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[Display omitted] • We use magnetotellurics to image a post-subduction Porphyry mineral system. • Ore bearing mineralisation may be linked to an enriched subcontinental lithospheric mantle. • Evaluation of mineral deposits are spatially associated with zones of low resistivity. Porphyry mineral systems provide a significant source of critical minerals for modern society, that are predominantly formed in subduction related settings from magmatic hydrothermal fluids derived from an underlying reservoir. However, in post-subduction settings the processes that entrain and focus magmatic hydrothermal fluids throughout the crust, from source to deposit are often poorly constrained. In this paper, we have undertaken a magnetotelluric (MT) survey in an intracontinental tectonic setting across the Adelaide Superbasin, which is a Neoproterozoic passive margin formed during rifting of the supercontinent Rodinia. This region contains the Burra magmatic copper deposit, along with numerous sedimentary-hosted copper deposits. Systematic three-dimensional modelling was undertaken, initially at regional-scale, with 55 km gridded long-period AusLAMP data over a 500 × 500 km area, followed by infilled 10 km gridded broadband MT data, at the district-scale, centred over an area of copper deposits in the Adelaide Rift Complex. The modelling reveals an elongated zone of low electrical resistivity (∼100 Ω.m), in an otherwise resistive crust, at lower crustal depth (20–40 km) that is contiguous with the regional lineament of the Adelaide Rift Complex and copper and gold mineralisation. A narrow zone of low resistivity (∼100 Ω.m) branches through the upper crust (5–20 km) to the surface, that is remarkably aligned with the Burra magmatic mineral system, in an otherwise quite resistive crust (∼1000 Ω.m). Additionally, in the upper crust a zone of low resistivity (1–10 Ω.m at a depth of 5–8 km) extends from the Burra magmatic copper deposit southwards, constrained by anticlinal folding from the ∼500 Ma Delamerian Orogenic deformation of the Adelaide Rift Complex and spatially aligned with the Kapunda sedimentary-hosted copper deposit. We argue that the low electrical resistivity signature encapsulates a whole-of-lithosphere magmatically-hosted copper system, that is further mobilised by low-temperature fluids by mapping the footprint of ore-forming fluids from the source to associated mineralisation. Where later basin wide fluid recycling in a permeability enhanced basin, via neo-tectonism along pre-existing structures/trends, has likely remobilised copper, from a prior magmatic event, with copper being leached in chloride-rich saline fluids at low temperatures. [ABSTRACT FROM AUTHOR]

This research presents a case study that employs the Fuzzy Ordered Weighted Averaging (FOWA) method to develop mineral prospectivity/potential maps (MPM) for the Chahargonbad district in southeastern Iran. The primary objective of the study is to uncover intricate and concealed relationships between various evidence layers and known ore occurrences through a comprehensive analysis of multi-disciplinary geospatial data. Consequently, thirteen evidence layers were meticulously derived from existing databases, encompassing geological, geochemical, geophysical, and remote sensing data, which were then integrated using the FOWA multi-criteria decision-making approach to delineate favorable zones for porphyry Cu mineralization.The FOWA methodology employs a diverse array of decision strategies to synthesize input geospatial evidence by incorporating multiple values for an alpha parameter. This parameter serves as the cornerstone of the algorithm, influencing experts' perspectives on MPM risk. The methodology generates seven mineral potential maps to identify the most suitable one(s). By considering a prediction-area plot for data-driven weight assignment to each evidence map, the hybrid FOWA outputs were scrutinized to pinpoint the most appropriate map for targeting significant Cu occurrences. The resulting synthesized evidence map indicates an ore prediction rate of 77%, with known Cu deposits primarily located within favorable zones occupying 23% of the entire district area.

Delineating and mapping alteration zones in porphyry copper exploration is of special importance. In this study, satellite image processing techniques were employed to highlight alteration zones in the Zafarghand exploration area. The Zafarghand area is located in the southeastern part of Ardestan and the northwestern part of Isfahan. It is situated within the geological structural zones of central Iran and the intermediate magmatic arc of Urmia-Dokhtar. Various alteration haloes are present in this area, including phyllic, potassic, propylitic, argillic, and slightly siliceous alterations. In this study, the detection of related alterations was carried out using ASTER sensor imagery. Accordingly, considering the raster nature and digital form of satellite images, the digital number values of each pixel from the image matrices were considered as samples in a systematic network. Finally, the U spatial statistic algorithm was implemented as a moving window algorithm for determining anomaly samples in the set of digital number (DN) values of ASTER satellite image pixels. The results of this technique show that the application of the U-statistic method, considering its structural nature and neighboring samples in decision-making, has been successful and has proven to be very effective in determining the alteration zones in the Zafarghand area. It could be observed the delineated propylitic alteration by the U-statistic method is closely associated with the defined zone of propylitic alteration, which is also consistent with the field and microscopic observation of the porphyry Cu mineralization in this alteration zone. It is also observed that the determined phyllic alteration by this image processing is spatially conformable with the sericitic alteration presented in the alteration map (based on field observations and geochemical sampling).

Delineating and mapping alteration zones in porphyry copper exploration is of special importance. In this study, satellite image processing techniques were employed to highlight alteration zones in the Zafarghand exploration area. The Zafarghand area is located in the southeastern part of Ardestan and the northwestern part of Isfahan. It is situated within the geological structural zones of central Iran and the intermediate magmatic arc of Urmia-Dokhtar. Various alteration haloes are present in this area, including phyllic, potassic, propylitic, argillic, and slightly siliceous alterations. In this study, the detection of related alterations was carried out using ASTER sensor imagery. Accordingly, considering the raster nature and digital form of satellite images, the digital number values of each pixel from the image matrices were considered as samples in a systematic network. Finally, the U spatial statistic algorithm was implemented as a moving window algorithm for determining anomaly samples in the set of digital number (DN) values of ASTER satellite image pixels. The results of this technique show that the application of the U-statistic method, considering its structural nature and neighboring samples in decision-making, has been successful and has proven to be very effective in determining the alteration zones in the Zafarghand area. It could be observed the delineated propylitic alteration by the U-statistic method is closely associated with the defined zone of propylitic alteration, which is also consistent with the field and microscopic observation of the porphyry Cu mineralization in this alteration zone. It is also observed that the determined phyllic alteration by this image processing is spatially conformable with the sericitic alteration presented in the alteration map (based on field observations and geochemical sampling). [ABSTRACT FROM AUTHOR]

This research presents a case study that employs the Fuzzy Ordered Weighted Averaging (FOWA) method to develop mineral prospectivity/potential maps (MPM) for the Chahargonbad district in southeastern Iran. The primary objective of the study is to uncover intricate and concealed relationships between various evidence layers and known ore occurrences through a comprehensive analysis of multidisciplinary geospatial data. Consequently, thirteen evidence layers were meticulously derived from existing databases, encompassing geological, geochemical, geophysical, and remote sensing data, which were then integrated using the FOWA multi-criteria decision-making approach to delineate favorable zones for porphyry Cu mineralization. The FOWA methodology employs a diverse array of decision strategies to synthesize input geospatial evidence by incorporating multiple values for an alpha parameter. This parameter serves as the cornerstone of the algorithm, influencing experts' perspectives on MPM risk. The methodology generates seven mineral potential maps to identify the most suitable one(s). By considering a prediction-area plot for datadriven weight assignment to each evidence map, the hybrid FOWA outputs were scrutinized to pinpoint the most appropriate map for targeting significant Cu occurrences. The resulting synthesized evidence map indicates an ore prediction rate of 77%, with known Cu deposits primarily located within favorable zones occupying 23% of the entire district area. [ABSTRACT FROM AUTHOR]

In exploratory projects, the identification of geochemical anomalies in different areas may become complicated under the influence of geological processes. To solve these ambiguities, different methods should be used for a correct understanding of the available information. In this research, by expressing the concept of hierarchical clustering to identify elements related to mineralization, singularity, and how to draw singularity maps in the form of multifractal models and support vector machine method, the anomalous areas where there is a possibility of mineralization are seprated from the context regions. At first, two elements, gold and copper, were identified as elements related to mineralization in the created clusters using the hierarchical clustering method and Ward's method. To calculate the singularity index of these two elements, the method based on the window and the power relation of grade area was used at each point. Finally, by separating the singularity index values into two parts, training and testing, and with the help of the SVM method, the process of classification and estimation of singularity index values was done to identify anomalous areas for unknown areas. A case study has been carried out on the data of the porphyry copper deposit rich in Dali gold with an area of 900×800 meters located in the Urmia-Dokhtar magmatic belt. The data is related to surface soil samples in the target area. The results of this method are consistent with the previous studies conducted in the region. The results of the hybrid method used in this research show good agreement with previous studies. As a result, the use of these introduced hybrid methods can be a suitable guide for the production of geochemical maps in unknown areas. [ABSTRACT FROM AUTHOR]

One of the specific features of porphyry copper (Cu) mineralization is the distinct occurrence of hydrothermal alteration zones, which can be mapped by processing various satellite images. Among free multispectral images, Landsat 8 OLI and ASTER data are known to be efficient in mapping different geological features, such as alteration zones and tectonic lineaments. This study aims to show the potential of these data types in mapping porphyry Cu mineralization by proposing a framework for employing and integrating different image processing methods. These methods include principal component analysis (PCA), spectral angle mapper (SAM), and matched filtering (MF) employed on these satellite images to map target al.teration zones. Moreover, PCA and directional filtering are applied to the ASTER dataset to enhance and map structural features. The results are evaluated and then combined to provide a potential map of Cu mineralization in the Chahargonbad area, located within the Urumieh-Dokhtar magmatic belt (UDMB) in Kerman province, Iran. The prediction-area plot and normalized density, which are data-driven methods, are used to assign the relative weight of each layer and evaluate them. Finally, using the calculated weights, data-driven multi-index overlay (DMIO) and fuzzy ordered weighted averaging (FOWA) methods are applied to combine the evidential layers. The potential mineralization maps created by the DMIO and FOWA provide a prediction rate of 80% and 82%, respectively. Furthermore, the accuracy of the integrated maps is investigated using the area under the curve (AUC) of the receiver operating characteristic (ROC) curves. The AUC scores obtained from the ROC curves of DMIO and FOWA methods are 0.85 and 0.88, respectively, representing powerful positive spatial relationships with mineralization areas. Based on the results, the proposed framework can be applied to provide a potential map of porphyry Cu mineralization, particularly in arid regions, with reasonable accuracy.

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

In integrating geospatial datasets for mineral potential mapping (MPM), the uncertainty model of MPM can be inferred from the Dempster – Shafer rules of combination. In addition to generating the uncertainty model, evidential belief functions (EBFs) present the belief, plausibility, and disbelief of MPM, whereby four models can be simultaneously utilized to facilitate the interpretation of mineral favourability output. To investigate the functionality and applicability of the EBFs, we selected the Naysian porphyry copper district located on the Urmia – Dokhtar magmatic belt in the northeast of Isfahan city, central Iran. Multidisciplinary datasets- that are geochemical and geophysical data, ASTER satellite images, Quickbird, and ground survey- were designed in a geospatial database to run MPM. Implementing the Dempster law through the intersection (And) and union (OR) operators led to different MPM performances. To amplify the accuracy of the generated favourability maps, a combinatory EBFs technique was applied in three ways: (1) just OR operator, (2) just And operator, and (3) combination of And and OR operators. The plausibility map (as mineral favourability map) was compared to Cu productivity values derived from drilled boreholes, where the MPM accuracy of the hybrid method was higher than each operator. Of note, the success rate of the hybrid method validated by 21 boreholes was about 84%, and it demarcates high favourability zones occupying 0.67 km2 of the studied area.

The Elatsite–Chelopech ore field in the northern part of the Panagyurishte district in Central Bulgaria comprises numerous spatially associated porphyry copper and epithermal gold deposits and prospects. In addition to the mineralization and alteration features, trace elements, lead and sulfur isotope signatures of sulfide minerals from porphyry copper, base metal and gold-base metal deposits/prospects have been studied. LA-ICP-MS analyses of pyrite, arsenopyrite and sulfosalt minerals validate them as major carriers for Au, Ag, Sb, Se and Co. Pyrite from the three types of mineralization has specific geochemical characteristics. Pyrite from the porphyry copper deposits/prospects has generally lower total trace element content compared to pyrite from the epithermal prospects, except for Se, Co and Ni. Pyrite from the base metal and gold-base metal veins is enriched in As, Au, Ag, Sb and Pb. In pyrite from the base metal deposits, Co and Ni have contents comparable to the pyrite from the porphyry copper deposits, while pyrite from the gold-base metal veins shows lower Co and Ni. Arsenopyrite from these deposits shows similar features. Similarly, sphalerite from the gold-base metal veins also has lower Co content compared to sphalerite from the base metal veins but higher In and Cu contents. In addition to the close spatial relationships between the Elatsite and Gorna Kamenitsa porphyry Cu deposits and Negarstitsa-West and Dolna Kamenitsa base metal prospects, as well as similarities in the mineralization and alteration styles, the lead isotopic (206Pb/204Pb = 18.61–18.68, 207Pb/204Pb = 15.64–15.65 for porphyry and 206Pb/204Pb = 18.55–18.67, 207Pb/204Pb = 15.64–15.68 for base metal) and sulfur isotopic (δ34S values of −3 to +1‰ for porphyry and δ34S values of −1.7 to +3.5‰ for base metal) signatures of sulfides support the idea of a genetic link between these two types of deposits. The porphyry and base-metal mineralization result from a common major ore-forming event during the Late Cretaceous, corresponding to deep/higher-temperature and shallower/distal/lower-temperature environments, respectively. In particular, more radiogenic lead (206Pb/204Pb = 18.41–18.47, 207Pb/204Pb = 15.67–15.76) and slightly different sulfur isotopic compositions (δ34S values of +3.5 to +10.6‰) of sulfides from the distal gold-base metal veins of Kordunsko Dere, Svishti Plaz and Shipkite might be a consequence of the interaction of the ore-forming fluids with an external older crustal and isotopically positive S source. Alternatively, a different fluid source/event for the formation of these gold-base metal veins may be suggested. [ABSTRACT FROM AUTHOR]

The Qulong porphyry copper deposit in Tibet is located in the Tethis–Himalaya metallogenic domain, one of the three major porphyry metallogenic domains in the world. At present, the mining area is mainly used for surface mining. The depth revealed by the drilling project is less than 2 km. The potential for deep resources is unknown. Based on an analysis of the geochemical characteristics of the primary halos around the No. 16 prospecting line, deep extension is discussed in this paper. Studies show that the metallogenic elements are Cu and Mo; the near-ore halo elements are Co, Au, Ag, and W; the supra-ore halo elements are Pb, Zn, Mn, and As; and the sub-ore halo elements are Sn and Bi. According to Gregorian's zoning index and the barycenter method, the primary halo zoning of the No. 16 exploration line from shallow to deep is Mn–P–Pb–Ni–Zn–V–As–Hg–Co–Au–Cu–W–Ag–Mo–Sb–Sr–Cd–Sn–Ti–Bi. This sequence has a distinct "reverse" zoning feature, indicating that there may be a blind ore body deep in the mine. The geochemical parameter evaluation index based on the element content contrast coefficient suggests that there may be a hidden ore body in the deep. The relative hydrothermal mineralization in the center position of the section may be located deep below the north side of borehole ZK1601-1 in the middle of the section. The ore body erosion parameter model shows that the bottom of the drilling engineering control is the middle tail of the ore body, and there is a certain amount of extension in the deep part. The ideal superimposed model of the primary halo reflects the ore body trend of the 16th line section. The ore body is inclined to the north as a whole; the ore fluid flows from the deep to the southern side of the north side, and the deep part of the northern side of the ore body has a downward trend. [ABSTRACT FROM AUTHOR]

In integrating geospatial datasets for mineral potential mapping (MPM), the uncertainty model of MPM can be inferred from the Dempster - Shafer rules of combination. In addition to generating the uncertainty model, evidential belief functions (EBFs) present the belief, plausibility, and disbelief of MPM, whereby four models can be simultaneously utilized to facilitate the interpretation of mineral favourability output. To investigate the functionality and applicability of the EBFs, we selected the Naysian porphyry copper district located on the Urmia - Dokhtar magmatic belt in the northeast of Isfahan city, central Iran. Multidisciplinary datasets-that are geochemical and geophysical data, ASTER satellite images, Quickbird, and ground survey-were designed in a geospatial database to run MPM. Implementing the Dempster law through the intersection (And) and union (OR) operators led to different MPM performances. To amplify the accuracy of the generated favourability maps, a combinatory EBFs technique was applied in three ways: (1) just OR operator, (2) just And operator, and (3) combination of And and OR operators. The plausibility map (as mineral favourability map) was compared to Cu productivity values derived from drilled boreholes, where the MPM accuracy of the hybrid method was higher than each operator. Of note, the success rate of the hybrid method validated by 21 boreholes was about 84%, and it demarcates high favourability zones occupying 0.67 km² of the studied area. [ABSTRACT FROM AUTHOR]

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

One of the specific features of porphyry copper (Cu) mineralization is the distinct occurrence of hydrothermal alteration zones, which can be mapped by processing various satellite images. Among free multispectral images, Landsat 8 OLI and ASTER data are known to be efficient in mapping different geological features, such as alteration zones and tectonic lineaments. This study aims to show the potential of these data types in mapping porphyry Cu mineralization by proposing a framework for employing and integrating different image processing methods. These methods include principal component analysis (PCA), spectral angle mapper (SAM), and matched filtering (MF) employed on these satellite images to map target al.teration zones. Moreover, PCA and directional filtering are applied to the ASTER dataset to enhance and map structural features. The results are evaluated and then combined to provide a potential map of Cu mineralization in the Chahargonbad area, located within the Urumieh-Dokhtar magmatic belt (UDMB) in Kerman province, Iran. The prediction-area plot and normalized density, which are data-driven methods, are used to assign the relative weight of each layer and evaluate them. Finally, using the calculated weights, data-driven multi-index overlay (DMIO) and fuzzy ordered weighted averaging (FOWA) methods are applied to combine the evidential layers. The potential mineralization maps created by the DMIO and FOWA provide a prediction rate of 80% and 82%, respectively. Furthermore, the accuracy of the integrated maps is investigated using the area under the curve (AUC) of the receiver operating characteristic (ROC) curves. The AUC scores obtained from the ROC curves of DMIO and FOWA methods are 0.85 and 0.88, respectively, representing powerful positive spatial relationships with mineralization areas. Based on the results, the proposed framework can be applied to provide a potential map of porphyry Cu mineralization, particularly in arid regions, with reasonable accuracy. [ABSTRACT FROM AUTHOR]

The eastern Lut block of Iran has a high potential for porphyry copper mineralization due to the subduction tectonic regime. It is located in an inaccessible region and has harsh arid conditions for traditional mineral exploration campaigns. The objective of this study is to use Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) remote sensing data for porphyry copper exploration in Simorgh Area, eastern Lut block of Iran. Hydrothermal alteration zones such as argillic, phyllic and propylitic zones associated with porphyry copper systems in the study were identified using false color composition (FCC), band ratio (BR), principal component analysis (PCA) and minimal noise fraction (MNF). The thematic alteration layers extracted from FCC, BR, PCA and MNF were integrated using hybrid Fuzzy-AHP model to generate a porphyry copper potential map for the study area. Four high potential zones were identified in the central, western, eastern and northeastern of the study area. Fieldwork was used to validate the approach used in this study. This investigation exhibits that the use of hybrid Fuzzy-AHP model for the identification of hydrothermal alteration zones associated with porphyry copper systems that is typically applicable to ASTER data and can be used for porphyry copper potential mapping in many analogous metallogenic provinces.

Introduction The widespread Cenozoic magmatic assemblages in Iran host a variety of ore deposits including porphyry Cu-Mo-Au, skarn type ores, and epithermal base and precious metals deposits. Silicic zones of variable sizes are common in the Kerman belt in the southern section of the Urumieh-Dokhtar arc, and some might be representing the upper parts of porphyry copper systems known as lithocap. To investigate this potential relation, a silicic zone in Meideh, north Pariz, is studied. The silicic zone lies in an area with several known porphyry copper deposits (PCD) including Sarcheshmeh, Nochun, Seridun, Sarkooh, and Bagh-Khoshk. For comparison, silica ledges and veins in Seridun and a mineralized silica vein system to the east of the Sarcheshmeh mine are also studied. Materials and methods The study is based on field studies and investigation of textures and structures, and sampling for mineralogy (microscopic and X-ray diffraction analysis), and fluid inclusions. The XRD analyses were accomplished in the Iranian Mines and Mining Industries Development and Renovation Organization (IMIDRO) and Kansaran Binaloud Co, Tehran. The fluid inclusion studies were performed in the Iranian Mineral Processing Research Center (IMPRC) using a Linkam THMS600 equipped with a Zeiss microscope. Results The silicic zone in Meideh is developed in andesitic lava flows and pyroclastic materials, and covers an area of ~ 1 km2. Silica occurs in white to grey colors and in massive, brecciated and locally vuggy textures; the grain sizes range between 0.01mm to 1mm. The silica is locally associated by minor sulfides (pyrite and locally chalcopyrite) carbonates, and clay minerals. The silicic zone grades outward into a silicic-argillic halo and into the host volcanic rocks with propylitic alteration. Chemical analysis of samples from the zone indicated enrichments in Cu, Mo, Ag, As, Bi and Au relative to the average composition of intermediate-mafic volcanic rocks in the Kerman belt. Small outcrops of a quartz-tourmaline rock occur in the southeast of the silicic zone. In Seridun, silica ledges and veins occur in the periphery and in the upper parts of a porphyry copper deposit developed in Miocene shallow intrusive bodies and older volcanic rocks. In east of Sarcheshmeh, several N-S striking silica veins locally containing pyrite, chalcopyrite, malachite, and Fe-oxides/hydroxides occur in Cenozoic volcanic and intrusive host rocks. In both areas, the silicic zones are products of pervasive silicic alteration, and occur in massive, breccia, and vuggy textures. Vuggy texture is well developed in Seridun. XRD analysis of representative samples from Meideh indicated the occurrence of kaolinite and illite, in addition to quartz. Minerals characteristic of advanced argillic alteration (i.e. alunite, pyrophyllite, diaspore and andalusite) are missing. The minerals, however, were identified in Seridun. Fluid inclusions in quartz from all three areas are dominated by two-phase liquid-vapor. Homogenization temperature (TH) varies between 140-263 oC (average: 202 oC) for Meideh, 195-320 oC (average: 247 oC) for Seridun, and 140-264 oC (average: 177 oC) for east of Sarcheshmeh. Salinities vary between 0.18-5.71 (average: 1.62), 1.22-4.18 (average: 2.27), and 0.7-3.39 (average: 1.57) wt.% NaCl eq., respectively. The quartz-tourmaline rock from Meideh is distinguished by the occurrence of liquid-vapor-halite±hematite and liquid-vapor-opaque inclusions, in addition to liquid-vapor inclusions. The TH and salinity for the liquid-vapor inclusions, homogenizing to liquid, varies, respectively, between 202-269 oC (average: 231 oC) and 3.71-7.16 (average: 5.43) wt.% NaCl eq. The TH and salinity for the halite bearing inclusions, homogenized by halite dissolution, varies between 240-480 oC (average: 345 oC) and 33.40-56.90 (average: 42.80) wt.% NaCl eq. Discussion The textures, structure, and spatial relations with the host volcanic rocks suggest that the Meideh silicic zone developed as a result of pervasive silicic alteration, rather than open space filling. Textures indicative of open space filling, including crustification and symmetric banding, are absent in Meideh. The silicic ledges in Seridun, and the N-S striking silicic zones in east of Sarcheshmeh, are the products of pervasive silicic alteration of the host volcanic and intrusive rocks. The XRD analysis of representative samples from Meideh indicated the occurrence of kaolinite and illite, in addition to quartz. Minerals characteristic of advanced argillic alteration (i.e. alunite, pyrophyllite, diaspore and andalusite) are missing. The minerals, however, were identified in Seridun. Fluid inclusions in quartz from the three silicic zones are dominated by two-phase liquid-dominant L-V inclusions. No distinction in salinity can be made between the three zones; Seridun, however, is distinguished by higher homogenization temperature. The local quartz-tourmaline zones in Meideh developed from distinctly higher temperature and salinity fluids (240-480 oC and 33.9-64 wt.% NaCl eq., respectively). A comparison of fluid inclusion data with several epithermal base and precious metals systems in the Urumieh-Dokhtar arc and elsewhere in Iran suggest that no meaningful distinction can be made between barren (i.e. Meideh, at current exposure level) and productive epithermal systems. Our data indicate that the silicic zone in Meideh cannot be considered as a porphyry-related lithocap at current exposure. The quartz-tourmaline rock developed from fluids of higher salinity and temperature suggests a link with magmatic-hydrothermal systems and warrants further investigation. Acknowledgements We would like to thank Mr. Afrouz for introducing the area, help with field works, and discussions. We are grateful to Mr. Imani from Parsolang for his help with field works and discussions, and to Ms. Aghajani from Iranian Mineral Processing Research Center for her invaluable help with the fluid inclusion studies. Dr. Ashrafpour kindly provided us with geological maps and chemical analysis of samples from the Meideh silicic zone. The study was supported by the Iranian Mines and Mining Industries Development and Renovation Organization (IMIDRO) and a Shahid Beheshti University grant to S.A.

A mineral resource assessment of porphyry copper deposits in the Andes Mountains of South America was done in 2005 in cooperation with geological surveys in South America. The study identified 590 million metric tons (Mt) of copper in identified resources. Continued exploration and development in the region over a 15-year period provide an opportunity to compare the predicted assessment results with new discoveries and resource growth in previously known deposits. The 2005 assessment estimated that 145 undiscovered deposits could contain a mean of 750 Mt of copper. The actual number of deposits increased (2005 to 2020) from 69 to 120 and the amount of identified copper resources increased from 590 Mt to 1600 Mt. Although most of the new deposits and copper resources are concentrated in Miocene-Pliocene and Eocene-Oligocene mineral belts, new deposits have been discovered in Jurassic and Cretaceous mineral belts. Resource growth in porphyry copper deposits known in the Andes in 2005 (1100 Mt copper) exceeds copper resources in new discoveries since 2005 (490 Mt copper) by a factor of 2. [ABSTRACT FROM AUTHOR]

Čukaru Peki is a recently discovered porphyry- high-sulfidation Cu-Au deposit located 5km south of the mining town of Bor in east Serbia. Three styles of mineralization are distinguished in the Čukaru Peki system: a high-sulfidation type with massive sulfides (named the Upper zone), a porphyry type (named the Lower zone) and a transition type (between porphyries and massive sulfides). This study investigates the concentration and distribution of trace elements in pyrite from these three mineralization zones of Čukaru Peki. The high-sulfidation pyrite contains elevated concentrations of V, Mn, Ni, Cu, As, Mo, Ag, Cd, In, Sn, Sb, Au, Hg, Tl, Pb and Bi, compared to pyrite from the porphyry zone. The porphyry zone pyrite contains elevated concentrations of Co and Se. The sample from the transition zone contains concentrations between the two other zones, with the exception of the relative enrichment of Co and Ag. This research also aims to separate different stages of ore deposition. The porphyry stage contains several types of veins: quartz A veins, quartz B veins, pyrite D veins, magnetite veins, purple anhydrite veins, sulfide veins and orange anhydrite veins. The high sulfidation stage also formed in several stages: pyrite1, pyrite-enargite veins, pyrite-covellite veins, pyrite2 veins and calcite-anhydrite veins. There are distinct differences between various vein generations found within each zone, notable examples are the enrichment of Se in quartz B veins pyrite and Cu in sulfide veins, compared to other veins from porphyry zone veins and the enrichment of several trace elements (Cu, Mo, Ag, Cd, In, Sn, Sb, Au, Hg, Tl, Pb and Bi) in pyrite from the Py-cov veins in comparison to the other high-sulfidation veins. The trace element data also indicates a change in fluid compositions; the earlier fluids responsible for the porphyry zone mineralization showing a slightly more magmatic fluid signature (higher Co/Sb and Se/As values) and the later high-sulfidation fluids bearing a more typical epithermal trace element signature, which indicates cooling and diluting of fluids. Some of the porphyry zone pyrite crystals (from B-type veins and Purple anhydrite-veins) contain elevated concentrations of elements attributed to the high-sulfidation zone (e.g. Cu, Ag, Cd, In, Sn, Pb and Bi), which suggests that these veins were affected by later high-sulfidation fluids. [ABSTRACT FROM AUTHOR]

This work presents a hybrid-based clustering approach for mineral potential mapping (MPM) of porphyry-type Cu mineralization at Kerman province in the SE of Iran. Whereby a multidisciplinary geospatial data set was processed and integrated in the Chahargonbad district. Data-driven prediction-area (P-A) plots were drawn for each evidence layer derived from geological, geochemical, geophysical and satellite imagery data. The P-A plots provide insight into the weight of evidence for synthesizing all geospatial layers. Out of many knowledge-driven methods which biasing from experts' opinions, index overlay and fuzzy operators were employed to find out an optimum Cu favorability map through calculating an efficiency index representing the performance of each MPM. A concentration-area (C-A) fractal model was implemented to separate the mineral favorability map into some populations to ensure correct determining the cluster numbers. Clusters number is a prerequisite which must be defined correctly to increase the performance of clustering analysis for generating reliable results in MPM. Such an appropriate number of clusters can be incorporated in running three prevalent groups of clustering methodologies as data-driven approaches in MPM. They are self-organizing map, fuzzy c-means, and k-means algorithms. One of the reasons for this tendency to consider a hybrid-based method is that it overcomes the shortcomings of the both methods (bias of experts’ opinions and unknown clusters number) in mineral favorability mapping. The unknown number of clusters was determined through a knowledge-driven method, and then it was passed to an unsupervised data-driven method, i.e. clustering algorithm. This hybrid method produces synthesized maps in close association with known porphyry-Cu mineralization in the Chahargonbad area.

The Elatsite–Chelopech ore field in the northern part of the Panagyurishte district in Central Bulgaria comprises numerous spatially associated porphyry copper and epithermal gold deposits and prospects. In addition to the mineralization and alteration features, trace elements, lead and sulfur isotope signatures of sulfide minerals from porphyry copper, base metal and gold-base metal deposits/prospects have been studied. LA-ICP-MS analyses of pyrite, arsenopyrite and sulfosalt minerals validate them as major carriers for Au, Ag, Sb, Se and Co. Pyrite from the three types of mineralization has specific geochemical characteristics. Pyrite from the porphyry copper deposits/prospects has generally lower total trace element content compared to pyrite from the epithermal prospects, except for Se, Co and Ni. Pyrite from the base metal and gold-base metal veins is enriched in As, Au, Ag, Sb and Pb. In pyrite from the base metal deposits, Co and Ni have contents comparable to the pyrite from the porphyry copper deposits, while pyrite from the gold-base metal veins shows lower Co and Ni. Arsenopyrite from these deposits shows similar features. Similarly, sphalerite from the gold-base metal veins also has lower Co content compared to sphalerite from the base metal veins but higher In and Cu contents. In addition to the close spatial relationships between the Elatsite and Gorna Kamenitsa porphyry Cu deposits and Negarstitsa-West and Dolna Kamenitsa base metal prospects, as well as similarities in the mineralization and alteration styles, the lead isotopic (206Pb/204Pb = 18.61–18.68, 207Pb/204Pb = 15.64–15.65 for porphyry and 206Pb/204Pb = 18.55–18.67, 207Pb/204Pb = 15.64–15.68 for base metal) and sulfur isotopic (δ34S values of −3 to +1‰ for porphyry and δ34S values of −1.7 to +3.5‰ for base metal) signatures of sulfides support the idea of a genetic link between these two types of deposits. The porphyry and base-metal mineralization result from a common major ore-forming event during the Late Cretaceous, corresponding to deep/higher-temperature and shallower/distal/lower-temperature environments, respectively. In particular, more radiogenic lead (206Pb/204Pb = 18.41–18.47, 207Pb/204Pb = 15.67–15.76) and slightly different sulfur isotopic compositions (δ34S values of +3.5 to +10.6‰) of sulfides from the distal gold-base metal veins of Kordunsko Dere, Svishti Plaz and Shipkite might be a consequence of the interaction of the ore-forming fluids with an external older crustal and isotopically positive S source. Alternatively, a different fluid source/event for the formation of these gold-base metal veins may be suggested.

Groundwaters recovered from the Salar de Punta Negra and Monturaqui basins in the Atacama Desert of northern Chile exhibit distinctly different isotopic, major, trace, and porphyry copper elemental compositions related to contrasting morphostructural, geochemical, and hydrodynamic settings. Comparison of these distinct groundwater signatures with groundwaters from known porphyry copper deposits (Salar de Hamburgo and Spence Deposit), can be used to determine if either basin might be prospective for porphyry copper mineralization. Groundwaters within the Punta Negra Basin exhibit geochemical characteristics consistent with other closed basin settings throughout the arid Andes. Elemental and isotopic compositions within the Punta Negra Basin reflect closed basin evaporitic processes consistent with the hyperarid, volcanic setting of the central Andes. Pathfinder metals and isotopic compositions are not consistent with porphyry copper type mineralization as described for groundwaters within the Salar de Hamburgo Basin, and the Spence Deposit. Within the Monturaqui Basin the geochemical composition of groundwaters are characteristic of diffuse hydrothermal activity. Sulfur isotopic composition within the waters of the northern Monturaqui Basin exhibit δ 34SCDT isotopic signatures that fall within the range for sulfide mineralization as reported for groundwaters in and around the Spence Deposit and the Salar de Hamburgo. However, porphyry copper related elements within the Monturaqui Basin are impoverished relative to groundwaters of the Spence and Escondida Deposit. Such impoverishment in porphyry related elements, taken in conjunction with enriched δ 13CPDB compositions, elevated groundwater temperatures, groundwater compositions dominated by HCO3, SO4, and Si, and the proximity of the Monturaqui Basin to the current magmatic arc are consistent with a volcanic hydrothermal origin. In summary, the groundwater geochemistry of the Monturaqui and Punta Negra Basins are not indicative of porphyry copper-type mineralization. Thematic collection: This article is part of the Hydrochemistry related to exploration and environmental issues collection available at: https://www.lyellcollection.org/cc/hydrochemistry-related-to-exploration-and-environmental-issues [ABSTRACT FROM AUTHOR]

The Qulong porphyry copper deposit in Tibet is located in the Tethis–Himalaya metallogenic domain, one of the three major porphyry metallogenic domains in the world. At present, the mining area is mainly used for surface mining. The depth revealed by the drilling project is less than 2 km. The potential for deep resources is unknown. Based on an analysis of the geochemical characteristics of the primary halos around the No. 16 prospecting line, deep extension is discussed in this paper. Studies show that the metallogenic elements are Cu and Mo; the near-ore halo elements are Co, Au, Ag, and W; the supra-ore halo elements are Pb, Zn, Mn, and As; and the sub-ore halo elements are Sn and Bi. According to Gregorian’s zoning index and the barycenter method, the primary halo zoning of the No. 16 exploration line from shallow to deep is Mn–P–Pb–Ni–Zn–V–As–Hg–Co–Au–Cu–W–Ag–Mo–Sb–Sr–Cd–Sn–Ti–Bi. This sequence has a distinct “reverse” zoning feature, indicating that there may be a blind ore body deep in the mine. The geochemical parameter evaluation index based on the element content contrast coefficient suggests that there may be a hidden ore body in the deep. The relative hydrothermal mineralization in the center position of the section may be located deep below the north side of borehole ZK1601-1 in the middle of the section. The ore body erosion parameter model shows that the bottom of the drilling engineering control is the middle tail of the ore body, and there is a certain amount of extension in the deep part. The ideal superimposed model of the primary halo reflects the ore body trend of the 16th line section. The ore body is inclined to the north as a whole; the ore fluid flows from the deep to the southern side of the north side, and the deep part of the northern side of the ore body has a downward trend.

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Mineral reserves are heterogeneous by nature, which can lead to a high variability in the intrinsic features of ores and in the responses to mineral processing operations. A geometallurgical model, along with a reliable reservoir block model, helps to quantify the significant variabilities and develop programs to deal with them. It is an important tool for mitigating production risks and improving economic performance in the modern mining industry. In complex porphyry ore deposits, samples with high sulphide copper and high oxide copper will be processed via flotation and heap-leaching units sequentially. Therefore, a geochemical domaining based on total copper grade and its oxide and sulfide fractions can be inferred as the block processing destinations to different processing units or waste dump. Routine classification methods separate two domains with a sharp boundary. Since the error in grade estimation is unavoidable, the geometallurgical classification based on geochemical domaining will face uncertainty. Selecting a range threshold for each boundary, defining fuzzy membership functions, and assigning a membership degree to different classes for each sample would be a solution for this problem. This approach helps remove uncertainty in decision making, reduces the risk and increases the profitability of the project. This geometallurgical model is applied for different block dimensions with the aim of comparing the results. [ABSTRACT FROM AUTHOR]

The reduction of oxidized sulfur is essential in porphyry copper deposits whose mineralization predominantly comprises copper sulfides, whereas their source magmas are oxidized with most of their sulfur as SO42− and with exsolved fluids having SO2>>H2S. To estimate the redox state of sulfur, we examined drill cores that intersect potassic and unaltered intrusive rocks in the deeper levels of the Grasberg porphyry copper-gold deposit. Magmatic oxybarometers such as the amphibole-titanite-magnetite-quartz assemblage, anhydrite, and amphibole consistently show that Grasberg ore-forming magmas were oxidized with fO2 > FMQ+3. Initial hydrothermal events formed sulfide-free, anhydrite-rich K-feldspar, and biotite alteration, followed by successive vein stages of (1) magnetite, (2) biotite, (3) quartz, (4) anhydrite-chalcopyrite, (5) chalcopyrite ± sericite selvages, and (6) pyrite-chalcopyrite-quartz + sericite selvages. The δ34S values of sulfide-sulfate mineral pairs indicate SO2-derived SO42− and H2S in SO42−/H2S molar proportions of ~ 4:1 to ~ 3:1 at > 550 °C. The hydrothermal fluid then likely followed a rock-buffered trajectory and became more reduced at < 550 °C. Hydrothermal biotite that replaces igneous amphibole and biotite has a phlogopitic composition, suggesting that Fe2+ was liberated from igneous mafic minerals and oxidized by reaction with SO42− to form magnetite, resulting in sulfide formation by the simplified reaction 12FeO + SO42− + 2H+ → 4Fe3O4 + H2S. [ABSTRACT FROM AUTHOR]

Introduction The formation of the Zagros orogenic belt is attributed to northeastward oblique subduction of the Neotethys beneath the western border of central Iran. This was followed by continental collision between the Afro-Arabian plate and the central Iran microcontinet (Zarasvandi et al., 2015). The Zagros orogen is characterized by three main parallel structural zones consisting of Zagros fold and thrust belt, the Sanandaj–Sirjan metamorphic zone, and the Urumieh–Dokhtar magmatic arc (Mohajjel et al., 2003). The Urumieh–Dokhtar magmatic arc is dominated by the widespread occurrence of Eocene to Quaternary intrusive and extrusive rocks. It is considered as being one of the main Cu bearing regions in the world, where world class giant porphyry deposits, as well as large and small sub-economic porphyry Cu ± Mo ± Au systems have been reported and investigated by many authors (Shafiei et al., 2009; Zarasvandi et al., 2005). In addition to UDMA, the Sanandaj-Sirjan zone (SSZ) hosts several Jurassic-Cretaceous intrusive complexes extending from the northwest to southeast SSZ. It should be noted that these granitoids are barren and porphyry mineralization has not been accompanied with these intrusions. This paper tried to compare the available geochemical data of productive granitoids in the Urumieh-Dokhtar (i.e., Dalli, Ali-Abad and Darreh-Zerreshk, Parkam, Sarcheshmeh, Meiduk and Sungun), and those of barren intrusions in the Sanandaj-Sirjan zone (i.e., Aligodarz, Bourujerd, Alvand, Astaneh, Hasan Robat, and Siah Koh). Materials and methods This investigation is based on the available geochemical data on the six barren intrusions in the SSZ (i.e., Aligodarz, Bourujerd, Alvand, Astaneh, Hasan Robat and Siah Kohe), and productive intrusive rocks (porphyry associated intrusions) in the UDMA (i.e., Dalli, Ali-Abad and Darreh-Zerreshk, Parkam, Sarcheshmeh, Meiduk and Sungun). Data for the UDMA porphyry intrusions (41 samples) were adopted from studies of Daneshjou (2014), Zarasvandi et al. (2005), Taghipour and Mohammadi Laghab (2014), Barzegar (2007), Taghipour (2007), and Hezarkhani (2006). Furthermore, the data of the SSZ barren intrusions (42 samples) comes from Esna Ashari et al. (2012), Khalaji et al. (2007), Aliani et al. (2012), Tahmasbi et al. (2010), Alirezaei and Hassanzadeh (2001), and Arvin et al. (2007). Two criteria were used for selection of 83 representative samples: (1) samples with a relatively similar mineralogical and compositional range (quartz diorite, quartz monzonite, granodiorite and granite), and (2) samples with the least amount of alteration (minimal amounts of Loss On Ignition; LOI wt.% = H2O + CO2). Results Productive intrusions in UDMA have positive Eu anomalies, LREE enrichment relative to HREE, and high Lan/Ybn ،Sr/Y، Dyn/Ybn، Lan/Smn ratios. In comparison, barren granitoids in the SSZ are characterized by steep downward LREE to HREE, negative Eu anomalies and low Lan/Ybn ، Sr/Y، Dyn/Ybn، Lan/Smn ratios. Discussion Based on the presented results, it is proved that due to the lack of considerable crustal thickness in SSZ (during the subduction of the Neotethyan oceanic lithosphere under the SSZ zone), and the presence of dry magma (low H2O contents), the SSZ granitoids exhibit barren characteristics. In contrast, during the ongoing processes of closure of Neo-Tethys and during compression and crustal shortening, magma mixing and evolution toward high magmatic water content lead to the increasing of metal endowment in the porphyry associated granitoids of (UDMA) It seems that magma generation from the melting of thickened lower crust (garnet amphibolite source) could be considered as one important key factors for the generation of metal-rich magmas with high oxidation state and high H2O contents has led to the development of porphyry Cu systems in the UDMA compared to those of SSZ granitoids. Acknowledgements The authors are grateful to the Shahid Chamran University of Ahvaz for the research funding by the Grant Commission in 2017. References Aliani, F., Maanijou, M., Sabouri, Z. and Sepahi, A.A., 2012. Petrology, geochemistry and geotectonic environment of the Alvand Intrusive Complex, Hamedan, Iran. Chemie der Erde-Geochemistry, 72(4): 363–383. Alirezaei, S. and Hassanzadeh, J., 2012. Geochemistry and zircon geochronology of the Permian A-type Hasanrobat granite, Sanandaj–Sirjan belt: A new record of the Gondwana break-up in Iran. Lithos, 15(151): 122–134. Arvin, M., Pan, Y.M., Dargahi, S., Malekizadeh, A. and Babaei, A., 2007. Petrochemistry of the Siah-Kuh granitoid stock southwest of Kerman, Iran: implications for initiation of neotethys subduction. Journal of Asian Earth Sciences, 30(3): 474–489. Barzegar, H., 2007. Geology, petrology and geochemical characteristics of alteration zones within the Seridune prospect, Kerman, Iran. Ph.D. thesis, Aachen University, Aachen, Germany, 320 pp. Daneshjou, M., 2014. Investigation of geology, geochemistry and genetic model of the Dalli porphyry Cu–Au deposit, Delijan, Markazi province. M.Sc. Thesis, Shahid Chamran University, Ahvaz, Iran, 150 pp. (in Persian with English abstract) Esna-Ashari, A., Tiepolo, M., Valizadeh, M.V., Hassanzadeh, J. and Sepahi, A.A., 2012. Geochemistry and zircon U–Pb geochronology of Aligoodarz granitoid complex, Sanandaj-Sirjan zone, Iran. Journal of Asian Earth Sciences, 43(1): 11–22. Hezarkhani, A., 2006. Petrology of the intrusive rocks within the Sungun porphyry copper deposit, Azerbaijan, Iran. Journal of Asian Earth Sciences, 27(3): 326–340. Khalaji, A.A., Esmaeily, D., Valizadeh, M.V. and Rahimpour-Bonab, H., 2007. Petrology and geochemistry of the granitoid complex of Boroujerd, Sanandaj-Sirjan Zone, Western Iran. Journal of Asian Earth Sciences, 29(5): 859–877. Mohajjel, M., Fergusson, C.L. and Sahandi, M.R., 2003. Cretaceous–Tertiary convergence and continental collision, Sanandaj–Sirjan zone, western Iran. Journal of Asian Earth Sciences, 21(4): 397–412. Shafiei, B., Haschke, M. and Shahabpour, J., 2009. Recycling of orogenic arc crust triggers porphyry Cu mineralization in Kerman Cenozoic arc rocks, southeastern Iran. Mineralium Deposita, 44(3): 265–283. Taghipour, N., 2007. The application of fluid inclusions and isotope geochemistry as guides for exploration, alteration and mineralization at the Meiduk porphyry copper deposit, Shahr-Babak, Kerman. Unpublished Ph.D. thesis, Shahid Bahonar University, Kerman, Iran, 321 pp. Taghipour, N. and Mohammadi Laghab, H., 2014. Sara (Parkam) Porphyry Copper Deposit in Kerman, Iran: Petrography, Geochemistry and Geodynamic Setting. Geochemistry Journal, 1(3): 14–26. Tahmasbi, Z., Castro, A., Khalili, M., Khalaji, A.A. and de la Rosa, J., 2010. Petrologic and geochemical constraints on the origin of Astaneh pluton, Zagros orogenic belt, Iran. Journal of Asian Earth Sciences, 39(3): 81–96. Zarasvandi, A., Liaghat, S. and Zentilli, M., 2005. Geology of the Darreh-Zerreshk and Ali-Abad porphyry copper deposits, central Iran. International Geology Review, 47(6): 620–646.

Bu çalışmanın temel amacı, yerel ölçekte Coğrafi Bilgi Sistemleri (CBS) temelli olasılık modeli kullanarak porfiri cevherleşme olasılığını ortaya koymak ve oluşturulan modelin geçerliliğini saha gözlemleri, yüzey örneklemesi ve sondaj verileriyle değerlendirmektir. Bu çalışmada konu edilen Sonajeel sahası, KB İran’da Arabasaran cevherleşme kuşağının bir parçasını oluşturmaktadır. Bir cevherleşme tipi ile ilgili matematiksel arama algoritması oluşturmak, karmaşık ve disiplinler arası bir çalışmadır. Bu amaçla, bu çalışmada jeoloji, jeokimya ve uzaktan algılama çalışmalarını da içeren farklı veri setlerinin işlenmesi ve yorumlanmasından elde edilen sonuçlar göz önünde bulundurulmuştur. Sillitoe (2010) tarafından önerilen aramaaşaması ve tanımlayıcı porfir cevherleşme modeli göz önünde bulundurularak kapsamlı bir arama bütünleştirme modeli oluşturulmuştur. CBS tabanlı arama modeline ait girdileri düzenlemek için bulanık üye eğrileri kullanarak değer atanmış gridler (ızgaralar) veya kanıt katmanları üretilmiş ve daha sonrasında da gama bulanık fonksiyonu ile birleştirilmiştir. Buna ek olarak, maden prospeksiyon haritasının tanımlanması ve bulanıklığının giderilmesi için olasılık haritasının piksel değerleri üzerinde Konsantrasyon-Alan (C-A) fraktal modeli uygulanmıştır. Son olarak sonuçlar, saha gözlemleri, yüzey örneklemesi ve sondaj verileri ile doğrulanmıştır. İlk öncelik olarak sondaj logları ortalama %0.5 Cu tenörlü bir zonu ortaya koymuştur.

A mineral resource assessment of porphyry copper deposits in the Andes Mountains of South America was done in 2005 in cooperation with geological surveys in South America. The study identified 590 million metric tons (Mt) of copper in identified resources. Continued exploration and development in the region over a 15-year period provide an opportunity to compare the predicted assessment results with new discoveries and resource growth in previously known deposits. The 2005 assessment estimated that 145 undiscovered deposits could contain a mean of 750 Mt of copper. The actual number of deposits increased (2005 to 2020) from 69 to 120 and the amount of identified copper resources increased from 590 Mt to 1600 Mt. Although most of the new deposits and copper resources are concentrated in Miocene-Pliocene and Eocene-Oligocene mineral belts, new deposits have been discovered in Jurassic and Cretaceous mineral belts. Resource growth in porphyry copper deposits known in the Andes in 2005 (1100 Mt copper) exceeds copper resources in new discoveries since 2005 (490 Mt copper) by a factor of 2.

Whether using a shallow neural network with one hidden layer, or a deep network with many hidden layers, the training data must represent subgroups of the deposit type being explored to be useful. Published examples of neural networks have mostly been limited to one individual mineral deposit for training. Variation of geologic features among deposits within a type are so large that a single deposit cannot provide proper information to train a neural net to generalize and guide exploration for other deposits. Models trained with only one deposit tend to be academic successes but are not of practical value in exploration for other deposits. This is why it takes much experience examining many deposits to properly train an economic geologist—a neural network is not any different. Two examples of shallow neural networks are used to demonstrate the power of neural networks to possibly locate undiscovered deposits and to provide some suggestions of how to deal with missing data. The training data needs to include information spatially related to known deposits and hopefully information from many different deposits of the type. Lessons learned from these and other examples point to a proposed sampling plan for data that could lead to a generalized neural network for exploration. In this plan, 10 or more well-explored gold-rich porphyry copper deposits from around the world with 100 or more sample sites near and some distance from each deposit would probably capture important variability among such deposits and provide proper data to train and test a shallow neural network to predict locations of undiscovered deposits. [ABSTRACT FROM AUTHOR]

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

The Daero Paulos porphyry copper prospect, in the Asmara region of the central Eritrean highlands, is part of the Nakfa tectono-stratigraphic terrane, which, along with four other major and several minor terranes that constitute the Neoproterozoic Arabian-Nubian Shield, is characterized by juvenile, intra-oceanic island-arc crust. Alteration and mineralization at Daero Paulos occupy a north-northeast-trending corridor of multiphase, rhyolitic to dacitic intrusions emplaced into mafic and intermediate volcanic and subvolcanic rocks and derivative volcaniclastic strata. New U-Pb geochronological data for the volcanic rocks in the region confirm a >860-Ma age for the Neoproterozoic (Tonian) host sequence. The porphyry copper alteration evolved from early epidote-chlorite-albite through sericite-chlorite to late quartz-sericite. Local advanced argillic alteration is the erosional remnant of the lithocap that formerly dominated the shallow parts of the Daero Paulos system. A post-mineralization, Alaskan-type pyroxenite-gabbro body intruded the porphyry copper corridor, and is interpreted as the feeder for mafic dikes along the periphery of the porphyry copper system. Re-Os ages of 881.0 ± 5.5 and 864.2 ± 3.6 Ma for molybdenite from veinlets at Daero Paulos constrain an early Tonian timing for porphyry copper formation during early opening of the Mozambique Ocean after Rodinian supercontinent break-up. The ages also imply a rapid transition from initial rifting to the start of subduction and consequent establishment of an intra-oceanic island arc in what is now the Nakfa terrane. The molybdenite ages show that Daero Paulos is currently the oldest dated mineralization in the Arabian-Nubian Shield, and ~60–200 and, possibly, ~250 m.yr. older than porphyry copper mineralization elsewhere in the Shield. However, volcanogenic massive sulfide (VMS) mineralization could have been forming at broadly the same time, albeit not genetically associated with Daero Paulos. Preservation of such shallowly formed Neoproterozoic mineralization is mainly attributed to burial beneath thick post-amalgamation volcano-sedimentary basinal cover, collision-generated thrust sheets, and later Phanerozoic strata. Unlabelled Image • Oldest dated mineralization in the Arabian-Nubian Shield • Formation in an embryonic intra-oceanic island arc • Porphyry copper mineralization spanned ~200 m.yr. of Shield development. [ABSTRACT FROM AUTHOR]

Porphyry copper deposits are formed by aqueous fluids exsolved by differentiated, mantle-derived magmas variably mixed with crustal melts. Water is essential to form porphyry Cu mineralization, and this explains why these deposits are found only at convergent margin settings, where subduction has enriched the mantle source of magmas with slab-derived H2O. Intuitively, the more water occurs in the parental magmas of porphyry deposits, the more fertile the latter should be. Indeed, several studies have proposed that anomalously high H2O contents in the source basalt, resulting, for instance, from subduction of large-scale serpentinized fracture zones of the oceanic slab, could increase the fertility of magmas. However, no studies have ever quantified the effects of variable H2O contents on the fertility of parental basalts to form porphyry deposits. Here, using petrological modeling with a Monte Carlo approach, I show that the optimum amount of slab-derived H2O in fertile parental basalts is ∼2–6 wt%, which coincides with the measured range of H2O content in arc basalts. Lower and higher amounts of H2O in the parental basalt lead to less porphyry-fertile magmas. The lower fertility of H2O-poor parent basalt (i.e., 6 wt%) predicted by the model is counterintuitive. The reason for the decreased fertility of parental basalts with >6 wt% H2O is that such H2O-rich magmas undergo fluid saturation, losing their fluid and metal cargo at deep crustal levels. Additionally, water saturation-induced crystallization of amphibole at these deep levels prevents such H2O-rich magmas from ascending to shallower crustal levels, where they can form porphyry deposits. The conclusion that arc basalts with normal H2O contents (∼2–6 wt%) are the most porphyry-fertile adds evidence to the hypothesis that intermediate-felsic magmas associated with porphyry Cu deposits are parented by arc basalts formed through normal subduction-related processes and that intracrustal and tectonic processes play the most relevant role in the modulation of Cu endowments of these deposits.

The Bukovik-Kadiica mineralized system is hosted by Tertiary dacitic and andesitic volcanic rocks which have intruded the basement of Palaeozoic schists in the Serbo-Macedonian Massif of eastern Macedonia. The latest geological exploration has confirmed that this porphyry copper mineralizationis characterized by a dominance of chalcocite and covellite with associated chalcopyrite, emplectite, and bornite, with the highest grades in a zone of supergene enrichment. Silicification is the dominant alteration within the mineralized system, whilst zones of potassic, phyllic, argillic, propylitic, and advanced argillic alteration are also present. Silicification and sulphide mineralization are located in stockworks in altered dacite and andesite breccia. Dissolution of primary sulphides and chemical leaching are evident in the zones of oxidation, dominated by limonite breccia.The main copper mineralization has a vertical extent between 90 and 220 m. Fluid inclusion studies of mineralized quartz veins have identified three separate groups of fluids: saline inclusions which homogenize at 326-501 °C and have a salinity of 32-45 wt% NaCl equiv., vapour-dominated inclusions which homogenize at 438-497 °C and have a salinity of 6–16 wt% NaCl equiv., and more dilute, two-phase vapour–liquid inclusions that homogenize at 360-627 °C and have a salinity of 3-24 wt% NaCl equiv.

Copper mineralization in Kahang porphyry mining district as a tectonically active region in the center of Iran, at the middle of Urmia–Dokhtar magmatic assemblage (UDMA), has been drastically controlled by structural lineaments. Determination of these footprint features is a good guide to identify the location of ore occurrences. One way to recognize lineaments is to process satellite imagery along with geophysical data. Although the visual extraction of lineaments from such data set is the most common method, automatic methods for detecting lineaments can highly reduce user errors and runtime. The most efficient automated methods in this regard are those that simultaneously take edge detection filters with lineament extraction algorithms into consideration. In this work, the CANNY algorithm was employed as an edge-detector filter at first and later Hough transform was used to extract linear features from satellite imagery and geophysical magnetometry data. The proposed methods were implemented on the high-resolution imagery data collected by QuickBird satellite along with ground-based magnetometry data to extract the shallow and deep-seated lineaments. After investigating and plotting this structural controller in a map, the dominant orientation was in the NE–SW direction perpendicular to the UDMA. Generated lineament density map also indicated that the eastern, southeast, and western portions of the area had high potential for porphyry copper mineralization. [ABSTRACT FROM AUTHOR]

Tailings from porphyry copper mines contain environmentally harmful amounts of elements such as copper, molybdenum, lead and cobalt. Geostatistical simulation of contaminants at unknown locations can be helpful in taking preventive measures for tailings management. In the presence of spatially cross-correlated variables, cosimulation has been the traditional method of evaluation. However, application of cosimulation is cumbersome due to modeling so many auto/cross-variograms at once regarding Cauchy–Schwarz inequality. Moreover, cosimulation may face with an unsolvable system of equations in its algorithm. Then, application of joint simulation using minimum/maximum autocorrelation factors which gives reasonable results would be advantageous. In this study, nine spatially cross-correlated attributes of the Sungun porphyry copper deposit are transformed into orthogonal factors. Each factor is independently simulated by generating one hundred equiprobable realizations through the direct sequential simulation or the sequential Gaussian simulation method. The independent simulations are jointly back-transformed into the original data space using a rotation matrix. Test of the final simulations shows reasonable reproduction of data statistics such as the mean and variance values, cumulative distribution functions, cross-correlations and auto/cross-variograms. For each realization, contamination degrees of the blocks are calculated considering the simulated values of variables, the recovery percentage of contaminants in the tailings and the maximum permissible concentrations of the elements in soils. Blocks are categorized regarding the specified contamination degree thresholds and probabilities of occurrence of low, moderate, high and very high contaminations. Sulfide minerals of copper, antimony, arsenic, zinc, molybdenum and silver consist almost 96% of contaminants. All contaminants are sulfide minerals so that additional bulk flotation of the tailings is suggested for reducing their amounts. [ABSTRACT FROM AUTHOR]

Introduction The Iju porphyry copper deposit is located in the southern part of the Urumieh-Dokhtar magmatic arc (Dehaj-Sarduieh belt) within the Kerman copper belt (Dimitrijevic, 1973). The Porphyry Copper mineralization in the Iranian plate occurs dominantly along the Urumieh-Dokhtar arc, which has resulted from the subduction of the Arabian plate beneath the central Iran and the closure of the Neo-Tethys Ocean during the Alpine orogeny (Hassanzadeh, 1993). The Iju porphyry copper deposit with 25 million tons of ore reserves is one of the main copper deposits within the Kerman copper belt. The mining area is composed of upper Miocene volcanic and subvolcanic rocks (mineralized and barren subvolcanic rocks) and quaternary deposits. Two hydrothermal alteration zones of quartz-sericite-pyrite and propylitic zones can be identified in the Iju area. The copper mineralization in the Iju deposit occurs as disseminated, stockwork and hydrothermal breccia. In the hypogene zone, the mineral paragenesis include chalcopyrite, pyrite, with minor occurrences of bornite and magnetite. This paper reports geological, mineralogical, fluid inclusion and S isotope data from the Iju deposit in order to investigate ore-bearing fluids’ characteristics and the mechanisms of ore deposition. Materials and methods Fifteen samples of syngenetic quartz+pyrite bearing veinlets within the quartz-sericite-pyrite zone were selected from different depths across the seven boreholes. Quartz was used for double-polished thin sections and pyrite was used for sulfur isotope analysis. Fluid inclusion studies were performed using the Linkam cooling and heating stage, the THMSG 600 model. The syngenetic pyrite with thermometry quartz sample was used for the sulfur isotope experiments. Stable isotope analysis was performed at the Hatch Stable Isotope Laboratory in the University of Ottawa, Canada. Results The fluid inclusions of the Iju deposit represent a wide range in the homogenization temperatures between 140 to 480°C and salinity between 0.18 to >52.99 wt.% NaCl equiv., which are most similar to the results of the other Iranian porphyry copper deposits. Being located in the quartz-sericite-pyrite alteration zone, the results of thermometry indicates that ore deposition in the Iju deposit has occurred via mixing of magmatic and surface fluids. Variations in salinity and paragenesis of the saline multiphase fluid inclusions and two-phase gas-rich fluid inclusions indicate the occurrence of boiling phenomenon in some samples of the Iju deposit. The amount of δ34S for pyrite has a limited range close to zero (average, 0.229‰) that shows a magmatic origin for sulfur. Considering the presence of subvolcanic rocks, the type and extension of alteration zones, the structure and texture of ore bodies, thermometry results of fluid inclusions and sulfur isotope values, the Iju deposit is similar to porphyry copper deposits. Discussion In the quartz-sericite-pyrite zone, three main groups of veinlets have been identified. The quartz+pyrite veinlets are more abundant than the other types and they were selected for fluid inclusions and stable isotope studies. Petrographic studies of fluid inclusions identifies two groups of fluids including: 1- fluid inclusions without the halite phase, including the types L+V, L+V+S1 and (L+V+S1+S2, that is secondary), 2- fluid inclusions with halite phase, including the types L+V+H, L+V+H+S1, L+V+H+S1+S2 and L+V+H+S1+An. Homogenization temperature and salinity for the fluid inclusions without halite phase are as follows: 140 to 380°C and 0.18 to 24 wt.% NaCl (Fig. 8A and C) and for the fluid inclusions with halite phase they range from 230 to 480°C and 30 to 52 wt.% NaCl (Fig. 9A, B and D), In addition, the pressure and depth for the fluid inclusions containing halite phase are 750 bar and 3500 m on the average. Fluid inclusions available at the quartz veinlets of porphyry copper deposits can be formed in a wide range of chemical composition and under different temperature and pressure conditions (Rusk and Reed, 2008). The wide range in fluid inclusions data of the Iju deposit can be justified by physicochemical changes in the fluid as it is boiling and mixing with the surface fluids. Cooling, fluids mixing, boiling and fluid-rock reaction play important roles in the settling of chalcopyrite from the hydrothermal fluid and the dilution of saline ore-bearing fluids can cause the formation of copper ores from the ore-bearing fluid (Ulrich et al., 2002). Pyrite δ34S value ranges from -0.86 to +1.27‰ (average, +0.22‰) and the δ34SH2S value of the syngenetic fluid with pyrite ranges from -0.23 to -2.36‰ (average, -1.17‰). The limited and near zero range that is observed about δ34S value of the sulfur minerals indicates the controlling role of magmatic processes in the mineralization events (Chen et al., 2009). Acknowledgments This article is related to Project No. 27124.3 dated 2015, 2, 7 at the Ferdowsi University of Mashhad. We are thankful to and appreciate the Research and Development center of National Iranian Cu Industries (Shahr-e-Babak, Meiduk), especially S.M. Mousavi, for the financial support of this project and the necessary proceedings. References Chen, Y.J., Piranjno, F., Li, N., Guo, D.Sh. and Lai, Y., 2009. Isotope systematica and fluid inclusion studies of the Qiyugou breccia pipe- hosted gold deposit, Qinling Orogen, Henan province, China: Implication for ore genesis. Ore Geology Reviews, 35(2): 245-261. Dimitrijevic, M.D., 1973. Geology of Kerman region. Geological Survey of Iran, Tehran, Report No. Yu/52, 334 pp. Hassanzadeh, J., 1993. Metallogenic and tectonomagmatic events in the SE sector of the Cenozoic active continental margin of central Iran (Shahr e Babak area, Keman Province). Ph.D. thesis, University of California, Los Angeles, America, 204 pp. Rusk, B.G. and Reed, M.H., 2008. Fluid inclusion evidence for magmatic-hydrothermal fluid evolution in the porphyry copper- molybdenum deposit at Butte, Montana. Economic Geology, 103(2): 307-334. Ulrich, T., Gunther, D. and Heinrich, C.A., 2002. The evolution of a porphyry Cu-Au deposit, based on LA-ICP-MS analysis of fluid inclusions: Bajo de la Alumbrera, Argentina. Economic Geology, 97(8): 1889-1920.

As part of the Natural Sciences and Engineering Research Council of Canada–Canada Mining Innovation Council (NSERC-CMIC) Mineral Exploration Footprints project, three selected magnetic inversion programs (VPmg, MAG3D and VINV) were used to process the same aeromagnetic data set from the Highland Valley Copper district, British Columbia, Canada. In each case, the inversion was constrained using available geological and physical property constraints. Analysis of magnetic susceptibility data suggests that the observed aeromagnetic anomaly pattern includes effects associated with boundaries between lithological units and fault zone alteration resulting from removal of magnetite. Susceptibility contrast associated with alteration is greater than that associated with changes in lithology. The inversions seek to define the three-dimensional geometry of geological boundaries and the fractures are treated as high-frequency noise. Results from the three programs, although similar, are sensitive to attributes of the different algorithms. VPmg emphasises physical boundaries between geological domains, MAG3D produces a more blurred image, whereas VINV produces reasonable geological images. Computer performance using the different programs ranges from reasonable for VPmg to computer intensive for MAG3D and VINV. Differences in the results reflect the inherent uncertainty in producing inversions from "noisy" aeromagnetic data. [ABSTRACT FROM AUTHOR]

• Enrichment and depletion in porphyry copper deposit is modeled. • Cosine Similarity method was used for targeting prospective areas. • Wunugetushan Cu–Mo deposit was used as reference. • The method take full advantage of available geochemical data. Recognizing distribution patterns of ore-related pathfinder elements requires an understanding of the corresponding ore-forming systems and may lead to the definition of more reliable exploration targets. Given that complex ore-forming processes in complex geological terrains can result in either enrichment or depletion of ore elements, simultaneous consideration of both processes in geochemical anomaly modelling would be advantageous for defining exploration targets. Here, we adapted the "cosine similarity measure" method for pattern recognition of ore-related geochemical anomalism to facilitate simultaneous modelling of element enrichment and depletion. We tested the performance of this new method on porphyry copper exploration data from the Manzhouli belt, China, and demonstrated that our method is highly efficient with respect to recognizing ore-related geochemical signatures and, thus, useful for "vectoring" towards porphyry copper deposits and defining more reliable geochemical exploration targets. [ABSTRACT FROM AUTHOR]

Abstract A magmatic volatile phase (MVP) may be exsolved from a silicate melt through decompression during ascent and/or the crystallization of anhydrous mineral phases. MVPs are commonly chloride-rich fluids and are hypothesized to induce hydrothermal alteration in and around igneous intrusions. Feldspars are common alteration products in these systems with K-feldspar (potassic alteration zone) often found in areas directly above cupolas of the igneous intrusions. Albite-bearing alteration assemblages are found generally on the flanks of the intrusions, below the cupolas, or more distally. Mineral alteration reactions near the intrusion are likely influenced wholly or partially by a subcritical, vapor undersaturated high-salinity liquid phase (brine). Whereas the K-feldspar-MVP system is well studied, there is a dearth of data on albite-brine systems at elevated temperatures and pressures. This study addressed mineral phase stability and equilibrium brine compositions in the albite-andalusite-quartz-brine system (65 wt% NaCl equivalent; NaCl-HCl-H 2 O) at 600, 650, and 700 °C and 80 MPa. The stable mineral phases were ascertained through an examination of crystal morphology, optical microscopy, and by chemical compositions. The albite + andalusite + quartz + brine phase boundary was found to be at C NaCl brine / C HCl brine molality values of 87.5 ± 12.5, 67.5 ± 7.5, and 40 ± 10 at 600, 650, and 700 °C, respectively. Apparent equilibrium constants, not accounting for activity coefficients, for the reaction: albite + HCl = 0.5 andalusite + NaCl +2.5 quartz +0.5 H 2 O were calculated as 70 ± 10, 54 ± 6, and 32 ± 8 at 600, 650, and 700 °C, respectively. The alteration of albite to andalusite occurs at much lower HCl concentrations than is required to alter K-feldspar to andalusite for equivalent concentrations of chloride salts. Thus, HCl concentrations of brines within the potassic and/or sericitic alteration zones can be much higher than in albite-bearing alteration zones. The data presented in this study indicate that albite-rich mineral zones on the flanks of igneous intrusions are most likely produced by a low-acidity fluid with an elevated C NaCl fluid / C KCl fluid . Fluids that meet these specifications, and may be significant sources of sodic alteration, include non-magmatic fluids flowing towards the intrusion or a descending magmatic brine depleted in cations and metals by mineral alteration reactions near the cupola. Although the sodic alteration zone is unlikely to host significant concentrations of metals in porphyry ore systems, it can provide significant constraints on metasomatic reactions and fluid flow pathways. Sodic and sodic-calcic alteration sequences in iron-oxide‑copper‑gold deposits are likely produced by a low-acidity, saline fluid and, unlike porphyry systems, correlate with high metal contents which indicate that the precipitation mechanisms controlling ore distribution in these systems may not be as dependent on neutralization reactions as in potassic and sericitic alteration sequences. Highlights • The C NaCl brine / C HCl brine in equilibrium with albite + andalusite + quartz decreases as temperature increases from 600 to 700 °C. • Sodic alteration zones are most likely produced by a low-acidity fluid with an elevated C NaCl fluid / C KCl fluid • Sodic alteration on the flanks of felsic intrusions are likely from a depleted magmatic fluid or influx of meteoric fluid. • Sodic alteration zones are unlikely to host significant metals in porphyry deposits, but can host ore zones in IOCGs. [ABSTRACT FROM AUTHOR]

Hydroxylation-oxidation reactions of the type H 2 O + Fe → 2 + Fe 3 + + OH− + 1/2 H 2 oxidise Fe2+ in olivine and pyroxenes in oceanic lithosphere prior to subduction and in the supra-subduction-zone mantle wedge and oxidise Fe2+ in silicate melts as dissolved H 2 O accumulates during magmatic differentiation. Collectively, the coupled hydroxylation-oxidation of melts and of minerals in melt sources tends to produce positive correlations of hydration state and oxidation state of silicate melts, about which there has been much dispute and discussion in literature. We introduce a melt "hygro-barometer" which provides evidence from trace elements in zircon that melt oxidation state rose as dissolved H 2 O accumulated in fluid-undersaturated residual melts during mafic-to-felsic differentiation at Moho-vicinity depths. Zircon-based measures are consistent with experimental evidence of melt oxidation during gain of dissolved H 2 O. Examples from many arc igneous complexes demonstrate further oxidation of residual melts as hydrothermal fluid exsolved and segregated during trans-crustal ascent of the magmas. Zircons in those suites show that much of the contrast between redox states of dry mid-ocean-ridge and hydrous arc magmas (especially porphyry copper magmas) develops as H 2 O is lost during trans-crustal ascent of arc magmas because decompression-induced exsolution and open-system fractional segregation of hydrothermal fluid selectively extracts reduced members of the principal redox couples (H 2 –H 2 O, S4+–S6+, Fe2+–Fe3+), thereby raising the oxidation state of residual melt. • A new zircon trace-element indicator of silicate melt hydration state is formulated. • Fluid-undersaturated magmas show tandem rise of oxidation and hydration states. • ƒO 2 and ƒH 2 O of subducted materials, mantle wedge and melts are interactive. • Zircon records dehydration and oxidation of fluid-saturated, ascending melts. • Porphyry copper-forming melts have distinctive zircon trends on ƒO 2 -H 2 O plots. [ABSTRACT FROM AUTHOR]

[Display omitted] • Transition from barren to fertile geochemical signatures of arc magmas in the Baguio-Mankayan Mineral District is intimately linked with arc development and subduction dynamics. • Late Eocene barren magmas were generated in a thin nascent Luzon arc. • Middle Pliocene fertile magmas were formed from mixing of mafic and silicic melts associated with ridge subduction. • More hydrous conditions of Early Pleistocene fertile magmas are attributed to progressive crustal thickening and compression induced by ride subduction. The Baguio-Mankayan Mineral District (BMMD) in Northern Luzon, Philippines, is renowned for its world-class auriferous porphyry-Cu and epithermal deposits, which are associated with arc magmatism during the Pliocene-Pleistocene. One of the less studied areas in this region is in southern Mankayan, where the Suyoc epithermal prospect is located. New U-Pb zircon ages, combined with whole-rock and in-situ geochemical analyses of igneous rocks in the Suyoc area, revealed a shift from barren to fertile magmatic episodes in the BMMD. 1) Late Eocene (36.93–37.20 Ma) barren magmas generated in a thin, nascent Luzon arc, 2) Fertile Middle Pliocene (2.87–3.4 Ma) magmatism attributed to the mixing of primitive mafic and silicic crustal melts due to ridge subduction, and 3) Early Pleistocene (1.73 Ma) fertile magmatism associated with more hydrous melts due to progressive crustal thickening. The Late Eocene barren magmatism enhanced both source and intra-crustal conditions for the onset of younger fertile magmatic events via sub-arc modification and crustal addition/thickening. Furthermore, we consider the fertile Pliocene and Pleistocene magmatism in the BMMD as two separate events with different petrogenesis. Mafic-silicic interaction in the Pliocene was documented through core-rim analysis of amphiboles from the Pliocene Suyoc Diorite. On the other hand, the Pleistocene fertile magmatism, represented by the Bato Dacite Porphyry, showed geochemical signatures consistent with a thickened crust and also reflected higher magmatic H 2 O contents ranging from 6.3 to 7.8 wt%. [ABSTRACT FROM AUTHOR]