Geochronology and geochemistry of the Shilu Cu–Mo deposit in the Yunkai area,Guangdong Province,South China and its implication

Shilu is a large porphyry–skarn deposit in the Yunkai district in Guangdong Province, South China. The Shilu granitic intrusion in the mine area is a granodiorite which is genetically related to Cu mineralization. Plagioclase in the granodiorite has a zoned texture and is mainly andesine with minor amounts of labradorite, whereas the K-feldspars exhibit Carlsbad twins and some are also characterized by a zonal texture. K-feldspars from the granodiorite show high contents of Or (87–92 wt.%) with minor Ab (8–13 wt.%) and negligible An value of 0–0.3 wt.%. Biotite can be classified as magnesio-biotite, and is characterized by Mg-rich [Mg/(Mg + Fe) = 0.54–0.60] and Al^VI-low (average values = 0.11). Hornblende is chiefly magnesiohornblende and tschermakite. LA-ICP-MS zircon U–Pb age of the Shilu granodiorite is 107 ± 0.7 Ma, which is consistent with molybdenites Re–Os age of 104.1 ± 1.3 Ma. Geochemical data indicate that the Shilu granodiorite is silica-rich (SiO₂ = 63.43–65.03 wt.%) and alkali-rich (K₂O + Na₂O = 5.45–6.05 wt.%), as well as calcium-rich (CaO = 4.76–5.1 wt.%). Trace element geochemistry results show enrichments in large ion lithophile elements (e.g., Rb, K, and Ba) and depletions in some high field strength elements (e.g., Nb, P, Ta, and Ti). The total rare earth element (REE) content of the granodioritic rocks is low (∑ REE < 200 ppm), and is characterized by light REE enrichment [(La/Yb)_N > 9] and moderately negative Eu anomalies (Eu/Eu* = 0.83–0.90). These mineralogical, geochronological, and geochemical results suggest that the Shilu granodiorite has a mixed crust–mantle source with a geochemical affinity to I-type granitoids. Hornblende thermobarometry yielded magmatic crystallization temperatures of 686–785 °C and crystallization pressures between 1.0 and 2.34 kbar, which is converted to depths in a range of 3.31 to 7.71 km. Biotite thermobarometry yielded similar temperatures and lower pressures of 680–780 °C and 0.8–2 kbar (depth 2.64–6.6 km), respectively. The parent magma had a high oxygen fugacity. The Shilu granodiorite has a relatively low ε_Nd/t–t value and high (⁸⁷Sr/⁸⁶Sr)_i value, and Nd isotopes yield two-stage depleted mantle Nd model ages of 969–1590 Ma. Our new data, combined with previous studies, imply that the granodiorite and the associated Shilu Cu–Mo deposit was formed in an extensional environment, closely related to remelting of residual subducted slab fragments in the Jurassic.     

Tourmalinites and Sn-Li mineralization in the Valdeflores area (Cáceres,Spain)

Summary Tourmalinites containing quartz, Li- and Cs-micas, and small amounts of arsenopyrite occur near Cáceres, Spain. The tourmalinites are developed within Ordovician pelites near the eastern margin of the Cabeza de Araya batholith and close to several small bodies of tectonized granite. Field and textural relationships document an epigenetic character for the tourmalinites. The tourmaline is fine to very fine-grained and its composition is intermediate within the schorl-dravite solid-solution series. Hydrothermal veins containing quartz, muscovite, amblygonite-montebrasite, apatite, fluorite, and/or cassiterite appear spatially related to the tourmalinites. The mineralized area is located in a shear zone that was active during D₃ Hercynian deformation and the emplacement of granitic bodies. Tourmalinites and veins derived from B- and Li-rich magmatic-hydrothermal fluids are believed to have been associated with the intrusion of a hidden granite dome, the tourmalinites being produced by extensive metasomatism of Ordovician metasedimentary rocks.

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Turmalinite and Sn-Li-Vererzungen im Valdeflores Gebiet (Cáceres, Spanien)

Zusammenfassung Turmalinite, die Quarz, Li- und Cs-Glimmer, sowie geringe Mengen an Arsenkies führen, kommen in der Ne von Cáceres, Spanien, vor. Sie sind an ordovizische Metapelite in der Nähe des Cabeza de Araya Batholiths und kleinere tektonisierte Granitkörper gebunden. Eine epigenetische Genese der Turmalinite ist auf Grund von Feldbeziehungen und texturellen Beobachtungen belegt. Die Zusammensetzung der sehr feinkörnigen Turmaline entspricht intermediären Gliedern der Schörl-Dravit- Reihe. Hydrothermale Gänge mit Quarz, Muskowit, Amblygonit-Montebrasit, Apatit, Fluorit und/oder Zinnstein treten benachbart zu den Turmaliniten auf. Der mineralisierte Bereich ist an eine Scherzone gebunden, die während der hercynischen D3 Deformation und der Platznahme der Granite aktiv war. Turmalinite und Gänge lassen sich genetisch von magmatisch-hydrothermalen Fluiden ableiten, die mit der Intrusion eines nicht aufgeschlossenen Granitdomes zusammenhängen. Die Turmalinite sind das Produkt einer weiträumigen Metasomatose der ordovizischen Metasedimente.

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With 8 Figures     

Multi-stage zeolite facies mineralization in the Hvalfjördur area,Iceland

The Hvalfjördur area, 30 km north of Iceland’s capital Reykjavik, belongs to the sequence of Late Tertiary to early Quaternary flood basalts with minor intercalations of hyaloclastites and rhyolites. The basalts are affected by progressive low-temperature metamorphism, caused by the burial of the lava succession and higher heat flow from nearby central volcanoes. Low-grade zeolite facies metamorphism of basaltic lavas in the Hvalfjördur area results in two distinct mineral parageneses that can be correlated to events in the burial and hydrothermal history of the lava pile. Stage Ia represents syn-eruptive near-surface alteration in which celadonite and silica were precipitated along primary pores. During regional burial metamorphism (stage Ib), hydrolysis of olivine and glass led to the formation of mixed-layer chlorite/smectite clays. The chlorite content of stage Ib phyllosilicate vesicle rims increases with increasing burial depth and temperature. Stage II occurred after the burial and is marked by zeolite mineralization caused by higher heat flow from the Laxárvogur and Hvalfjördur central volcanoes. Altogether 11 different zeolites were found in the Hvalfjördur area: analcime, chabazite, epistilbite, heulandite, laumontite, levyne, mesolite, stilbite, stellerite, thomsonite and yugawaralite. In total, three separate depth and temperature-controlled “zeolite zones” occur in the Hvalfjördur area.     

Timing and formation of porphyry Cu–Mo mineralization in the Chuquicamata district, northern Chile: new constraints from the Toki cluster

The recently discovered Toki cluster, which includes the Toki, Quetena, Genoveva, Miranda, and Opache porphyry Cu–Mo prospects, is located 15 km south–southwest of the Chuquicamata–Radomiro Tomic mines in northern Chile. These prospects occur in an area of 5?×?6 km and are completely covered with Neogene alluvial deposits. Inferred resources for the cluster are estimated at about 20 Mt of fine copper, with Toki and Quetena contributing ～88 % of these resources. Mineralization in these deposits is associated with tonalite porphyries that intruded andesites and dacites of the Collahuasi Group and intrusions of the Fortuna–Los Picos Granodioritic Complex. Hypogene mineralization in the Toki cluster consists mainly of chalcopyrite–bornite with minor molybdenite with mineralization grading outward to a chalcopyrite–pyrite zone and ultimately to a pyrite halo. Alteration is dominantly of the potassic type with K-feldspar and hydrothermal biotite. Sericitic alteration is relatively restricted to late quartz–pyrite veins (D-type veins). Previous K–Ar geochronology for the cluster yielded ages within a range of 34 to 40 Ma. Four new Re–Os ages for Toki indicate that molybdenite mineralization occurred in a single pulse at ～38 Ma. Re–Os ages for three different molybdenite samples from Quetena are within error of the Toki mineralization ages. These ages are concordant with a new zircon U–Pb age of 38.6?±?0.7 Ma from the tonalite porphyry in Quetena. Two Re–Os ages for Genoveva (38.1?±?0.2 and 38.0?±?0.2 Ma) are also within error of the Toki and Quetena molybdenite ages. Four Re–Os molybdenite ages for Opache range between 36.4 and 37.6 Ma. The Miranda prospect is the youngest with an age of ～36 Ma. Four new Re–Os ages for the Chuquicamata deposit range between 33 and 32 Ma, whereas nine new ⁴⁰Ar/³⁹Ar ages of biotite, muscovite, and K-feldspar range between 32 and 31 Ma. Analyzed molybdenites have Re and Os concentrations that vary between 21–3,099 ppm and 8–1,231 ppb, respectively. The highest Re and Os concentrations are found in the Toki prospect. Three new ⁴⁰Ar/³⁹Ar ages for the Toki cluster are younger than the Re–Os mineralization ages. The age spectra for these three samples show evidence of excess argon and have similar inverse isochron ages of 35 Ma that probably reflect a late hydrothermal phyllic event. The new geochronological data presented here for the Toki cluster indicate that molybdenite mineralization occurred within a very short period, probably within 2 Ma, and synchronously (at ～38 Ma) in three mineralization centers (Toki, Quetena, and Genoveva). Furthermore, mineralization at the Toki cluster preceded the emplacement of the Chuquicamata deposit (35–31 Ma) and indicates that porphyry Cu–Mo mineralization occurred episodically over a period of several million years in the Chuquicamata district.     

Geology,mineralization, and fluid inclusion characteristics of the Chorukh-Dairon W–Mo–Cu skarn deposit in the Middle Tien Shan,Northern Tajikistan

The Chorukh-Dairon deposit is part of the metallogenic belt of WMo, CuMo, AuW, and Au deposits along the Late Paleozoic active continental margin of the Tien Shan. It is related to the Late Carboniferous multiphase pluton, with successive intrusive phases of early monzogabbro through monzonite-quartz monzonite to monzogranite and leucogranite, and the latest lamprophyre dikes. The deposit is an example of complex W–Mo–Cu magmatic-hydrothermal system related to magnetite-series shoshonitic igneous suite. It contains zones of W–Cu–Mo oxidized prograde and retrograde skarns, with abundant scapolite, plagioclase, K-feldspar, andradite garnet, magnetite, as well as molybdoscheelite and minor chalcopyrite, and molybdenite. Skarns are overprinted by hydrosilicate alteration assemblages, with amphibole, chlorite, epidote, quartz, calcite, scapolite, albite, scheelite, and chalcopyrite, and are cut by quartz-carbonate-barite-fluorite-sulfide veins.The fluid evolution included a release of high temperature (~ 400–500 °C), high pressure (900–1100 to 700–800 bars), high salinity magmatic-hydrothermal aqueous chloride fluid, with its direct separation from crystallizing magma and formation of prograde and retrograde skarns. Fluid enrichment in Ca (up to 15–22 wt.% CaCl₂) at the retrograde skarn stage was possibly related to magmatic differentiation and provided intense molybdoscheelite deposition from a homogenous fluid. In contrast, hydrosilicate alteration assemblages were formed at lower temperatures (~ 350–400 °C) initially from a homogenous and then from a boiling Ca-rich (20–22 wt.% CaCl₂) magmatic-hydrothermal fluid, with the latter contributing to the most intense scheelite deposition. The stable isotope data (δ¹³C_CO2 = − 3.0 ± 0.5‰ and δ¹⁸О_H2O = + 6.5 ± 0.5‰, δ³⁴S = + 7.5 to + 7.7‰) obtained for the hydrosilicate stage minerals suggest significant fluid sourcing from magmatic and meteoric waters as well as from sedimentary rocks enriched in seawater sulfate, possibly evaporites, although a strongly homogenous character of the isotopic composition reveals intense isotope homogenization in a magmatic chamber. Some light sulfur isotope enrichment of sulfides from the quartz-carbonate-barite-fluorite-sulfide veins (δ³⁴S = + 6.0 to + 6.1‰) may be linked to the evolution of the magmatic source toward more mantle-related sulfur species, as these veins were formed after emplacement of the late mafic (lamprophyre) dikes.     

Fault tectonics,neotectonic stresses,and hidden uranium mineralization in the area adjacent to the Strel’tsovka Caldera

The scheme of recent fault tectonics and neotectonic stresses of the area adjacent to the Strel’tsovka Caldera in the southeastern Transbaikal region has been compiled for the first time on the basis of structural and geomorphic study. The faults were ranked by criteria of slip direction stability along separate segments and their expression in topography. Neotectonic stresses of corresponding ranks were ascertained as well. The heterogeneity of neotectonic stress field is related to the mosaic development of compression, extension, and the three-axial stress state. Comparison of morphogenetic features of recent and older faults shows the different character of the deformation mechanism and orientation of tectonic displacements. It has been established that the Strel’tsovka Caldera and its northwestern segment, in particular, developed as an echeloned system of pull-apart grabens, but the caldera itself is situated in a recent rise, whereas the northwestern segment is located in a neotectonic depression corresponding to the Dry Urulyungui Basin filled with volcanic and sedimentary rocks. Such a structure markedly expands the outlook for discovery of hidden uranium mineralization in the studied area. The elaborated scheme of neotectonic faults and stresses reflects the postore geodynamic setting and completes the reconstruction of geodynamic conditions pertaining to the periods of preore preparation and ore-forming tectonomagmatic reactivation.     

Carboniferous magmatism and mineralization in the area of the Fuxing Cu deposit,Eastern Tianshan,China: Evidence from zircon U–Pb ages,petrogeochemistry, and Sr–Nd–Hf–O isotopic compositions

The newly discovered Fuxing porphyry Cu deposit is located in the Dananhu–Tousuquan arc, adjacent to the Tuwu–Yandong Cu deposits of Eastern Tianshan, in the southern Central Asian Orogenic Belt. The Fuxing deposit is hosted by volcanic rocks (basalt and dacite) in the Early Carboniferous Qi'eshan Group and Carboniferous felsic intrusions (plagiogranite porphyry, monzogranite, and quartz diorite). New SIMS zircon U–Pb dating indicates that the plagiogranite porphyry and monzogranite emplaced at 332.1 ± 2.2 Ma and 328.4 ± 3.4 Ma, respectively. The basalts are characterized by low SiO₂ contents (47.47–54.90 wt.%), a lack of Eu anomalies, strong depletion of Na, Ta, and Ti elements but positive Sr, U, and Pb anomalies, high Y (20.8–28.2 ppm) and HREE concentrations (Yb = 2.23–3.06 ppm), and relatively low (La/Yb)_N (2.20–3.92) values; the dacite samples have high SiO₂ contents (66.13–76.93 wt.%), clearly negative Eu anomalies, high Mg^# values (36–51), and high Y (41.8–54.9 ppm) and Yb (5.76–8.98 ppm) concentrations. The basalts and dacites exhibit similar signatures as normal arc rocks, and were considered to be derived from partial melting of mantle-wedge peridotite that was previously metasomatized by slab melts. In contrast, the plagiogranite porphyry, monzogranite, and quartz diorite show the same geochemical affinity with modern adakites, which are characterized by high SiO₂ contents (67.55–79.00 wt.%), minor negative to positive Eu anomalies, strong depletion of heavy rare earth elements (Yb = 0.17–1.19 ppm) and Y (1.86–10.1 ppm), positive K, Rb, Sr, and Ba but negative Nb, Ta, Th, and Ti anomalies, and high (La/Yb)_N ratios and Mg^# values. Moreover, these adakitic felsic intrusions display relatively high positive zircon ε_Hf(t) values (+ 11.4 to + 18.3), low ⁸⁷Sr/⁸⁶Sr (0.706080–0.711239), high ¹⁴³Nd/¹⁴⁴Nd (0.512692–0.512922) ratios, and consistent zircon δ¹⁸O values (4.41‰–5.48‰), suggesting that their parental magma were most likely derived from partial melting of the subducted oceanic crust followed by mantle peridotite interaction. Based on the whole-rock geochemical and Sr–Nd–Hf–O isotopic data, as well as detailed petrographic analyses, we further suggest that the Fuxing igneous rocks and associated porphyry Cu mineralization were generated by the northward subduction of the paleo-Tianshan oceanic plate beneath the Dananhu–Tousuquan island arc during the Early Carboniferous.     

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.     

Review of Mesozoic multiple magmatism and porphyry Cu–Mo (W) mineralization in the Yidun Arc,eastern Tibet Plateau

The Yidun Arc was formed in response to the westward subduction of Garze–Litang Ocean (a branch of Paleotethys) in the Late Triassic, where abundant porphyry Cu–Mo deposits (221–213 Ma) developed along the regional NW–SE sinistral faults and emplaced in the southern portion of the arc. The ore-related porphyries are mostly metaluminous or slightly peraluminous, belonging to shoshonitic high-potassium calc-alkaline I-type granites, with ε_Hf(t) values of −6.64 to +4.12. The ore-bearing magmas were probably derived from the partial melting of subduction-metasomatic-enriched mantle, with the contamination of underplated mafic materials. The Late Cretaceous (88–80 Ma) highly fractionated I-type granite belt and related porphyry Cu–Mo deposits and magmatic-hydrothermal Cu–Mo–W deposits occur along approximately N–S-trending faults in the Yidun Arc. This belt extended across the Yidun Arc and Garze–Litang suture zone to the north and across the Yangtze Craton to the south, intruding the Late Triassic porphyry belt. The ore-related porphyries are characterized by high silica and high total alkalis, with enrichment in large ion lithophile elements (LILEs; Rb, U and K) and depletion in high field strength elements (HFSE; Nb, Ta, P and Ti) and Ba. They have lower ε_Hf(t) values varying from −9.55 to −2.75, and significant negative Eu anomalies, indicating that the ore-bearing porphyritic magmas originated from ancient middle-upper crust. Two-stage magmatism and mineralization were superimposed in the Xiangcheng-Shangri-La district. Some ore deposits comprise two episodes of magmatism and associated mineralization such as both 207 ± 3.0 Ma granodiorite and 82.1 ± 1.2 Ma monzogranite intruded in the Xiuwacu deposit, causing Cu–Mo–W polymetallic mineralization. To date, 11 Late Triassic porphyry Cu deposits (e.g. the Pulang giant deposit with 5.1 Mt Cu), and five Late Cretaceous porphyry Cu–Mo (W) deposits (e.g. Tongchanggou Mo deposit with 0.59 Mt Mo) have been evaluated in the Xiangcheng-Shangri-La district. The continuity and inheritance of multiphase magmatism and the new understanding of superimposed mineralization will help to guide future exploration.     

Tectonics,magmatism, and mineralization of Circum–Balkash–Junggar area in the Central Asian Orogenic Belt

ABSTRACT

The Circum–Balkhash–Junggar area, including mostly Kazakhstan, NW China, Russia, Kyrgyzstan, Tajikistan, Uzbekistan, and Mongolia, occupies an important tectonic position of the Central Asian Orogenic Belt (CAOB) (Figure 1). Tectonically, this vast area records the complicated geodynamic processes, among which the most prominent stages are the formation of the U-shaped Kazakhstan Orocline and its interactions with adjacent Altai (Altay), Junggar (West Junggar, Junggar Basin, and East Junggar), and Tianshan orogenic collages in the Palaeozoic, bearing large-scale mineral deposits. The formation of the Late Palaeozoic mineral deposits is related to the tectonic evolution of the Devonian and Carboniferous–Permian volcano-magmatic arcs in the region. However, the link between the metallogeny and the evolution of the volcano-magmatic arcs is not well understood and existing geodynamic models have not explained satisfactorily the mechanism of the huge metallogenic belt. Therefore, this special issue focuses on the formation of the Late Palaeozoic porphyry Cu deposits and their link to the tectonic evolution of the Devonian and Carboniferous–Permian volcano-magmatic arcs with emphasis on comparative studies across the international borders.     

Geology,geochronology, and Hf isotope geochemistry of the Longtougang skarn and hydrothermal vein Cu–Zn deposit,North Wuyi area,southeastern China

The recently discovered Longtougang skarn and hydrothermal vein Cu–Zn deposit is located in the North Wuyi area, southeastern China. The intrusions in the ore district comprise several small porphyritic biotite monzonite, porphyritic monzonite, and porphyritic granite plutons and dikes. The mineralization is zoned from a lower zone of Cu-rich veins and Cu–Zn skarns to an upper zone of banded Zn–Pb mineralization in massive epidote altered rocks. The deposit is associated with skarn, potassic, epidote, greisen, siliceous, and carbonate alteration. Molybdenite from the Cu-rich veins yielded a Re–Os isochron age of 153.6 ± 3.9 Ma, which is consistent with U–Pb zircon ages of 154.0 ± 1.3 Ma for porphyritic monzonite, 154.0 ± 0.8 Ma for porphyritic biotite monzonite, and 152.0 ± 0.8 Ma for porphyritic granite. Geological observations suggest that the Cu mineralization is genetically related to the porphyritic biotite monzonite and porphyritic monzonite. All the zircons from intrusive rocks in the ore district are characterized by ε_Hf(t) values between − 13.41 and − 4.38 and Hf model ages (T_DM2) between 2054 and 1482 Ma, reflecting magmas derived mainly from a Proterozoic crustal source. Molybdenite grains from the deposit have Re values of 14.6–27.7 ppm, indicative of a mixed mantle–crust source. The porphyry–skarn abundant Cu and hydrothermal vein type Pb–Zn–Ag deposits in the North Wuyi area are related to the Late Jurassic porphyritic granites and Early Cretaceous volcanism, respectively. The Late Jurassic mineralization-related granites were derived from the crustal anatexis with some mantle input, which was triggered by asthenospheric upwelling induced by slab tearing during oblique subduction of the paleo-Pacific plate beneath the South China block, and the Early Cretaceous mineralization-related granitoids mainly from crust material formed within a series of NNE-trending basins during margin-parallel movement of the plate.     

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.     

Deciphering a multistage history affecting U–Cu(–Fe) mineralization in the Singhbhum Shear Zone,eastern India,using pyrite textures and compositions in the Turamdih U–Cu(–Fe) deposit

The ～200-km-long intensely deformed Singhbhum Shear Zone (SSZ) in eastern India hosts India’s largest U and Cu deposits and related Fe mineralization. The SSZ separates an Archaean cratonic nucleus to the south from a Mesoproterozoic fold belt in the North and has a complex geologic history that obscures the origin of the contained iron-oxide-rich mineral deposits. This study investigates aspects of the history of mineralization in the SSZ by utilizing new petrographic and electron microprobe observations of pyrite textures and zoning in the Turamdih U–Cu(–Fe) deposit. Mineralization at Turamdih is hosted in intensively deformed quartz–chlorite schist. Sulfides and oxides include, in inferred order of development: (a) magmatic Fe(–Ti–Cr) oxide and Fe–Cu(–Ni) sulfide minerals inferred to be magmatic (?) in origin; followed by (b) uranium, Fe-oxide, and Fe–Cu(–Co) sulfide minerals that predate most or all ductile deformation, and are inferred to be of hydrothermal origin; and (c) Fe–Cu sulfides that were generated during and postdating ductile deformation. These features are associated with the formation of three compositionally and texturally distinct pyrites. Pyrite (type-A), typically in globular–semiglobular composite inclusions of pyrite plus chalcopyrite in magnetite, is characterized by very high Ni content (up to 30,700 ppm) and low Co to Ni ratios (0.01–0.61). The textural and compositional characteristics of associated chalcopyrite and rare pyrrhotite suggest that this pyrite could be linked to the magmatic event via selective replacement of magmatic pyrrhotite. Alternatively, this pyrite and associated sulfide inclusions might be cogenetic with hydrothermal Fe-oxide. Type-B pyrite that forms elongate grains and irregular relics and cores of pyrite with high Co contents (up to 23,630 ppm) and high Co to Ni ratios (7.2–140.9) are interpreted to be related to hydrothermal mineralization predating ductile deformation. A third generation of pyrite (type C) with low Co, low Ni, and moderate Co to Ni ratios (0.19–13.93) formed during and postdating the ductile deformation stage overgrowing, replacing, and surrounding type-B pyrite. The textural evolution of pyrite parallels the tectonometamorphic evolution of the shear zone demonstrating grain elongation during progressive ductile deformation and prograde metamorphism, annealing at the peak metamorphic condition, porphyroblastic growth at the retrograde path and cataclasis following porphyroblastic growth. Compositional characteristics of hydrothermal pyrite and available geological information suggest that the U–Cu(–Fe) deposit at Turamdih might be a variant of the Fe oxide (–Cu–U–rare earth elements) family of deposits.     

Early Mesozoic tectono-magmatic activity and mineralization in Northeast China: evidence from Re–Os to U–Pb studies of the Taipingchuan porphyry Cu–Mo deposit in the Derbugan metallogenic belt

The Taipingchuan Cu–Mo deposit is a recently discovered large porphyry deposit located in the north of the Derbugan metallogenic belt of northeastern China. The geochronological data of the deposit yielded a Late Triassic zircon U–Pb age of 202 ± 6 Ma from a granodiorite porphyry that hosts the Cu–Mo mineralization. Measured Re–Os isotopes of seven disseminated molybdenite samples yielded an isochron age of 200 ± 5 Ma with mean square of weighted deviates of 2.7, while those of seven veinlet molybdenite samples also produced an isochron age of 200.1 ± 2.5 Ma and mean square of weighted deviates of 3.3. These isochron ages show that a Cu–Mo mineralization event occurred at ca. 200 Ma. Based on regional tectonic evolution, we propose that the Late Triassic Cu–Mo mineralization of the host porphyry in the Derbugan metallogenic belt was mainly associated with the subduction of the Mongol–Okhotsk Ocean slab under the Ergun block, contrary to previous suggestion that it was related to the subduction of the Mesozoic Palaeo-Pacific plate.     

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.     

Multi-stage Ag–Bi–Co–Ni–U and Cu–Bi vein mineralization at Wittichen,Schwarzwald, SW Germany: geological setting,ore mineralogy,and fluid evolution

The Wittichen Co–Ag–Bi–U mining area (Schwarzwald ore district, SW Germany) hosts several unconformity-related vein-type mineralizations within Variscan leucogranite and Permian to Triassic redbeds. The multistage mineralization formed at the intersection of two fault systems in the last 250 Ma. A Permo-Triassic ore stage I with minor U–Bi–quartz–fluorite mineralization is followed by a Jurassic to Cretaceous ore stage II with the main Ag and Co mineralization consisting of several generations of gangue minerals that host the sub-stages of U–Bi, Bi–Ag, Ni–As–Bi and Co–As–Bi. Important ore minerals are native elements, Co and Ni arsenides, and pitchblende; sulphides are absent. The Miocene ore stage III comprises barite with the Cu–Bi sulfosalts emplectite, wittichenite and aikinite, and the sulphides anilite and djurleite besides native Bi, chalcopyrite, sphalerite, galena and tennantite. The mineral-forming fluid system changed from low salinity (<5 wt.% NaCl) at high temperature (around 300°C) in Permian to highly saline (around 25 wt.% NaCl + CaCl₂) at lower temperatures (50–150°C) in Triassic to Cretaceous times. Thermodynamic calculations and comparison with similar mineralizations worldwide show that the Mesozoic ore-forming fluid was alkaline with redox conditions above the hematite–magnetite buffer. We suggest that the precipitation mechanism for native elements, pitchblende and arsenides is a decrease in pH during fluid mixing processes. REE patterns in fluorite and the occurrence of Bi in all stages suggest a granitic source of some ore-forming elements, whereas, e.g. Ag, Co and Ni probably have been leached from the redbeds. The greater importance of Cu and isotope data indicates that the Miocene ore stage III is more influenced by fluids from the overlying redbeds and limestones than the earlier mineralization stages.