mantle source. To build upon our understanding of this metasomatism, the Mg–Fe isotope compositions of these rocks have been determined, and variations are assessed with respect to the magmatic processes that could have occurred at different stages of their formation. The mineralized Marathon Series (δ26Mg = −0.28‰ to −0.19‰), associated metabasalt (δ26Mg = −0.24‰ to −0.23‰), and the Geordie Lake gabbro (δ26Mg = −0.31‰ to −0.22‰) are characterized by δ26Mg values that are within the range of mantle values, whereas the unmineralized Layered Series (δ26Mg = −0.2‰ to −0.05‰) is heavier than mantle. In contrast, the δ56Fe values of all the Coldwell basaltic–gabbroic rocks (δ56Fe = 0.07 ± 0.08‰) are heavier than mantle but within the range of terrestrial basalts and mafic–ultramafic layered intrusions. We propose that the Mg–Fe isotope compositions of these rocks was not significantly modified by processes such as partial melting or garnet retention/fractionation in the mantle, fractional crystallization, or contamination during ascent through the crust, as the isotope values do not correlate with proxies for these processes (e.g. La/Sm and La/Yb, Gd/Yb, MgO–CaO–TiO2, and Th/Nb and Th/La, respectively). Their isotope compositions are, therefore, proposed to reflect the compositions of their metasomatized mantle sources. We conclude that metasomatism was not caused by a carbonate melt, subduction-altered oceanic crust and sediments, or an evolved silicate melt, as these processes generate light δ26Mg, variably fractionated δ56Fe, and heavy δ56Fe values, respectively, which are not observed in our dataset for the Coldwell Complex. The agent that metasomatized the mantle beneath the Coldwell Complex was likely slab-derived fluids characterized by isotopically heavy δ26Mg and basaltic δ56Fe values. This scenario can account for the lack of Fe isotope fractionation from basaltic values in all of the Coldwell rocks. The variably heavier δ26Mg of the Layered Series (−0.20 ± 0.01‰ to −0.05 ± 0.05‰) relative to the mantle (−0.25 ± 0.07‰) suggests that the magmas for the Coldwell rocks were derived by tapping of an isotopically heterogeneous mantle source that had undergone variable degrees of metasomatism. The distinctive geochemistry of mafic sequences in the Coldwell and numerous mafic dykes located in the northeast shoulder of the Midcontinent Rift suggests the presence of a variably metasomatized mantle source beneath a large area of the rift.

Chalcopyrite from the Cu–PGE sulfide deposits in the Eastern Gabbro, Coldwell Complex, Canada, exhibit a > 2‰ variation in δ65Cu. In the Marathon deposit, the δ65Cu of chalcopyrite increases from the lower Footwall Zone (− 1.49 to − 0.75‰), to the Main Zone (− 1.04 to 0.08‰), to the upper W Horizon (− 0.35 to 1.07‰). In the northern deposits, chalcopyrite at Four Dams and Sally have δ65Cu that range from − 0.08 to 0.47‰ and − 0.59 to − 0.05‰, respectively. Notably, samples from the Marathon deposit with lower chalcopyrite δ65Cu values tend to have higher S/Se and Cu/Pd ratios. Integrated geological and geochemical evidence suggests that secondary hydrothermal alteration and redox processes are unlikely to have been the primary causes of the observed Cu isotope variation. Numerical modeling of δ65Cu–Cu/Pd–S/Se of mineralization in the Eastern Gabbro illustrates three key aspects of Cu isotope behavior in magmatic Ni–Cu–PGE systems. First, R factors less than ~ 10,000 can exhibit significant control on the δ65Cu of sulfides. Second, sulfide liquid–silicate melt fractionation factors for Cu (Δ65Cusul–sil) greater than − 0.5‰ are applicable to Ni–Cu–PGE systems. Third, sulfide segregation exhibits no measurable control on the δ65Cu of sulfides at degrees of fractionation typical of Ni–Cu–PGE systems (< 0.3%). In the Marathon deposit, the range of δ65Cu–S/Se–Cu/Pd is attributed to the addition of Archean sedimentary Cu to a pool of sulfide liquid located at depth, followed by progressive dilution of the contaminated δ65Cu–S/Se signature and decrease in Cu/Pd ratio by influxes of uncontaminated pulses of magma (i.e., increasing R factor), some of which had Cu isotope compositions heavier than the mantle. Variably contaminated and enriched, with respect to Pd, sulfides from this pool were entrained by magma pulses and emplaced to form the Marathon deposit. This contribution demonstrates that Cu isotopes can fractionate at high temperatures and, when combined with other geochemical proxies, can be valuable in characterizing magmatic–post-magmatic processes in Ni–Cu–PGE sulfide deposits and for identifying PGE-rich sulfide deposits.

The Eastern Gabbro of the alkaline Coldwell Complex, Canada, represents a Ni-poor conduit-type system that comprises two rock series, the Layered Series and Marathon Series, which intruded into a metabasalt package. Based on distinct variations in magnetite compatible (e.g., Ni, Cr) and incompatible (e.g., Sn, Nb) elements in Fe–Ti oxide intergrowths, the metabasalts, Layered Series, and Marathon Series must have crystallized from magmas that originated from compositionally distinct sources. Of these rock units, the metabasalts crystallized from a more primitive melt than the Layered Series as Fe–Ti oxides in the former have higher concentrations of magnetite-compatible elements. Unlike the metabasalts and Layered Series, the Marathon Series crystallized from multiple, compositionally distinct magmas as Fe–Ti oxides in this series exhibit large variations in both magnetite compatible and incompatible elements. Accordingly, the various rock types of the Marathon Series cannot be related by fractional crystallization of a single batch of magma. Rather, the magmas from which the rock types crystallized had to have interacted to variable degrees with a late input of more primitive melt. The degree of this magma interaction was likely controlled by the geometry of the conduit and the location of emplacement given that Fe–Ti oxides in the oxide-rich rocks occur in pod-like bodies and exhibit no compositional evidence for magma mixing. Mirrored variations in magnetite compatible and incompatible elements in Fe–Ti oxides in the Footwall Zone, Main Zone, and W Horizon of the Marathon Cu–PGE deposit indicate that these zones could not have formed from a single, evolving magma, but rather multiple batches of compositionally distinct magmas. Fe–Ti oxides exhibit no compositional difference between those hosted by barren and mineralized rock. This is likely because sulfide liquated at depth in all of the magmas from which the Marathon Series crystallized. The composition of Fe–Ti oxides in the Eastern Gabbro fall outside of the compositional fields for Ni–Cu mineralization defined by Dupuis and Beaudoin (Mineral Deposita 46:319–335, 2011) and Ward et al. (J Geochem Explor 188:172–184, 2018) demonstrating that their discrimination diagrams can distinguish between Ni-rich and Ni-poor systems that contain disseminated and massive sulfides.

Magnetite (mag)–ilmenite (ilm) intergrowths are more common than mag–ulvospinel (usp) intergrowths in mafic–ultramafic Ni–Cu–PGE systems, yet the former has no known solid solution. The most accepted model for the formation of mag–ilm intergrowths in terrestrial environments is fluid-induced oxidation of mag–usp assemblages by oxygen in water. In this study, we re-examine this model in light of the fact that crustal fluids have very low pO2 and that mag–ilm intergrowths commonly occur in rocks that show little or no evidence of hydrothermal alteration. We also characterize the chemical changes that occurred during the formation of mag–ilm intergrowths and how they affect the use of Fe–Ti oxide chemistry for petrogenesis and mineral exploration. In the Eastern Gabbro, Coldwell Complex, a continuum of Fe–Ti oxide intergrowths occur ranging from cloth (mag–usp) to trellis (mag–ilm) types. Trellis-textured intergrowths have higher bulk Fe3+:Fe2+ ratios and are predominantly enriched not only in some multivalent (Ge, Mo, W, Sn) elements, but also in Cu and Ga, consistent with their formation via oxidation by a metal-rich fluid. These compositional changes are significant relative to typical elemental abundances in Fe–Ti oxides and could potentially lead to erroneous interpretations regarding primary magmatic processes if they are not taken into consideration. The irregular distribution of the intergrowths throughout the Eastern Gabbro suggests that different rock series and mineralized zones experienced variable degrees of fluid-induced oxidation. It is proposed that C in CO2 rather than O2 in water could potentially be an important oxidizing agent in mafic systems: $$ 9{\mathrm{Fe}}_2^{2+}\mathrm{Ti}{\mathrm{O}}_4+0.75{\mathrm{CO}}_2+1.5{\mathrm{H}}_2\mathrm{O}\leftrightharpoons 9{\mathrm{Fe}}^{2+}\mathrm{Ti}{\mathrm{O}}_3+3{\mathrm{Fe}}_2^{3+}{\mathrm{Fe}}^{2+}{\mathrm{O}}_4+0.75\mathrm{C}{\mathrm{H}}_4 $$ The applicability of this model is supported by the common occurrence of CO2 and CH4 in fluid inclusions in mafic rocks.

The Eastern Gabbro, Coldwell Complex, hosts several geochemically and mineralogically distinct Cu-platinum group element (PGE) deposits, including the high-grade W Horizon (>100 ppm Pd-Pt-Au over 2 m). Several magmatic and/or hydrothermal models have previously been proposed to explain the range of enrichment in PGEs observed in the Marathon deposit, but no work has integrated textural and compositional variations in sulfides to elucidate which of these models is most suitable. Additionally, comparatively little work has been done to characterize the genesis of Cu-PGE mineralization that occurs to the northwest of the Marathon deposit in the Eastern Gabbro. Through integration of base metal sulfide (BMS) mineralogy, texture, and trace element chemistry, a wide range of magmatic and postmagmatic processes have been characterized that contributed to the formation of these deposits. In all zones of mineralization in the Eastern Gabbro, chalcophile elements were remobilized from primary chalcopyrite by hydrothermal fluids and precipitated as secondary chalcopyrite, which occurs as a replacement of pyrrhotite and as intergrowths with hydrous silicates. BMSs in the mineralized zones in the Marathon deposit (Footwall zone, Main zone, and W Horizon) experienced higher R factors than those deposits located northwest of the Marathon deposit (Four Dams, Area 41, and Redstone), with BMSs in the W Horizon having experienced the highest R factors. The silicate melts from which the Footwall zone crystallized likely experienced some degree of sulfide segregation at depth, albeit to a much lesser degree than the northern deposits. Additionally, the melts from which the mineralized zones in the Marathon deposit crystallized were likely contaminated by high-S/Se Archean sedimentary rocks, whereas the northern deposits were likely contaminated by low-S/Se igneous and/or metamorphic rocks. BMSs in a chalcopyrite-rich pod located within the vicinity of the Coldwell Complex experienced both high R factors and high degrees of contamination (cf. W Horizon and Footwall zone, respectively). This study illustrates the complexity of processes that generate and modify mineralization in conduit-type Ni-Cu-PGE systems.

Equilibrium isotope fractionation factors are the basis for application of stable isotopes in geological studies. Experimental calibration and theoretical calculations have been employed to determine Fe isotope fractionation factors for a variety of minerals, however, these methods have their limitations. An alternative approach to calibrating inter-mineral Fe isotope fractionation factors is to use well-characterized geological samples; this approach has unique advantages over the other methods including attainment of equilibrium at relatively low temperatures. In this study, we investigated the Fe isotope composition of magnetite (Mt), garnet (Grt), amphibole (Amp) and biotite (Bt) from the metamorphosed Yingshan iron formation in South China. Two independent geothermometers, quartz–magnetite oxygen isotope and amphibole–garnet–biotite Fe–Mg exchange geothermometers, give a consistent metamorphic temperature of 538 ± 39 °C. The Fe isotope composition of the different Fe-bearing minerals is highly variable in different ironstone samples, with δ56Fe values (relative to IRMM-014) ranging from −0.23 to +0.37‰ in magnetite, −0.44 to +0.09‰ in amphibole, −0.78 to +0.02‰ in garnet, and −0.61 to +0.04‰ in biotite. Despite that, the offsets of δ56Fe values for mineral pairs are consistent, implying attainment of equilibrium isotope fraction between these minerals. Inter-mineral Fe isotopic fractionations (±2 standard deviation) measured from the multiple mineral pairs are Δ56FeMt–Grt = +0.55 ± 0.08‰, Δ56FeMt–Amp = +0.25 ± 0.06‰, Δ56FeMt–Bt = +0.42 ± 0.11‰, Δ56FeAmp–Grt = +0.34 ± 0.15‰, Δ56FeAmp–Bt = +0.26 ± 0.04‰, and Δ56FeBt–Grt = +0.13 ± 0.08‰. Based on the well-defined metamorphic temperature (538 ± 39 °C) and internally consistent inter-mineral fractionation factors, the temperature-dependent functions for equilibrium Fe isotope fractionation between the following mineral pairs are derived: 103lnαMt–Grt = 0.36(±0.05) × 106/T2, 103lnαMt–Bt = 0.28(±0.07) × 106/T2, 103lnαMt–Amp = 0.16(±0.04) × 106/T2, 103lnαAmp–Grt = 0.22(±0.10) × 106/T2, 103lnαAmp–Bt = 0.17(±0.03) × 106/T2, and 103lnαBt–Grt = 0.09(±0.05) × 106/T2, where Fe3+/ΣFe ratio is 0.05 ± 0.02 in garnet, 0.29 ± 0.04 in biotite, and 0.24 ± 0.06 in amphibole for the above functions. The equilibrium Fe isotope fractionation factors derived in this study enable estimation of the metamorphic temperature of rocks that contain these mineral pairs, and identification of secondary processes that may have induced disequilibrium Fe isotope distribution in rocks, such as retrograde metamorphism and hydrothermal alteration.

Understanding the mechanisms responsible for the interplay between mafic and felsic magmas is the key to retrieving information on their sources, and characterizing the exchange of mass between them. In order to characterize compositional and mineralogical changes in the mafic end-member during mafic-felsic magma interaction and to better understand the nature of early Paleozoic intracontinental magmatism in the South China Block (SCB), a detailed study was conducted on an early Paleozoic hornblendite-quartz monzonite suite in the SCB. The amphibole phenocrysts in the hornblendite are zoned with respect to major and trace elements. From the brown core to the light-green rim, these amphibole phenocrysts display significant increases in Si, Mg, and Mn, coupled with abrupt decreases in Al, Ti, Na, K, and most of the trace elements, but only minor variations in Ca, Fe, Co, and Ni. The light-green matrix amphiboles in the hornblendite have similar compositions to the outer rim of amphibole phenocrysts (except Na). It is important to note that the amphibole grains in the quartz monzonite have significantly higher rare-earth element (REE) contents than the amphibole grains in the hornblendite. There is convincing evidence to support a significant transfer of incompatible elements (e.g., K, Na, LILE, LREE, U, and Th) from the felsic magma to the mafic magma, such as (1) the absence of high-Ca plagioclase in hornblendite, with the majority of feldspar grains being albite (Ab96–97) and orthoclase (Or94–96), and (2) uniform Sr-Nd-Hf isotope compositions (initial 87Sr/86Sr = 0.7081–0.7098; eNd(t) = −6.8 to −6.3; weighted mean zircon eHf(t) = −8.0 to −7.4) for the hornblendite and quartz monzonite samples. It is, therefore, suggested that during mafic-felsic magma interaction, water was transferred from the quartz monzonite magma to the coeval hornblendite magma and promoted the formation of the amphibole crystals in the latter. The incompatible elements transferred from the quartz monzonite magma to the hornblendite magma were mainly incorporated into the late-crystallized anhedral phases in the hornblendite (e.g., orthoclase, sodic plagioclase, quartz, zircon, and apatite). This study suggests that water, which behaves as a supercritical fluid in most mafic-felsic magmas, may play a key role in the exchange of mass between mafic and felsic magmas, and this may be extended to the petrogenesis of biotite-amphibole aggregations in intermediate-felsic magmas.

To better understand the fluid migration in orogenic zones and associated chemical remagnetization, we have conducted a detailed magnetic, petrographic, and strontium isotope study in an important orogenic belt of China, the Jurassic Dabashan fold and thrust belt. This belt formed by the continued collision of the North and South China blocks after the Late Triassic closure of the Paleo‐Tethys Ocean. Samples were collected in a variety of rock units of Ediacaran to Permian age, in both the thrust and the fold belts. Paleomagnetic analysis indicates that all the samples were remagnetized and carry a Middle‐Late Jurassic paleo‐direction. Rock magnetic data and scanning electron microscopy observations found that the proposed remagnetization is carried by framboidal magnetite, which likely formed by the replacement of pyrite. The pervasive nature of the chemical remagnetization in these units and belts and its temporal and spatial association with the orogeny suggest that it resulted from the alteration of orogeny‐induced fluids. Sr‐isotopic analysis of the units that are thought to be remagnetized suggests that the sediments in the thrust belt were altered by externally derived evolved fluids, whereas the Permian samples in the fold belt were altered by internal pore fluid mixing during the orogeny. Together with the lithological and structural features, we conclude that the external orogenic fluids migrated preferentially along thrust faults and unconformities but were blocked by layers of low‐permeability gypsum. Our results help to constrain the origin of widespread remagnetization in South China.

Triassic magmatism has been increasingly identified in the Eastern Tianshan and played a crucial role in the tectonic evolution of the Tianshan Orogenic Belt. The petrogenesis and geodynamic setting of the Triassic magmatism, however, are poorly constrained. In this study, we integrate new field and petrological observations, zircon U Pb ages and Hf isotopic compositions, and whole-rock geochemical data for the microgranular enclaves (MEs) and their host Triassic Tianhu granitoids to investigate their origin and the tectonic regime of the Eastern Tianshan during the Triassic. Based on zircon U Pb geochronology, the Tianhu granitoids and MEs have indistinguishable Early Triassic crystallization ages of 247.1 ± 1.8 Ma, 249.5 ± 2.0 Ma, and 251.0 ± 3.2 Ma. The MEs in the Tianhu granitoids are typically sub-rounded to ellipsoidal in shape. They contain abundant acicular apatite, plagioclase that has been partially resorbed, and megacrysts of feldspar and quartz. They are characterized by high Mg# (50–52), positive eHf(t) values of 3.41–5.83, and young one-stage Hf model ages, all of which are indicative of crystallization from mantle-derived melts. The host Tianhu granitoids, which belong to I-type granites, contain higher SiO2 contents (68.3–69.8 wt%) and lower Mg# (38.3–45.4) than the MEs, are metaluminous (A/CNK = 0.97–0.98), and are characterized by high eHf(t) values of 2.26–5.46 and young two-stage Hf model ages. These geochemical characteristics indicate that the Tianhu granitoids and the MEs likely formed through mixing between mafic and felsic magmas. The mafic magma was originally derived from partial melting of a depleted mantle source, and subsequently evolved via fractional crystallization and modification by the felsic magma. In contrast, the felsic magma was generated by partial melting of the juvenile continental lower crust. The Tianhu granitoids would likely form in an intracontinental extensional environment, in which upwelling of the asthenospheric mantle led to partial melting of the lithospheric mantle to form the mafic magmas. And the felsic magmas were produced by partial melting of the deep juvenile crust with a heat source either from the ascending mafic magmas or the upwelling asthenospheric mantle along the thinned orogenic lithosphere. In either case, there would be significant Triassic crust–mantle interaction in the Eastern Tianshan and its adjacent Beishan area. This interaction was responsible for the formation of widespread Triassic granites and related ore deposits in this intracontinental region.

The Huangshandong Ni–Cu sulfide deposit is the largest magmatic sulfide deposit in the Huangshan–Jing’erquan mafic–ultramafic belt in the Eastern Tianshan; it was overprinted by post-magmatic hydrothermal fluids, and metamorphosed and deformed as a result of regional ductile shearing. Ore-forming elements were remobilized as a result of post-magmatic hydrothermal fluid flow, but the extent of this remobilization is still unclear. In this contribution, detailed mineralogical–textural characteristics of silicates and base-metal sulfides in different types of ores in the Huangshandong Ni–Cu sulfide deposit were integrated with spatially resolved trace-element compositions of olivine, serpentine, pyrrhotite, pentlandite, and chalcopyrite to identify the metals that were mobilized, the scale and quantity of metal remobilization, and the phases into which the mobilized metals were incorporated. Based on varying degrees of serpentine and talc alteration, three different types of ores are identified – weakly serpentinized magmatic ores, which are most representative of the primary magmatic mineralization, strongly serpentinized and deformed ores, and talc-altered ores. The cracks consisting of serpentine and magnetite in weakly serpentinized magmatic ores caused by the expansion of olivine during serpentinization; this, serpentine is enriched in ore-forming metals (e.g., Ni, Co, Cu) relative to olivine. The expansion cracks extend from olivine to sulfides also enriched in ore-forming metals, suggesting that some metals were mobilized from olivine during serpentinization. Based on the higher Ni content of secondary pyrrhotite compared to primary pyrrhotite, it is suggested that base-metal sulfides in the primary, weakly serpentinized ores were dissolved and reprecipitated in the strongly serpentinized and deformed ores from metal-rich fluids that interacted with olivine.

The variation of crustal thickness is a critical index to reveal how the continental crust evolved over its four billion years. Generally, ratios of whole-rock trace elements, such as Sr/Y, (La/Yb)n and Ce/Y, are used to characterize crustal thicknesses. However, sometimes confusing results are obtained since there is no enough filtered data. Here, a state-of-the-art approach, based on a machine-learning algorithm, is proposed to predict crustal thickness using global major- and trace-element geochemical data of intermediate arc rocks and intraplate basalts, and their corresponding crustal thicknesses. After the validation processes, the root-mean-square error (RMSE) and the coefficient of determination (R2) score were used to evaluate the performance of the machine learning algorithm based on the learning dataset which has never been used during the training phase. The results demonstrate that the machine learning algorithm is more reliable in predicting crustal thickness than the conventional methods. The trained model predicts that the crustal thickness of the eastern North China Craton (ENCC) was ~45 km from the Late Triassic to the Early Cretaceous, but ~35 km from the Early Cretaceous, which corresponds to the paleo-elevation of 3.0 ± 1.5 km at Early Mesozoic, and decease to the present-day elevation in the ENCC. The estimates are generally consistent with the previous studies on xenoliths from the lower crust and on the paleoenvironment of the coastal mountain of the ENCC, which indicates that the lower crust of the ENCC was delaminated abruptly at the Early Cretaceous.

The Tianshan is one of the largest gold provinces on Earth and hosts several giant gold deposits, while most giant gold deposits are distributed in the western and central segments of the Tianshan (i.e., the Western Tianshan) but not in Chinese Tianshan. Thus, the differences for metallogenesis of gold deposits between the Western and Chinese Tianshan attract intensive interest but remain ambiguous. Here we present sericite 40Ar/39Ar ages and S–Pb isotope compositions of pyrite from the Kanggur gold deposit, the largest shear zone-related gold deposit in the Chinese Tianshan. By integrating new sericite 40Ar/39Ar plateau ages (262.71 ± 2.95 Ma and 263.40 ± 2.94 Ma) with previous geochronological results, three peaks in gold mineralization are identified for the entire Tianshan: an early peak at ca. 330 Ma during which time subduction–accretion-related porphyry-type and orogenic gold deposits formed, a middle peak at ca. 290 Ma during which time post-collisional magmatism-related orogenic gold deposits formed in a collisional compressional to post-collisional extensional environment, and a late peak at ca. 260 Ma during which time strike–slip shear zone-related orogenic gold deposits formed in a post-collisional extensional environment. The sulfur (δ34SV-CDT of −1.0 to +2.5‰ for pyrite from ores and −1.9 to +2.6‰ for pyrite from wall rocks) and lead (18.199–18.231 for 206Pb/204Pb, 15.585–15.624 for 207Pb/204Pb, 38.104–38.229 for 208Pb/204Pb for pyrite from ores, and 18.176–18.244 for 206Pb/204Pb, 15.583–15.611 for 207Pb/204Pb, 38.090–38.205 for 208Pb/204Pb for pyrite from wall rocks) isotope compositions of pyrite indicate that the metals in gold deposits throughout the Tianshan were sourced from different reservoirs. In the Western Tianshan, the ore-forming metals for the deposits southwest of longitude 70°E were mainly sourced from upper crustal reservoirs, whereas those east of longitude 70°E were mainly sourced from lower crustal reservoirs. In the Chinese Tianshan, however, the ore-forming metals were dominantly sourced from lower crustal and/or mantle reservoirs. These different reservoirs were likely responsible for the distinct characteristics of the gold deposits located in the Western and Chinese Tianshan.

The petrogenesis of continental mafic rocks that are enriched in large-ion lithophile elements (LILE) and that have enriched Sr–Nd–Hf isotope compositions is debated, with some models suggesting an enriched mantle source and others arguing for crustal contamination. Crustal contamination has generally not been favored as numerical models indicate that this would require the addition of significant amounts of crustal materials. Here we present the first detailed study of the oxygen isotope composition of zircons from representative early Paleozoic mafic, intermediate, and felsic magmatic rocks in the South China Block (SCB), and combine this information with available geochemical data to re-examine whether crustal contamination or an enriched mantle source is the principal cause of the crustal geochemical signatures in these rocks. Zircon grains in the high-MgO mafic rocks (MgO > 8 wt%) with low eNd(t) values (

The Kanggur gold polymetallic deposit, located in the western segment of the Kanggur–Huangshan Shear Zone (KHSZ) of the Chinese North Tianshan, is the largest shear zone-controlled gold polymetallic deposit in this region. The gold mineralization is hosted by Early Carboniferous volcanic rocks of the Yamansu Formation, which is predominantly composed of andesite, dacite, and tuff. In this contribution, we present U–Pb age data and Hf isotopes of zircon from wall rocks associated with mineralization in the Kanggur deposit, as well as whole-rock geochemistry of the wall rocks with the goal of characterizing the petrogenesis of the deposit, and the sources of the ore-forming materials. Our new LA–ICP–MS zircon age data indicate that the wall rocks formed at ca. 340 Ma in the Early Carboniferous (andesite at 338.0 ± 1.7 Ma, dacite at 338.1 ± 2.2 Ma, rhyolite 332.4 ± 2.8 Ma, and granite porphyry at 342.6 ± 1.9 Ma). These wall rocks are enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs; e.g., U, K, and Pb), and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, and Ti). Based on the lack of ancient crustal basement rocks in the Qoltag Arc, the lithological assemblage of andesite–dacite–rhyolite, the presence of chert, and the enrichment of andesite and dacite in Na2O (3.35–6.89 wt%) relative to K2O (0.67–2.42 wt%), it is inferred that the Early Carboniferous volcanic wall rocks of the deposit formed in an oceanic arc setting. Considering the similar isotopic compositions of andesite, dacite, rhyolite, and granite porphyry (eNd (t) = −0.12 to 0.64 and eHf(t) = 6.05 to 8.96 for andesite, eNd(t) = 1.01 to 3.02 for dacite; eNd(t) = 4.20 to 4.91 and eHf(t) = 11.02 to 13.79 for rhyolite, and eNd(t) = 1.65 to 2.13 and eHf(t) = 4.70 to 6.80 for granite porphyry) and juvenile Hf model ages (TDM1 = 610 to 730 Ma for andesite, TDM2 = 460 to 640 Ma for rhyolite, and TDM2 = 910 to 1050 for granite porphyry), it is suggested that the primary magma from which the andesite and dacite crystallized was derived from partial melting of metasomatized mantle wedge, whereas, the magma from which the rhyolite and granite porphyry crystallized was derived from partial melting of juvenile lower crust. The bulk S isotope composition (δ34SV-CDT) of these wall rocks varies from −0.8 to 8.7‰ (average of 4.8‰), with the S isotope composition of the andesite and rhyolite being similar to that of pyrite in mineralized rock. The bulk Pb isotope composition of these wall rocks ranges from 17.561 to 18.258 206Pb/204Pb, 15.535 to 15.602 207Pb/204Pb, and 37.593 to 38.118 208Pb/204Pb, with the Pb isotope composition of andesite being similar to that of pyrite from gold-bearing ores in the Kanggur deposit. The high abundance of sulfides in the wall rocks, and the similar S–Pb isotope compositions of ores and andesite suggests that the ore-forming materials were likely derived from the andesite wall rocks.

The Dajingou gold deposit is one of the typical gold deposits in the Quruqtagh metamorphic terrane, north of the Tarim Craton. The deposit mainly comprises gold-bearing quartz veins hosted in Precambrian metamorphic rocks and structurally controlled by the subsidiary faults and ductile shear zone. To determine the age of gold mineralization in the Dajingou deposit, a single sericite 40Ar/39Ar age of 829.4 ± 4.8 Ma (MSWD = 0.57) and hydrothermal zircon weighted average U–Pb ages (812 ± 15 Ma, MSWD = 3.2) from auriferous quartz veins were obtained in this study, indicating that mineralization occurred in the mid-Neoproterozoic (ca. 0.83 Ga), corresponding to regional metamorphism of the Tarim Craton, termed the Tarim orogeny. The Dajingou deposit is the first Precambrian gold deposit identified in North Xinjiang, NW China. The δ18O and δD of quartz ranges from 14.7‰ to 15.9‰ and −104‰ to −75‰, respectively; the calculated δ18OH2O of the fluids ranges from 0.9‰ to 5.0‰. This suggests that the ore-forming fluids in the Dajingou gold deposit were derived from dehydration of metamorphic rocks during regional metamorphism, with a subsequent input of meteoric water. Based on its similarities with typical orogenic gold deposits, the Dajingou deposit is proposed to be an orogenic gold deposit formed during the mid-Neoproterozoic Tarim orogeny in the Tarim Craton.

The Nizhne-Derbinsk mafic-ultramafic complex is located between the Central Asian Orogenic Belt and the Siberian Craton and, is associated with the Ballyk fault. The largest, spatially related to each other, plutons in the central part of the complex are the Burlakski and Nizhne-Derbinsk. Rocks in the main units of these plutons are divided into three groups: peridotites (ultramafic), pyroxenites (sub-ultramafic), and gabbroic rocks (mafic). The ultramafic and sub-ultramafic cumulate series are devoid of plagioclase and contain &lt, 3 vol. % chromian spinel. The Fo content of olivine in the sub-ultramafic cumulates from both plutons ranges from Fo79 to Fo86. The En content [= Mg/(Mg + Fe + Ca) &times, 100 atomic ratio] of clinopyroxenes and orthopyroxenes varies from 46&ndash, 56, and 63&ndash, 80, respectively. Plagioclase corresponds to labradorite with An contents between 55 and 57. Hornblende is compositionally similar to pargasite. The sequence of change of rock units corresponds to the paragenesis: olivine &minus, olivine + clinopyroxene (orthopyroxene) &minus, clinopyroxene + orthopyroxene &ndash, clinopyroxene + orthopyroxene + plagioclase &ndash, orthopyroxene. Petrographic, mineralogical, and mineral chemical features of the Burlakski and Nizhne-Derbinsk plutons suggest that the diversity of the material composition of these plutons is due to the processes of magmatic differentiation in deep-seated conditions. Estimates of crystallization pressures and temperatures of the Burlakski and Nizhne-Derbinsk plutons suggest that they crystallized at high pressures &ge, 10kb and temperatures ranging from 1000&ndash, 1400 &deg, C. Mineralogical and petrological features suggest that the mafic-ultramafic cumulates were derived from a high-Mg basaltic magma. The presence of magmatic hornblende and hydrous mineral assemblages within the ultramafic cumulates indicates that the parental melts had been enriched in dissolved volatile constituents. Taking into account the age of the gabbronorites of the Burlakski pluton (~490 &plusmn, 11.8 Ma), the magmatism likely occurred during the Ordovician collision stage of the evolution of the Central Asian Fold Belt.