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Remote sensing methods are a vital alternative for regional exploration surveys. Many ore deposits (e.g., epithermal, porphyry-related, volcanogenic massive sulphides, etc.) have distinct distribution patterns of alteration zones that can be used for recognizing this mineralization. Several known goldfields are distributed within the basement rocks of western Nigeria. The area of interest, Malumfashi Schist Belt, is located in North-Western Nigeria and is characterized by gneisses and metasediments that were intruded by Pan-African granitoids. Gold mineralization occurs as veins and veinlets that are associated with hydrothermal alteration zones (i.e., argillic, phyllic, and propylitic). Hence, the discrimination of these alteration zones is one of the key indicators for new prospective zones of gold mineralization in this metallogenic belt. In the present study, Landsat Enhanced Thematic Mapper+ (Landsat-7 ETM+) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data were processed and integrated with the aim to identify possible locations for gold mineralization within the Malumfashi Schist Belt. For this purpose, the band ratio techniques and Principal Component Analysis (PCA) were applied to identify, enhance and map the different alteration types, while fractal analysis was utilized to quantify the degree of alteration within each processed image. Using the multi-criteria evaluation method, the discretized images obtained from the fractal analysis were weighted and integrated into an enhanced possible location for gold occurrences. A receiver operating curve/Area under curve analysis was then used to evaluate the reliability of the predictive model. Both spatial and GIS analyses indicate that gold mineralization displays a proximal relationship to hydrothermal alteration data. We can map sets of alteration minerals which mainly represent new and good ore prospects for the investigated area. A sensitivity analysis points out a predictive accuracy of 78%, which suggests the model is capable of predicting gold occurrences within the study region. Besides, the results showed that the prospective zones of gold accumulations mainly occur within metasedimentary units. It is recommended that the studied dataset provide a potential tool for mapping alteration minerals related to gold deposits that can be applied in other regions with analogous geological setting.

Precambrian iron oxide copper-gold (IOCG) deposits are generally encountered with multistage hydrothermal overprints and hence have complex isotopic records. Precise dating of ore-forming and overprinting events and assessment of time-resolved metal sources are fundamental for understanding ore genesis. Here, we quantify the evolution history by integrating in situ U-Pb dating of texturally constrained allanite and Sm-Nd isotope data of ores and major rare earth element (REE) minerals in the breccia-hosted Lanniping Fe-Cu deposit in Kangdian region, southwestern China. The economically mineralized breccia in Lanniping Fe-Cu deposit is characterized by pervasive and texturally destructive replacement of polymictic clasts, including host metasedimentary packages, the intruded dolerite, and pre-ore halokinetic breccia. Ore minerals in cements are mainly composed of magnetite, chalcopyrite, bornite, and variable amounts of REE-rich minerals (e.g., apatite and allanite/epidote). Two types of allanite were identified in ores. Type I prismatic allanite texturally intergrown with magnetite has a SHRIMP U-Pb age of 1728 ± 20 Ma (1σ), which matches a zircon U-Pb age of 1713 ± 14 Ma (2σ) for the dolerite clasts and provides the direct age constraint on the Fe-Cu mineralization event. Type II anhedral allanite shows complex zoning and is spatially associated with, but texturally later than, magnetite, apatite, and chalcopyrite. This type of allanite yields significantly younger SHRIMP dates of 1015 ± 33 (1σ) and 800 ± 16 Ma (1σ) for cores and rims, respectively, which correspond to discrete regional magmatic events and hence record hydrothermal overprint/remobilization events of ore minerals in the deposit. Integrated Sm-Nd isotope compositions of type I allanite, apatite, and whole ores generally align along the reference Sm-Nd isochron of 1728 Ma, further confirming the primary ore formation at ~1.7 Ga. Corresponding εNd(1728 Ma) values ranging from –2.8 to 0.3 are significantly higher than those of the host metasedimentary rocks (–9.5 to –6.2) but comparable to those of contemporaneous igneous intrusions (–0.3 to 5.3) in the region, demonstrating that REE components of the primary ores were dominantly sourced from rocks of mantle-derived affinity. Both cores and rims of the younger type II allanite grains have Nd isotope compositions consistent with the unique time-evolved line of the ~1.7 Ga ores, implying that REEs incorporated into type II allanite were ultimately sourced from the primary ores in this deposit. The combined texture, chemical, U-Pb, and Sm-Nd isotope data thus demonstrate that REE remobilization was localized during post-ore hydrothermal overprint with negligible external inputs of REEs to the primary ores in the Lanniping deposit. In this contribution, we not only date primary ore formation but also recognize several younger allanite generations that record internal metal redistributions in response to post-ore tectonothermal events. Our study highlights the potential of ore-associated REE minerals such as allanite for resolving the age of multiple stages of hydrothermal events in complex ore deposits by ion probe, provided that careful examination of textural and paragenetic relationship of ores is conducted. Our finding of these younger allanite generations also exemplifies the significance of evaluation on time-resolved metal input for better characterizing the evolution history of the IOCG deposits.

The Golden Mile fault zone is a key controlling structure to the estimated 75 Moz gold endowment of the Kalgoorlie gold camp in the Yilgarn craton of Western Australia. The earliest structures in the fault are F1 folds that developed during D1 recumbent-fold and thrust deformation (

How to more effectively perform anomaly detection of combination information has always been an important issue for the scholars in various fields. In order to identify and extract the geochemical anomaly information related to polymetallic mineralization in the Hunjiang area, this article uses the hybrid method that combines multivariate canonical harmonic trend analysis (MCHTA), singularity analysis with radius-areal metal amount and improved adaptive fuzzy self-organizing map (IAFSOM). First, multiple sets of combination feature information with multi-dimensional variables will be obtained through the MCHTA method, which information is considered as the initial information for the subsequent analysis. Next, the singularity analysis method is used to process the combination concentration value to calculate the singularity indexes. Finally, the singularity indexes are classified by the IAFSOM method, and nine groups of sample data are obtained. The analysis results found that the samples information in fourth group covered most of the low α-values. The main conclusions in this study are as follows: (1) The MCHTA method can effectively detect the combination information related to geochemical anomaly; (2) The application of singularity analysis method with radius-areal metal amount can reveal the significant characteristics of mineralization combination elements; (3) IAFSOM can be used as an effective tool for the classification and identification of geochemical anomaly with combination information; (4) the hybrid method that combines MCHTA method, singularity analysis and IAFSOM model has a good indication significance in the prospecting of geochemical anomalies, and could provide a good method for geochemical prospecting.

In the central Taupo Volcanic Zone, extensive zeolite (mordenite ± clinoptilolite) alteration occurs in late Quaternary rhyolitic vitric tuffs that were deposited in a lake formed by caldera collapse following the ~290 ka Ohakuri ignimbrite eruptions. Glass shards in lacustrine vitric tuffs of the Ngakuru Formation and in the underlying Ohakuri Formation ignimbrite are replaced by mordenite ± clinoptilolite, along with hydrothermal adularia, opal-A, opal-CT, and cristobalite. This mineral assemblage is also found in the outer alteration zones of the nearby Ohakuri and Tahunaatara epithermal gold prospects. Evaluation of whole-rock chemical analyses indicates that the zeolitized vitric tuffs show a slight gain in K, and Na, Ca loss relative to unaltered Ohakuri Formation pumice, which is reflected in the presence of hydrothermal adularia in the alteration assemblage. The mordenite ± clinoptilolite alteration is associated with siliceous sinters and hydrothermal eruption breccias that were formed in recently active (39–1.5 ka) geothermal systems. By analogy with geothermal systems elsewhere in the Taupo Volcanic Zone at Wairakei and Ohaaki, the mordenite ± clinoptilolite alteration was formed from dilute alkali-chloride aqueous liquid at 60° to 150°C. Based on the close association of the mordenite ± clinoptilolite alteration with siliceous sinters and hydrothermal eruption breccias in the central Taupo Volcanic Zone, it is classified as shallow, low-temperature, epithermal alteration. Mordenite ± clinoptilolite alteration has also been identified in Quaternary rhyolitic caldera settings in Japan and the United States, where it is termed “caldera-type zeolitization.” In exploration for epithermal Au-Ag deposits in rifted arc settings, such alteration may be overlooked, given its subtle appearance and distal location relative to veins that mark upflow areas.

The Laowan super-large (208 t Au) gold deposit is located in the Tongbai orogenic belt, along with a newly-discovered molybdenite deposit at its depth in the northern periphery. The gold deposit is a fault-controlled lode gold deposit featuring sulfide quartz vein-type and altered rock-type mineralization hosted within the metamorphic rocks, whereas the molybdenum deposit is a typical porphyry-type deposit. These two deposits have their respective paragenetic sequences and mineralization types without spatial overlapping in the ore field. Here, we present U–Pb dating of zircon, hydrothermal rutile, and REE phosphates, and Re–Os dating of molybdenite to constrain the relationship between the Au and Mo mineralization, and their relation to Mesozoic granitic magmatism. Textural features indicate that rutiles and associated phosphate minerals are of hydrothermal origin, generated by re-precipitation and dissolution of titanite crystals hosted in the metamorphic host rocks due to hydrothermal alteration during Au and Mo mineralization. LA-ICP-MS U–Pb dating of rutile from the auriferous altered rocks yields a 206Pb/238U age of 120.0 ± 6.7 Ma (MSWD = 1.4), consistent with the ages of the associated monazite (125.0 ± 2.4 Ma) and xenotime (126.3 ± 2.0 Ma), representing the timing of the gold mineralization, coeval with Laowan monzogranite (zircon U–Pb: 128.8 ± 0.7 Ma). Rutile from the molybdenum deposit show an older 206Pb/238U age of 141.0 ± 11 Ma (MSWD = 1.1), consistent with the molybdenite Re–Os age (141.5 ± 1.7 Ma; MSWD = 0.27) and the zircon U-Pb age (141.6 ± 0.8 Ma; MSWD = 1.5) of the Songpa porphyry. Hence, the Au and Mo mineralization in the Laowan district represent two episodic mineralization events related to the late Mesozoic granitic magmatism. Our study also suggested that multiple isotopic dating is helpful to precisely constraint the ages for complex hydrothermal deposits.

The late Palaeozoic Yong’an–Meizhou depression belt is an important iron (Fe) and polymetallic metallogenic belt in southern China. It has undergone a transformation from Tethys to the circum-Pacific tectonic domain. The Luoyang deposit is one of the typical Fe skarn deposits in the Yong’an–Meizhou depression belt of eastern China. Garnet is a characteristic mineral in the deposit. Two generations of garnets are detected in the deposit based on their textural characteristics and trace-element contents, and are represented by Fe-enriched andradite. The first generation of garnets (Grt1) have two types of garnets (Grt1-A and Grt1-B). Type A garnets of the first generation (Grt1-A) (Adr80-88) replaced by massive diopside-magnetite assemblage exhibit distinct oscillatory zonings and display patterns of enriched light rare earth elements (LREE) to weak heavy rare earth elements (HREE), with weak negative to positive Eu anomalies, and highest U, ΣREE and Sn contents. Type B garnets of the first generation (Grt1-B) are irregular zones (Adr94-96) coexisting with magnetite, in which Grt1-A is generally dissolved, and have obviously LREE-enriched and HREE-depleted patterns, with weak negative to positive Eu anomalies, and moderate U, ΣREE and Zn contents. Garnets of the second generation (Grt2) (Adr96-99) that replaced massive magnetite together with sphalerite show unzoned patterns, with a flat REE pattern and pronounced negative Eu anomalies as well as contents of lowest U and ΣREE, and highest W. The substitution of REEs in garnets occurs as [X2+]VIII –1[REE3+]VIII +1[Si4+]IV –1[Z3+]IV +1in an Al-enriched environment. Luoyang hydrothermal fluids shifted from reducing conditions with relatively high-U and -ΣREE characteristics to oxidizing conditions with relatively low-U and -ΣREE characteristics. The reduced siderophile elements and increased fO2 in fluid during Grt1-B formation caused magnetite mineralization and reduced Zn contents during Grt2 formation, causing the deposition of sphalerite. All garnets formed from magmatic fluid and were controlled by infiltrative metasomatism in an opened system.

Research subject. Large orogenic gold deposits in the fold belts of Central and Northeast Asia.Materials and methods. Geological mapping of various scales on a number of large orogenic gold deposits was conducted using the methods of structural-paragenetic analysis of metamorphic strata, accompanied by obligatory linking of ore mineralization manifestations to specific structures. In a number of cases, various statistical methods were used to geometrize mineralization, identify patterns of its location and determine the paths of paleofluid flows. Available publications on the objects under consideration were reviewed. The geological and structural features of large orogenic gold deposits – Muruntau, Kokpatas, Sukhoi Log and Pavlik – were considered.Results. The Muruntau, Kokpatas and the Sukhoi Log ore deposits are of shariyage-thrust type. Compared to these objects, the Pavlik field is confined to a zone of volumetric fracturing between a series of reverse faults, feathering a large deep fault and belonging to the transpression type. At the Muruntau and Pavlik deposits, the analysis of the location of the most intensive mineralization substantiated the paths of paleofluid flows, along which the fluid migration and ore formation took place.Conclusions. The distribution of ore mineralization in the Muruntau deposit obeys the orientation of planar (cleavage) and linear (orientation of fold hinges) elements. Apparently, the former (main) direction may indicate the orientation and position of the main migration route of ore-bearing fluids, while the latter corresponds to secondary channels, the position of which is due to the intersection of syn-napping structures with favourable lithological horizons. For the Pavlik deposit, the position of ore pillars is compared with the paths of paleofluid flows, the root parts of which are promising for identifying the most powerful and intense mineralization.

Research subject. The petrological and geochemical features of the rocks of the Voznesensky intrusive massif and its dyke series were studied in order to clarify the composition, possible sources and geodynamic settings of magma generation that produced Au- and Cu-porphyry mineralization.Methods. The content of petrogenic oxides was determined by the chemical method, trace elements – by ICP-MS analysis.Results. Among the rocks of the Voznesensky massif, which have the geochemical characteristics of suprasubduction formations, varieties with calc-alkaline and adakite-like properties were established. The main phase of the massif is represented by gabbro-diorites and diorites belonging to the calc-alkaline series. Ore-bearing dykes of gabbro-diorites, diorites and granodiorites of the Au-porphyry Bolshekaransky deposit are of calc-alkaline composition, while the post-ore dykes of granodiorites and plagiogranites of this deposit exhibit adakite-like characteristics.Conclusions. The ore-bearing dyke series of the Voznesensky deposit is represented by calc-alkaline diorites and adakite-like granodiorites and plagiogranites. The metallogenic specialization of the dykes was influenced by the silicic acidity and the redox state of the ore-generating melts. Granitoids with Cu-porphyry mineralization, compared to their gold-bearing varieties, crystallized from more acidic melts with a higher degree of oxidation. It is assumed that the main mantle component of magmas for the Voznesensky rocks were relatively weakly depleted spinel peridotites of the suprasubduction lithospheric mantle. Calc-alkaline magmas were melted from a mantle substrate previously metasomatized by aqueous fluids, and magmas with adakite-like properties – metamorphosed by melts of basalts and sedimentary rocks of slab. Melting of slab rocks may have been associated with additional heating due to friction caused by changes in direction and/or velocity of oblique subduction.

Genesis of magmatic Ni-Cu-(PGE) deposits involves many interconnected and multiple-scale processes in the fields of thermodynamics, kinetics and fluid dynamics. The main focus of quantitative work on magmatic sulfide ore genesis has been on equilibrium thermodynamics since the initial studies over 50 years ago, while the significance of kinetics and dynamics to sulfide mineralization in dynamic magmatic systems has received little attention. Taking the komatiite-hosted Ni-Cu-(PGE) deposits of the Raglan area as an example, we have developed a quantitative model for assimilation of sulfidic substrates during lava emplacement through the consideration of these three fields. We show that the dominant control on the composition of externally derived sulfide xenomelts throughout their residence within the flowing magma is exerted by relative rates of diffusion of sulfur and metals. In rapid channelized flow of komatiites, the kinetically-controlled extraction of chalcophile elements from silicate melt into externally-derived sulfide droplets released from underlying sediments is the quickest way to produce orebodies with economic value, without the necessity of reaching either sulfide saturation throughout the mass of magma or indeed compositional equilibrium in the magmatic system as our long-held understanding would suggest. The kinetic upgrading of initially metal-poor sulfide xenomelts is enhanced for sulfide droplets of smaller size and increasing downstream distance from the source, approaching to equilibrium mass distribution for the fast-diffusing elements such as Cu during prolonged or especially vigorous processes (e.g., chaotic magma mixing). In this kinetically-driven process, differences in diffusivities between Pt and Pd may account for the anomalous excess Pd/Pt ratios (~2) of disseminated ores from many komatiite-related deposits compared with the compositions of the parental magmas. Sedimentation of sulfide on the bottom of the flowing magma terminates this kinetically-controlled process, while the number density of droplets imposes a restriction on sulfide compositions due to mass conservation. Therefore, sulfide mineralization in komatiite-associated deposits is mostly controlled by diffusion kinetics with additional interactions and restrictions from the dynamics of transport and settling of sulfide droplets. By analogy, multiple cycles of dynamic processes predominate in the conduit-type magmatic deposits. A quantitative grasp of the relative importance of these three fundamental mechanisms, i.e., thermodynamic driving forces, kinetics of diffusive equilibration, and fluid dynamics of transport and deposition, is of great value in understanding ore genesis in complex mineral systems and even the origin of igneous rocks in general.

Weakly disseminated sulphide mineralization is present in the outcrops of several mafic–ultramafic intrusions in the Beishan region of the Central Asian Orogenic Belt in western China, but the pote...

Magmatism in northern Colorado beginning in the late Eocene is associated with the formation of Pb-Zn-Ag carbonate-replacement and polymetallic vein deposits, the onset of caldera-forming magmatism, and eventually, the formation of rift-related, F-rich Mo porphyries (“Climax-type” intrusions). We use high-precision U/Pb zircon geochronology to better evaluate the temporal framework of magmatism and mineralization in the region. Our results demonstrate that mineralization in the Leadville area occurred between 43.5 and 39.7 Ma and was followed by mesothermal mineralization in the Montezuma area at approximately 38.7 Ma. Mineralization is associated with a suite of approximately 43 to 39 Ma intermediate magmatic centers that extended from Twin Lakes through Montezuma. The oldest porphyries associated with F-rich Mo prospects and deposits (Middle Mountain; 36.45 Ma) intruded 900 kyr after the start of the ignimbrite flare-up in the region. Spatiotemporal analyses reveal that the pattern of magmatism shifted in orientation between 40 and 35 Ma. We propose a model wherein magmatism before 39 Ma was the result of fluids evolved from the subducted Farallon slab being focused through weak zones in the lithospheric mantle and into the lower crust. This was followed by a more diffuse and higher power melting event that corresponds to a distinct change in the spatial patterns of magmatism. Our data suggest that low-grade Mo porphyry deposits can form close in time to calderas. We hypothesize that the transition from subduction to extensional tectonics in the region was responsible for this more widespread melting and a distinct shift in the style of magmatic-hydrothermal mineralization.

The Kapalagulu intrusion in eastern Tanzania hosts a major, 420-m-thick, stratiform/stratabound platinum group element (PGE)-bearing sulfide zone—the Lubalisi reef—within a prominent, chromititiferous, harzburgite unit close to its stratigraphic base. Several features of the vertical base and precious metal distributions (in a composite stratigraphic section based upon two deep exploration drill holes) display similarities to those of offset-type PGE reefs that formed under the overall control of Rayleigh fractionation: (1) composite layering (at several scales) defined by systematic vertical variations of sulfide and precious metal contents and intermetallic ratios, indicating repeated cycles of PGE enrichment and depletion in the order Pd-Pt-Au-Cu, and (2) in the lower part of the reef, stratigraphic offsets of the precious metal peaks below peak sulfide (Cu) content. The form and geochemistry of the reef are consistent with overturns of basal liquid layers within a liquid layering system (i.e., stable density-driven stratification of a magma chamber), plus at least two minor inputs of parental magma during which the resident magma was recharged with sulfur and metals, and the effective depletion of precious metals in the magma midway through reef development. The Lubalisi reef differs from classic offset-type PGE reefs, however, principally because individual Pd, Pt, and Au enrichment peaks are coincident, not offset. The reef is set apart from other offset-type PGE reefs in three additional ways: (1) its association with olivine cumulates that crystallized soon after initial magma emplacement and well below the first appearance of cumulus pyroxene or plagioclase (implying attainment of sulfide saturation and precious metal enrichment without prolonged concentration of sulfur and chalcophile metals by normal magma cooling and differentiation), (2) the probable role of chromite crystallization in not only triggering sulfide segregation during reef formation but also facilitating precious metal enrichment in the early stages of reef development, and (3) its great width. The early stage of fractionation may also help explain the coincident precious metal peaks through its effect on apparent precious metal partition coefficients.

We present new age constraints for igneous rocks and ore-metasomatic formations of the gold deposits in the Akzhal-Boko-Ashalin ore zone. In terms of their ore formation, these deposits correspond mainly to the orogenic type, which generally reflects specific metallogeny of the West Kalba gold-bearing belt in East Kazakhstan. Gold-quartz veins and mineralized zones of the gold-sulphide formation are confined to fractures feathering regional NW-striking and sublatitudinal faults. Their common features include the following: gold-bearing veinlet-disseminated pyrite-arsenopyrite ores that are localized in carbonaceous-sandy-schist and turbidite strata of different ages; structural-tectonic control of mineralization, numerous dikes of medium-basic compositions in ore-control zones; and the presence of post-orogenic heterochronous granite-granodiorite rocks, although their relation to gold-ore mineralization is not obvious. Igneous rocks of the study area have similar ages in a narrow range from 309.1±4.1 to 298.7±3.2 Ma, which is generally consistent with the previously determined age of granitoid massifs of gold-ore fields in East Kazakhstan. A younger age (292.9±1.3 to 296.7±1.6 Ma) is estimated for felsic rocks of the dyke complex. For the ore mineralization, the 40Ar/39Ar dating of sericite from near-ore metasomatites yields two age intervals, 300.4±3.4 Ma and 279.8±4.3 Ma. A gap between of the ages of the ore mineralization and the igneous rocks is almost 20 Ma, which may indicate that the processes of ore formation in the ore field continued in an impulse-like pattern for at least 20 Ma. Nevertheless, this confirms a relationship between the hydrothermal activity in the study area and the formation and evolution of silicic igneous rocks of the given age interval, which belong to the Kunush complex, according to previous studies. This interpretation is supported by reconstructed tectonic paleostress fields, showing that directions of the main normal stress axes changed during the ore mineralization stage, which is why the ore bodies significantly differ in their orientations. The above-mentioned data are the first age constraints for the study area. Additional age determinations are needed to further improve understanding of the chronology of ore-forming processes. Actually, all the features characterizing the gold mineralization of the Akzhal, Ashalin and Dauba ore fields, including the data on lithology, stratigraphy, structural tectonics, magmatism, isotope geochronology, mineralogy and geochemistry, can be used as criteria when searching for similar ore fields in East Kazakhstan.

The Bayan Obo ore deposit in Inner Mongolia, North China, the largest-known rare earth element (REE) deposit in the world, has attracted considerable attention over the past decades. However, its genesis has been highly debated, especially whether the host dolomite is of sedimentary or igneous origin. In this study, we present a comprehensive study on field geology, petrographic, geochemical, and apatite fission track analyses on REE-mineralized dolomite (H8) and its wall-rock (H9), in an effort to provide additional insights into the formation and preservation of this giant ore deposit. According to field geology and petrology analyses, the ore-hosted dolomite of the H8 unit in/around the Bayan Obo deposit displays the characteristics of sedimentary carbonates and demonstrates complicated deformation and hydrothermal events that resulted in the complex REE mineralization. The parameter of w(As) in pyrite ranging from 100 to 1600 ppm suggesting that the pyrite of the Bayan Obo deposit was mainly formed in a hydrothermal environment, and the thermal event from pyrite at ~440 Ma may represent the mineralization event of the Bayan Obo deposit, or it is an important disturbance event after the mineralization of the deposit. The geochemical research depicts that the evolution process of carbonatite was originated from calcium carbonatites and magnesio-carbonatites to ferro-carbonatite, indicating that the different genesis models of the Bayan Obo deposit that ranging from sedimentary carbonate to volcano-sedimentary and igneous carbonatites are reasonable. The two apatite ages obtained from granite on the east side of the Bayan Obo deposit and the dolomite in the Bayan Obo deposit are ~173 Ma and ~54 Ma, respectively. Time–temperature (t–T) histories of rocks yield new information about the timing of deformation of the Bayan Obo deposit, implying that the east side of the deposit experienced a rapid cooling process between ~300 Ma to ~54 Ma (especially ~300–180 Ma), this reflects the granite underwent a rapid cooling process which coeval with the plate subduction during the closure of the Palaeo-Asian Ocean, while the tectonic movement has little effect on the broken of the H8 dolomite in the mining area. Although the slate of the H9 unit from the east of the Bayan Obo deposit experienced a strong fragmentation in the later tectonic movement, it still made a great contribution to the mineralization for better preservation of REE-rich fluids, leading to the formation of the giant Fe-REE-Nb deposit.

The Hehuashan sediment-hosted Pb–Zn deposit is a large-scale (Pb + Zn＞1 Mt) deposit hosted in the Tongling mining district of the Middle-Lower Yangtze River belt (MLYB). The Pb–Zn ore bodies are composed of two main mineralization types, namely breccia type and massive type. The breccia type ore bodies are hosted by the Triassic limestone and dolostone, while the massive ore bodies are hosted by marble dolostone which are close to the diorite intrusions. The previous research showed that the Hehuashan Pb–Zn deposit is a Mississippi Valley-type (MVT) deposit formed in Middle Triassic and overprinted by late mineralization of magmatic-hydrothermal fluids in Yanshanian period. In this research, we aimed to declare the age of the late mineralization and it's relationship with diorite intrusions. The mineralization age (132.8 ± 3.1 Ma) of the massive ore rocks (late mineralization) is similar to the zircon U–Pb age of the diorite (133–130 Ma), showing that this type mineralization is contemporaneous to the Yanshanian intrusive events. Furthermore, similar initial 87Sr/86Sr values between sphalerite and diorite indicating a magmatic fluid was involved during the mineralization process and the emplacement of diorite also might have provided ore-forming materials. The heavy sulfur compositions (δ34S = +8.6‰ to +12.8‰) of the sphalerite in massive ore rocks indicate that the sedimentary sulfate may have provided reduced sulfur for sulfides precipitation by sulfate thermochemical reduction process. Sr–Nd isotopic compositions of the diorite in the Hehuashan deposit area showed that the massive Pb–Zn mineralization was related to the intrusion of diorite in an extensional tectonic setting. In summary, the Hehuashan Pb–Zn deposit composes a late Yanshanian Pb–Zn mineralization event and represents a younger Pb–Zn mineralization in the Tongling district and MLYB. The Triassic carbonates have the potential for Pb–Zn deposit exploration in the Tongling district and Middle–Lower Yangtze River belt.

A mechanism is suggested to explain the transport of sulfide material by means of its dissolution and subsequent redeposition under the effect of an ascending infiltrating flow of intercumulus melt during the compaction of cumulates in layered plutons. Evidences of this process are observable in the Burakovo–Aganozero intrusion. Analysis of data on Cu concentrations in rocks of the pluton (more than 10 000 samples of core material from 160 boreholes) reveals two distribution types of the low-sulfide mineralization. The vertical sections of the first type are characterized by mineralization distributed throughout the whole thickness of the lower unit of clinopyroxene–orthopyroxene (Cpx–Opx) cumulates and the almost absolute absence of sulfides in all overlying rocks. In the second type, Cu mineralization is constrained to the top part of this unit of clinopyroxene–orthopyroxene (Cpx–Opx) cumulates, and the overlying rock sequence of the zone of clinopyroxene–orthopyroxene–plagioclase (Cpx–Opx–Pl) cumulates includes intensely mineralized rocks. Physicochemical analysis within the scope of D.S. Korzhinskii’s theory of acid–basic interaction and numerical simulations of the effects of major components of the melt on the solubility of the sulfide phase indicate that Ca and Mg play an important role in the liquid immiscibility/dissolution of the sulfides. A model is proposed for the origin of the low-sulfide mineralization of this pluton: clinopyroxene emergence on the liquidus resulted in the onset of liquid immiscibility of sulfide and produced Cu distribution of the first type. The infiltration of the intercumulus melt during the compaction of the cumulus material led to the dissolution and upward transport of the sulfide material for hundreds of meters and thus produced Cu distribution of the second type.

In the Angara part of the Yenisei Ridge, a sequential section of the metapicritic–basalt sequence and overlying carbonate rocks of the Gorevskaya Formation is established. This section is considered as a single volcanic–sedimentary complex formed at the Late Mesoproterozoic–Early Neoproterozoic boundary in the riftogenic marginal–continental paleobasin in the southwestern Siberian Craton. It is proposed to introduce the metapicrite–basaltic sequence into the stratigraphic legend of the Shirokaya Group of the western Yenisei Ridge under the name “Nizhnerechinskaya Sequence”. In the studied section, metamorphosed picrobasalts and picrites predominate in the lower part of the Nizhnerechinskaya Sequence, while the middle and upper parts consist mainly of basalts containing Pb–Zn mineralization (Stepanovsky ore occurrence). At the contact with carbonate deposits of the Gorevskaya Formation, an alternation of volcanogenic rocks and terrigenous–carbonate sediments and metabasaltic sills are observed. The petrochemical and trace-element composition of metavolcanic rocks has much in common, which indicates the paragenetic relationship of rocks of this high-Mg rock association. All these rocks are enriched in Fe and Ti, while metabasalts and metagabbros show elevated alkalinity and P2O5 content. In terms of total alkalinity, metabasalt–picrobasalts deviate from the normal petrochemical series towards the subalkaline series, which correlates with their elevated Ti content. Basites enriched in alkalis, especially, in potassium and corresponding to trachybasalts are observed among them. The contents of incompatible trace elements clearly increase from picrites to basalts and reach maximum in trachybasalts, which show 1.5–3 times enrichment in high-field strength elements compared to the basalts. The paragenetic nature of the considered association is supported by the similar REE distribution patterns: (La/Yb)n = 6–7 at Eu/Eu* = 0.9–1. The Late Mesoproterozoic–Early Neoproterozoic rifting of the Earth’s crust in the Angara region led to the opening of the marginal–continental sea basin, where basalt-picrite volcanism occurred simultaneously with accumulation of terrigenous–carbonate sediments, including ore–bearing (Pb–Zn) rocks of the Gorevskaya Formation, which host the Gorevskoye Pb–Zn deposit. The basin under consideration is interpreted as a relict rift-related paleobasin on the western margin of the Siberian craton, while the volcanic–sedimentary Nizhnerechinskaya Sequence is considered as the lower potential stratigraphic level of the base-metal mineralization in the Gorevsky ore field.

In this work, mineralogical and geochemical data are presented for sulfide-rich phoscorites and carbonatites in the Kovdor massif. The PGE and Ag-bearing mineralization of bornite–chalcopyrite and Ag‑bearing mineralization of pyrrhotite–chalcopyrite associations were investigated. In carbonatite stage formation of massif, the noble metal minerals occurred during evolution of alkaline–ultrabasic melt and after separation of primary sulfide melt enriched in PGE, Au and Ag. According to the observed relationships, the minerals of PGE, Au, and Ag in bornite–chalcopyrite association are crystallized sequentially from magmatic to hydrothermal stages. Crystallization of Os, Ir, Pt and Pd minerals (erlichmanite, rustenburgite, isoferroplatinum, mertieite–II, etc.) occurred at temperature close to 480°С, while further decrease in the temperature and an increase in the Cu and Fe activity in the melt leads to the crystallization of Sb, Pb, As, Bi and Te-bearing minerals (sperrylite, tatyanaite, moncheite, stumpflite, etc.). Formation of Au and Ag-bearing minerals (electrum, silver, stromeyerite, lenaite, etc.) occurred at temperatures below 300 °C with relatively low sulfur activity. In carbonatites and phoscorites of the middle and late magmatic stages enriched with magnetite, pyrrhotite–chalcopyrite association with silver-bearing minerals was formed at temperatures below 300°C. Ag-bearing minerals were produced during hydrothermal recrystallization of Cu–Fe–Ni sulfides at temperature close to 150°C.

This study illustrates the application of a geometric average integration of aeromagnetic, radiometric and satellite imagery data over a region prone to Cu‐bearing mineralization at Chahargonbad area in Kerman province of Iran. Processing aeromagnetic, radiometric and Advanced Spaceborne Thermal Emission and Reflection Radiometer satellite data can provide exploratory insights about favourable zones in association with porphyry‐type ore occurrences, which can be synthesized through a combination of knowledge‐ and data‐driven approaches as a geometric average and be represented in a mineral prospectivity map. The existence of known deposits in a prospect region can facilitate the investigation of significant exploratory footprints extracted from airborne data by calculating each indicator layer's weight by plotting a prediction–area curve accompanied by a concentration–area fractal curve. Among various indicators, the most important ones are determined based on derived weights from the prediction–area plots to be synthesized in a single Cu favorability map. To fulfil this aim, indicator layers from airborne geophysics (magmatic bodies, magnetic lineaments and potassium radiometry) and remote‐sensing data (alterations such as argillic, phyllic, propylitic and iron oxide along with geological lineaments) were prepared and evaluated using the known porphyry Cu mineralization by the simultaneous plot of the concentration–area fractal model and the prediction–area curve to attain the ore prediction rate and the relevant occupied area of each map for weight assignment of indicators. The geometric average prospectivity model was applied to synthesize the leading indicators, and the result was compared with a multi‐class index overlay map. This study's significance lies in improvement of the performance of the mineral prospectivity/potential mapping after running a geometric average by a higher ore prediction rate of 79%, which has occupied 21% of the area as potential zones for further mining investigations.

Research subject. The gold-sulphide-quartz deposits of Central Chile are typical prospecting objects, having small ore intervals (from the first tens of centimetres to 1 m), intermittent and nested ore distribution and extremely uneven gold contents.Materials and methods. The patterns of ore mineralization distribution are considered against the background of the results of modern geophysical studies of the lithosphere: the Moho surface, density and thermal regime of the upper mantle. Detailed studies were conducted on the Yapin ore field.Results. It was shown that the faults controlling gold-sulphidequartz mineralization are derivatives of shear tectonics under the conditions of a transpression regime along the Chilean active margin. At an early stage, these faults developed in a right-shift environment, which was accompanied by the introduction of diabase dikes into the northeastern faults, and gold-sulfide-quartz mineralization superimposed on the dikes was deposited during the left-shift stage. The geological structure of the deposits in the ore field Yapin was characterized. It was shown that a diverse mineralization is developed in the ore field - copper-porphyry, IOCG-type and gold-sulphide-quartz. According to geochemical data, the latter is characterized by a clear enrichment of chalcophilic elements (Au, As, Ag, Cd, Cu, Bi, Pb, Zn, Te, Co). The marked enrichment of Bi, Te and Co ores indicates the participation of magmatic fluid in ore formation and the similarity of the mineralization of the Escondida deposit with the type of gold deposits associated with granitoid intrusions. According to geochemical features, gold-sulphide-quartz mineralization in the general zoning pattern occupies a boundary position between IOCG-type objects and copper-porphyry deposits.Conclusions. The conclusion is drawn about the independence of gold-sulphide-quartz mineralization and its difference from epithermal gold deposits. It is noted that, in the volcanic belts of the North-East of Russia, the prospects for discovering unconventional gold-sulphidequartz deposits similar to those of Central Chile are rather real.

The recently developed fluorite (U–Th)/He thermochronology (FHe) technique was applied to date fluorite mineralization and elucidate the exhumation history of the Mazandaran Fluorspar Mining District (MFMD) located in the east Central Alborz Mountains, Iran. A total of 32 fluorite single-crystal samples from four Middle Triassic carbonate-hosted fluorite deposits were dated. The presented FHe ages range between c. 85 Ma (age of fluorite mineralization) and c. 20 Ma (erosional cooling during the exhumation of the Alborz Mountains). The Late Cretaceous FHe ages (i.e. 84.5 ± 3.6, 78.8 ± 4.4 and 72.3 ± 3.5 Ma) are interpreted as the age of mineralization and confirm an epigenetic origin for ore mineralization in the MFMD, likely a result of prolonged hydrothermal circulation of basinal brines through potential source rocks. Most FHe ages scatter around the Eocene Epoch (55.4 ± 3.9 to 33.1 ± 1.7 Ma), recording an important cooling event after heating by regional magmatism in an extensional tectonic regime. Cooling of the heated fluorites, as a result of thermal relaxation in response to geothermal gradient re-equilibration after the end of magmatism, or exhumation cooling during extensional tectonics characterized by lower amount of erosion are most probably the causes of the recorded Eocene FHe cooling ages. Oligocene–Miocene FHe ages (i.e. 27.6 ± 1.4 to 19.5 ± 1.1 Ma) are related to the accelerated uplift of the whole Alborz Mountains, possibly as a result of the initial collision between the Afro-Arabian and Eurasian plates further to the south.

А new Vovchansk Uranium Ore district is allocated within the Orikhiv-Pavlohrad structural-metallogenic zone (SMZ) of the Azov metallogenic region. It is represented by Dibrova REE-U-Th deposit and a number of less studied ore occurrences. This deposit, according to ore mineralogy and age, geological and structural features, can be related to potassium-uranium metasomatite type. Dibrova deposit is considered to be possible analogue of mineralization of the Central Ukrainian Uranium Ore district. Among the main diagnostic characteristics of Dibrova deposit are: 1) location within the Mesoarchean trough-like structure superimposed on the Paleoarchean basement. 2) Spacial and genetic association with Paleoproterozoic two-feldspar granitoids of Dibrova type, which are considered to be related to Saltychia intrusive complex. 3) Regional and local faults, favorable for emplacement of numerous bodies of aplite-pegmatitic granitoids and associated intensive metasomatic alterations of rocks. The flexural fold was formed at the intersection of multidirectional faults, which is also favorable for ore mineralization. 4) Mineralization is confined to metasomatically altered aplite-pegmatites, less often to microcline quartzites of Dibrova suite. 5) K2O/Na2O ratio of ore-bearing granitoids reaches 3.5 and thorium-uranium ratio varies from 1.0 to 4.0. 6) Ores are composed by quartz (70–90 %) as predominant mineral and microcline. Minor minerals (up to 10–15 %) are represented by sillimanite, muscovite, biotite. 7) Accessory minerals include monazite, zircon, rutile, nasturan, brannerite, uraninite, molybdenite. 8) Among trace elements are niobium, lead, molybdenum, bismuth, copper, zinc and tin. Economic REE-U-Th mineralization was da­ted at 1.9–2.2 billion years. It is formed through circulation of hydrothermal-metasomatic fluids associated with the emplacement of Paleoproterozoic aplite-pegmatitic granites of the Dibrova type. Study of monazite and uraninite inclusions by the CHIME techniques confirms the Paleoproterozoic age of mineralization, 2085–2115 Ma. At the same time, the influence of Mesoarchean Yanvarske granitoids for the formation of REE mineralization during early pre-ore stage is not excluded.

The Dahongliutan rare-metal pegmatite deposit, associated with the pegmatite dikes hosted by Dahongliutan pluton and metasedimentary rocks, is a new discovered Li–Be deposit in the the West Kunlun ...

Marmato, Colombia, has been an important centre of gold mining since before the first Spanish colonizers arrived in 1536. The Marmato deposit is hosted in a dacite and andesite porphyry stock as sheeted sulphide-rich veinlet systems. The district is currently experiencing a surge in both major mining projects and artisanal mining, driven by sustained high gold prices. Ore from small-scale and artisanal gold mining is processed in numerous small mills (entables) around Marmato, which impact surface water quality through the discharge of milled waste rock slurry, highly alkaline cyanide-treated effluent, and high dissolved metal loads. To investigate the impact of artisanal mining and ore processing, water samples were collected in January 2012 from streams around Marmato. The average dissolved metal concentrations in impacted streams were Zn, 78 mg L−1; Pb, 0.43 mg L−1; Cu, 403 µg L−1 Cd, 255 µg L−1; As, 235 µg L−1; Ni, 67 µg L−1; Co, 55 µg L−1; Sb, 7 µg L−1; and Hg, 42 ng L−1, exceeding World Health Organization drinking water guidelines. In addition, arsenic speciation was conducted in-situ and indicated that 91–95% of inorganic arsenic species is in the form of As(V). Spatial analysis of the data suggests that entables processing ore for artisanal miners are the main contributor to water pollution, with high sediment loads, alkalinity and elevated concentrations of dissolved arsenic, cadmium, mercury and lead, caused by the processing of gold-bearing sulphides in the entables. Geochemical data from surface water were compared to a comprehensive data set of whole rock analyses from drill core and channel samples from the deposit, indicating that the deposit is significantly enriched in gold, silver, lead, zinc, arsenic, antimony, and cadmium compared to crustal averages, which is reflected in the surface water geochemistry. However, elevated mercury levels in surface water cannot be explained by enrichment of mercury in the deposit and strongly suggest that mercury is being added to concentrates during ore processing to amalgamate fine gold.

In this paper, the east ore section of the Pulang porphyry copper deposit is selected as the research object. The micro-thermometer and laser Raman spectroscopic technique are utilized to study the parameters of ore-forming fluids such as pressure, temperature, and compositions. In the meantime, the fractal models, including the perimeter-area (P-A) model and number-size (N-S) model, are introduced to quantify the shape of fluid inclusions, and distinguish the stages of ore-forming fluids, respectively. The results show that the types of fluid inclusions are diversified, namely two-phase liquid-rich type, two-phase vapor-rich type, three-phase CO2-rich type, three-phase halite-bearing type and pure liquid type. The fluids of main mineralization stage are characterized by medium-high temperature (170.2–421.4 °C), medium-high salinity (9.3 wt.%–33.3 wt.%), and low density (0.73–1.06 g/cm3). With the migration and evolution, the temperature, salinity, and pressure of ore-forming fluids gradually decrease, while the density of fluids increases. The liquid-phase compositions mainly include H2O, and the vapor-phase compositions consist of H2O, CH4, N2, and CO2, indicating the characteristics of reducing fluids and the mixing of atmospheric precipitation. In general, the characteristics of ore-forming fluids in the east ore section are similar to those of the first mining area, suggesting that the ore-forming fluids in the east ore section may not migrate from the first mining area. And the east ore section may be a relatively independent metallogenic system. Moreover, the fractal analysis results demonstrate that the shape of fluid inclusions formed in the same hydrothermal activity features self-similarity. The DAP values of fluid inclusions in B veins, ED veins, and D veins are 1.04, 1.06 and 1.10, respectively, showing a gradually increasing trend from the main stage to the late stage of mineralization. Meanwhile, the shape of fluid inclusions ranging from B veins to D veins becomes increasingly irregular. It also reveals that the homogenization temperature satisfies fractal distribution with four scale-invariant intervals, suggesting that all B veins, ED veins, and D veins have experienced at least four hydrothermal activities. Compared with histogram, the N-S fractal model is able to describe the distribution characteristics of the ore-forming fluids’ homogenization temperature more precisely. Therefore, it presents a potential tool for the stage division of ore-forming fluids. This research provides information about the characteristics of ore-forming fluids in the east ore section of the Pulang porphyry copper deposit, which is beneficial for further exploration in this region, and the extension of the application of fractal models in the study of fluid inclusions. However, further testing of fractal models on the fluid inclusion study is warranted to fully determine the universality.

The tin (Sn)-tungsten (W) polymetallic ore concentrated district in SE Yunnan is distributed at the junction region of the Yangtze Block, the Cathaysian Block and the Indosinian Block, where there are several giant deposits of tin, tungsten, copper, silver, lead, zinc and indium closely associated with a large scale Late Cretaceous magmatism. Bi-dimensional empirical mode decomposition (BEMD) is used to extract aeromagnetic anomalous components at the survey scale of 1: 200 000 from the original aeromagnetic data of SE Yunnan. Four intrinsic mode functions (IMFs) and a residues component are obtained, which may reflect the geological structures and geological bodies at different spatial scales from high frequency to low frequency. The results are shown as follows: (1) Two different types of Precambrian basement in the study area were recognized: one is the Yangtze Block basement characterized by a strong positive magnetic anomaly, the other is the Cathaysian Block basement with a weak negative magnetic anomaly. The former consists of high grade metamorphic rocks including metamorphosed basic igneous rocks, while the latter consists of low grade metamorphosed sedimentary rocks. (2) The aeromagnetic anomalies associated with Sn-W polymetallic mineralization and related to granites in the study area illustrate a pattern of a skarnized alteration-mineralization zone with a positive ring magnetic anomaly enclosing a granitic intrusion with negative magnetic anomaly; (3) The ring positive magnetic anomaly zones enclosing the negative magnetic anomaly are defined as the Sn-W polymetallic ore-searching targets in the study area.

With the decrease in surface and shallow ore deposits, mineral exploration has focused on deeply buried ore bodies, and large-scale metallogenic prediction presents new opportunities and challenges. This paper adopts the predictive thinking method in this era of big data combined with specific research on the special exploration and exploitation of deep-earth resources. Four basic theoretical models of large-scale deep mineralization prediction and evaluation are explored: mineral prediction geological model theory, multidisciplinary information correlation theory, mineral regional trend analysis theory, and mineral prediction geological differentiation theory. The main workflow of large-scale deep resource prediction in the digital and information age is summarized, including construction of ore prospecting models of metallogenic systems, multiscale 3D geological modeling, and 3D quantitative prediction of deep resources. Taking the Lala copper mine in Sichuan Province as an example, this paper carries out deep 3D quantitative prediction of mineral resources and makes a positive contribution to the future prediction and evaluation of mineral resources.

Pyrite geochemistry has proven useful for tracking changes in the composition and physico-chemical conditions of hydrothermal fluids in ore-forming environments. Here, we investigated the microtextural features and chemical composition of pyrite, a main Au-bearing phase in the Akeshi and Kasuga deposits (Southern Kyushu, Japan), to better constrain the ore-forming processes in these high-sulfidation epithermal Au deposits. Despite the widespread distribution of Au-bearing pyrite in both deposits, no visible Au minerals coexist with pyrite. However, in situ laser ablation inductively coupled plasma mass spectrometry results show that Au concentrations in pyrite vary from below the detection limit to 41 ppm and are positively correlated with Cu (r = 0.4; up to 7400 ppm) and Bi concentrations (r = 0.44; up to 640 ppm). In both deposits, high Cu and Au concentrations occur in small (< 25 μm) anhedral grains of pyrite, which are interpreted to have rapidly crystallized from the ore-forming hydrothermal fluid. In addition, dissolution–reprecipitation textures and thin, concentric, Cu-rich overgrowths were identified in a number of larger (> 25 μm) pyrite grains and aggregates. These abrupt changes in the trace element compositions of pyrite grains likely record episodic metal-rich fluid inputs. We also propose that gold adsorption onto growing pyrite surfaces played a key role in the mineralization of these deposits.

Proterozoic limestone in a north British terrane contains a newly recognised occurrence of Nb-REE minerals. The mineralized Loch Shin Limestone is in the Lewisian Complex of the Northern Highlands ...

The Palaeozoic mafic-ultramafic complexes hosting Ni-Cu-Co mineralization occurred discontinuously and coexisted with early Palaeozoic eclogites in the East Kunlun orogenic belt (EKOB), western Chi...

The paper presents data on noble-metal mineralization in carbon-bearing rocks of the Sarma Group in the southern flank of the Baikal inlier of the Siberian craton basement. The phase composition of the accessory ore minerals (pyrite, arsenopyrite, microinclusions of native Ni, Sn, Zn, Cu, Fe–Ni and Ni–Fe–Ti composite compounds, Cu and Pb sulfides, rutile, monazite, zircon, and barite) were determined by X-ray microanalysis. Gold, silver, and all elements of the platinum group were determined by scintillation arc atomic emission spectrometry in rock samples from the Ilikta and Hulurtui formations. These elements occur as particles of native noble metals, their intermetallic compounds, sulfides, arsenides, selenides, and sulfosalts. Noble-metal mineralization in the Hulurtui and Ilikta formations of the Sarma Group is proved to be genetically related to tectono-metasomatic processes that affected the primary metasedimentary rocks.

The article presents the results of a comparative analysis of fluorite from various mineralization types of the Saf’yanovka massive sulfide deposit in the Central Urals. The predominant green fluorite is intergrown with barite, quartz, and carbonates in hydrothermal colloform and massive pyrite, veinlet–disseminated chalcopyrite–pyrite–sphalerite and pyrite–chalcopyrite ores, as well as in hydrothermally altered rhyolite. In colloform pyrite ore, fluorite together with galena, sphalerite, chalcopyrite, fahlore, and barite fills interstices between crystals. In altered rhyolite, yellow-green fluorite occurs as veins of 1 cm thick, 2–3 cm pockets, and intergrowths with quartz, carbonate, and barite. The rare-earth element (REE) and yttrium concentrations have been determined by ICP-MS. The highest Y content (160 ppm) is measured in fluorite from metasomatic rock; the intermediate Y content (40–130 ppm) is determined in fluorite from pyrite ore, and the lowest one (4–9 ppm) is typical of fluorite from chalcopyrite–pyrite–sphalerite and chalcopyrite ore. The total REE content in fluorite is 70–150 ppm (chalcopyrite–pyrite–sphalerite and chalcopyrite ore), 100–280 ppm in pyrite ore, and reaches 180 ppm in altered rhyolites. The highest REE concentration is caused by the presence of xenotime, goyazite, monazite, barite or apatite inclusions in fluorite. The Tb/La and Tb/Ca ratios suggest that fluorite resulted from hydrothermal processes. The REE distribution patterns with an evident Eu anomaly (Eu/Eu* > 1) show enrichment in LREE. Positive Eu anomalies reflect the high-temperature conditions (≥250°C) during fluorite crystallization. The pressure-corrected (~100–150 bar) temperature of fluorite formation is 190–260°С.

The Tengshan'ao Sn deposit, located at the Dayishan ore field, Nanling Range, is one of the recently explored deposits in this region. In this study, LA-MC-ICP-MS cassiterite U–Pb and muscovite 40Ar-39Ar isotopic dating analyses for altered granite-type Sn ores yielded ages of 156.7 ± 4.3 Ma and 151.1 ± 1.5 Ma, respectively. These ages are consistent to the LA-MC-ICP-MS zircon U–Pb age of the fine-grained two-mica monzogranite (158.2 ± 1.6 Ma), indicating a coeval magmatism and mineralization for the Late Jurassic Tengshan'ao Sn deposit. It is further demonstrated that the formation of this deposit is related to the Early Yanshanian (160-150 Ma) large-scale diagenesis and mineralization in Nanling Range. It is suggested that the late-stage fine-grained two-mica (muscovite) granite has an indicative significance for searching the altered granite type Sn polymetallic mineralization.

The paper reports petrochemical and isotope data on the ferromanganese ores and host volcanosedimentary rocks of the Taloi–Usoi interfluve of the Ikat terrane, the Central Asian Fold Belt. Obtained data indicate that the formation of the Taloi ferromanganese mineralization was related to the explosive and volcanic activity of synsedimentation suprasubduction volcanism. The age of the volcanogenic rocks is 799 ± 3 Ma. This indicates the manifestation of Neoproterozoic (Riphean) epoch of manganese accumulation related to active continental margin setting in the Transbaikalian segment of the CAFB.

In the northwestern margin of the Youjiang basin (NWYB) in SW China, many Carlin-like gold deposits are highly antimony (Sb)-rich, and many vein-type Sb deposits contain much Au. These deposits have similar ages, host rocks, ore-forming temperatures, ore-related alterations and ore mineral assemblages, but the Au and Sb metallogenic relations and their ore-forming process remain enigmatic. Here we investigate the large Qinglong Sb deposit in the NWYB, which has extensive sub-economic Au mineralization, and present a new metallogenic model based on in-situ trace elements (EPMA and LA-ICP-MS) and sulfur isotopes (NanoSIMS and fs-LA-MC-ICP-MS) of the ore sulfides. At Qinglong, economic Sb ores contain coarse-grained stibnite, jasperoid quartz and fluorite, whilst the sub-economic Au–Sb ores comprise dominantly veined quartz, arsenian pyrite and fine-grained stibnite. Three generations of ore-related pyrite (Py1, Py2 and Py3) and two generations of stibnite (Stb1 and Stb2) are identified based on their texture, chemistry, and sulfur isotopes. The pre-ore Py1 is characterized by the lower ore element (Au, As, Sb, Cu and Ag) contents (mostly below the LA-ICP-MS detection limit) and Co/Ni ratios (average 0.31) than the ore-stage pyrites (Py2 and Py3), implying a sedimentary/diagenetic origin. The Py2 and Py3 have elevated ore element abundance (maximum As ​= ​6500 ​ppm, Au ​= ​22 ​ppm, Sb ​= ​6300 ​ppm, Cu ​= ​951 ​ppm, Ag ​= ​77 ​ppm) and Co/Ni ratios (average 1.84), and have positive As vs. Au–Sb–Cu–Ag correlations. Early-ore Stb1 has lower As (0.12–0.30 ​wt.%) than late-ore Stb2 (0.91–1.20 ​wt.%). These features show that the progressive As enrichment in ore sulfides is accompanied by increasing Au, Sb, Cu and Ag with the hydrothermal evolution, thereby making As a good proxy for Au. As-rich, As-poor and As-free zones are identified via NanoSIMS mapping of the Au-bearing pyrite. The As-rich zones in the Qinglong Au-bearing pyrites (Py2 and Py3) and ore stibnites (Stb1 and Stb2) have narrow δ 34 S H 2 S ranges (−8.9‰ to +4.1‰, average −3.1‰) and −2.9‰ to +6.9‰, average ​+ ​1.3‰), respectively, indicating that the Au-rich and Sb-rich fluids may have had the same sulfur source. Published in-situ sulfur isotopic data of pyrite As-rich zones from other Carlin-like Au deposits (Shuiyindong, Taipingdong, Nayang, Getang and Lianhuashan) in the NWYB have similar ore-fluid δ S H 2 S 34 values (−4.5‰ to +6.7‰, average −0.6‰) to those of Qinglong. Therefore, we infer that the sulfur of both Au and Sb mineralization was derived from the same magmatic-related source (0 ​± ​5‰) in the NWYB. Moreover, the core of pyrites (Py1) has variable S isotope fractionation (−18.9‰ to +18.1‰, mostly +3‰ to +12‰), suggesting that the higher-34S H2S was produced by bacterial sulfate reduction (BSR). The hydrothermal pyrite (Py2 and Py3) δ34S values gradually decrease with increasing As concentrations, and ultimately, within the restricted range (−5‰ to +5‰) in As-rich zones. This variation implies that the As-rich pyrite was formed through ongoing interactions of the magmatic-hydrothermal fluid with pre-existing sedimentary pyrites, causing the progressive decreasing δ34S values with As content increase, Hence, the fluid/mineral interaction may have generated the observed variation in δ34S and As contents. Overall, comparing the Au and Sb deposits in the NWYB, we favor a magmatic-related source for the Au–Sb–As-rich fluids, but the Au- and Sb-ore fluids were likely evolved at separate stages in the ore-forming system.

Background. Volcanogenic massive sulphide deposits (VMS) are the most important sources of Cu and Zn; they account for a large share of the world production of Pb, Ag, Au, Se, Te, Bi and Sb, as well as small amounts of many other metals. The polymetallic VMS deposits of economic value of varying degrees are known in the rocks of the Los Pasos Cretaceous Formation, Cuba.Aim. To show the potential of the Cretaceous volcanic deposits of Central Cuba for gold, silver, copper, zinc and lead deposit prospecting.Materials and methods. The study characterises the San Fernando, Independencia, Antonio, Los Cerros VMS deposits and the Boca del Toro and El Sol ore occurrences located in the Los Pasos Formation. The similarities and differences in the mineral and elemental composition and structures of the ores of these objects are described, which underlie the assessment of their economic importance.Results. The latitudinal zoning of VMS and noble metal mineralisation of the Central Cuban ore region is outlined. In the west, copper-VMS deposits with accompanying gold ore objects prevail. In the east, copper-zinc VMS deposits with barite and gold-silver objects are widespread.Conclusions. It is necessary to assume the different erosional sections corresponding to the blocks of the Cretaceous volcanic arc of Central Cuba, which is larger in the west and smaller in the east. Proceeding from the presence of veinlet gold ores, their confinement to tectonic zones and the lack of correlation between noble and chalcophile metals at the San Fernando deposit, as well as significantly different gold-silver ratios in the considered ore objects, it could be assumed that some of the gold-silver ores were formed after VMS. The obtained Au/Ag ratios are close to the ores of the high sulphidation type (high sulphide ores) from similar ore regions of Venezuela and the Kur-il island arc. In this regard, one can expect hidden gold deposits in the west and gold-silver deposits in the east of the studied area.

The occurrence of unconformity-related uranium mineralization requires the combination of three components: fluids with the right composition, geochemical traps with the right agents that produce precipitation, and structural traps with the right geometry. In the Athabasca Basin unconformity-related uranium deposits, while basinal brines are commonly accepted as the principal mineralized fluids and graphite and gases (CH4, CO2, and H2S) are well known as the reductants, only few case studies describing structural traps are published. A number of recent works, including numerical modelling, have improved the understanding of the role of inherited shear zones on fluid flow and the development of uranium deposits at a micro- and regional-scale. Nevertheless, there is still a lack of knowledge about the meso- or deposit-scale structural controls that lead to the present (and potentially predictive) localization of uranium deposits along a given shear zone. The present work examines new structural data from drill holes and deals with (i) the identification of mesoscale structural traps that lead to the formation of the Athabasca unconformity-related uranium deposits hosted within the basement and (ii) with the understanding of the role and mode of reactivation of the inherited shear zones. The Sue deposits (McClean Project), the Tri-Island showing (Martin Lake Project) in the Eastern Athabasca, and the Spitfire prospect (Hook Lake Project) in the Western Athabasca have been selected for a detailed analysis of structures and related uranium mineralization. The structural analysis performed brings new insights about the mesoscale structural controls, the role the inherited ductile fabric had on the mode of brittle reactivation and to trap mineralization, and the tectonic regime to which basement-hosted uranium deposits may be associated in the Athabasca Basin.

High sensitivity laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) has been utilized for the determination of trace elements in pyrite from the Tharsis VMS deposit, one of the most significant volcanogenic massive sulphide deposits in the southern Iberian Pyrite Belt. The study tracks the content and distribution of trace elements within the different facies of massive sulphides. Widespread and variable enrichment in elements such as Cu, Zn, and Pb in pyrite is interpreted to be due to the presence of nanoinclusions of chalcopyrite, sphalerite, and galena, respectively. A second group of elements, including As, Au, Tl, Mn and Mo, shows significant chemical variations according to the type of mineralization and the textural evolution of the pyrite. This behaviour is thought to be due to the fact that these metals are included in the mineral lattice and its incorporation is controlled by the degree of crystallinity, the temperature, and the redox conditions during crystallization. Early, spongiform and colloform pyrite in the stockwork is enriched in As and Au and interpreted to have formed from a high temperature and low fS2–fO2 fluid. Thallium, Mn, and Mo are enriched in pyrite precipitated at lower temperature and higher oxidation state, i.e., in the exhalative part of the system or in distal facies to the hydrothermal vents. In general, both Co and Ni show an irregular distribution and do not have the sympathetic distribution observed in equivalent studies.

Abra is a high-grade sedimentary-hosted Pb deposit located in the Paleoproterozoic Edmund Basin in Western Australia. Mineralization is blind, with the top of the deposit occurring 250 m beneath the land surface. The deposit consists of a stratiform apron of Pb-Ag-Ba mineralization in laminated iron-oxide- and barite-altered dolomite and siltstone, which overlies a feeder zone of chlorite-altered, brecciated, and veined carbonatic siltstone that contains Pb-Ag mineralization in the core that transitions to Pb-Cu and Cu-Au at depth. Abra is characterized by discrete geophysical anomaly responses in magnetic, gravity, time-domain electromagnetic (TDEM), and induced polarization survey data. A +450 nT magnetic anomaly is caused by magnetite in the lower stratiform zone. Dense galena, barite, dolomite, and iron-oxide mineralization in the apron and galena in the feeder zone is surrounded by lower-density sedimentary host rocks, which results in a +1 mGal gravity anomaly. Airborne, ground, and downhole TDEM surveying resolved known mineralization as weak electromagnetic conductor responses, and petrophysical testing on core samples shows that this is caused by galena. Pole-dipole-induced polarization surveying resolved a +20 ms chargeability anomaly on the southern flank of the deposit. This chargeable anomaly response is related to disseminated galena, pyrite, chalcopyrite, and alteration. Joint audiomagnetotelluric-magnetotelluric 2D inverted data sections resolved Abra as a broad weakly conductive anomaly. Weak conductor responses associated with Abra were also resolved in 2D and 3D inversion modeling of airborne Z-axis tipper electromagnetic data. 2D seismic reflection surveying resolved Abra as strong flat-lying seismic reflectors, which are bounded and offset by faults and surrounded by a seismically bland zone. The seismic reflections are related to significant density contrasts between high-density stratiform mineralization that is in contact with low-density sedimentary host rocks, as the mineralization and host rocks have similar seismic velocities. Passive seismic horizontal to vertical spectral ratio surveying resolved the top of the deposit as a subtle layer sitting below a flat impedance contrast horizon that is interpreted as weathered siltstone on top of diagenetically cemented siltstone.

The Jiaodong Peninsula is one of the most important Au ore provinces in China. There is an ongoing debate on the correlation between ore formation and magmatism in this province, because few intrusive rocks exhibit a clear association with ore deposits. A mineralized biotite monzodiorite (BM) stock, with disseminated ore, pervasive phyllic alteration, and no deformation, was found in a borehole in the footwall of the Zhaoping fault within the Luanjiahe Au deposit, which may shed light on this debate. The biotite monzodiorite contains explosion breccias, miarolitic cavities, skeletal and dendritic quartz, and late-stage evolved aplite dikes, and the in-situ δ34S values of the disseminated pyrite which is associated with Au mineralization are −1.7‰ to 7.3‰ (mean=3.5‰), indicative of a magmatic-hydrothermal system. These findings, combined with the reported age of 123 Ma, show that the intrusion has close spatial, temporal, and geochemical relationships with Au mineralization in the area. The biotite monzodiorite is metaluminous, high-K calc-alkaline and shoshonitic, with enrichment in light rare earth elements (REEs) and large-ion lithophile elements (LILEs), depletion in high-field-strength elements (HFSEs), and enriched Sr-Nd isotopic compositions. The intrusion may be the product of partial melting of enriched lithospheric mantle with a small lower crustal component. The hydrous, Au-bearing, enriched mantle source, and the strongly oxidized magma that was generated, created favorable conditions for Au mineralization.

The Qingchengzi ore field is an important gold-polymetallic center of the North China Craton. It has been recognized that the gold deposits in Qingchengzi were controlled by structures like lithological interfaces and fractures along mechanically weak bedding and foliation planes, but it still remains poorly understood how the structures affected the localization of the gold deposits. Finite element based numerical modeling was used to reproduce the deformation process of the Baiyun gold deposit during the mineralization period. Paleoproterozoic schist and marble are widely exposed in Qingchengzi, and a large part of the Baiyun gold ores occurs along the interfaces between the schist and the marble. The modeling results suggest that the mechanical contrast between the schist and the marble may be a major reason why the stress was localized along their lithological interfaces under a compressional stress regime. Two parts of their lithological interfaces were identified to be easily stress-localized and first fractured: the interface between the schist and its underlying marble at shallower levels and the one between the schist and its overlying marble at deeper levels. Stress concentration in these two parts is independent on the dipping angle and direction of the interfaces. Therefore, mineralizing fluids may have been concentrated into these two parts. The first one is consistent with the present ore bodies of the Baiyun gold deposit, and the second one could be considered for deep prospecting. These findings also provide implications for the structural controls of lithological interfaces on the mineralization in other gold deposits of this region.

The Aqishan-Yamansu metallogenic belt (AYMB) in East Tianshan hosts abundant submarine volcanic-hosted iron deposits. Although there is agreement with the magmatic source of the ore-forming materials and the role of hydrothermal replacement in iron ore formation, the mineralization processes of these iron deposits remain uncertain. Three ore types are identified on the basis of the geological occurrences of minerals and the sequence of mineral in ores. The type I ores are characterized by magnetite, diopside, amphibole with a few pyrite, and chalcopyrite. The type II ores are mainly composed of magnetite, garnet, chlorite with a few pyrite, while the type III ores are mainly composed of magnetite, quartz, calcite with a few pyrite. In order to constrain the mineralization processes of these ore types, we performed iron isotopes and trace element compositions of magnetite from three typical iron deposits (Yamansu, Duotoushan and Luotuofeng). Trace element and Fe isotope investigations of the three ore types reveal two major groups. The group I consists of analyses of the type I and II ores, with both showing a narrow range of positive δ56Fe values (+0.08‰ to +0.22‰ for type I ores and +0.15‰ to +0.22‰ for type II ores) and plotting in the range of the ortho-magmatic field. In contrast, the group 2 is composed merely of the type III ores, showing a wider range of negative δ56Fe values (-0.49‰ to -0.01‰), which is similar to the features of Fe-skarn magnetite. As shown in the binary diagrams of magnetite trace elements and a fractionation of the Fe isotopes, different ore types were likely produced during gradually changing ore-forming stages from magmatic to hydrothermal. Collectively, the submarine volcanic-hosted iron deposits in the East Tianshan are likely the results of a continuous magmatic-hydrothermal mineralization process.

Large-scale gold mineralization during the Early Cretaceous is identified in the Jiaodong Peninsula of China. Sources of ore-forming fluids remain debated. We study the Qilishan gold deposit in the northwestern Jiaodong Peninsula with detailed mineralogical observation and in-situ sulfur isotope analyses, in order to reveal the gold occurrence and the origin of ore-forming fluids. The Qilishan gold deposit is mainly clastic altered rock-type in mineralization, and ore minerals are visible native gold, electrum, pyrite, chalcopyrite and galena, gangue minerals as quartz, sericite and calcite. The gold occurrence includes inclusion and intergranular types, formed within pyrites and chalcopyrites and along their fissures. In-situ sulfur isotope analysis of gold-bearing sulfides suggests that the Qilishan deposit is enriched in heavy sulfur, with δ34S values mainly from +8.0‰ to +12.0‰. δ34S values increase gradually with the fluid evolution from the early to late stages, which is interpreted to be related to the loss of sulfur via sulfide precipitation. The crystallization of sulfides from hydrothermal fluids may have triggered the instability of Au(HS)2, and finally led to gold precipitation. Combined with sulfur isotope compositions of other gold deposits (n=43) and wall-rocks in the Jiaodong Peninsula, it is proposed that the ore-forming fluids were probably not directly originated from metamorphic wall-rocks (e.g., Jiaodong Group). Moreover, the relatively long time interval rules out the possibility that the gold mineralization (ca. 120 Ma) was associated with granitic magma activities (mostly 160–150 Ma). Possible ore genesis scenario is that, long-term subduction of slabs (e.g., the Paleo-Pacific) with gold-enriched pyritic materials and crustal sedimentary rocks resulted in both high Au contents and positive δ34S values of sulfur in the lithospheric mantle below the North China Craton. Subsequently, devolatilization of the metasomatized mantle produced auriferous fluids that migrated upward along translithospheric fault systems, and gold finally precipitated in favorable structural positions, generating the world-class Jiaodong deposits in the Early Cretaceous.

Overprinting of an earlier formed deposit may obscure the nature of the deposit and hinder our understanding of regional metallogeny. The Qiaoxiahala Fe(-Cu/Au) deposit in eastern Junggar, NW China, is characterized by magnetite mineralization later replaced by sulfide minerals such as chalcopyrite. To reveal the genesis of Qiaoxiahala, we conducted Re-Os dating on post-magnetite molybdenite separated from chalcopyrite and rare earth elements (REEs) for basaltic volcanic rock, magnetite, chalcopyrite and diorite. An isochron age of 377±7 Ma was obtained together with a weighted mean age of 375±3 Ma, which is indistinguishable from mineralization ages determined in previous studies. Rare earth element (REE) data for basaltic volcanic rocks hosting the ore are comparable to that of the magnetite, while the REE signatures of chalcopyrite from the Cu ore and local intrusive diorite share a similar pattern. These suggest that two distinct fluid sources are responsible for the deposition of Fe and Cu in the Qiaoxiahala deposit. According to these experimental results, we consider that the iron mineralization in Qiaoxiahala is the result of fluid exsolution from basaltic volcanism which was further overprinted by fluids that deposited copper and gold, which may have been sourced from nearby dioritic intrusions.

Porphyry Cu-Au deposits (PCDs) have commonly multiphase porphyry intrusions, yet only one (or a few) of the intrusive phase is/are ore-causative. Understanding the criteria to form ore-causative porphyry is important for both ore deposit research and PCD exploration. At the giant Pulang PCD in western Yunnan, there are three generations of porphyries, i.e., (from oldest to youngest) the quartz diorite porphyry (QDP), quartz monzonite porphyry (QMP) and granite porphyry (GP), and only the QMP has major mineralization. Based on ore deposit geology, and zircon U–Pb–Hf–O isotope systematics, we suggested that the QMP is spatially and temporally ore-related. Oxygen fugacity of the QMP and GP magmas is estimated to be higher than that of the QDP. In addition, Hf–O isotope compositions of the QMP and GP are close to those of the average mantle. We suggested that with the continuous Late Triassic subduction of the Garze–Litang ocean basin, the subducted-slab dehydration and the addition of mantle-wedge materials to the ore-forming magmas increased gradually. The younger magmas (e.g., QMP and GP) are thus more oxidized, and have higher water and ore-material contents, giving them higher ore-forming potential. The reason maybe that the late GP is barren may be due to the depletion of ore-forming materials by the main-stage mineralization during the QMP intrusion.