SHRIMP U–Pb and Ar–Ar geochronology of major porphyry and skarn Cu deposits in the Balkhash Metallogenic Belt,Central Asia,and geological implications

The Balkhash Metallogenic Belt (BMB) in Kazakhstan, Central Asia, with the occurrence of the super-large Kounrad and Aktogai, the large Borly porphyry Cu–Mo deposits, and the large Sayak skarn polymetallic ore-field, is one of the central regions of the Paleozoic Central Asian metallogenic domain and orogenic belt. In this study, newly obtained SHRIMP zircon U–Pb ages of nine samples and ⁴⁰Ar/³⁹Ar ages of six mineral samples (inclding hornblende, biotite and K-feldspar) give more detailed constraints on the timing of the granitic intrusions and their metallogeny. Porphyritic monzonite granite and tonalite porphyry from the Kounrad deposit yield U–Pb zircon SHRIMP ages of 327.3 ± 2.1 Ma and 308.7 ± 2.2 Ma, respectively. Quartz diorite and porphyritic granodiorite from the Aktogai deposit yield U–Pb SHRIMP ages of 335.7 ± 1.3 Ma and 327.5 ± 1.9 Ma, respectively. Porphyritic granodiorite and granodiorite from the Borly deposit yield U–Pb SHRIMP ages of 316.3 ± 0.8 Ma and 305 ± 3 Ma, respectively. Diorite, granodiorite, and monzonite from the Sayak ore-field yield U–Pb SHRIMP ages of 335 ± 2 Ma, 308 ± 10 Ma, and 297 ± 3 Ma, respectively. Hornblende, biotite, and K-feldspar from the Aktogai deposit yield ⁴⁰Ar/³⁹Ar cooling ages of 310.6 Ma, 271.5 Ma, and 274.9 Ma, respectively. Hornblende, biotite, and K-feldspar from the Sayak ore-field yield ⁴⁰Ar/³⁹Ar cooling ages of 287.3 ± 2.8 Ma, 307.9 ± 1.8 Ma, and 249.8 ± 1.6 Ma, respectively. The new ages constrain the timing of Late Paleozoic felsic magmatism to ∼336 to ∼297 Ma. Skarn mineralization in the Sayak ore-field formed at ∼335 and ∼308 Ma. Porphyry Cu–Mo mineralization in the Kounrad deposit and the Aktogai deposit formed at ∼327 Ma, and in the Borly deposit at ∼316 Ma. The Late Paleozoic regional cooling in the temperature range of ∼600 °C to ∼150 °C occurred from ∼307 to ∼257 Ma.     

U–Pb and Ar–Ar geochronology of the Fujiawu porphyry Cu–Mo deposit,Dexing district,Southeast China: Implications for magmatism,hydrothermal alteration,and mineralization

The Fujiawu porphyry Cu–Mo deposit is one of several porphyry Cu–Mo deposits in the Dexing district, Jiangxi Province, Southeast China. New zircon SHRIMP U–Pb data yield a weighted mean ²⁰⁶Pb/²³⁸U age of 172.0 ± 2.1 and 168.5 ± 1.4 Ma from weakly altered granodiorite porphyry and quartz diorite porphyry, respectively. Two hydrothermal biotites from granodiorite porphyry give an Ar–Ar step-heating plateau age of 169.9 ± 1.8 and 168.7 ± 1.8 Ma. Hydrothermal apatite exsolved from altered biotite yields an isotope dilution thermal ionization mass spectrometry isochron age of 164.4 ± 0.9 Ma. The apatite age is similar to the ages obtained from hydrothermal rutile (165.0 ± 1.1 and 164.8 ± 1.6 Ma) and indicates that the magmatism and hydrothermal activity in the Fujiawu deposit occurred in the Middle Jurassic. Hydrothermal fluid circulation related to multiple stages of magma emplacement resulted in Cu–Mo mineralization in the Fujiawu porphyry deposit. The zircon SHRIMP U–Pb ages and the published molybdenite Re–Os age (170.9 ± 1.5 Ma) represent the timing of magma crystallization and Mo mineralization, whereas the rutile and apatite U–Pb ages reflect the timing of Cu mineralization following quartz diorite emplacement. The data suggest slow cooling after emplacement of the quartz diorite porphyry.     

Chemical composition of rock-forming minerals in granitoids associated with Au–Bi–Cu,Cu–Mo,and Au–Ag mineralization at the Freegold Mountain,Yukon, Canada: magmatic and hydrothermal fluid chemistry and petrogenetic implications

The chemical compositions of rock-forming minerals have been determined for both altered and least-altered igneous rocks spatially associated with numerous mineralized zones (Nucleus Au–Bi–Cu–As deposit, Revenue Au ± Cu and Stoddart Cu–Mo ± W mineral occurrences, and Laforma Au–Ag deposit) across the Freegold Mountain area, Yukon, Canada. Within the study area, K-feldspar has a narrow compositional range (89.4–91% Or), whereas plagioclase spans a wide range (4.4–70.07% An). In all of the investigated samples, T _Ab = T _An = T _Or, suggesting that magmatic equilibrium between the coexisting plagioclase and K-feldspar was maintained. Igneous amphibole phenocrysts from hypabyssal dikes are typically calcic, whereas the Stoddart Cu–Mo ± W, Laforma Au–Ag, and Goldy Au mineralization are associated with Mg-enriched primary amphibole of edenite composition, and Au–Bi–Cu–As mineralization from Nucleus is related to Al-enriched primary amphibole of ferropargasite composition. Primary biotite phenocrysts across the Freegold Mountain area re-equilibrated with oxidized magma (f(O₂) values between 10–13 and 10–11.5 bars, lying between the Ni/NiO and the magnetite/haematite buffers). However, biotite and amphibole phenocrysts from Stoddart, Goldy, Laforma, and the Highway zones crystallized from a more oxidized magma, as indicated by their elevated X _Mg up to 0.65, relative to biotite and hornblende from Nucleus and Revenue characterized by a lower X _Mg (typically < 0.50). This suggests that various sources and (or) rapid emplacement were involved in magma genesis, as further supported by the considerable variation of pressure (1.8–7.3 kb) of amphibole crystallization and of the total Al content in least-altered biotite (2.6–2.9 afu) within the Freegold Mountain area. Biotite and apatite equilibrated within the T range of 520–780°C, consistent with temperatures of equilibration between ilmenite and magnetite, and their compositions indicate that they formed from an oxidized I-type magma. Magma differentiated by fractional crystallization (indicated by the presence of normally zoned plagioclase with Ca-rich cores and Na-enriched outer rims) and multiple magma mixing (supported by the presence of reversed zoned plagioclase and coexistence of normally and reversely zoned plagioclase). Lower X _Mg biotite associated with the mineralized (Cu–Mo ± W) potassic alteration incorporated more F and Cl relative to least-altered biotite with higher X _Mg. In both Nucleus and Revenue Au–Cu mineralizations, secondary biotite composition varies with respect to the associated alteration mineral assemblages. Although secondary biotite in the skarn re-equilibrated with F-poor fluids, secondary biotite from the pervasive biotitization is related to F- and Cl-enriched fluids, and secondary biotite from the phyllitic zone is related to F-, Cl-, and Mg-depleted fluids, thus consistent with a change in mineralizing fluid composition during mineralization.     

K–Ar and Ar–Ar dating of the Palaeozoic metamorphic complex from the Mid-Bosnian Schist Mts., Central Dinarides, Bosnia and Hercegovina

Summary K–Ar and Ar–Ar whole rock and mineral ages are presented for 25 samples of metamorphic rocks from the Mid-Bosnian Schist Mts., representing one of the largest allochthonous Palaeozoic terranes incorporated within the Internal Dinarides. Four main age groups can be distinguished: 1) Variscan (343Ma), 2) post-Variscan (288–238Ma), 3) Early Cretaceous (mainly 121–92Ma), and 4) Eocene (59–35Ma) ages. Apart from this, an Oligocene (31Ma) age was obtained on Alpine vein hyalophane. The radiometric dating indicates a polyphase metamorphic evolution of the Palaeozoic formations and suggests a pre-Carboniferous age of the volcano-sedimentary protoliths, an Early Carboniferous age of Variscan metamorphism and deformation, post-Variscan volcanism, an Early Cretaceous metamorphic overprint related to out-of-sequence thrusting of the Palaeozoic complex, and an Eocene and Oligocene metamorphic overprint related to the main Alpine compressional deformation and subsequent strike-slip faulting, and uplift of the metamorphic core. Accordingly, the Mid-Bosnian Schist Mts. can be correlated in its multistage geodynamic evolution with some Palaeozoic tectonostratigraphic units from the Austroalpine domain in the Eastern Alps.Deceased     

Carboniferous porphyry Cu–Au deposits in the Almalyk orefield,Uzbekistan: the Sarycheku and Kalmakyr examples

The Almalyk porphyry cluster in the western part of the Central Asian Orogenic Belt is the second largest porphyry region in Asia and hence has attracted considerable attention of the geologists. In this contribution, we report the zircon U–Pb ages, major and trace element geochemistry as well as Sr–Nd isotopic data for the ore-related porphyries of the Sarycheku and Kalmakyr deposits. The zircon U–Pb ages (Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS)) of ore-bearing quartz monzonite and granodiorite porphyries from the Kalmakyr deposit are 326.1 ± 3.4 and 315.2 ± 2.8 Ma, and those for the ore-bearing granodiorite porphyries and monzonite dike from the Sarycheku deposit are 337.8 ± 3.1 and 313.2 ± 2.5 Ma, respectively. Together with the previous ages, they confine multi-phase intrusions from 337 to 306 Ma for the Almalyk ore cluster. Geochemically, all samples belong to shoshonitic series and are enriched in large-ion lithophile elements relative to high field strength elements with very low Nb/U weight ratios (0.83–2.56). They show initial (⁸⁷Sr/⁸⁶Sr)_i ratios of 0.7059–0.7068 for Kalmakyr and 0.7067–0.7072 for Sarycheku and low ε_Nd(t) values of ?1.0 to ?0.1 for Kalmakyr and ?2.3 to 0.2 for Sarycheku, suggesting that the magmas were dominantly derived from a metasomatized mantle wedge modified by slab-derived fluids with the contribution of the continental crust by assimilation-fractional-crystallization process. Compared to the typical porphyry Cu deposits, the ore-bearing porphyries in the Almalyk cluster are shoshonitic instead of the calc-alkaline. Moreover, although the magmatic events were genetically related to a continental arc environment, the ore-bearing porphyries at Sarycheku and Kalmakyr do not show geochemical signatures of typical adakites as reflected in some giant porphyry deposits in the Circum-Pacific Ocean, indicating that slab-melting may not have been involved in their petrogenesis.     

Petrogenesis and Mineralization of the Tongshan Skarn Cu–Au Deposit, Lower Yangtze Metallogenic Belt

Please refer to the attachment(s) for more details     

Mineralization and fluid evolution of the Jiyuan polymetallic Cu–Ag–Pb–Zn–Au deposit,eastern Tianshan,NW China

The newly discovered Jiyuan Cu–Ag–(Pb–Zn–Au) deposit is located in the southern section of the eastern Tianshan orogenic belt, Xinjiang, northwestern China. It is the first documented deposit in the large Aqikekuduke Ag–Cu–Au belt in the eastern Tianshan orogen. Detailed field observations, parageneses, and fluid inclusion studies suggest an epithermal ore genesis for the main Cu–Ag mineralization, accompanied by a complicated hydrothermal alteration history most likely associated with the multi-stage tectonic evolution of the eastern Tianshan. The Jiyuan Cu–Ag ore bodies are located along the EW-striking, south-dipping Aqikekuduke fault and are hosted by Precambrian marble and intercalated siliceous rocks. Early-stage skarn alteration occurred along the contact zone between the marble layers and Early Carboniferous diorite–granodiorite and monzogranite intrusions; the skarns are characterized by diopside–tremolite–andradite–pyrite–(magnetite) assemblages. Local REE-enriched synchysite–rutile–arsenopyrite–(clinochlorite–microcline–albite) assemblages are related to K–Na alteration associated with the monzogranite intrusions and formed under conditions of high temperature (310°C) and high salinity (19.9 wt.% NaCl). Subsequent hydrothermal alteration produced a series of quartz and calcite veins that precipitated from medium- to low-temperature saline fluids. These include early ‘smoky’ quartz veins (190°C; 3.0 wt.% NaCl) that are commonly barren, coarse-grained Cu–Ag mineralized quartz veins (210°C; 2.4 wt.% NaCl), and late-stage unmineralized calcite veins (140°C; 1.1 wt.% NaCl). Tremolite and Ca-rich scapolite veins formed at an interval between early and mineralized quartz veins, indicating a high-temperature, high-salinity (>500°C; 9.5 wt.% NaCl) Ca alteration stage. Fluid mixing may have played an important role during Cu–Ag mineralization and an external low-temperature Ca-rich fluid is inferred to have evolved in the ore-forming system. The Jiyuan auriferous quartz veins possess fluid characteristics distinct from those of the Cu–Ag mineralized quartz veins. CO₂-rich fluid inclusions, fluid boiling, and mixing all demonstrate that these auriferous quartz veins acted as hosts for the orogenic-type gold mineralization, a common feature in the Tianshan orogenic belt.     

Late Cretaceous porphyry Cu and epithermal Cu–Au association in the Southern Panagyurishte District,Bulgaria: the paired Vlaykov Vruh and Elshitsa deposits

Vlaykov Vruh–Elshitsa represents the best example of paired porphyry Cu and epithermal Cu–Au deposits within the Late Cretaceous Apuseni–Banat–Timok–Srednogorie magmatic and metallogenic belt of Eastern Europe. The two deposits are part of the NW trending Panagyurishte magmato-tectonic corridor of central Bulgaria. The deposits were formed along the SW flank of the Elshitsa volcano-intrusive complex and are spatially associated with N110-120-trending hypabyssal and subvolcanic bodies of granodioritic composition. At Elshitsa, more than ten lenticular to columnar massive ore bodies are discordant with respect to the host rock and are structurally controlled. A particular feature of the mineralization is the overprinting of an early stage high-sulfidation mineral assemblage (pyrite ± enargite ± covellite ± goldfieldite) by an intermediate-sulfidation paragenesis with a characteristic Cu–Bi–Te–Pb–Zn signature forming the main economic parts of the ore bodies. The two stages of mineralization produced two compositionally different types of ores—massive pyrite and copper–pyrite bodies. Vlaykov Vruh shares features with typical porphyry Cu systems. Their common geological and structural setting, ore-forming processes, and paragenesis, as well as the observed alteration and geochemical lateral and vertical zonation, allow us to interpret the Elshitsa and Vlaykov Vruh deposits as the deep part of a high-sulfidation epithermal system and its spatially and genetically related porphyry Cu counterpart, respectively. The magmatic–hydrothermal system at Vlaykov Vruh–Elshitsa produced much smaller deposits than similar complexes in the northern part of the Panagyurishte district (Chelopech, Elatsite, Assarel). Magma chemistry and isotopic signature are some of the main differences between the northern and southern parts of the district. Major and trace element geochemistry of the Elshitsa magmatic complex are indicative for the medium- to high-K calc-alkaline character of the magmas. ⁸⁷Sr/⁸⁶Sr_(i) ratios of igneous rocks in the range of 0.70464 to 0.70612 and ¹⁴³Nd/¹⁴⁴Nd_(i) ratios in the range of 0.51241 to 0.51255 indicate mixed crustal–mantle components of the magmas dominated by mantellic signatures. The epsilon Hf composition of magmatic zircons (+6.2 to +9.6) also suggests mixed mantellic–crustal sources of the magmas. However, Pb isotopic signatures of whole rocks (²⁰⁶Pb/²⁰⁴Pb = 18.13–18.64, ²⁰⁷Pb/²⁰⁴Pb = 15.58–15.64, and ²⁰⁸Pb/²⁰⁴Pb = 37.69–38.56) along with common inheritance component detected in magmatic zircons also imply assimilation processes of pre-Variscan and Variscan basement at various scales. U–Pb zircon and rutile dating allowed determination of the timing of porphyry ore formation at Vlaykov Vruh (85.6 ± 0.9 Ma), which immediately followed the crystallization of the subvolcanic dacitic bodies at Elshitsa (86.11 ± 0.23 Ma) and the Elshitsa granite (86.62 ± 0.02 Ma). Strontium isotope analyses of hydrothermal sulfates and carbonates (⁸⁷Sr/⁸⁶Sr = 0.70581–0.70729) suggest large-scale interaction between mineralizing fluids and basement lithologies at Elshitsa–Vlaykov Vruh. Lead isotope compositions of hydrothermal sulfides (²⁰⁶Pb/²⁰⁴Pb = 18.432–18.534, ²⁰⁷Pb/²⁰⁴Pb = 15.608–15.647, and ²⁰⁸Pb/²⁰⁴Pb = 37.497–38.630) allow attribution of ore-formation in the porphyry and epithermal deposits in the Southern Panagyurishte district to a single metallogenic event with a common source of metals.     

Formation of the Vysoká–Zlatno Cu–Au skarn–porphyry deposit, Slovakia

The central zone of the Miocene Štiavnica stratovolcano hosts several occurrences of Cu–Au skarn–porphyry mineralisation, related to granodiorite/quartz–diorite porphyry dyke clusters and stocks. Vysoká–Zlatno is the largest deposit (13.4 Mt at 0.52% Cu), with mineralised Mg–Ca exo- and endoskarns, developed at the prevolcanic basement level. The alteration pattern includes an internal K- and Na–Ca silicate zone, surrounded by phyllic and argillic zones, laterally grading into a propylitic zone. Fluid inclusions in quartz veinlets in the internal zone contain mostly saline brines with 31–70 wt.% NaCl eq. and temperatures of liquid–vapour homogenization (Th) of 186–575°C, indicating fluid heterogenisation. Garnet contains inclusions of variable salinity with 1–31 wt.% NaCl eq. and Th of 320–360°C. Quartz–chalcopyrite veinlets host mostly low-salinity fluid inclusions with 0–3 wt.% NaCl eq. and Th of 323–364°C. Data from sphalerite from the margin of the system indicate mixing with dilute and cooler fluids. The isotopic composition of fluids in equilibrium with K-alteration and most skarn minerals (both prograde and retrograde) indicates predominantly a magmatic origin (δ¹⁸O_fluid 2.5–12.3‰) with a minor meteoric component. Corresponding low δD_fluid values are probably related to isotopic fractionation during exsolution of the fluid from crystallising magma in an open system. The data suggest the general pattern of a distant source of magmatic fluids that ascended above a zone of hydraulic fracturing below the temperature of ductile–brittle transition. The magma chamber at ∼5–6 km depth exsolved single-phase fluids, whose properties were controlled by changing PT conditions along their fluid paths. During early stages, ascending fluids display liquid–vapour immiscibility, followed by physical separation of both phases. Low-salinity liquid associated with ore veinlets probably represents a single-phase magmatic fluid/magmatic vapour which contracted into liquid upon its ascent.     

Geological,geochronological, and H–O isotopic constraints on the genesis of the Tongjing Cu–Au deposit in the Ningwu basin,east China

The Tongjing Cu–Au deposit is a medium-sized deposit within the Ningwu volcanic basin, east China, and is hosted by Cretaceous volcanic rocks of the Dawangshan and Niangniangshan Formations. The veined and lenticular Cu–Au orebodies are spatially and temporally related to the volcanic and subvolcanic rocks of the Niangniangshan Formation in the ore district. The wall-rock alteration is dominated by silicification, siderite alteration, carbonation, sericitization, chloritization, and kaolinization. On the basis of field evidence and petrographic observations, two stages of mineralization are recognized: (1) a siderite–quartz–sulfide stage (Stage 1) associated with the formation of chalcopyrite and pyrite in a quartz and siderite gangue; and (2) a quartz–bornite stage (Stage 2) cutting the Stage 1 phases. Stage 1 is the main mineralization stage. Quartz that formed in Stage 1 has δ¹⁸O_H2O values of − 4.3‰ to 3.5‰ with δD values of fluid inclusion waters of − 97.1‰ to − 49.9‰, indicating that the ore-forming fluids were derived from early magmatic fluids and may have experienced oxygen isotopic exchange with meteoric water during Stage 1 mineralization.LA–MC–ICP–MS zircon U–Pb dating of the mineralization-related nosean-bearing phonolite and nosean-bearing phonolitic brecciated tuff at Tongjing yields ages of 129.8 ± 0.5 Ma and 128.9 ± 1.1 Ma, respectively. These results are interpreted as the crystallization age of the volcanic rocks of the Niangniangshan Formation. A hydrothermal sericite sample associated with Cu–Au mineralization at Tongjing yields a plateau ⁴⁰Ar–³⁹Ar age of 131.3 ± 1.3 Ma. These results confirm a genetic link between the volcanism and associated Cu–Au mineralization. The Tongjing Cu–Au deposit in the Ningwu basin is genetically and possibly tectonically similar to alkaline intrusion-related gold deposits elsewhere in the world.     

Mesoproterozoic fluid events affecting Archean crust in the northern Olympic Cu–Au Province,Gawler Craton: insights from 40Ar/39Ar thermochronology

The Olympic Cu–Au Province, Gawler Craton, is host to the Olympic Dam and Prominent Hill iron oxide–copper–gold (IOCG) deposits. Both of these deposits and the region between the two are covered by Neoproterozoic to Cenozoic sediment, making inferences about prospectivity in this portion of the Olympic Domain reliant on geophysical interpretation and sparse drill hole information. We present new U–Pb zircon sensitive high resolution ion microprobe (SHRIMP) dates from two basement intersecting drill holes in the region between Olympic Dam and Prominent Hill that show bimodal volcanism occurred at 2555 ± 5 Ma, and was followed by intrusion of tonalite at 2529 ± 6 Ma. Laser ⁴⁰Ar/³⁹Ar dating of biotite and muscovite from the tonalite yields ages around ca 2000 Ma, consistent with slow cooling trends observed in Archean rocks elsewhere in the northern Gawler Craton. Step heating experiments on K-feldspar from the same tonalite yields an age spectrum with older ages around 1740 Ma from the highest temperature steps becoming progressively younger to a minimum of 1565 Ma in the lowest temperature heating steps; this is consistent with either Paleoproterozic cooling to final closure of K-feldspar by 1565 Ma or a reheating event at ca 1565 Ma, with the latter more likely, given the evidence for sub-solidus alteration of the K-feldspar. Sericite within hematite–sericite–chlorite altered portions of the tonalite yield a poorly defined age of ca 1.6 Ga. Taken together the ⁴⁰Ar/³⁹Ar data providing evidence for a fluid event affecting this region between Olympic Dam and Prominent Hill during the early Mesoproterozoic. Low temperature quartz–carbonate–adularia veins occur in <10 cm wide fractures within basalt in one drill hole in this region. Adularia from these veins yields ⁴⁰Ar/³⁹Ar ages that span from ca 1.3–1.1 Ga. This age range is interpreted to approximate either the timing of adularia formation during a hydrothermal event or the timing of resetting of the ⁴⁰Ar/³⁹Ar systematics within the adularia as a result of fluid flow in this sample. This is evidence for a mid-Mesoproterozoic fluid event in the Gawler Craton and necessitates a reconsideration of the long-term stability of the craton, as it appears to have been affected, at least locally, by fluid flow related to a much larger event within the Australian continent, the Musgrave Orogeny.     

Petrogenesis and metallogenic setting of porphyries of the Duobuza porphyry Cu–Au deposit,central Tibet,China

Given that the Duobuza deposit was the first porphyry Cu–Au deposit discovered in central Tibet, the mineralization and mineralized porphyry in this area have been the focus of intensive research, yet the overall porphyry sequence associated with the deposit remains poorly understood. New geological mapping, logging, and sampling of an early granodiorite porphyry, an inter-mineralization porphyry, and a late-mineralization diorite porphyry were complemented by LA–ICP–MS zircon dating, whole-rock geochemical and Sr–Nd isotopic analyses, and in situ Hf isotopic analyses for both inter- and late-mineralization porphyry intrusions. All of the porphyry intrusions are high-K and calc-alkaline, and were emplaced at ca. 120 Ma. The geochemistry of these intrusions is indicative of arc magmatism, as all three porphyry phases are enriched in light rare earth elements and large ion lithophile elements, and depleted in heavy rare earth elements and high field strength elements. These similar characteristics of the intrusions, when combined with the relatively high (⁸⁷Sr/⁸⁶Sr)_i, negative ε_Nd(t), and positive ε_Hf(t) values, suggest that the magmas that formed the porphyries were derived from a common source region and shared a single magma chamber. The magmas were generated by the mixing of upwelling metasomatized mantle-wedge-derived mafic magmas and magmas generated by partial melting of amphibolite within the lower crust.The inter-mineralization porphyry has the lowest ε_Nd(t) and highest (⁸⁷Sr/⁸⁶Sr)_i values, suggesting that a large amount of lower-crust-derived material was incorporated into the melt and that metals such as Cu and Au from the enriched lower crust were scavenged by the parental magma. The relative mafic late-mineralization diorite porphyry phase was formed by the residual magma in the magma chamber mixing with upwelling mafic melt derived from metasomatized mantle. The magmatic–hydrothermal evolution of the magma in the chamber released ore-forming fluid that was transported mainly by the inter-mineralization porphyry phase during the mineralization stage, which ultimately formed the Duobuza porphyry Cu–Au deposit.These porphyritic intrusions of the Duobuza deposit have high Mg^# and low (La/Yb)_N values, and show some high LILE/HFSE ratios, indicating the magma source was enriched by interaction with slab-derived fluids. Combined with age constraints on the regional tectonic evolution, these dating and geochemical results suggest that the Duobuza porphyry Cu–Au deposit formed in a subduction setting during the final stages of the northward subduction of the Neo-Tethyan Ocean.     

Geological characteristics and genesis of the Laoshankou Fe–Cu–Au deposit in Junggar,Xinjiang, Central Asian Orogenic Belt

The Laoshankou Fe–Cu–Au deposit is located at the northern margin of Junggar Terrane, Xinjiang, China. This deposit is hosted in Middle Devonian andesitic volcanic breccias, basalts, and conglomerate-bearing basaltic volcanic breccias of the Beitashan Formation. Veined and lenticular Fe–Cu–Au orebodies are spatially and temporally related to diorite porphyries in the ore district. Wall–rock alteration is dominated by skarn (epidote, chlorite, garnet, diopside, actinolite, and tremolite), with K–feldspar, carbonate, albite, sericite, and minor quartz. On the basis of field evidence and petrographic observations, three stages of mineralization can be distinguished: (1) a prograde skarn stage; (2) a retrograde stage associated with the development of Fe mineralization; and (3) a quartz–sulfide–carbonate stage associated with Cu–Au mineralization. Electron microprobe analysis shows that garnets and pyroxenes are andradite and diopside-dominated, respectively. Fluid inclusions in garnet yield homogenization temperatures (T_h) of 205–588 °C, and salinities of 8.95–17.96 wt.% NaCl equiv. In comparison, fluid inclusions in epidote and calcite yield T_h of 212–498 and 150–380 °C, and salinities of 7.02–27.04 and 13.4–18.47 wt.% NaCl equiv., respectively. Garnets yield values of 6.4‰ to 8.9‰ δ¹⁸O_fluid, whereas calcites yield values of − 2.4‰ and 4.2‰ δ¹⁸O_fluid, and − 0.9‰ to 2.4‰ δ¹³C_PDB, indicating that the ore-forming fluids were dominantly magmatic fluids in the early stage and meteoric water in the late stage. The δ³⁴S values of sulfides range from − 2.6‰ to 5.4‰, indicating that the sulfur in the deposit was probably derived from deep-seated magmas. The diorite porphyry yields LA–MC–ICP–MS zircon U–Pb age of 379.7 ± 3.0 Ma, whereas molybdenites give Re–Os weighted mean age of 383.2 ± 4.5 Ma (MSWD = 0.06). These ages suggest that the mineralization-related diorite porphyry was emplaced during the Late Devonian, coincident with the timing of mineralization within the Laoshankou Fe–Cu–Au deposit. The geological and geochemical evidence presented here suggest that the Laoshankou Fe–Cu–Au deposit is a skarn deposit.     

Re–Os and U–Pb geochronology of the Duobaoshan porphyry Cu–Mo–(Au) deposit,northeast China,and its geological significance

The large-scale Duobaoshan porphyry Cu–Mo–(Au) deposit is located at the north segment of the Da Hinggan Mountains, northeast China. Six molybdenite samples from the Duobaoshan deposit were selected for Re–Os isotope measurement to define the mineralization age of the deposit, yieldings a Re–Os isochron age of 475.9 ± 7.9 Ma (2σ), which is accordant with the Re–Os model ages of 476.6 ± 6.9–480.2 ± 6.9 Ma. This age is consistent with the age of the related granodiorite porphyry, which was dated as 477.2 ± 4 Ma by zircon U–Pb analysis using LA-ICP-MS. These ages disagree with the previous K–Ar age determinations that suggest a correlation of intrusive rocks of the Duobaoshan area with the Hercynian intrusive rocks of Carboniferous–Permian age. These ages demonstrate that the Duobaoshan granodiorite porphyry and related Cu–Mo deposit occurred in the Early Ordovician. The rhenium content of molybdenite varies from 290.9 to 728.2 μg/g, with an average content of 634.8 μg/g. The high rhenium content in molybdenite of the Duobaoshan deposit suggests that the ore-forming materials may be mainly of mantle source.     

Geochemical and geochronological constraints on the formation of shear-zone hosted Cu–Au–Bi–Te mineralization in the Stanos area,Chalkidiki, northern Greece

Copper–gold–bismuth–tellurium mineralization in the Stanos area, Chalkidiki Peninsula, Greece, occurs in the Proterozoic- to Silurian-aged Serbomacedonian Massif, which tectonically borders the Mesozoic Circum-Rhodope metamorphic belt to the west and crystalline rocks of the Rhodope Massif to the east. This area contains the Paliomylos, Chalkoma, and Karambogia prospects, which are spatially related to regional NW–SE trending shear zones and hosted by marble, amphibolite gneiss, metagabbro, and various muscovite–biotite–chlorite–actinolite–feldspar–quartz schists of the Silurian Vertiskos Unit. Metallic minerals occur as disseminated to massive aggregates along foliation planes and in boudinaged quartz veins. Iron-bearing sulfides (pyrite, arsenopyrite, and pyrrhotite) formed prior to a copper-bearing stage that contains chalcopyrite along with galena, sphalerite, molybdenite, and various minerals in the system Bi–Cu–Pb–Au–Ag–Te. Fluid inclusion homogenization temperatures of primary aqueous liquid–vapor inclusions in stage I quartz veins range from 170.1 °C to 349.6 °C (peak at ~ 230 °C), with salinities of 4.5 to 13.1 wt.% NaCl equiv. Calculated isochores intersect P–T conditions associated with the upper greenschist facies caused by local overpressures during late-stage tectonic movement along the shear zone in the Eocene, which produced stretching and unroofing of rocks in the region. Values of δ³⁴S for sulfides in the Stanos shear zone range from 2.42 to 10.19‰ and suggest a magmatic sulfur source with a partially reduced seawater contribution. For fluids in equilibrium with quartz, δ¹⁸O at 480 °C varies from 5.76 to 9.21‰ but does not allow for a distinction between a metamorphic and a magmatic fluid.A ¹⁸⁷Re–¹⁸⁷Os isochron of 19.2 ± 2.1 Ma for pyrite in the Paliomylos prospect overlaps ages obtained previously from intrusive rocks spatially-related to the Skouries porphyry Cu–Au, the Asimotrypes Au, and the intrusion-related Palea Kavala Bi–Te–Pb–Sb ± Au deposits in northern Greece, as well as alteration minerals in the carbonate-replacement Madem Lakkos Pb–Zn deposit. Ore-forming components of deposits in the Stanos area were likely derived from magmatic rocks at shallow depth that intruded an extensional shear environment at ~ 19 Ma.     

Geology,mineralogy, and geochemistry of fault-controlled hydrothermal Cu–Au mineralization in the Shanmen Volcanic Basin,SE China

The Yukeng–Banling deposit is a typical fault-controlled hydrothermal Cu–Au deposit in the Shanmen Volcanic Basin (SVB), SE China. Ore bodies commonly occur as lodes, lenses and disconnected pods dipping SW with vertical zonation of ore minerals. Ore-related hydrothermal alteration is well developed on both sides of the veins, dominated by silicification, sericitization, chloritization and argillation with a banded alteration zonation. The mineralization can be divided into three stages (stages I, II and III). Native gold is present as veinlets in fractures of fine-grained pyrite from stage II.Zircon U–Pb and Rb–Sr isochron ages indicate that the Cu–Au mineralization is coeval with the Caomen alkaline granite and Xiaokeng quartz-diorite, both emplaced at ca. 102 Ma. Microthermometric measurements of fluid inclusions in quartz and sphalerite from stage II veins indicate that the Yukeng–Banling deposit is an epithermal deposit. Six ore-related quartz grains have δD_H2O values of − 69 to − 43‰, and δ¹⁸O_H2O values calculated using total homogenization temperatures that range from − 2.0 to 0.7‰. All samples plot in an area between the magmatic field and the meteoric line, suggesting that the ore-forming fluids are derived from a mixed source of magmatic and meteoric waters. δ³⁴S values for eight pyrite separates range from − 2.1 to + 4.1‰ with an average of + 1.7‰, and δ³⁴S values for galena and sphalerite are 2.3‰ and 2.2‰, similar to magmatic sulfur. Four alkaline granite samples have Pb isotopic ratios (²⁰⁶Pb/²⁰⁴Pb)_t = 18.175–18.411, (²⁰⁷Pb/²⁰⁴Pb)_t = 15.652–15.672 and (²⁰⁸Pb/²⁰⁴Pb)_t = 38.343–38.800. Three quartz-diorite samples have ratios (²⁰⁶Pb/²⁰⁴Pb)_t, (²⁰⁷Pb/²⁰⁴Pb)_t and (²⁰⁸Pb/²⁰⁴Pb)_t of 18.277–18.451, 15.654–15.693 and 38.673–38.846, respectively. These age-calculated lead isotopic data for alkaline granite are similar to those for the analyzed sulfides. Co/Ni ratios for stage II pyrites range from 1.42 to 5.10, indicating that the Yukeng–Banling deposit records the past involvement of magmatic hydrothermal fluids. The isotope data, together with geological, mineralogical and geochronological evidence, favor a primary magmatic source for sulfur and metals in the ore fluids. Mixing of the Cu- and Au-rich fluids with meteoric water led to precipitation of the Cu–Au veins along NW-trending faults.The Yukeng–Banling deposit, the contemporaneous Caomen alkaline granite and Xiaokeng quartz-diorite in the SVB formed under an extensional setting, due to high-angle subduction of the paleo-Pacific plate. The extensional setting facilitated the formation of Cu- and Au-rich magmas which was derived from enriched mantle and lower crust.     

Platinum Mineralization in Multimetal Gold–Polymetallic,Au–Bi,Cu–Mo Porphyry,Cu–Ni,Titanomagnetite, and Copper–Sulfide Ore Deposits and Occurrences of the Upper Amur Region (Far East,Russia)

New data on platinum mineralization in ores, metasomatic rocks, concentrates, and tailings and wastes of some gold–polymetallic, Au–Bi, Cu–Mo porphyry, Cu–Ni, and titanomagnetite ore deposits and occurrences of the Upper Amur Region are presented. The contents of platinoids, Au and Ag in multimetal ores of gold-polymetallic, Au–Bi, Cu–Mo porphyry, Cu–Ni, and titanomagnetite ore deposits and ore occurrences are given. In addition, recommendations on the necessity of continuing scientific studies, revision, and resampling works in the search for platinoids in other complex ores of deposits and occurrences of the Upper Amur Region are given.     

Contrasting fluids and reservoirs in the contiguous Marcona and Mina Justa iron oxide–Cu (–Ag–Au) deposits,south-central Perú

The Marcona–Mina Justa deposit cluster, hosted by Lower Paleozoic metaclastic rocks and Middle Jurassic shallow marine andesites, incorporates the most important known magnetite mineralization in the Andes at Marcona (1.9 Gt at 55.4% Fe and 0.12% Cu) and one of the few major iron oxide–copper–gold (IOCG) deposits with economic Cu grades (346.6 Mt at 0.71% Cu, 3.8 g/t Ag and 0.03 g/t Au) at Mina Justa. The Middle Jurassic Marcona deposit is centred in Ica Department, Perú, and the Lower Cretaceous Mina Justa Cu (Ag, Au) prospect is located 3–4 km to the northeast. New fluid inclusion studies, including laser ablation time-of-flight inductively coupled plasma mass spectrometry (LA-TOF-ICPMS) analysis, integrated with sulphur, oxygen, hydrogen and carbon isotope analyses of minerals with well-defined paragenetic relationships, clarify the nature and origin of the hydrothermal fluid responsible for these contiguous but genetically contrasted deposits. At Marcona, early, sulphide-free stage M-III magnetite–biotite–calcic amphibole assemblages are inferred to have crystallized from a 700–800°C Fe oxide melt with a δ¹⁸O value from +5.2‰ to +7.7‰. Stage M-IV magnetite–phlogopite–calcic amphibole–sulphide assemblages were subsequently precipitated from 430–600°C aqueous fluids with dominantly magmatic isotopic compositions (δ³⁴S = +0.8‰ to +5.9‰; δ¹⁸O = +9.6‰ to +12.2‰; δD = −73‰ to −43‰; and δ¹³C = −3.3‰). Stages M-III and M-IV account for over 95% of the magnetite mineralization at Marcona. Subsequent non-economic, lower temperature sulphide–calcite–amphibole assemblages (stage M-V) were deposited from fluids with similar δ³⁴S (+1.8‰ to +5.0‰), δ¹⁸O (+10.1‰ to +12.5‰) and δ¹³C (−3.4‰), but higher δD values (average −8‰). Several groups of lower (<200°C, with a mode at 120°C) and higher temperature (>200°C) fluids can be recognized in the main polymetallic (Cu, Zn, Pb) sulphide stage M-V and may record the involvement of modified seawater. At Mina Justa, early magnetite–pyrite assemblages precipitated from a magmatic fluid (δ³⁴S = +0.8‰ to +3.9‰; δ¹⁸O = +9.5‰ to +11.5‰) at 540–600°C, whereas ensuing chalcopyrite–bornite–digenite–chalcocite–hematite–calcite mineralization was the product of non-magmatic, probably evaporite-sourced, brines with δ³⁴S ≥ +29‰, δ¹⁸O = 0.1‰ and δ¹³C = −8.3‰. Two groups of fluids were involved in the Cu mineralization stage: (1) Ca-rich, low-temperature (approx. 140°C) and high-salinity, plausibly a basinal brine and (2) Na (–K)-dominant with a low-temperature (approx. 140°C) and low-salinity probably meteoric water. LA-TOF-ICPMS analyses show that fluids at the magnetite–pyrite stage were Cu-barren, but that those associated with external fluids in later stages were enriched in Cu and Zn, suggesting such fluids could have been critical for the economic Cu mineralization in Andean IOCG deposits.