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The paper presents the first isotopic U–Pb study data (LA–ICP–MS method) of zircon from intrusive rocks of the Molo-Sarychat pluton situated along the deep-seated fault system of the "Nikolaev Line" in the eastern Kyrgyzstan. The intrusive rocks from this pluton belong to the high-potassic calc-alkaline to shoshonitic series. Intense Mo(–W–Cu–Au) (mainly molybdenum-porphyry) mineralization is spatially and genetically associated with this pluton. Together with the other Au, W and Cu deposits and occurrences, this mineralization is part of the extended metallogenic belt of Tien Shan; however, occurrences of molybdenum-porphyry mineralization are still rare in this belt. The concordant isotopic U–Pb ages of zircon autocrysts indicate the crystallization of quartz monzonite (293.3 ± 4.2 Ma) and monzogranite (286.6 ± 2.4 Ma) in the Early Permian. Zircon antecrysts dated at 306–320 Ma are also present. The crystallization age obtained corresponds to a post-collisional epoch of the development of this territory but the presence of the antecrysts expands the pluton emplacement to the Late Carboniferous-Early Permian, which, as a result, spanned over initially subduction-related and then post-collisional tectonic settings. Correspondingly, a post-collisional setting of the Mo(–W–Cu–Au) (molybdenum-porphyry) mineralization is established; it is related to the pluton studied and was formed after the emplacement of quartz monzonite (early stage) and monzogranite (late stage). Significant enrichment in Mo can be related to its progressing accumulation during magmatic differentiation causing the emplacement of quartz monzonite and especially monzogranite. These processes occurred under the more mature post-collisional tectonic regime, with possible formation of intermediate magma chambers in the Paleoproterozoic metamorphic rocks and ancient granitoids. The age dates determined for rocks from the Molo-Sarychat pluton are similar to those identified for the igneous and metasomatic rocks of the large Kumtor gold deposit that is also associated with the "Nikolaev Line." [ABSTRACT FROM AUTHOR]

Zircon is a common, widely distributed accessory mineral in most igneous rocks and its refractory nature records magmatic evolution in terms of oxygen and U-Th-Pb isotopes, and trace-element contents all of which reflect the intrinsic physio-chemical evolution of the magmatic systems in which it crystallized. Zircon compositions can be used as an indicator of relative fertility of hypabyssal intrusions in terms Cu ± Mo ± Au porphyry mineralization. To further characterize syn-to post-collisional adakitic Devonian oxidized I-type granitoids in the New Brunswick (specifically, those with Cu ± Mo ± Au porphyrystyle mineralization), LA-ICP-MS analyses (guided by µXRF-EDS mapping and SEM-BSE imaging of polished thin sections) of zircons from 13 granitoids was conducted. The zircons studied were similar in terms of their textures (homogenous cores, patchy zoning, oscillatory zoning, and some unzoned zircon); however, they have a wide range of trace- and minor-element (Hf, HREE, Y, Th, U) compositions. Specifically, Zr/Hf ranges between 24-60, whereas Th/U ranges between 0.15 and 5.37. The presence of inherited zircon affects the concentrations of Th and U, as well as other key elements. Estimated crystallization temperatures of granitoids, ranging from 737 to 899°C, were calculated via Ti-in-zircon geothermometry assuming reduced TiO[sub 2] and SiO[sub 2] activities. The calculated log fO2 values for zircons from some of these granitoids indicate a highly oxidized magmatic signature. Zr/Hf, Eu/Eu*, and (Eu/Eu*)/Y in zircon, as well as zircon (Ce/Nd)/Y are some of the best indicators of porphyry fertility. The Ce/Ce* in zircon exhibit a large range (1.1-590), with higher Ce/Ce* reflecting more metallogenically favourable oxidizing conditions. If Eu/Eu* in zircon is ≥0.4 (relatively oxidized conditions), it indicates a high potential for an ore-forming porphyry Cu mineralizing system. Lower Eu contents reflect relatively reducing conditions, as Eu anomalies vary with oxygen fugacity as well, and the relative abundance of Eu2+ is higher, but does not substitute into the zircon lattice. The evidence extracted from analyzing the zircon composition within New Brunswick's I-type granitoids indicates the fertility of these hypabyssal intrusions. [ABSTRACT FROM AUTHOR]

The Gangdese belt in Xizang has experienced both Jurassic subduction and Cenozoic continental collision processes, making it a globally renowned region for magmatic rocks and porphyry copper deposits. Numerous Jurassic intrusions have been identified in the belt. Apart from the quartz diorite porphyry in the large Xietongmen deposit, the Cu mineralization potential of other Jurassic intrusions in this belt remains unclear. This study presents zircon U–Pb dating and trace elements, apatite major and trace elements as well as published whole-rock geochemical and isotopic data of the Dongga tonalite in the central part of the Gangdese belt, aiming to reveal the petrogenesis, oxidation state, volatile content, and Cu mineralization potential of this intrusion. The Dongga tonalite has a zircon U–Pb age of 179.4 ± 0.9 Ma. It exhibits high whole-rock V/Sc values (8.76–14.6), relatively low apatite CeN/CeN* ratios (1.04–1.28), elevated zircon (Eu/Eu*)N values (an average of 0.44), high Ce4+/Ce3+ values (205–1896), and high ∆FMQ values (1.3–3.7), collectively suggesting a high magmatic oxygen fugacity. The Dongga tonalite features amphibole phenocrysts, relatively high whole-rock Sr/Y ratios (20.3–58.9), and lower zircon Ti temperatures (502–740 °C), reflecting a high magmatic water content. Estimation of magmatic sulfur content (0.002–0.024 wt%) based on apatite SO3 contents indicates an enriched magma sulfur content. Combined with previous studies and the collected Sr–Nd–Hf isotopes, the Dongga tonalite is derived from juvenile lower crust related with subduction of the NeoTethys oceanic slab. When compared with Xietongmen ore-bearing porphyries, the Dongga tonalite exhibits remarkable similarities with the Xietongmen ore-bearing porphyries in terms of magma source, tectonic background, magmatic redox state, and volatile components, which indicates that the Dongga tonalite has a high porphyry Cu mineralization potential, and therefore, provides important guidance for the future mineralization exploration. [ABSTRACT FROM AUTHOR]

Paleoproterozoic A-type granites are widely distributed in the southern margin of the North China Craton (SNCC), providing important information for understanding the Paleoproterozoic tectonic regimes in this area. This paper reports newly obtained whole-rock compositions and zircon U-Pb ages for the Tieluping syenogranite porphyry (TLP) and Huoshenmiao alkali granite porphyry (HSM) in the SNCC. Zircons from the TLP and HSM have U-Pb ages of 1 805 ± 12 and 1 792 ± 14 Ma, respectively. These ages are taken to date the emplacement of these intrusions. They had high total alkali contents (K2O + Na2O > 7.13 wt.%), with high 10 000 × Ga/Al ratios (3.06–3.41) and Zr + Y + Nb + Ce values (709 ppm–910 ppm) as well as high zircon saturation temperatures (864–970 °C), indicative of A-type granite affinities. High Y/Nb (1.75–3.32), Ce/Nb (7.72–9.72), and Yb/Ta (2.89–5.60) ratios suggested that TLP and HSM belonged to the A2-type granite. The negative whole rock εNd(t) values (−8.4 to −6.6) and negative zircon εHf(t) values (−15.9 to −6.3) confirmed that TLP and HSM were likely generated by the partial melting of an ancient continental crust. The εHf(t) (−7.4 to +4.0) values of inherited zircons in the TLP suggested that they were derived from the partial melting of Archean basement rocks. Considering the geochemical similarity of the 1.80 Ga A-type granitoids in the SNCC, we propose that the TLP and HSM were formed in a post-collisional regime that was likely associated with the break-off of the Paleoproterozoic subducted slab. Upwelling of the asthenosphere provided huge heat to generate the regional 1.80 Ga A-type granite in the SNCC. [ABSTRACT FROM AUTHOR]

The Wunugetu deposit, a large-scale porphyry copper–molybdenum deposit, is located in the southern Erguna block. Its ore bodies are primarily found within monzogranites, granite porphyries, and biotite monzogranites. Additionally, the deposit contains late-stage intrusive dykes of rhyolitic porphyries. This study examined the deposit's monzogranites and rhyolitic porphyries using lithogeochemistry, zircon U-Pb dating, and Hf isotopic analysis. The main findings include: (1) Zircon U-Pb dating showed that the monzogranites formed around 209.0 ± 1.0 Ma, whereas the rhyolitic porphyries in the northern portion formed around 170.49 ± 0.81 Ma, suggesting magmatic activity in the deposit spanned from the Late Triassic to the Middle Jurassic. (2) The monzogranites exhibited high silicon content (73.16–80.47 wt.%) and relatively low aluminum content (10.98–14.37 wt.%). They are enriched in alkalis (content: 3.42–10.10 wt.%) and deficient in magnesium and sodium, with aluminum saturation indices (A/CNK) ranging from 1.1 to 2.9. In addition, the monzogranites are enriched in large-ion lithophile elements (LILEs) such as Rb, K, and Ba and deficient in high-field-strength elements (HFSEs) like Nb, P, and Ti. (3) The monzogranites have low Zr + Nb + Ce + Y contents of (151.3–298.6 ppm) × 10−6 and 10,000 × Ga/Al ratios varying between 1.20 and 2.33, suggesting that they are characteristic of I-type granites. (4) Positive zircon εHf(t) values ranging from +0.3 to +7.6 in both rhyolitic porphyry and monzogranite samples, increasing with younger emplacement ages, imply that the deposit's rocks originated from magmatic mixing between mantle-derived mafic magmas and remelts of the juvenile crust. Considering these results and the regional geological evolution, this study proposes that the Wunugetu deposit was formed in an active continental margin setting and was influenced by the Late Triassic–Middle Jurassic southeastward subduction of the Mongol-Okhotsk Ocean. [ABSTRACT FROM AUTHOR]

Volcaniclastic deposits are cynosures for reconstructing volcanic archives and evaluating the tectonic imprints of the study area. This paper presents an elaborate geological field litholog, petrography and geochemistry of ~1.2 km thick sequence of the quartz-feldspar porphyry (QFP) and rhyolites in the Kadiri–Hindupur section of the Kadiri Greenstone belt from Eastern Dharwar Craton (EDC). The QFP exhibits primary stratification; the thickness of the beds varies from very thin to thick (3–8 cm) and shows large-scale tabular cross-bedding in the lower half of the section. The bedding surfaces of QFPs are marked by current crescent-shaped marks (long axis: 5–25 cm, short axis: 2–8 cm), speculated as possible remnants of volcanic bombs and pyroclastic debris during the explosive volcanism. Petrographically, these QFPs are characterised by spectacular blue opalescent quartz grains with embayed grain boundaries, anhedral feldspar with sieved texture, fractured plagioclase and polycrystalline groundmass suggesting a volcaniclastic origin. They are also endowed with significant post-depositional textures such as domino-listric faulting and sigma-shaped porphyroblasts. Geochemically, QFPs are unaltered with trachyte-trachy dacite compositions showing high-potash, calc-alkaline nature displaying shoschonitic affinity. The primitive mantle normalised trace and rare earth elements are marked by an enriched LREE-LILE pattern coupled by negative zircon–hafnium, niobium–tantalum and titanium anomalies affirming their common genetic link to a prominent island arc–back-arc system where explosive volcanism produced the felsic crystal tuffs that were deposited and preserved as volcaniclastic QFP. The associated blocks and bombs produced the current crescent-shaped marks preserved on the bedding surfaces of QFPs. Research highlights: Research Highlights Quartz-feldspar porphyry (~1.2 km thick) occurs in the Kadiri Greenstone Belt, Eastern Dharwar Craton. Blue opalescent quartz and deformed plagioclase porphyry indicate volcaniclastic origin. Enigmatic current crescent-shaped marks represent remnants of volcanic bombs and pyroclastic debris. The primitive mantle normalised REE diagram is characterised by LREE-LILE enrichment. They represent Neoarchean pyroclastic volcanism and sedimentation in an island arc–back-arc setup. [ABSTRACT FROM AUTHOR]

Porphyry copper ore-forming magmas worldwide are chemically distinguished from ordinary arc granitoids by lower Zr and by higher Sr/Zr ratios at equivalent SiO2 contents. Low ppm Zr in zircon-saturated melts and high whole-rock Sr/Zr in granitoid samples retaining igneous plagioclase are useful discriminants of Cu-fertile intrusive complexes. These and other chemical discriminants of porphyry-copper-forming melts of tonalite-granodiorite-adamellite composition cannot develop during crystallisation-differentiation at upper-crustal pressures. They indicate unusually high dissolved H2O (≥ 9 wt%) in residual melts at depths near the base of the crust. We compare Zr behaviour during mafic-to-felsic magmatic differentiation in orogenically deforming, copper-mineralised arc segments with behaviour during differentiation in non-orogenic, unmineralised arc segments laterally adjacent along the same subduction zones. In orogenically deforming segments, horizontal compressive stress provides resistance to opening of tensile dyke fractures and promotes entrapment of mantle-derived basaltic melts in magma chambers embedded in hot country rock at Moho-vicinity depths, where magmas cool slowly and residual melts tend to last long enough to experience intermittent chamber replenishment by basaltic melts from the deeper mantle. Over several cycles of replenishment and fractional crystallisation, residual melts acquire high concentrations of inherited chemical components that were largely excluded from cumulus minerals—H2O, Cl, CO2, SO3, etc. Accumulating H2O re-orders the high-pressure crystallisation sequence of igneous minerals in successive cycles and leads to early and prolific production of hornblende and early zircon saturation in mafic melts (< 60 wt% SiO2) of later cycles and leads to low Zr contents of zircon-saturated intermediate-composition residual melts. [ABSTRACT FROM AUTHOR]

Northwest Zhejiang area (NWZJ) is one of the important parts of the large Qingzhou-Hangzhou mineralized belt in South China formed during the Late Jurassic–Early Cretaceous period. Through the study of zircon LA-ICPMS U-Pb dating, whole-rock geochemistry, and Sr-Nd isotopes for the Wujinshan granitoid in NWZJ, two distinct S-type granitic rocks of porphyry type granodiorite and granite were identified, and the two ages of 146.4 ± 1.5 Ma for granodiorite porphyry and 141.9 ± 1.4 Ma for granite porphyries were obtained. These rocks exhibited a geochemical affinity for S-type granitoid, and the two magmatic ages indicate that these rocks were intruded in two magmatic pulses. The Late Jurassic granodiorite porphyry showed moderate SiO2 (64.38–67.89 wt.%) with higher K2O + Na2O (6.22–6.78 wt.%), lower K2O/Na2O (0.57–0.96), moderate Zr (170–215 ppm), high Sr (302–475 ppm), and low Mg# (31–32) contents. The Early Cretaceous granite porphyries contained high SiO2 (69.68–74.85 wt.%), variable K2O + Na2O (4.60–6.99), high K2O/Na2O (1.72–23.53), slightly higher Zr (160–255 ppm), variable Sr (25–412 ppm), and very low to intermediate Mg# (13–44). The granodiorites had intermediate ∑REE (149–177 ppm), while granite samples showed moderate to high ∑REE content (147–271 ppm), and both rocks showed negative Eu anomalies (0.18–0.29). We propose that these two rocks were predominantly generated by the partial melting of Mesoproterozoic metamorphic basement and underwent variable degrees of fractionation and evolution. The Late Jurassic granodiorite porphyry was formed by the partial melting of Mesoproterozoic metamorphic basement with slab-derived melts or basaltic lower crust input following fractional crystallization, while the Early Cretaceous granite porphyries were generated by the partial melting of Mesoproterozoic metamorphic basement and crystal fractionation with variable magma mixing and assimilation in the upper crust. Tectonically, the Wujinshan granitoid formed in a volcanic arc setting largely affected by the subduction and slab rollback of the paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]

Oxygen fugacity (fO2) is a critical factor that controls the formation mechanisms of the porphyry Cu deposits. However, the differentiation of the fO2 in post-collisional Au-mineralized and Cu-mineralized porphyry intrusions remains unclear. The post-collisional Jinshajiang–Ailaoshan metallogenic belt hosts several Eocene Cu–Au–Mo porphyry systems including the Yulong Cu, Machangqing Cu, Chang'anchong Cu, and Beiya Au deposits and contains several barren porphyry intrusions, such as the Jianchuan, Putaishan, and Bailiancun granite porphyries. This study compares the zircon chemistry, magmatic fO2, and petrogenesis among the Cu-mineralized, Au-mineralized, and ore-barren porphyries. Our results show that the fO2 of the Cu- and Au-porphyry systems (average ΔFMQ = + 1.59 ± 0.77) is higher than that of the ore-barren (average ΔFMQ = − 0.43 ± 0.91) granite porphyry. Notably, compared to the Au-mineralized porphyries (average ΔFMQ = + 0.99 ± 0.70), the Cu-mineralized porphyries crystallized from more oxidized magma (average ΔFMQ = + 1.89 ± 0.60). All the Cu-mineralized, Au-mineralized, and ore-barren porphyry intrusions originated from partial melting of a thickened lower crust with minor input from the enriched lithospheric mantle-derived melts. The lithosphere of the Au-mineralized and ore-barren porphyry intrusions was influenced mainly by the slab-derived fluids, whereas the lithosphere of the Cu-mineralized porphyry intrusions was metasomatized by slab-derived melts. Therefore, we propose that the parental magmas for the Cu–mineralized porphyry possibly inherited the high oxidation state of the slab-derived melts and then contributed to the high fO2 of the Cu-mineralized granite porphyries. Collectively, the magmatic processes at deep levels played an essential role in determining the fO2 of the granite porphyry, thus controlling the mineralization diversity. [ABSTRACT FROM AUTHOR]

Large volume, intermediate-felsic magma reservoirs are the source of melt and mineralising fluids which generate porphyry copper deposits. Cooling and crystallisation of hydrous magmas drives the exsolution and expulsion of a magmatic volatile phase—a process which remains challenging to constrain in porphyry Cu systems where the record of magma volatile compositions is rarely preserved. Here, we use the halogen compositions of apatite inclusions shielded as inclusions within zircon to constrain volatile evolution in magma reservoirs which pre-date and are synchronous with porphyry Cu mineralisation at Quellaveco, Southern Peru. Geochemical and textural data confirm that the zircon-included apatites escaped re-equilibration with hydrothermal fluids, unlike apatites found in the groundmass of the same rocks. We, therefore, recommend that future studies attempting to reconcile magmatic volatile budgets using apatite in porphyry Cu systems should focus on apatite inclusions in zircon. By combining the apatite inclusion data with numerical modelling, we find evidence that the magma reservoir sourcing porphyry Cu mineralisation remained fluid-saturated for the entire period recorded by apatite crystallisation. By contrast, the pre-mineralisation batholith shows more variable, potentially fluid-undersaturated behaviour. Our modelling suggests that in order to attain the porphyry melt volatile compositions inferred from apatite, the magma reservoir must have exsolved a large proportion of its volatile budget, consistent with having been held at high crystallinity (40–60% crystals). This crystallisation interval coincides with peak chlorine and copper extraction from intermediate-felsic magmas, and would have permitted efficient fluid migration and accumulation at the roof of the system. We suggest that the storage of large-volume, long-lived, crystal-rich magma reservoirs in magmatic arcs may be a critical step in generating world-class porphyry copper deposits. [ABSTRACT FROM AUTHOR]

The origin of intermediate to felsic potassic magmas is debated, and not much is known about the volatile content of potassic magmas associated with porphyry Cu (Au, Mo) deposits. To better understand the liquid line of decent of mafic potassic magmas and the behavior of volatiles during magma differentiation, we performed 19 experiments at 1.0 GPa and 1150 °C to 850 °C using piston cylinder presses. We developed a new experimental technique that involves a capsule liner made of single-crystal zircon to prevent the loss of Fe and S in the starting material to the noble metal capsule. The starting material is a high-Mg, basaltic trachyandesite (52 wt% SiO2, 12 wt% MgO, 1.9 wt% Na2O and 5.3 wt% K2O) from the Sanjiang region in southwestern China, doped with geologically realistic amounts of volatiles (i.e. 4.0 wt% H2O, 0.34 wt% CO2, 0.27 wt% Cl and 0.25 wt% S). The addition of 0.25 wt% S in the form of anhydrite internally buffered the experiments at an oxygen fugacity of 2.0 ± 0.5 log units above the fayalite–magnetite–quartz buffer, which is similar to the redox state of the Sanjiang variously evolved potassic magmas. The experimentally produced silicate melts match well with the Sanjiang intermediate to felsic magmas in terms of major, minor and trace element compositions, and also with regard to the S and Cl contents. The sequence of crystallizing minerals (olivine + clinopyroxene –> biotite ± orthopyroxene –> apatite –> K-feldspar) also fits with the one observed in the Sanjiang mafic to intermediate magmas. These results suggest that the Sanjiang intermediate to felsic magmas, including the porphyry Cu (Au, Mo)-forming magmas, can form solely by differentiation of potassic mafic magmas without any involvement of old crustal material. During experimental differentiation at 1.0 GPa, the S content of the evolving silicate melt first increased until ~57 wt% melt SiO2, and then decreased in response to precipitation of sulfides, sulfate melt and/or anhydrite, whereas the H2O and Cl contents of the evolving silicate melt increased exponentially until saturation in a CO2-rich fluid was reached at 60 to 65 wt% melt SiO2 and ~ 8 wt% melt H2O. During further magma differentiation the H2O and Cl contents of the evolving silicate melt remained constant until ~70 wt% melt SiO2, after which point the Cl content of the silicate melt decreased due to increased partitioning of Cl into the fluid phase ± increased fluid/melt ratio. Based on these experimental results and petrographic and geochemical evidence from natural samples, the Sanjiang porphyry Cu (Au, Mo)-forming magmas (65–70 wt% SiO2) are interpreted to have formed through differentiation of primitive, mantle-derived, potassic magmas in the lower crust (≥1.0 GPa), and to have ascended ±directly from the lower crust to shallow crustal levels. They likely contained 8 to 13 wt% H2O, 0.37 to 0.90 wt% Cl and 0.07–0.29 wt% S. This case study on the magma evolution in the Sanjiang region may have implications for the origin and nature of intermediate to felsic potassic magmas in various tectonic settings. [ABSTRACT FROM AUTHOR]

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The recently discovered 460 Gaodi porphyry Mo-Cu deposit is a sub-economic deposit characterized by low Mo-Cu grades, dispersed mineralization, and separated Mo- and Cu-ore bodies. This study aims to elucidate the factors underlying this type of sub-economic mineralization. Electron-microprobe analyses of biotite from ore-related granite porphyry yielded Ti-in-biotite crystallization temperatures of 677–734 °C (an average of 719 °C) and biotite phenocryst crystallization depths of 6.0 to 12.9 km. LA-ICP-MS analyses of zircons from the same sample revealed average zircon Ce4+/Ce3+ ratios of 299.7 and elevated zircon lg(ƒO2) ratios, with an average ΔFMQ of +6.6 ± 1.9. These discoveries suggest that the magma responsible for ore formation boasts a high degree of oxidation, yet also possesses a magma chamber located at a significant depth within the upper crust. This implies an extensive exsolving depth for fluids. Furthermore, our microthermometry analysis of fluid inclusions reveals that a portion of the fluid experiences considerable conductive cooling as it ascends along the conduit, owing to the depth of fluid exsolution. This process results in the ore fluids remaining in the liquid-only region without undergoing boiling, which is conducive to the enrichment of metals. We emphasize the fact that fluid-exsolving depth plays a critical role in determining the metal grades and economic value of a porphyry deposit by regulating the P-T evolution path of the ore fluids [ABSTRACT FROM AUTHOR]

The origin of the anorthosite-rapakivi granite-bearing rock complexes was a topic of research for geologists for more than a century. Magmatic systems that produce these complexes were widely developed in the Precambrian and have no direct analogues in modern times. The main goal of this study was to characterize the conditions under which primitive granitoids formed and to shed light on the history of ore matter transport during these stages. The object of the research was granite porphyry dikes—a subeffusive analogue of rapakivi granite from the Salmi batholith in the Fennoscandian Shield. Characteristic solid-phase inclusions of a mineral paragenesis of mafic rocks, as well as inclusions of sulfide melts, were found in zircon from this type of rock. These sulfide inclusions were homogenized by heating, and subsequently, the trace element composition was determined by the LA-ICP-MS method. The geochemistry of zircons was studied by the SIMS method, and the temperature of their formation was determined using a Ti-geothermometer. The temperature of the studied zircon grain formation varied from 925 to 765 °C. The values of ƒO2 for the early stages of the rock formation were in the region below the boundary of the FMQ buffer. The presence of two sulfide melts at the time at which the sulfide inclusions were captured by the zircon, pyrrhotite-chalcopyrite, and sphalerite-chalcopyrite compositions was established. The capture of sulfide inclusions from the pyrrhotite-chalcopyrite composition occurred above 841 °C, while in sphalerite-chalcopyrite, they occurred at a lower temperature of 765 °C. The connection between the formation of granite porphyry with mafic melts that form rocks of the gabbro and anorthosite types was established. [ABSTRACT FROM AUTHOR]

The texture and morphology of igneous zircon indicates magmatic conditions during zircon crystallization and can be used to constrain provenance. Zircons from porphyry copper deposits are typically prismatic, euhedral, and strongly oscillatory zoned which may differentiate them from zircons associated with unmineralized igneous systems. Here, cathodoluminescence images of zircons from the Quellaveco porphyry copper district, Southern Peru, were collected to compare zircon textures between the premineralization Yarabamba Batholith and the Quellaveco porphyry copper deposit. Quellaveco porphyry zircons are prismatic, euhedral, and strongly oscillatory zoned, whereas the batholith zircons are subhedral‐anhedral with weaker zoning. We adopt a deep convolutional neural network (CNN) approach to demonstrate that a CNN can classify Quellaveco porphyry zircons with high success. We trial several CNN architectures to classify zircon images: LeNet‐5, AlexNet and VGG, including a transfer learning approach where we used the weights of a VGG model pretrained on the ImageNet data set. The VGG model with transfer learning is the most effective approach, with accuracy and receiver operating characteristic‐area under curve (ROC‐AUC) scores of 0.86 and 0.93, indicating that a Quellaveco porphyry zircon CL image can be ranked higher than a batholith zircon with 93% probability. Visualizing model layer outputs demonstrates that the CNN models can recognize crystal edges, zoning, and mineral inclusions. We trial implementing trained CNN models as unsupervised feature extractors, which can empirically quantify crystal textures and morphology. Therefore, deep learning provides a tool for the extraction of information from large, imaged‐based petrographic data sets which can facilitate petrologic and provenance studies. Plain Language Summary: Zircon is a common mineral found in rocks associated with magmatism. Zircons can have a range of shapes, sizes, and internal structures which reflect the conditions in the magma chamber where the zircon crystallized. It has been suggested that zircons derived from magmas associated with porphyry copper deposits, economically valuable sources of copper, may possess specific morphologies and textures. Here, we performed textural imaging of zircons from the Quellaveco porphyry deposit in Southern Peru and neighboring granitic rocks not associated with porphyry Cu mineralization. We find the porphyry zircons have the expected characteristic shapes and textures previously proposed, whereas the other rocks do not. We trained a deep learning model to effectively classify images of zircons from porphyry Cu rocks, which is capable of recognizing the edges, zones, and inclusions within zircon crystals. Our approach can be used to identify zircons that are associated with porphyry Cu deposits, and similar methods can be used to constrain the provenance (host rock) of zircons in stream sediments. Key Points: Collection and analysis of zircon cathodoluminescence images from porphyry copper‐related and premineralization intrusions from South PeruApplication of transfer learning on a state‐of‐the‐art convolutional neural network for zircon texture classificationExtraction of quantitative information on mineral morphology and zoning using unsupervised deep learning [ABSTRACT FROM AUTHOR]

Magmatic sources of porphyry deposits in postcollisional settings remain controversial. We have used new and published petrological and geochemical data for the Eocene–Oligocene porphyry Cu ± Mo ± Au deposits in the Sanjiang region, SW China, to address this outstanding issue. New data for three deposits (Machangqing, Tongchang, and Beiya) in the Ailaoshan–Red River porphyry Au-Cu-Mo belt (southern part of the Sanjiang region) suggest that ore-forming porphyries were emplaced at ~ 35 Ma, have high (87Sr/86Sr)i (0.7068–0.7071) and negative εNd(t) (− 6.9 to − 5.0), low zircon εHf(t) (− 5.3 to 4.5), and relatively high δ18O (5.9–9.0‰). Magmatic amphibole phenocryst compositions indicate that the parental magmas are all relatively oxidized (ΔFMQ = 1.7 ± 0.6), and H2O-rich (3.8 ± 0.3 wt% H2O). These results are consistent with those estimated from zircon compositions (ΔFMQ = 1.8 ± 0.8) and high whole-rock Sr/Y ratios (75 ± 31), respectively. Based on the new and published data, we suggest that the parental magmas for the Ailaoshan–Red River porphyry Au-Cu-Mo belt were derived from a preserved juvenile arc lower-crust and the underlying metasomatized subcontinental lithospheric mantle (SCLM) attributed to a Neoproterozoic subduction event, whereas the parental magmas for the Yulong porphyry Cu-Mo belt (northern part of the Sanjiang region) originated from the Permian–Triassic juvenile arc lower-crust and metasomatized SCLM. Additionally, parental magmas for these porphyry deposits are all oxidized and H2O-rich, and we attribute such characteristics to inheritance from mixed mantle-crust sources that were modified by previous oceanic slab subduction. [ABSTRACT FROM AUTHOR]

The Naruo porphyry copper deposit containing more than 2 Mt of copper is located in the Duolong ore district in the west of the Bangongco–Nujiang belt in central Tibet. New zircon U‐Pb, biotite 40Ar/39Ar, zircon (U‐Th)/He ages, published age data together with thermal modeling were presented in this paper to investigate the thermal history of Naruo deposit. Thermal modeling reveals a prolonged magmatic‐hydrothermal evolution firstly cooling from ∼700°C to ∼350°C at 120 Ma, then cooling to 230°C at 106 Ma and maintaining at 200°C from 106 to 90 Ma which is attributed to multiple magmatic events and thermal effect of strike‐slip fault. Affected by thrust nappe structure, the sample was consistent with 120°C from 70 to 63 Ma. The Naruo deposit started to experience exhumation at a rate of ∼0.07 km/Myr since 60 Ma which is related to India‐Asia collision. The prolonged magmatic‐hydrothermal evolution process might have important influence on the Naruo deposit. The ore‐related intrusions preserved in the foot walls of strike‐slip fault and thrust nappe structure are the objects of future exploration in the Duolong ore district. [ABSTRACT FROM AUTHOR]

Porphyry indicator zircons (PIZ) are often used as an exploratory guide to distinguish fertile granitoid-hosted porphyry copper deposits (PCD). Alumina-saturated granitoids with higher zirconium (> 200 ppm) contents are often the hosts of PCD. REE profiling of zircon is used here to evaluate the chemistry of zircon from a blend of I- and A-type granitoids that hosts the ‘Kaziranga’ porphyry copper mineralization in the Karbi Hills of the Shillong Plateau. Zircon Hf(t) (1.69–9.88; av.4.65) and whole rock 87Sr/86Sr (0.703) of the Kaziranga granitoids suggest magma derivation in an intraplate or primitive island arc tectonic setting, in which the active mechanism of magma derivation was partial melting of a metasomatically enriched lithospheric mantle that was probably fertilized by an intraplate mantle plume. The fertility indicators with PIZ are grouped with respect to the distribution pattern of normalized REEs, as they exhibit low LREE and enriched HREE, large + Ce, and small -Eu anomalies. The hypogene alteration zones have developed on a regular basis, the potassic alteration zone being close to the central zone around Kuthori in the north Karbi Hills. Although the hosts demonstrate expansion and development of the hypogene alteration zones, the zircons from the mineralized granitoids of Kuthori central zone and granitoids of the nearby Panbari–Dallamara shear zone have similar REE pattern. The target zone’s zircon has higher values of ΣHREE, U, Th, Y, Nb, and Hf. The admissible range of fertile PCD is matched by the cross plots of critical element ratios, demonstrating high calculated Ti in zircon temperature (up to 828 °C).Graphical abstract: Porphyry indicator zircons (PIZ) are often used as an exploratory guide to distinguish fertile granitoid-hosted porphyry copper deposits (PCD). Alumina-saturated granitoids with higher zirconium (> 200 ppm) contents are often the hosts of PCD. REE profiling of zircon is used here to evaluate the chemistry of zircon from a blend of I- and A-type granitoids that hosts the ‘Kaziranga’ porphyry copper mineralization in the Karbi Hills of the Shillong Plateau. Zircon Hf(t) (1.69–9.88; av.4.65) and whole rock 87Sr/86Sr (0.703) of the Kaziranga granitoids suggest magma derivation in an intraplate or primitive island arc tectonic setting, in which the active mechanism of magma derivation was partial melting of a metasomatically enriched lithospheric mantle that was probably fertilized by an intraplate mantle plume. The fertility indicators with PIZ are grouped with respect to the distribution pattern of normalized REEs, as they exhibit low LREE and enriched HREE, large + Ce, and small -Eu anomalies. The hypogene alteration zones have developed on a regular basis, the potassic alteration zone being close to the central zone around Kuthori in the north Karbi Hills. Although the hosts demonstrate expansion and development of the hypogene alteration zones, the zircons from the mineralized granitoids of Kuthori central zone and granitoids of the nearby Panbari–Dallamara shear zone have similar REE pattern. The target zone’s zircon has higher values of ΣHREE, U, Th, Y, Nb, and Hf. The admissible range of fertile PCD is matched by the cross plots of critical element ratios, demonstrating high calculated Ti in zircon temperature (up to 828 °C). [ABSTRACT FROM AUTHOR]

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X24080014 [ABSTRACT FROM AUTHOR]

This work presents data on the age of the volcanites of Sommers Island located to the south of the submarine extension of the Vyborg massif, as potential comagmates of rapakivi granites. The U–Pb system of zircon from Early Riphean volcanics is studied to determine their geochronological age using the SHRIMP-II ion microprobe (VSEGEI). For quartz porphyries composing the southern part of Sommers Island, the oldest age determinations of volcanics (1663 ± 8 Ma) were obtained for the Gulf of Finland area for the first time, which can be assigned to the lower parts of the Hogland series of the Early Riphean. In the northern part of the island, there are various rocks: quartz–feldspar porphyries (rhyodacites), andesibasalts, trachybasalts, and granodiorites. All of them underwent modifications under conditions of greenstone metamorphism in contrast to the relatively fresh rocks in the southern part of the island. The trachybasalts (1591 ± 5 Ma) are older than the quartz–feldspar porphyries (rhyodacite, 1578 ± 14 Ma), and a similar modification from older basic rocks to younger acidic ones is typical of all magmatic occurrences of the anorthosite–rapakivi granite formation in the Gulf of Finland region. The "young" ages of the rocks from the northern part of Sommers Island are likely to represent the presence of a younger massif of rapakivi granites than the Vyborg massif in the center of the Gulf of Finland. In this case, the Riphean trough structure traced eastward from Sommers Island is composed not only of rocks of the Hogland series, but part of it correlates with the bottoms of the Pasha graben section and the Priozerskaya Formation. [ABSTRACT FROM AUTHOR]

The intrusions of Permian monzonites and granitoids exposed in the Koni–Taigonos arc, which composes the basement of the Uda–Murgal magmatic arc, are revealed for the first time in northeastern Asia. On the Taigonos Peninsula, a small Aichan pluton of Early Permian monzonitoids with an age of 297–290 ± 2 Ma (zircon, SHRIMP-II) intrudes the Permian sedimentary rocks, and, on the Koni-P'yagina Peninsula, two intrusions of leucocratic and porphyry granites with ages of 275 and 257 ± 2 Ma (zircon, LA-ICP-MS) are exposed in the basement blocks and are intruded by Early Cretaceous granitoids. The primary Sr and Nd isotope ratios of the Permian granitoids are close to the characteristics of the mantle (87Sr/86Sr = 0.07030‒0.07038, 143Nd/144Nd = 0.51245‒0.51270, εNd of +2 to +7.7). In the geochemical features, the rocks studied belong to type I aluminous granites of volcanic arcs of the shoshonite and high-K calc-alkaline series. These Permian granitoids are compared with those exposed in Japan (Maizuru belt) and Primor'e (Grodekovo batholith in the Khanka Block) and probably reflect the beginning of the most ancient subduction processes on the Pacific continental margin. [ABSTRACT FROM AUTHOR]

Zircon Hf-isotopic mapping can be regarded as a useful tool for evaluating the coupling relationship between lithospheric structure and metallic mineralization. Hence, this method shows important significance for mineral prediction. To explore this potential, the published granite zircon Hf isotope data from the Sanjiang Tethyan Orogen were systematically compiled. This study uses the Kriging weighted interpolation in the Mapgis software system to contour Hf isotopes, revealing a relation between the crustal structure and metallogenesis. The mapping results suggest that the Changning–Menglian suture zone is the boundary between ancient and juvenile crust, viz., the western terranes have ancient crust attributes, whereas the eastern terranes exhibit the properties of new juvenile crust. In addition, this study also found that the mineralization and element types in the Sanjiang Tethyan Orogen have a coupling relationship with the crustal structure. The distribution of porphyry Cu-Mo-Au deposits is mainly controlled by the new juvenile crust, whereas the magmatic-hydrothermal Sn-W and porphyry Mo-W(-Cu) deposits are closely related to the reworked ancient crust. The results of zircon Hf isotope mapping prove that the formation and spatial distribution of deposits are related to the composition and properties of the crust. Hf isotope mapping can reveal the regional metallogenic rules and explore metallogenic prediction and metallogenic potential evaluation. [ABSTRACT FROM AUTHOR]

Explanation: From Lakange Mo (Cu) deposit to Jiama Cu polymetallic deposit to Bangpu Mo mineralization to Qulong Cu-Mo deposit to Bangpu Cu mineralization, the Cl contents in apatite gradually increase, but the F contents in apatite gradually decrease, and the S content is similar but variation. It indicates that the Mo-dominated porphyry deposit formed from F-S-rich magma, whereas the Cu-dominated porphyry deposit formed from Cl-S-rich magma. [Display omitted] • There are two different magmatic-hydrothermal systems that formed the Bangpu Mo-Cu deposit. • Cu and Mo mineralization contain zircon and apatite with different geochemical features. • Cu mineralization was related to Cl-rich porphyry system, whereas Mo-mineralization was related to F-rich porphyry system. The Bangpu deposit, located in the eastern part of the Gangdese Porphyry Copper Belt, Tibet, is a porphyry Mo-Cu deposit in a continental collisional orogenic belt. Cu and Mo mineralization occurred separately in the Bangpu deposit. Mo (Cu) mineralization occurred mainly in the monzogranite porphyry (MP), while Cu (Mo) mineralization occurred mainly in the diorite porphyry (DP). The cause of such spatial differences in Cu and Mo mineralization in the Bangpu deposit remains unclear. In this study, the mineral chemistry of apatite and zircon was investigated to reveal the differences in the nature of ore-forming magma between Cu (Mo) and Mo (Cu) mineralization in the Bangpu deposit. The chondrite-normalized REE patterns of the apatite grains from the MP were enriched in LREEs with negative Eu anomalies, whereas those from the DP and biotite monzonitic granite (BM) had strong negative Eu anomalies with no obvious differentiation between LREEs and HREEs. The DP, MP, and BM have a low T TiZ range from 657 °C to 917 °C and a high AST range from 687 °C to 1079 °C. The zircon grains from the DP and MP had different Th/U ratios and T TiZ values, indicating that these porphyry samples probably experienced different magma crystallization or crystal fractionation histories. The zircon Ce4+/Ce3+ and Eu/Eu* ratios indicate that the ore-bearing DP and MP have higher oxygen fugacity than the BM. The F, Cl, and S contents in the apatite showed that the DP magmas were Cl- and S- rich, whereas the MP magmas magmas were F- and S- rich. The Bangpu porphyry Mo-Cu deposit results from two superimposed magmatic-hydrothermal systems. Mo was mainly partitioned into the F-rich magmatic-hydrothermal system released from the MP, and Cu was mainly partitioned into the Cl-rich magmatic-hydrothermal system released from the DP. Our results show that zircon and apatite geochemistry can be used to explain the spatial distribution of Cu and Mo mineralization in porphyry Cu-Mo systems. [ABSTRACT FROM AUTHOR]

Huangmeijian composite pluton is a uranium-bearing A-type granite in Middle-lower Yangtze River valley metallogenic belt. Huangmeijian composite pluton can be divided into four emplacement stages from earliest to latest, including stage Ⅰ biotite quartz syenite, stage Ⅱ syenite porphyry, stage Ⅲ quartz syenite and stage Ⅳ alkali feldspar granite. The vein-type uranium mineralization predominantly occurs along the contacts between the stage Ⅰ biotite quartz syenite and the clastic rocks. The study on the micro-textures, REE characteristics and U-Pb dating of zircons in Huangmeijian composite pluton was carried out. The results show that the zircons of biotite quartz syenite, syenite porphyry and quartz syenite are of magmatic genesis, and yield zircon U-Pb ages of(131.8±1.1),(129.7±1.6),(124.7±1.6)Ma, respectively. The cores of zircons in alkali feldspar granite are of magmatic genesis and undergo metamictization, while the rims of zircons in alkali feldspar granite are altered by hydrothermal fluid, and probably undergo recrystallization. The zircon U-Pb dating of alkali feldspar granite yields the crystallization age of(111.5±1.3)Ma and the hydrothermal activity age of(107.6±2.1)Ma. Based on the previous geochronological studies, the A-type granites in Middle-lower Yangtze River valley metallogenic belt can be divided into three periods. The early period is represented by biotite quartz syenite and syenite porphyry with crystallization age of 132-129 Ma; the main period is represented by quartz syenite and syenogranite with crystallization age of 128-124 Ma; the late period is represented by alkali feldspar granite with crystallization age of 115-110 Ma. The crystallization ages of alkali feldspar granite and hydrothermal activity time are close to the uranium mineralization ages; combining with the stable isotope studies, it probably indicates that stage Ⅳ alkali feldspar granite of Huangmeijian composite pluton has provided the ore-forming fluid and heat for the uranium mineralization. [ABSTRACT FROM AUTHOR]

The Zhaiping Ag–Pb–Zn vein deposit in the Coastal Volcanic Belt of southeastern China, which resulted from subduction of the paleo-Pacific oceanic lithosphere beneath the South China Block, is hosted by Early Cretaceous sub-volcanic rocks (rhyolite porphyry) and younger granite porphyry and quartz porphyry. Three generations of veins have been recognized: (i) pre-ore quartz + pyrite, (ii) syn-ore silver + pyrite + pyrrhotite + base metal sulfides + quartz + sericite, and (iii) post-ore quartz + calcite + fluorite veins. Rubidium–Sr dating of syn-ore pyrite yielded an isochron age of 132.2 ± 2.1 Ma (2σ, MSWD = 2.0, n = 4), which is roughly coincidental with the age of the granite porphyry and quartz porphyry (zircon U–Pb age: ca. 133 Ma). The age data, together with Pb, S, H, and O isotopic compositions, indicate a close temporal and possibly genetic relationship between mineralization and porphyry magmatism at Zhaiping. Geochemical and isotope data demonstrate that the Zhaiping sub-volcanic rocks were derived from partial melting of Proterozoic crustal sources and underwent fractionation of feldspars, monazite, and/or allanite. The 87Sr/86Sr ratios of pre-ore (Aph1) and syn-ore (Aph2) stage apatite are in the ranges of 0.71350 to 0.71441 and 0.71260 to 0.71328, respectively, which are distinct from those of the sub-volcanic intrusive rocks (0.7119–0.7125). The Sr isotope signature, together with lower fluid temperatures (< 360 °C) relative to typical magmatic fluid, points at addition of an external fluid. It is suggested that the sub-volcanic intrusion acted as a heat source that drove the dehydration of, and subsequent fluid circulation within, the host rocks. Lower 87Sr/86Sr ratio but higher Sr content of Aph2 relative to Aph1 possibly indicates continuous fluid–rock interaction and progressive decomposition of feldspar in the host rocks, thus supplying large amounts of Sr and probably Pb to the ore fluid. [ABSTRACT FROM AUTHOR]

The essential sources and processes required for the formation of Cu–(Au)-porphyry deposits have been part of a long-standing debate. In this study we investigate one of the youngest and best-preserved world-class Cu–(Au)-porphyry systems in order to learn more about melt sources and what geochemical tracers in zircon and apatite might be useful to identify ore-forming intrusions within porphyry systems. Combined, in-situ Hf, O, and Nd isotope analyses in zircon and apatite imply that the Tampakan magmas were derived from depleted mantle sources. Hence, we suggest that older crustal components or metasomatized mantle are not required for the production of metallogenically fertile magmas in island arc settings. Based on the compositions of apatite and zircon, we confirm that previously established fertility-indicator signatures of these minerals are useful to identify fertile porphyry systems. Our data show that intrusions directly associated with mineralization events contain apatite with elevated Cl and S concentrations compared to pre- and post- mineralization igneous events. [ABSTRACT FROM AUTHOR]

Recently, a new kind of volcanic rock, felsite porphyry, has been revealed by drilling in Xiangshan area, Jiangxi Province, China. To better understand petrogenesis and magmatic evolution sequence of the Xiangshan volcanic-intrusive complex, we studied systematic petrology, geochemistry, LA-ICP-MS zircon U–Pb dating, and Hf isotope results of the felsite porphyry. Results show that the felsite porphyry has similar geochemical characteristics to the porphyroclastic rhyolite, which is the predominant lithology of Xiangshan uranium orefield. Felsite porphyry and porphyroclastic rhyolite have high SiO2, Al2O3, and K2O contents, low Na2O, and MgO contents, and slightly negative Eu anomalies. Moreover, these rocks are relatively depleted in large ion lithophile elements (K, Ba, and Sr) and are enriched in high field strength elements (Th, Zr, and Hf). LA-ICP-MS zircon U–Pb dating of the felsite porphyry yielded a crystallization age of 132.2 ± 0.9 Ma, which is coeval to that of the porphyroclastic rhyolite. These ages signified that Xiangshan volcanic-intrusive complex formed in the Early Cretaceous, during which the entire South China was in the back-arc extension tectonic setting related to the subduction of the Pacific Plate under the Euroasian Plate. In-situ zircon Hf isotope data on a felsite porphyry sample show εHf(t) values from − 8.82 to − 5.11, while the Hf isotope two-stage model age (TDM2-Hf) ranges from 1513 to 1747 Ma. Combined with petrological, mineralogical, geochemistry, and geochronology results of the felsite porphyry, it is concluded that the felsite porphyry in Xiangshan might be originated from the partial melting of the Mesoproterozoic ancient metamorphic rocks, with possible input of small amounts of mantle materials. [ABSTRACT FROM AUTHOR]

The reduced nature of the subducting slab has been used to explain the relatively poor endowment of economic porphyry copper deposits in Paleo-Tethyan arc systems. The presence of numerous porphyry Cu deposits in the southern Yidun terrane potentially challenges this model, because these deposits are thought to be the product of Paleo-Tethyan subduction. To investigate this, two representative deposits (i.e., Pulang and Songnuo porphyry Cu deposits) from the southern Yidun terrane have been studied. Zircon U-Pb ages of pre- and syn-mineral porphyries in Pulang are 221 ± 2 Ma (MSWD = 0.89) and 215 ± 2 Ma (MSWD = 1.50), respectively. Zircon and garnet U-Pb ages of the Songnuo syn-mineral porphyry are 217 ± 2 Ma (MSWD = 1.15) and 223 ± 5 Ma (MSWD = 0.97), respectively. The Pulang and Songnuo porphyries both have high whole-rock Sr/Y ratios with minor or no negative Eu anomalies, consistent with derivation from hydrous magmas that underwent minor early plagioclase crystallization but abundant amphibole fractionation. The two porphyry intrusions are characterized by high large-ion-lithophile elements (LILE: Th, U, Ba, Rb) abundances, and low concentrations of high-field-strength elements (HFSE: Nb, Ta, Ti, Zr, Hf). They have similar initial Sr isotope ratios from 0.7055 to 0.7073, ƐNd (t) values from − 4.3 to − 1.6 and zircon ƐHf (t) values of − 1.81 ± 1.34 (n = 47) that are distinct from published results for the Permian–Early Triassic Paleo-Tethyan arc granitoids in the Sanjiang region but similar to the Neoproterozoic arc intrusions in the nearby western Yangtze craton. The Pulang and Songnuo porphyries have relatively high zircon EuN/EuN* ratios (0.59 ± 0.04, n = 52) and calculated Δ log fO2 (FMQ) values (1.61 ± 0.23, n = 52), consistent with relatively oxidized magmas. This feature is similar to the published data for the Neoproterozoic arc intrusions (EuN/EuN* = 0.55 ± 0.08; Δ log fO2 (FMQ) = 2.14 ± 0.60), but distinct from the published data for the reduced normal Paleo-Tethyan arc magmas (EuN/EuN* = 0.29 ± 0.10; Δ log fO2 (FMQ) = − 0.68 ± 0.88). Given that the most recent tectonic reconstruction models suggest that the Paleo-Tethys Ocean closed before ~ 220 Ma, we propose that the Pulang and Songnuo porphyries Cu deposits were formed in a postsubduction setting from oxidized melts generated by reactivating the Neoproterozoic arc root, unrelated to Paleo-Tethyan subduction. [ABSTRACT FROM AUTHOR]

[Display omitted] • A comparative study between ore-related and barren suites in the Zijinshan orefield. • The high f O 2 is not the sole constraint in the Zijinshan orefield. • Apatites from the ore-related suites have lower Cl contents than the barren suites. The Zijinshan orefield (Fujian Province) is a representative Cu-Au-Mo-Ag porphyry-epithermal mineralization system in eastern China. It contains both Cu ore-bearing and ore-barren granitoids, which provide an opportunity to study the unique properties of fertile magmas. This study focuses on chemistry of minerals such as zircon, apatite, amphibole, and plagioclase in ore-related (zircon U–Pb ages of 103–101 Ma) and ore-barren (zircon U–Pb ages of 157–156 Ma and ∼105 Ma) granitoids to constrain the characteristics of mineralized magmas. The results of whole-rock geochemistry and zircon Hf isotopes suggest that both ore-barren and ore-related granitoids were derived from partial melting of the lower crust, with the ore-related magma being influenced by mantle materials. The analysis of mineral chemistry reveals that the Zijinshan Cu ore-bearing porphyry magmas have high oxidation states (ΔFMQ +0.23–+2.25), high water contents (4.4–4.9 wt%), and shallow emplacement depths (1.9–4.0 km). These magmatic conditions are favorable for fluid exsolution and mineralization, similar to the global Cu-fertile porphyry magmas, but distinct from regional pre-mineralization ore-barren igneous rocks. Apatites from the ore-related granitoids have significantly lower Cl contents (0.03–0.83 wt%) and higher F/Cl ratios (1.52–377) compared to coeval ore-barren monzogranites (Cl = 0.14–2.42 wt%; F/Cl = 0.07–2.82). Additionally, the apatites' volatile budgets, including X OH , X Cl and X F values, and their covariation relationship, in the ore-related intrusions are consistent with apatite crystallization in H 2 O-saturated conditions. This suggests that extensive fluid exsolution from the parent magma in the chamber plays a crucial role in the formation of porphyry Cu deposits from a low-Cl magma. These low-Cl-apatite intrusions have the potential to form porphyry deposits. Together, we propose that the high oxygen fugacity, high water contents, and fluid exsolution of the parent magma may have triggered the Zijinshan porphyry mineralization. [ABSTRACT FROM AUTHOR]

The Zafarghand pluton, having ~10 km2 of outcrop exposure, lies within the central Urumieh–Dokhtar magmatic arc (UDMA) in Iran, of ~34 Ma age. Zafarghand plagioclase is albitic, with amphibole and chlorite being the distinctive mafic minerals. Although productive porphyry Cu deposits (PCDs) occur nearby, Zafarghand and its immediate neighboring plutons are sub-productive. Values of SiO 2 and K 2 O span a narrow compositional range from 69 to 73 wt% and 2.2 to 3.5 wt%, respectively, corresponding to granodiorite or granite and calc-alkaline in affinity. εNd (t) values are ranging from ~0 to +1.2, a diagnostic range for the mantle-dominant melts. The Sr Nd isotopic values are significantly lower and higher than those of slab melting- and crust melting adakites, respectively. The 34 Ma age of Zafarghand plutons make them to be the oldest Cu porphyry deposits yet to be found in the UDMA, in which mineralization had occurred during a mature, late stage of subduction (pre -collisional). We propose multi-stage refertilizing of Cu in lithospheric mantle beneath the UDMA, negligibly during Eocene to Early Oligocene slab roll-back accompanied by middle to rather high f O 2 context, and dominantly, during the Middle–Late Miocene slab break-off, the latter significantly tapping into influxing of asthenosphere mantle melt. Buffering of f O 2 at a sufficiently high level (and not partial melting of slab or thickened crust) is the most plausible explanation for forming Late Eocene–Oligocene sub-productive (–and non-adakitic) Zafarghand Cu-bearing plutons. • Radiometric dating yield ~34 Ma for Zafarghand host rocks • The oldest hitherto known porphyry copper deposit in the UDMA • ~96 % mantle-derived magma with contributions of ~4 % upper crustal material • Multi-stage refertilizing of Cu in lithospheric mantle beneath the UDMA • Change in f O 2 (not melting of slab or thickened crust) as the reason for PCDs [ABSTRACT FROM AUTHOR]

This work explores the potential of geochemical and petrographic characteristics of detrital zircons coming from the sedimentary record of the Centinela District in Northern Chile to identify the presence of buried porphyry copper deposits under a transported gravel cover. The sampled sedimentary section was recovered from the pit of the exotic copper deposit of El Tesoro, located approximately 2 and 4 km west of the Esperanza and Mirador porphyries, respectively. The sedimentary cover comprises four units, Tesoro II, Tesoro III, Arrieros and Recent gravels, deposited since the late Cenozoic in an arid continental environment dominated by alluvial fans. Except for the Tesoro III gravels, all other units contain exotic-Cu mineralisation. In order to interpret the geochemical footprint of the investigated zircons, the Porphyry Indicator Zircon (PIZ) concept (Pizarro et al., 2020) is used. A PIZ need to comply with each of the following geochemical values: Hf >8750 (ppm), Ce/Nd >1, Eu/Eu* >0.4, 10,000 × (Eu/Eu*)/Y > 1, (Ce/Nd)/Y > 0.01, Dy/Yb <0.3 and 0.1 < Th/U < 1. These zircons also have Ti <9 ppm and Ce/Ce* <100 and usually show euhedral morphologies characterised by prismatic forms of type {110}. The geochemical and petrographic characteristics of the PIZs collected in the gravels are similar to zircons from the nearby Mirador and Esperanza porphyries. The highest PIZ concentration coincides with the gravel horizons with exotic-Cu mineralisation. Therefore, the PIZs found in the sedimentary record are a potential tracer of adjacent copper porphyries and represent a promising exploration tool for this type of hidden ore deposits in challenging sediment-covered areas. [Display omitted] • Group of geochemical indicators summarized as Porphyry Indicator Zircon (PIZ). • 36 % of zircons found in the gravels of Centinela district correspond to PIZ. • The gravels with exotic-Cu mineralisation have highest concentration of PIZ. • PIZ in sedimentary records are a good tracer of adjacent copper porphyries. • PIZ are a promising exploration tool in search for hidden copper porphyries. [ABSTRACT FROM AUTHOR]

The Zhunuo porphyry copper deposit in the Gangdese belt of southern Tibet contains 2.37 Mt at 0.57% Cu. In this deposit, Eocene rhyolite (51.6 ± 1.0 Ma) and quartz porphyry (49.1 ± 0.6 Ma) were intruded by monzogranite (14.7 ± 0.3 Ma) and monzogranite porphyry (14.5 ± 0.2 Ma) which commonly host mafic microgranular enclaves (14.9 ± 0.3 Ma). Late-mineralization diorite porphyry (14.2 ± 0.2 Ma) and post-mineralization lamprophyre dikes (12.2 ± 0.1 Ma) and granite porphyry (12.0 ± 0.2 Ma) crosscut the Miocene intrusions. Two quartz–molybdenittie veins yielded molybdenite Re-Os model ages of 14.8 ± 0.1 Ma and 14.4 ± 0.1 Ma, and another two quartz–muscovite–llite–pyrite–molybdenite veins yielded molybdenite Re-Os model ages of 14.2 ± 0.1 Ma and 13.5 ± 0.1 Ma. Zhunuo is characterized by early potassic alteration and associated quartz A veins centered on the monzogranite porphyry and adjacent monzogranite, distal propylitic alteration in the rhyolite, and late-stage phyllic alteration and associated quartz B veins, followed by D veins that affected quartz porphyry and potassic-altered rocks. Copper ores are mainly distributed in the potassic alteration zone that was overprinted by phyllic alteration. Copper mineralization likely occurred during potassic alteration stage and was locally remobilized and redeposited during phyllic alteration stage, or occurred during phyllic alteration stage. The post-mineralization granite porphyry has lower whole-rock Sr/Y (< 20) and εNd(t) (− 9.3 to − 9.0) and higher zircon U/Yb (4 to 27) than the Miocene intrusions (Sr/Y > 40; εNd(t) = − 6.9 to − 6.1; U/Yb = 1 to 10). Limited input of juvenile melts could explain the low potential for copper mineralization in the post-mineralization granite porphyry at Zhunuo. [ABSTRACT FROM AUTHOR]

The Late Triassic Guichon Creek batholith is a large (~ 1800 km2), composite, zoned batholith that hosts several large porphyry Cu-Mo deposits of the Highland Valley Copper district. The batholith consists of intrusive rocks that range in composition from gabbro to quartz monzonite. Adjacent to the mafic margin of the batholith is the Gump Lake granodiorite to quartz monzonite stock. A new U-Pb zircon age of 218 ± 0.18 for the Gump Lake stock indicates that magmatism in the region began at least seven million years prior to the emplacement of the main Guichon Creek batholith rocks at 211 Ma. Zircons from fifteen samples from the Guichon Creek batholith were analyzed by laser ablation ICP-MS to characterize the magmatic evolution and ore fertility of the batholith. The trace element composition of zircon record early, lower crustal, fractional crystallization followed by five pulses of magma recharge and mixing in an upper-crustal, oxidized, magma chamber as well as degassing of the magmatic-hydrothermal fluids that formed the porphyry copper deposits. Zircons from the early barren rocks have chondrite-normalized Eu/EuN* values of 0.19 to 0.56 and estimated temperatures of 850 to 750 °C. The middle to late intrusions that host porphyry copper mineralization have zircon Eu/EuN* values of 0.30 to 0.74 and slightly lower estimated temperatures of 800 to 600 °C. Late porphyritic stocks and dikes from the mineralized centers contain zircon crystals elevated in Y, Nb, Ta, and REE concentration relative to zircon from the earlier intrusions. This distinct change in zircon composition coincides with the copper mineralization, suggesting that zircon chemistry can be used as a tool to identify the genetic evolution of a crystallizing magma chamber and potential for mineralization. [ABSTRACT FROM AUTHOR]

This study investigates apatite and anhydrite inclusions in zircon from ore-forming intrusions in the Duolong porphyry Cu-Au deposit, central Tibet (Fig. 2 Geological characteristics (a) and cross sections (b, c) of the Duolong porphyry Cu-Au deposit, central Tibet, showing sample locations (Li et al. [21], [25]) The Duolong magmatic complex evolved from diorite to granodiorite porphyry and quartz diorite porphyry, the hosts of Cu-Au mineralization (Fig. Apatite inclusions ( I n i = 98) in zircon from the granodiorite porphyry and quartz diorite porphyry have F contents of 1.14-2.99 wt%, Cl of 0.16-2.51 wt%, and SO SB 3 sb of 0.04-1.38 wt%, with minor SiO SB 2 sb (0.05-1.39 wt%), MnO (0.12-0.93 wt%), Na SB 2 sb O (0-0.28 wt%), and FeO (0.01-0.64 wt%; Supplementary Table 1). Apatite and anhydrite were randomly enclosed by zircon crystals, which were later hosted in ore-forming porphyries One apatite inclusion coexisting with an anhydrite inclusion in a single zircon grain contains 0.69 wt% SO SB 3 sb with a low I X i SB F sb / I X i SB Cl sb ratio of ~ 1.2 (Fig. [Extracted from the article]

Porphyry Cu ore deposits are a rare product of arc magmatism that often form spatiotemporal clusters in magmatic arcs. The petrogenetic evolution of igneous rocks that cover the temporal window prior to and during porphyry Cu deposit formation may provide critical insights into magmatic processes that are key in generating these systems. This study documents the magmatic evolution of the Palaeocene–Eocene Yarabamba Batholith, Southern Peru, that was incrementally assembled between ~ 67 and ~ 59 Ma and hosts three, nearly contemporaneous, giant porphyry Cu–Mo deposits that formed at 57–54 Ma (Quellaveco, Toquepala and Cuajone). Whole-rock geochemistry, U–Pb geochronology and zircon trace element chemistry are reported from Yarabamba rocks that span the duration of plutonic activity, and from six porphyry intrusions at Quellaveco that bracket mineralisation. A change in whole-rock chemistry in Yarabamba intrusive rocks to high Sr/Y, high La/Yb and high Eu/Eu* is observed at ~ 60 Ma which is broadly coincident with a change in vector of the converging Nazca plate and the onset of regional compression and crustal thickening during the first stage of the Incaic orogeny. The geochemical changes are interpreted to reflect a deepening of the locus of lower crustal magma evolution in which amphibole ± garnet are stabilised as early and abundant fractionating phases and plagioclase is suppressed. Zircons in these rocks show a marked change towards higher Eu/Eu* (> 0.3) and lower Ti (< 9 ppm) compositions after ~ 60 Ma. Numerical modelling of melt Eu systematics and zircon-melt partitioning indicates that the time series of zircon Eu/Eu* in these rocks can be explained by a transition from shallower, plagioclase-dominated fractionation to high-pressure amphibole-dominated fractionation at deep crustal levels from ~ 60 Ma. Our modelling suggests that any redox effects on zircon Eu/Eu* are subordinate compared to changes in melt composition controlled by the fractionating mineral assemblage. We suggest that growth and intermittent recharge of the lower crustal magma reservoir from ~ 60 Ma produced a significant volume of hydrous and metallogenically fertile residual melt which ascended to the upper crust and eventually generated the three giant porphyry Cu–Mo deposits at Quellaveco, Toquepala and Cuajone from ~ 57 Ma. Our study highlights the importance of high-pressure magma differentiation fostered by strongly compressive tectonic regimes in generating world-class porphyry Cu deposits. [ABSTRACT FROM AUTHOR]

The Kekura gold deposit (76.2 t Au at 8.1 g/t) is situated in Western Chukotka, a region that hosts several Au, Ag, Cu, and Mo deposits and prospects. The Kekura deposit is related to the eponymous granite intrusion that is cut by porphyry dikes. The U-Pb zircon age of one of these dikes is 112 ± 1 Ma (2σ) that corresponds to the latest Aptian/earliest Albian. Both intrusion and dikes are hydrothermally altered and are cut by gold-quartz and molybdenite-quartz veins and stringers. Two molybdenite samples yield Re-Os model ages of 112.5 ± 0.6 and 112.3 ± 0.6 Ma (2σ). These Re-Os ages indicate the close temporal relationship between the molybdenite mineralization and the porphyry dikes. The age of the Kekura mineral system is similar to that of the post-collisional granitic plutons of the Anyui zone spatially scattered, between 140 and 210 km northwest of Kekura. We suggest that this temporal relationship may increase the likelihood of further discoveries of economic gold mineralization related to the currently underexplored Aptian post-collisional magmatic complexes of the Western Chukotka area. [ABSTRACT FROM AUTHOR]

The Zhilingtou polymetallic deposit, South China, provides an excellent opportunity to investigate the magmatic-hydrothermal evolution of the porphyry Mo to epithermal Au–Ag–Pb–Zn ore spectrum. New zircon U–Pb, sphalerite 40Ar/39Ar, and pyrite Rb–Sr ages, together with previous molybdenite Re–Os ages, indicate that the granitic magmatism and Mo–Au–Ag–Pb–Zn mineralization were coeval and cogenetic in the Early Cretaceous (~ 113 Ma). Fluid inclusions and H–O isotope results have established the evolution from an early high-temperature H2O–NaCl magmatic fluid system (Mo mineralization), to a medium-temperature mixed fluid system of magmatic and meteoric water (Au–Ag mineralization), to a peripheral late-stage low-temperature H2O–NaCl meteoric water fluid system (epithermal Au–Ag–Pb–Zn mineralization). Moreover, the sulfur isotopic compositions (δ34S = 2.1–7.8‰) of the sulfide minerals confirm a genetic link to the granitic magma. Lead isotope data from pyrite and the granite–rhyolite porphyries are similar, indicating that they share a common Pb source. The geochronological, geochemical, and isotopic lines of evidences consistently suggest that the porphyry Mo and epithermal Au–Ag–Pb–Zn mineralization formed in one magmatic–hydrothermal system. The porphyry-epithermal mineralization model for Zhilingtou has significant importance for prospecting work in South China, where Mo and associated Pb–Zn–Ag resources are abundant. [ABSTRACT FROM AUTHOR]

We present detailed petrography, geochemistry and zircon U–Pb–Hf isotopes of the Mante Aobao granite porphyry in East Ujimqin Banner, Inner Mongolia, with the aim of determining its age and petrogenesis, important for understanding the early Palaeozoic tectonic evolution of the Xing'an–Mongolian Orogenic Belt. The Mante Aobao granite porphyry consists of plagioclase, quartz and minor biotite, but without amphibole. Zircon U–Pb analyses yield ages of 450 ± 1 Ma and 445 ± 2 Ma for the granite porphyry, indicating that it formed during Late Ordovician time. The granite porphyry is metaluminous to slightly peraluminous (aluminous saturation index A/CNK = 0.98–1.11) with high SiO2, K2O and Na2O concentrations and differentiation index (DI = 85–90). Chondrite-normalized rare earth element (REE) patterns display enrichment of light REEs (LREEs) with high ratios of (La/Yb)N and negative Eu anomalies. In the mantle-normalized multi-element variation diagrams, all samples are characterized by depletions of high-field-strength elements (HFSEs; Nb, Ta and Ti) and enrichments of large-ion lithophiles (LILEs; Rb, Th, U and K). These geochemical features indicate that the granite porphyry is a highly fractionated I-type granite and formed in a subduction-related setting. Zircon grains have positive εHf(t) values of +9.2 to +11.2, and TDM2(Hf) ages of 691–821 Ma, suggesting that the granite porphyry was generated by partial melting of Neoproterozoic juvenile crust with involvement of fractional crystallization during magmatic evolution. It is likely that underplating of mantle-derived magmas during Late Ordovician time provided the necessary heat to partially melt this juvenile crust. Combined with the regional geological data, we infer that the Mante Aobao granite porphyry was emplaced in an active continental margin setting that was probably related to the northwards subduction of the Paleo-Asian Plate beneath the South Mongolian Terrane along the Sonid Zuoqi–Xilinhot axis. [ABSTRACT FROM AUTHOR]

The Great Xing'an Range (GXR), Northeast (NE) China, is a major polymetallic metallogenic belt in the eastern segment of the Central Asian Orogenic Belt. The newly discovered Xiaokele porphyry Cu (–Mo) deposit lies in the northern GXR. Field geological and geochronological studies have revealed two mineralization events in this deposit: early porphyry‐type Cu (–Mo) mineralization, and later vein‐type Cu mineralization. Previous geochronological studies yielded an age of ca. 147 Ma for the early Cu (–Mo) mineralization. Our 40Ar/39Ar dating yielded 40Ar/39Ar plateau ages of 124.8 ± 0.4 to 124.3 ± 0.4 Ma on K‐feldspar in altered Cu‐mineralized diorite porphyrite dikes that represent the overprinting vein‐type Cu mineralization, consistent with zircon U–Pb ages of the diorite porphyrite (126.4 ± 0.5 to 125.0 ± 0.5 Ma). The Cr and Ni contents and Mg# of the Xiaokele diorite porphyrites are high. The diorite porphyrites at Xiaokele are enriched in light rare‐earth elements (REEs), and large‐ion lithophile elements (e.g., Rb, Ba, and K), are depleted in heavy REEs and high‐field‐strength elements (e.g., Nb, Ta, and Ti), and have weak negative εHf(t) values (+0.29 to +5.27) with two‐stage model ages (TDM2) of 1,164–845 Ma. Given the regional tectonic setting in Early Cretaceous, the ore‐bearing diorite porphyrites were likely formed in an extensional environment related to lithospheric delamination and asthenospheric upwelling induced by subduction of the Paleo‐Pacific Plate. These tectonic events caused large‐scale magmatic activity, ore mineralization, and lithospheric thinning in NE China. [ABSTRACT FROM AUTHOR]

The Xietongmen large deposit is the only known subduction‐related porphyry Cu deposit in the Gangdese Belt, Tibet, which is composed of the No. I and No. II deposits. Previous work suggests that the No. I deposit is reduced while the No. II deposit is oxidized. However, it is ambiguous that both oxidized and reduced porphyry Cu deposits occur in close proximity, in the same tectonic setting, and within a short time period. Detailed examination of the ages, whole‐rock geochemistry, zircon and apatite compositions of the Xietongmen No. I and No. II ore‐bearing porphyries are conducted to investigate their magma characteristics and the genetic types of the Xietongmen No. I and No. II deposits. Zircon U–Pb dating results show that the Xietongmen No. I and No. II ore‐bearing porphyries formed at 166.3 ± 2.6 Ma and 175.5 ± 1.0 Ma, respectively. The Xietongmen No. I and No. II ore‐bearing porphyries have similar mineral assemblage (containing amphibole phenocryst), high Sr/Y ratios and negligible negative Eu anomalies, low Ti‐in‐zircon temperatures (633−749 and 633−763°C, respectively), which indicate that their magmas are water‐rich. In addition, the Xietongmen No. I and No. II ore‐bearing porphyries have: (a) high whole‐rock V/Sc ratios (10−15 and 8−16, respectively); (b) high zircon Ce4+/Ce3+ and EuN/EuN* ratios, falling into the field of the ore‐bearing intrusions in northern Chile; (c) low apatite CeN/CeN* ratios (0.97−1.02 and 0.99−1.02, respectively), which suggest that their magmas are oxidized. The estimated magmatic S contents, based on the magmatic apatite SO3 contents, yield 0.0113−0.0507 wt% and 0.0012−0.0118 wt%, respectively for the Xietongmen No. I and No. II ore‐bearing porphyries, which suggest their magma are sulfur‐rich. Hydrous, oxidized and sulfur‐rich magmas are the parent magma of oxidized porphyry Cu deposits, together with the oxidized minerals of hematite and magnetite, therefore, both Xietongmen No. I and No. II deposit are oxidized porphyry Cu deposits, rather than that the Xietongmen No. I deposit is a reduced porphyry Cu deposit. [ABSTRACT FROM AUTHOR]

Demingding is a poorly studied post‐collisional porphyry Cu‐Mo deposit, located in the eastern part of the Gangdese porphyry copper belt. In this study, we present LA‐ICP‐MS zircon U‐Pb dating, whole‐rock geochemistry, and zircon trace elemental data for the mineralization related biotite monzogranite porphyry in Demingding. Zircon U‐Pb dating shows that the weighted mean 206Pb/238U ages of the Miocene biotite monzogranite porphyry is 20.36 ± 0.46 Ma (MSWD = 2.6, n = 21). The Miocene biotite monzogranite porphyry is characterized by high SiO2, K2O, and Al2O3 contents and shows adakite‐like signatures. These rocks have high Sr/Y ratios, fractionated REE patterns with low HREE abundances, enrichment in LILE compared with HFSE, and have (87Sr/86Sr)i values of 0.7059 to 0.7062, εNd(t) values of −2.35 to −1.67 and (206Pb/204Pb)i ratios of 18.50–18.55. These features are similar to other Miocene adakite‐like intrusions in the Gangdese belt. We propose that the biotite monzogranite porphyry shares the same petrogenesis with other Miocene ore‐bearing adakite‐like intrusions in the Eastern Gangdese belt and was derived from remelting of the subduction‐modified, eclogitized Tibetan lower crust and mixing with hydrous mafic magmas from metasomatized Tibetan mantle. The zircons from biotite monzogranite porphyry have only minimal negative Eu anomalies (EuN/EuN* > 0.3), and exhibit large ratios of Ce4+/Ce3+(average value of 113), 10,000*(EuN/EuN*)/Y (3.94–8.14, >1), Ce/Nd (9–58, Average value of 30), (Ce/Nd)/Y (0.008–0.127, >0.003), and low value of Dy/Yb (0.15–0.24, <0.3), indicating that the biotite monzogranite porphyry is relatively hydrous and oxidized. The biotite monzogranite porphyry, therefore, is believed to be a relatively fertile intrusion with certain exploration potential. [ABSTRACT FROM AUTHOR]

New SIMS U-Pb (zircon) data for intrusive rocks of the Macquarie Arc and adjacent granitic batholiths of the Lachlan Orogen (southeastern Australia) provide insight into the magmatic and tectonic evolution of the paleo-Pacific Gondwana margin in the early Paleozoic. These data are augmented by Re-Os dates on molybdenite from four Cu-Au mineralised porphyry systems to place minimum age constraints on igneous crystallization. The simplicity of the zircon age distributions, and absence of older inheritance, stands in contrast to previous geochronological studies. The earliest magmatism within the Macquarie Arc is registered by a ca. 503 Ma gabbro from the Monza igneous complex, whereas a monzodiorite from the same drillhole records the youngest (ca. 432 Ma). Igneous activity in the Macquarie Arc thus overlapped deformation and magmatism in the craton-proximal Delamerian Orogen to the west, and the emplacement of the Lachlan granitic batholiths at 435–430 Ma; the thermal pulse associated with the latter may have triggered the formation of richly mineralised Silurian porphyries in the Macquarie Arc. The juvenile Hf isotope signature of the Monza Gabbro, together with the lack of zircon inheritance and the radiogenic Hf-Nd isotope systematics of Ordovician Macquarie Arc rocks, is consistent with early development of the arc, or a precursor magmatic belt, in an oceanic setting remote from continental influences, and with the arc being built on primitive Cambrian mafic crust. Outboard arc magmatism in the Cambrian may have initiated in response to convergent Delamerian orogenesis adjacent the Gondwana margin. Overlapping radiogenic isotope-time trends are consistent with the evolution of the Macquarie Arc and the Gondwana continental margin being linked from the Cambrian to the Silurian. These data provide further evidence for the growth of continental crust along the southeastern Australian segment of this margin being related to the dynamics of an extensional accretionary orogenic system. Unlabelled Image • Zircon U-Pb ages from the Macquarie arc intrusives range from 503 Ma to 432 Ma. • Molybdenite Re-Os dates overlap or slightly postdate zircon ages. • Porphyry Cu-Au mineralisation overlapped with an S-type granite 'flare up'. • Macquarie arc magmatism initiated in an intra-oceanic setting. • The Ordovician Macquarie arc was built on juvenile Cambrian mafic arc crust. [ABSTRACT FROM AUTHOR]

The Shimadong porphyry Mo deposit is located in eastern Yanbian, in the eastern part of the north margin of the North China craton, northeastern China. Here, we present the whole-rock major and trace elements, zircon U–Pb and Hf isotope data, and molybdenite Re–Os data for the Shimadong deposit. The porphyry was emplaced at 163.7 ± 0.9 Ma and the mineralization at 163.1 ± 0.9 Ma, suggesting that the mineralization was associated with the emplacement of the Shimadong porphyritic monzogranite. The porphyritic monzogranite had high SiO2 (70.09–70.55 wt%) and K2O + Na2O (7.98–8.27 wt%) contents and low MgO (0.51–0.53 wt%), TFeO (2.4–2.47 wt%), CaO (2.19–2.26 wt%), and K2O/Na2O (0.8–0.82) contents. The porphyry was rich in large ion lithophile elements Rb, Ba, K, and Sr, depleted in high-field-strength elements Y, Nb, Ta, P, and Ti, without significant Eu anomaly (δEu = 0.86–1.00), and depleted in heavy rare earth elements with light rare earth elements/heavy rare earth elements = 18.25–20.72 and (La/Yb)N = 27.10–34.67. These features are similar to those of adakitic rocks derived from a thickened lower crust. Zircon εHf(t) values for the porphyritic monzogranite ranged from –19.2 to 6.3, and the two-stage Hf model ages (TDM2) were 2421–811 Ma. These data indicate that the primary magma of the Shimadong porphyritic monzogranite was mainly derived from partial melting of the thickened lower crust consisting of juvenile crust and pre-existing crust. Combined with the results of previous studies, our data suggest that the Shimadong porphyry Mo deposit was emplaced along an active continental margin related to the westward subduction of the paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]

North- to northeast-trending intermediate to felsic porphyry dykes in the McKenzie Gulch (MG) area intrude Upper Ordovician through Silurian calcareous sedimentary rocks of the Matapédia Group. These dykes are spatially associated with numerous copper–silver skarn occurrences. In this area, two distinct suites of dykes are recognized: plagioclase–hornblende porphyry (P–H) and quartz–plagioclase porphyry (Q–P). These suites yielded U–Pb (zircon) ages of 386.2 ± 3.1 Ma and 386.4 ± 3.3 Ma, respectively, indicating a coeval relationship and similar genesis despite slight geochemical and petrographical differences. Geochemical data indicate that the dykes are granodioritic to granitic to slightly tonalitic in composition with I-type and slab failure signatures. When compared with other granitoids in the region, the Murdochville suite in Gaspésie, Québec, is the only intrusion that exhibits slab failure magmatic signatures similar to the MG dykes. Magmas with slab failure signatures are compositionally similar to tonalite–trondhjemite–granodiorite (TTG) suites and adakites. They exhibit low Y and Yb concentrations and subsequent high Sr/Y and La/Yb ratios, which are interpreted to be the result of melting of subducting slab and mantle during the waning stages of collision and consequent slab failure. These processes were followed by assimilation and fractional crystallization of minerals such as hornblende and clinopyroxene (± titanite), which preferentially partition Y and heavy rare earth elements (HREE) in the absence of significant plagioclase. Magmas with similar geochemical characteristics worldwide have been proposed to be an important source for metals in most porphyry Cu and skarn deposits and consequently are a target during mineral exploration. [ABSTRACT FROM AUTHOR]

In the past decade, significant research efforts have been devoted to mineral chemistry studies to assist porphyry exploration. These activities can be divided into two major fields of research: (1) porphyry indicator minerals (PIMs), which are used to identify the presence of, or potential for, porphyry-style mineralization based on the chemistry of magmatic minerals such as zircon, plagioclase and apatite, or resistate hydrothermal minerals such as magnetite; and (2) porphyry vectoring and fertility tools (PVFTs), which use the chemical compositions of hydrothermal minerals such as epidote, chlorite and alunite to predict the likely direction and distance to mineralized centres, and the potential metal endowment of a mineral district. This new generation of exploration tools has been enabled by advances in and increased access to laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), short-wave length infrared (SWIR), visible near-infrared (VNIR) and hyperspectral technologies. PIMs and PVFTs show considerable promise for exploration and are starting to be applied to the diversity of environments that host porphyry and epithermal deposits globally. Industry has consistently supported development of these tools, and in the case of PVFTs encouraged by several successful blind tests where deposit centres have successfully been predicted from distal propylitic settings. Industry adoption is steadily increasing but is restrained by a lack of the necessary analytical equipment and expertise in commercial laboratories, and also by the ongoing reliance on well-established geochemical exploration techniques (e.g. sediment, soil and rock chip sampling) that have aided the discovery of near-surface resources over many decades, but are now proving less effective in the search for deeply buried mineral resources and for those concealed under cover. Thematic collection: This article is part of the Exploration 17 collection available at: https://www.lyellcollection.org/cc/exploration-17 [ABSTRACT FROM AUTHOR]

New data are presented on the quartz porphyry dikes of the Salmi batholith belonging to anorthosite–rapakivi granite rock complexes. The relationships of various igneous rocks of the Salmi batholith and metasomatites were determined along with the isotopic U–Pb age by the LA–ICP–MS technique and the temperature of zircon formation by the Ti content. [ABSTRACT FROM AUTHOR]

The Nigerian alkaline ring complexes have long been regarded as typical anorogenic A-type granite. However, uncertainty still surrounds many aspects of their petrogenesis and tectonic implication. In this paper, a combined study of whole rock geochemistry, Nd-Pb isotope and zircon U-Pb dating was carried out on the Kudaru ring complex from north-central Nigeria. The complex consists of mildly alkaline fayalite granite porphyry, peralkaline arfvedsonite granite and metaluminous biotite granite, which were emplaced between 176.9 ± 2.5 and 180.55 ± 0.6 Ma. These rocks are characterized by variably high alkalis, HFSEs, Ga/Al ratios, and zircon saturation temperature, typically of A-type granites. Notably, the popular subdivision scheme of A-type granite permits the discrimination of the alkaline-peralkaline granites as typical "A1-type" granites and the metaluminous granite as "A2-type". These co-existing A1 and A2 granites show distinct isotopic compositions with less negative εNd (t) values and higher 206Pb/204Pb ratios for the former, indicating that the magma which gave rise to the A1 and A2 suites was derived from an enriched mantle source but modified to different extent during ascent. Notably, the coexistence of A1-A2 granites do not indicate discrete tectonic regimes (intraplate setting for A1 and post-orogenic setting for A2), but rather point to a significant role of crustal contamination, as seen also from the differences in Y/Nb ratios. [ABSTRACT FROM AUTHOR]

Northeastern China is an important Mo resource region in China, with more than 80 Mo deposits and occurrences. The Huojihe deposit located in the Lesser Xing'an Range represents one of the many Mesozoic porphyry Mo deposits in NE China and has been selected for investigation attempting to clarify the possible mechanisms controlling Mo mineralization. In this study, accessory minerals, including zircon and apatite from the causative intrusions (biotite monzogranite and granodiorite), have been analyzed to reveal their chemical and isotopic compositions, which provide insights into the nature of the source magmas and a better understanding of the factors affecting their mineralization potential. Zircon U-Pb dating shows that the biotite monzogranite from the Huojihe deposit formed at 181.6 ± 0.6 Ma, which is identical to the previously reported molybdenite Re-Os age (~181 Ma), indicating that the Mo mineralization is probably genetically related to the intrusion. The intrusion samples share homogeneous geochemical and Sr-Nd isotopic compositions, with initial 87Sr/86Sr ratios of 0.7072-0.7075 and slightly negative εNd (t) values from -2.3 to -1.4, reflecting a uniform magma source. The least-altered apatites show similar (or slightly enriched) initial 87Sr/86Sr ratios (0.7080-0.7108) and εNd (t) values (-4.0 to -1.8), whereas the hydrothermally altered apatites are characterized by significantly higher initial 87Sr/86Sr ratios (0.7091-0.7119) and more negative εNd(t) values (-4.9 to -4.4), probably due to the interaction between the hydrothermal fluids and wall rocks. The zircon εHf(t) values vary from -0.9 to 1.7, corresponding to a restricted range of TDM2 ages from 1279 to 1120 Ma. The Sr-Nd-Hf isotope results suggest that the primary magmas associated with the Mo mineralization could be generated from a dominantly Mesoproterozoic lower crust source, with rare contributions from the depleted mantle. The low Ga and Ce and high Eu contents in the magmatic apatite demonstrate that the original magmas have a relatively high oxygen fugacity, which is also supported by the high zircon CeN/CeN* (22-568) and EuN/EuN* (0.38-0.71) values. Estimates of absolute sulfur concentrations in the mineralization-related melt using available partitioning models for apatite return relatively low magmatic sulfur concentrations in Huojihe (20-100 ppm), indistinguishable from those of larger or smaller deposits or even barren magmatic bodies. Using the sulfur concentration data, a minimum volume of 10-50 km³ magma has been suggested to be necessary to produce the Huojihe Mo deposit based on mass balance modeling. Besides, the Mo concentration in the original magma has also been roughly estimated based on the magma size (10-50 km³) and the contained Mo in Huojihe (0.275 Mt). The magmatic Mo concentrations (2-10 ppm) are similar to many other porphyry Mo systems (e.g., the Climax-type porphyry Mo deposits), and are also comparable to subeconomic to barren magma systems. This study suggests that pre-degassing enrichments of Mo and S in the original magma is not necessarily important in the formation of the Huojihe Mo deposit; rather, factors other than melt composition may be more critical in forming a porphyry Mo deposit. This understanding might also apply to other porphyry Mo mineralized systems worldwide. [ABSTRACT FROM AUTHOR]

[Display omitted] • We report the discovery of a Molybdenum (Mo) porphyry deposit at Shuvuutai, central-east Mongolian. • Molybdenum mineralization spatially and genetically related to Early Permian multi-phase porphyry intrusions. • Ore-forming fluids were initially magmatic and later hydrothermal mineralization evolved with four main stages. • We suggest a new strategy for exploration for Mo and related porphyry deposits in Mongolia and China. We document the newly discovered Shuvuutai Molybdenum (Mo) porphyry deposit located in the central-east Mongolian volcanic/-plutonic belt of the southern Altaids. The deposit is characterized by quartz vein- and veinlet-disseminated-type Mo ore bodies mainly hosted in a Late Permian-Early Triassic granitic intrusion. In this study, we provide a detailed study that integrates detailed geology with petrographic, mineralogic, geochemical, and geochronologic date to determine the tectonic setting of the deposit. Fluid inclusion analysis is used to reconstruct the fluid evolution history of the Shuvuutai Mo mineralization system and to understand the origin of the deposit. The ore bodies occur mainly as veins, lenses, and pods in positions from inner intrusions through contact zones to the host rocks distal to causative intrusions. The host rocks are variable in lithology, including granites, porphyries, volcanic breccias and tuffs, and sedimentary rocks. Outward from ore bodies to host rocks, the wall rock alteration is zoned from potassic (K-feldspar-quartz-mica), through phyllic (quartz-sericite-chlorite-epidote), to propylitic or argillic alterations. Two samples from porphyry stock intrusions at Shuvuutai were selected for U–Pb zircon geochronology and trace element composition studies, including the ore-hosting monzodiorite porphyry and quartz syenite porphyry. Our new ages are consistent with, or slightly postdate published zircon U-Pb ages of early phase of monzodiorite porphyry (268–232 Ma) and the main phase of quartz syenite porphyry (251.6 ± 1.7 Ma). Hydrothermal mineralization generally includes four stages, from early to late, represented by (1) potassic feldspar-quartz veins or veinlets, (2) quartz-molybdenite stockworks, (3) quartz-sulfide stockworks, and (4) quartz ± carbonate veins or veinlets. The ore-forming fluids were initially magmatic in origin and show high-temperature and high-salinity, containing daughter mineral and CO 2 -bearing fluid inclusions; and eventually evolved to low-temperature, low-pressure, low-salinity and CO 2 -poor meteoric water. S isotopic compositions of sulfides from the Shuvuutai Mo porphyry deposit indicate that the source of the ore-forming material was derived from the felsic magma. The Central-Eastern Mongolian volcanic-plutonic belt continues from Mongolia into northeast China, where similar Mo deposits are not yet recognized, suggesting that a new exploration strategy, based on the characteristics and history of the Shuvuutai discovery, is needed for the Chinese segment of the Altaids. [ABSTRACT FROM AUTHOR]

Granitoids are the most important component of continental crust, yet there has been debate regarding the classification and petrogenesis of peraluminous I- and S-type. As a result of fractional crystallizing and crustal contamination, whole-rock geochemistry sometimes fails to accurately reflect the type of primitive magma. Recent studies, however, suggest that the accessory mineral compositions can shed light on the character and petrogenesis of their primitive magma. In this contribution, we use apatite and zircon as indicators to explore the distinctions between peraluminous I- and S-type granitoids, and the petrogenesis of typical peraluminous I-type granitoids (Baoshan granitoids). Apatite trace elements indicate that their initial magma was mafic I-type, even though whole-rock compositions appear to be the hybrids of I- and S-type granitoids. Additionally, we propose that the assimilation and fractional crystallization processes are responsible for the decoupling between the compositions of whole-rock and accessory minerals. The compositions and isotopes of zircon can also reveal the components of the magma source region. The zircons ε Hf (t) values of the Baoshan granodiorite porphyry and lamprophyre have comparable Hf (t) values (−9.5 to −6.2 and −12.5 to −6.2, respectively). Based on the spotting of ~900 Ma inherited zircons and enriched ε Hf (t) values, we propose that the granitoids were formed by the partial melting of felsic Paleoproterozoic crust and a little of Neoproterozoic mafic juvenile crust, while lamprophyre was generated by the cooling of upwelling magma from the same source region as granitoids. According to the apatite trace element ratios (Sr/Th vs. La/Sm), the source region of the Baoshan intrusion is identified to been metasomatized by slab-derived fluid. Our data, in conjunction with previous studies, suggest that the paleo-Pacific slab roll-back triggered the high-temperature asthenosphere mantle upwelling, while the assimilation and fractional crystallization occurring along with the rising melts in route to the surface. [ABSTRACT FROM AUTHOR]