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The Xiaokele Cu (–Mo) deposit is a recently discovered porphyry deposit in the northern Great Xing’an Range (GXR) of northeast China. The ore bodies in this deposit are mainly hosted within granodiorite porphyry intrusions. Potassic, phyllic, and propylitic alteration zones develop from center to edge. In this paper, we present zircon LA–ICP–MS U–Pb ages, zircon Hf isotopic compositions, and whole-rock geochemistry of the ore-bearing granodiorite porphyries from the Xiaokele Cu (–Mo) deposit. Zircon U–Pb dating suggests that the Xiaokele granodiorite porphyries were emplaced at 148.8 ± 1.1 Ma (weighted-mean age; n = 14). The Xiaokele granodiorite porphyries display high SiO2, Al2O3, Sr, and Sr/Y, low K2O/Na2O, MgO, Yb, and Y, belonging to high-SiO2 adakites produced by partial melting of the subducted oceanic slab. Marine sediments were involved in the magma source of the Xiaokele granodiorite porphyries, as indicated by enriched Sr–Nd isotopic compositions (eNd(t) = − 1.17– − 0.27), low positive zircon eHf(t) values (0.4–2.2), and high Th contents (4.06–5.20). The adakitic magma subsequently interacted with the mantle peridotites during ascent through the mantle wedge. The Xiaokele granodiorite porphyries were derived from slab melting during the southward subduction of the Mongol–Okhotsk Ocean.

Tirtomoyo in Wonogiri district is known as an ore mineralization region, in which one of the prospects occurred is Hargosari. No previous studies on the ore characteristucs have been done. A set of study on Hargosari prospect is aimed to characterize gold mineralization covering some aspects such as mineralogy, textures, ore chemistry and ore forming condition. To achieve the objectives, some research methods were performed suh as mapping, sampling and laboratory analyses for selected samples on term of petrography, ore microscopy and ore chemistry. Oligo-Miocene andesitic lava from Panggang Formation is identified as host rock. Opening system of veins is of jogs type to form en-´echelon tension gash veins. Quartz veins are enveloped by argillic and propylitic alteration zones, in association with pyrite, chalcopyrite, sphalerite, galena, gold, silver, chrysocolla, covellite and hematite. The approximately 5 cm thick quartz veins exhibit massive, swarm, low angle veins and stockwork structures, which is characterized by normal banded, crustiform, comb and saccaroidal textures. The quartz veins contain high base metals of up to 5.45% Cu, 9.9% Pb and 12.85% Zn, with significant grade of gold and silver of up to 3.85 g/t Au dan 395 g/t Ag. From mineral assemblages, the veins might be formed at temperatures of about 250-300°C. On the basis of those mentioned characteristics, gold mineralization in Hargosari prospect is categorized into an intermediate sulfidation epithermal. Keywords: characteristics, gold, epithermal, Hargosari, Wonogiri.

Halmahera Island retains several gold deposits. One of the gold deposits is called as low sulphidation epithermal (LSE) quartz veins which is currently being mined and is situated in the Gosowong goldfield. The veins mostly originated in N-S and NNE-SSW direction. This study is aimed to determine the prospect area in the northern portion of Gosowong goldfield covering the West Kao sub district based on surface mapping and rock/float- and BLEG stream sediment survey. A total of 16 rock/vein float and 120 BLEG samples were analyzed by FA/AAS and CNO2 cyanide leach methods, respectively. The study area is occupied by tuffaceous sandstone, andesite, porphyritic andesite and lava andesite units. In the eastern part, tuffaceous sandstone is suffered from argillic and propylitic alteration, which may be controlled by the NW-SE-trending structures. The gold grade of rock/float samples is up to 0.044 ppm. BLEG data indicates a calculated threshold of 10 ppb for Au and 72 ppb for Ag. The highest Au and Ag contents (anomalies) are identified in the eastern part of the study area. This is spatially (and maybe genetically) related to the argillic-altered tuffaceous sandstone, structures and occurrences of quartz vein floats. To follow up this finding, a detailed exploration is recommended to be conducted within the prospect area.

Subduction related Miocene porphyry type deposits are found in the east-west trending Chagai magmatic belt (CMB) in Pakistan's western margin, Balochistan. This arc exists on the west segment of the Tethyan metallogenic belt in the south-west of Pakistan. Tethyan metallogenic belt is widely spread over 12,000 km from east to west direction from Indochina, Tibet, Pakistan, Iran, Turkey and Alpine mountain range in Europe. During the last thirty to forty years several porphyry deposits have been reported in the Chagai magmatic arc, including the very large Reko Diq H14-H15, large Saindak, Tanjeel, H35, H8 and medium Dasht-e-Kain porphyry deposits and many small porphyry copper deposits. These porphyry deposits were developed within the phase of calc-alkaline type magmatism in the Chagai arc. Tonalite, quartz diorite, and monzonite host the porphyry deposits within the adjacent sedimentary wall rock units of Sinjrani Volcanic Group, Juzzak, Saindak, and Amalaf Formations. The concentric zonal pattern of hydrothermal alteration in these porphyry deposits of the Chagai magmatic arc follows the world's major porphyry deposits' alteration pattern. Zones of hydrothermal alteration from distal to proximal part includesa potassic alteration, sericitic-clay-chlorite alteration, sericitic alteration, argillic alteration and propylitic alteration. Major ore mineralization in these deposits is of copper, gold, silver, molybdenum, and minor constituents of other base metals that have been reported to occur within hydrothermal alteration zones in the Miocene porphyry Chagai magmatic arc.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery was used to identify argillic, phyllic and propylitic alteration zones and mapping geological structural feat...

Oyu Tolgoi is a world-class, Late Devonian porphyry district in southern Mongolia. Because of its age and geodynamic setting, it has undergone a complex geological history that includes major postmineralization magmatic-hydrothermal events in close proximity to the porphyry deposits. The propylitic alteration halos that surround the Cu-Au deposits contain widespread hydrothermal titanite, as do the younger altered volcanic and intrusive rocks. Here, we present a comprehensive laser ablation-inductively coupled plasma-mass spectrometry U-Pb study on in situ, propylitic titanite from the Oyu Tolgoi district. The results identify district-wide hydrothermal alteration episodes that coincide with known magmatic events: Devonian porphyry mineralization (~372 Ma); the intrusion of granodiorite plutons and andesite dikes in the Carboniferous (~320–310 Ma); and the emplacement of the Permian Khanbogd Granite alkaline batholith (~290 Ma). Both Carboniferous and Permian alteration events variably overprint the earlier porphyry alteration halo. Overdispersion in the U-Pb data from some samples, due to Pb and/or U mobility, makes interpretation of some titanite ages more difficult, but further exemplifies the complex alteration history of the district. We conclude that U-Pb dating of propylitic titanite is a viable means by which explorers can identify alteration within a prospect that is synchronous with potentially fertile intrusions of known age. The extent of the coeval propylitic alteration and its mineral chemistry can then be used to assess the likelihood of a major porphyry center being present.

The Shaxi porphyry Cu–Au deposit is located in the northern part of the Luzong Basin on the outer edge of the southern Middle-Lower Yangtze River metallogenic belt, China. It is typical of the porphyry Cu–Au deposits in the metallogenic belt, with more than 1 Mt Cu at 0.55 wt% and 45 tons Au at 0.47 g/t. Hydrothermal alteration consists of a core of potassic alteration overprinted by a phyllic alteration zone. Propylitic alteration occurs peripheral to the potassic zone, but can also be recognized in the core of the deposit, where vein density is low. The main mineralization occurs as sulfide veinlets in the potassic zone where it is superposed by phyllic alteration. The paragenetic sequence show that chalcopyrite began to precipitate late in stage 1, associated with potassic alteration, forming quartz-sulfide veins with potassium feldspar halos, and reached a peak in stage 3, forming chalcopyrite-pyrite ± quartz ± anhydrite ± chlorite ± illite veins that accompanied phyllic alteration. Sulfur, hydrogen-oxygen and strontium isotopes, fluid inclusions, and pyrite trace element data indicate that the stage 1 assemblage associated with potassic alteration were deposited from a magmatic brine. With the change from lithostatic to hydrostatic pressure late in stage 1, the brine generated stage 1 g quartz-pyrite-chalcopyrite ± anhydrite ± bornite ± molybdenite ± potassium feldspar veins with minor copper and gold. Mixing with minor external fluids (meteoric water or gypsum-saturated groundwater) in stage 2 triggered the peripheral propylitic alteration. As the proportion of external fluid increased with the onset of hydrostatic conditions, it changed the redox state and composition of the hydrothermal system, resulting in extensive stage 3 Cu and Au precipitation with phyllic alteration. Argillic alteration associated with stage 4 veins was generated by external fluids mixed with minor hydrothermal fluid, at shallow depths.

Indonesia is a country with abundant geothermal energy potential. One of the locations that have potential geothermal energy sources is Tiouw Village, Saparua, Central Maluku. This study was conducted on the types of mineral deposits using the petrographic method, X-Ray Diffraction (XRD), and X-Ray Fluorescence (XRF). Based on the results of petrographic analysis and XRD, rock samples 1, 2, and 3 of Tiouw include andesite igneous rocks with propylitic alteration type. While sample 4 is dacite igneous rock with argillic alteration type. Each rock sample has a mineral set of kaolinite, chlorite, quartz, cristobalite, epidote, and plagioclase. The XRF results showed the highest chemical composition of SiO 2 , followed by Al 2 O 3 and K 2 O. This mineral content can indicate the subsurface temperature of the geothermal field in the range of 200–300 oC with varying salinity, pH close to neutral, and low permeability. This interpreted that the type of mineral deposits in Tiouw Village was high sulfidation epithermal deposits. DOI: http://dx.doi.org/10.17977/um024v4i22019p037

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 ( 40; eNd(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.

Dongguashan is one of the largest porphyry-skarn Cu-Au deposits in eastern China and titanite is found in the ore system. Five types of both magmatic and hydrothermal titanites are distinguished, based on their textural and chemical characteristics. Types 1 and 2 titanites are magmatic in origin whereas types 3, 4, and 5 are hydrothermal. Magmatic titanites are wedge-shaped and display concentric and sector zoning, whereas hydrothermal titanites show a wide range of textures that vary with different alteration stages. REE, Sn, Mo, and Cu are enriched in magmatic titanites (types 1 and 2). In contrast, vanadium and HFSE are enriched in hydrothermal titanites, especially in type 4 titanite from the propylitic alteration zone. Magmatic titanite (type 1) coexists with magnetite and K-feldspar and crystallized in oxidized and H2O-rich magma at 730–760 °C. Type 2 titanite contains ilmenite inclusions reflecting changes in the fO2 of the magma chamber, possibly caused by input of mafic magma. The mobility and enrichment of HFSE and association with fluorapatite reflect the F-rich composition of the magmatic-hydrothermal fluid at Dongguashan. The relationship between titanite textures and chemistry indicates that titanite can serve as a recorder of magmatic-hydrothermal processes in porphyry copper systems. U-Pb dating of type 4 titanite from the propylitic alteration zone and type 5 titanite from skarn yielded ages of 139.0 ± 2.6 Ma and 137.0 ± 2.0 Ma, respectively, indicating that it formed synchronously with the associated quartz monzodiorite.

Hydrothermal alteration is widespread in a series of Eocene intermediate dikes and sills known as the Scatter Creek Formation, which are hosted in Permian-Triassic sedimentary rocks across the Republic Graben, in northeastern Washington. Input of multiple magmas during regional extension resulted in a complex unit of variable texture and composition. These intrusions have been interpreted as conduits for hydrothermal ore mineralization via geochemical interaction with contact metamorphosed sediments. However, mineral exploration has not accounted for the widespread propylitic alteration often seen in conjunction with orebodies. As such, this study provides new analyses dedicated to the distribution of geochemical signatures and hydrothermal alteration minerals in the Scatter Creek Formation, with a broader goal of linking surface observations to a possible source as a case study for future exploration., Hand sample and thin section observations, along with electron microprobe, whole rock major and trace element, and X-ray diffraction analyses suggest that the Scatter Creek Formation geochemically links intrusive and extrusive equivalent rocks. However, hydrothermal alteration has resulted in feldspar albitization and mafic minerals reacting to magnetite-epidote-calcite-chlorite-pyrite; vesuvianite, barite, and zeolites are sometimes present. Chloritization is widespread and varies in iron content. Coarse quartz is mainly an alteration phase. Unreacted igneous minerals include rutile, zircon, sphene, pyroxene, and magnetite-ilmenite with occasional inclusions of Pb- Ni- sulfides; REE’s were also detected. Alteration had little effect on non-alkalic oxide and trace element concentrations, but elevated concentrations of As and Sb possibly relate to Au mineralization. Stable oxygen and carbon isotope ratios do not show strict connections to hydrothermal alteration progress but do relate to proximity with nearby replacement ore bodies. Continued circulation of an evolving fluid during propylitic alteration is indicated by the relation of low to high isotopic ratios with achieved reaction progress., These observations are consistent with a distal propylitic alteration shell resulting from interactions of magmatic and meteoric water surrounding a magma body, which served as a heat source to drive the hydrothermal system. As such, widespread propylitic alteration in the Scatter Creek Formation, in association with Au-mineralization, suggests that a porphyry-type deposit may lie at depth in a hidden parent intrusion.

We studied the fluid inclusions of the Jiguanshan Mo deposit in China, which is a large porphyry deposit located in the southern Xilamulun Metallogenic Belt. The irregular Mo ore body with various types of hydrothermal veinlets is hosted by Late Jurassic granite porphyry. Intense hydrothermal alterations in the deposit from the core to margin are silicification–potassium feldspar alteration, pyrite–quartz–sericite–fluorite alteration, and propylitic alteration. Based on the mineral assemblages and crosscutting relationships of ore veins, the ore-forming process were divided into three stages and two substages: quartz–pyrite veins (stage I) associated with potassic alteration; quartz–molybdenite–chalcopyrite–pyrite veins (substage II-1) and quartz–molybdenite–fluorite veins (substage II-2) associated with phyllic alteration; and fluorite–quartz–carbonate veins (stage III) with carbonation. Five major fluid inclusions (FIs) types were distinguished in the quartz associated with oxide and sulfide minerals, i.e. polyphase brine (Pb-type), opaque-bearing brine (Ob-type), solid halite (S-type), two-phase aqueous (A-type), and vapor (V-type) inclusions. The FIs of stage I were composed of liquid-rich S-, A-, and V-type FIs with homogenization temperatures and salinities of 490 to 511 °C and 8.9 to 56.0 wt% NaCl equiv., respectively. The FIs of substage II-1 are composed of Pb-, Ob-, S-, A-, and V-type FIs with homogenization temperatures and salinities of 352 to 460 °C and 3.7 to 46.1 wt% NaCl equiv, respectively. The FIs of substage II-2 are Ob-, S-, A-, and V-type FIs with homogenization temperatures and salinities of 234 to 309 °C and 3.7 to 39.2 wt% NaCl equiv, respectively. The FIs of stage III are A-type FIs with homogenization temperatures and salinities of 136 to 172 °C and 1.1 to 8.9 wt% NaCl equiv, respectively. Fluid boiling, which resulted in the precipitation of sulfides, occurred in stages I and II. The initial ore-forming fluids of the Jiguanshan deposit had high temperature, high salinity, and belonged to an F-rich NaCl ± KCl–H2O system. The fluids gradually evolved to low temperature, low salinity, and belonged to a NaCl–H2O system. Studies of the hydrogen and oxygen isotope compositions of quartz (δ18OH2O = − 7.3 to 6.3‰, δDH2O = − 104.3 to − 83.3‰) show that the ore-forming fluids gradually evolved from magmatic water to meteoric water.

The Muara Laboh geothermal system is a liquid-dominated, fracture-controlled reservoir showing some characteristics of both intrusion-related and fault circulation systems. The developed reservoir has moderate to high-temperature (230–310 °C) with a long NNW outflow (160–230 °C) extending to the Sapan Malulong boiling chloride springs. Reservoir fluids generally have low salinity (∼400-1600 ppm Cl) with benign chemistry and low non-condensable gas (NCG) content (∼0.5 to 2 wt% in steam). The proven reservoir is divided into distinct SW and NE sectors. The principal deep upflow zone (270 to 310 °C) is located in the SW and is associated with Patah Sembilan volcano and satellite vents (Anak Patah Sembilan). The SW upflow is characterized by relatively low salinity (∼400-600 ppm Cl), whereas fluids in the NE emerge from a second upflow along faults and fractures at 240–250 °C (1200–1600 ppm Cl) and ascend to an initial-state steam cap near the Idung Mancung fumarole. The shallow NE part of the geothermal system is hosted mainly by Quaternary to Miocene Age andesitic to rhyolitic rocks, whereas the deeper SW part of the system occurs in a Mesozoic to Cenozoic Age plutonic complex and its host rocks that are cut by younger dikes. Rock porosity and permeability trends can be related to reservoir age, volcanic deposit type, and alteration history. Fracture permeability is high, whereas matrix porosity ( Permeable fracture patterns and their origins differ somewhat between the deep SW and the shallow NE reservoir. In the deep SW reservoir, fluids ascend along fractured margins of stock and dike intrusions. Steeply dipping intrusions and open fractures strike from WNW to NNW, subparallel to the main Great Sumatra Fault trend, with a secondary set of N to NE fractures and intrusions parallel with the inferred maximum horizontal stress direction (SHMax). In the shallower NE steam cap and outflow, N to NE steeply dipping fractures dominate, with bounding N to NNW faults. Bulk rock alteration includes shallow argillic and transitional clay zones overlying phyllic and propylitic zones. High-T propylitic alteration (secondary amphibole) and rare potassic alteration (secondary biotite) are associated with intrusion. Vein paragenesis in the SW reservoir indicates that portions of the initially permeable propylitic zone have been sealed by calcite and quartz ± prehnite. Late calcite veins suggest ingress of steam-heated bicarbonate waters contributed to resealing of the system. These relationships suggest that the SW system underwent extensive boiling, fluid loss, and inflow of dilute bicarbonate waters, possibly related to sector collapse and partial excavation of the topseal of the system (now Patah Sembilan crater).

The Atlas porphyry Cu–Au deposit is located in central Cebu Island in the Philippines, with a proven mineral reserve of 1420 Mt at 0.45% Cu, 0.24 g/t Au, 0.018 g/t Mo, and 1.8 g/t Ag. It is associated with the Lutopan quartz diorite porphyry stock that was emplaced into the Cretaceous volcano-sedimentary sequences of the Cansi Formation. Two stages of hypogene alteration have been identified at Atlas: stage I quartz–magnetite ± chalcopyrite ± pyrite veins associated with potassic and propylitic alteration and stage II anhydrite–pyrite–chalcopyrite ± specularite veins associated with phyllic alteration. Supergene gypsum veins are also present. Mineralization is mainly associated with the stage I and stage II veins. The Lutopan quartz diorite porphyry yielded a zircon U–Pb age of 108.5 ± 1.6 Ma and is characterized by high Sr/Y (54–69), with the corresponding magma having high oxygen fugacity (avg. ΔFMQ +2.7, avg. Ce4+/Ce3+ of zircon = 439) and H2O concentrations (presence of amphibole and biotite phenocrysts) and low magmatic temperatures (avg. Ti-in-zircon thermometry = 706 °C). The relatively low La/Yb ratios (9–11), listric-shaped normalized REE patterns with weak or absent Eu anomalies, together with zircon eHf(t) values of 3.4 to 10.0, whole-rock ISr values of 0.70373–0.70382, eNd(t) values of 2.4–3.4 and Mg numbers of 49–53 suggest that the Lutopan quartz diorite porphyry was likely derived from partial melting of young lower continental crust or interaction between asthenospheric melts and lower crust melts, that evolved to adakite-like trace element compositions through amphibole fractionation. Stage I veins yielded a pyrite Re–Os isochron age of 110.2 ± 5.6 Ma, making Atlas the only Mesozoic porphyry deposit discovered in the Philippines.

In the Zajkan Pb–Zn–Cu (Au–Ag) deposit of the Tarom–Hashtjin metallogenic belt (THMB), northwest Iran, mineralization occurs as quartz-base metal sulfide veins hosted by Eocene volcanic and volcaniclastic rocks of the Karaj Formation. Four stages of ore formation are identified at Zajkan: (1) quartz-chalcopyrite-pyrite veins, (2) quartz-galena-sphalerite ± chalcopyrite ± pyrite veins and breccias, (3) quartz-hematite veins and breccias, and (4) barren quartz-carbonate veinlets. The primary metallic minerals are pyrite, chalcopyrite, sphalerite, galena, and trace amounts of hematite; gangue minerals are mainly quartz, sericite, chlorite, and calcite. The main wall-rock alteration is silicification, and intermediate argillic, and propylitic alteration. The coexistence of different types of fluid inclusions (LV, VL, and V) in individual fluid inclusion assemblages in quartz and sphalerite suggests boiling and heterogeneous trapping. Excluding the heterogeneously entrapped fluid inclusions, the microthermometric measurements of primary LV fluid inclusion assemblages in quartz and sphalerite indicate that the veins were formed at temperatures between 217 and 273 °C from fluids with salinities between 1.7 and 6.4 wt% NaCl equiv. The oxygen isotopic compositions (δ18Owater-VSMOW of +3.7 to +1.1‰) indicate that the ore-forming fluids were mainly derived from magmatic water with the input of meteoric water in the later ore-stages. Sulfur isotopic values of sulfide minerals vary over a narrow range from −5.0 to −0.9‰VCDT (averaging −2.2‰VCDT), suggesting that sulfur was derived from a homogeneous magmatic source. The fluid inclusion and stable isotope data indicate that fluid boiling and mixing facilitated hydrothermal alteration and mineralization at Zajkan. Our data suggest that the Zajkan deposit is an intermediate-sulfidation style epithermal mineralization. The estimated ore formation depth of Zajkan indicates minor denudation in the region and may imply a great prospecting potential for other epithermal mineralization in the THMB.

Clay minerals are the signature of hydrothermal alterations related to fluid circulation in volcanic and crystalline rocks. In the French part of the Upper Rhine Graben, in the deep-seated granites, illitic minerals (illite and I/S mixed layers (ml)) are typical products of the structurally-controlled argillic alteration in the Paleozoic granitic basement. In the new Illkirch geothermal well, GIL-1, drill-cuttings were studied with various petrographic methods to determine the characteristics of illite in paleo- and present-permeable zones, and to compare the alteration mineralogy with that of geothermal Soultz-sous-Forêts and Rittershoffen sites. Alteration petrography, crystal structure as well as the chemical composition of the illitic minerals and the altered bulk rocks were performed all along the well. This complete characterization, combined with geophysical logs and structural results, highlighted that the illitic minerals at Illkirch, Soultz-sous-Forêts, and Rittershoffen are composed of illite and illite-rich illite-smectite mixed layers (I/S ml) (&lt, 10% smectite). Two mineralogical assemblages were distinguished: chlorite + illite resulting from the propylitic alteration after the emplacement of the granitic basement under temperatures higher than 350 °C, and illite + I/S ml + carbonates + quartz resulting from the argillic alteration due to fluid circulation in the fractures at temperatures between 130 and 160 °C. Fracture zones are characterized by the occurrence of illitic minerals (illite and I/S ml), and specifically, by higher quantities of I/S ml in present-day permeable zones than in paleo-permeable zones. A conceptual model of the fracture zones at the interface between the overlying sedimentary rocks and the granitic basement is proposed. The present-day permeability distribution is controlled by the fault and fracture network, which consists of sealed zones and unsealed zones. Fluid convection in the URG implies paleo and present fluids circulating in both fractured sedimentary and crystalline reservoirs. Such circulations develop illitic minerals that could be considered as exploration guides for future geothermal sites in the URG. At Illkirch, the repartition of the present-permeable fracture zones (KFZs) in the GIL-1 well indicates that the moderately argillically altered granite distally situated from the Eschau fault is more permeable than the intensely argillically altered granite close to the Eschau fault.

The intermediate-sulfidation epithermal Strauss deposit is part of the Drake Goldfield of north-eastern NSW. The mineralisation in this deposit is gold-dominant with minor silver and significant levels of zinc, copper and lead. Strauss has a combined total resource of 2.66 Mt @ 1.5g/T Au and 1.9g/T Ag. Mineralisation mainly occurs in the form of vein stockworks of three main orientations. Structural analysis indicates these to be the result of two fault system events and one conjugate fault system. Petrographic and SEM analysis shows that there are two separate mineralisation styles, a pyrite dominant and sphalerite dominant style, with at least three mineralisation events. Correlation analysis for the assay data indicates that Au has a strong relation with Ag and moderate correlation with Pb. Petrographic analysis has shown the deposit to be made-up of varying layers of dacitic ash flow tuffs and a cross-cutting lamprophyre dyke though previous authors classified some of the tuffs as intrusive andesites. XRD analysis indicates widespread argillic-phyllic and propylitic alteration. Silver tellurides have been found as late-stage grains associated with sphalerite mineralisation. Sr shows a significant strong depletion, due to the intense and pervasive alteration at Strauss. The carbon and oxygen isotopes of vein carbonates suggest that the carbon from the late-stage carbonates was derived from a magmatic source with a significant influence of low-temperature meteoric water alteration, while the sulphur isotopes indicate a magmatic sulphur source.

The Don Manuel porphyry copper system, located in the Miocene–Pliocene metallogenic belt of central Chile, contains spatially zoned alteration styles common to other porphyry copper deposits including extensive potassic alteration, propylitic alteration, localized sericite-chlorite alteration and argillic alteration but lacks pervasive hydrolytic alteration typical of some deposits. It is one of the youngest porphyry copper deposits in the Andes. Timing of mineralization and the hydrothermal system at Don Manuel are consistent with emplacement of the associated intrusions (ca. 4 and 3.6 Ma). Two molybdenite samples yielded consistent ages of 3.412 ± 0.037 and 3.425 ± 0.037 Ma. 40Ar/39Ar ages on hydrothermal biotites (3.57 ± 0.02, 3.51 ± 0.02, 3.41 ± 0.01, and 3.37 ± 0.01 Ma) are associated with potassic alteration. These ages are younger than the youngest intrusion by ~300 k.y. recording the cooling of the system below 350 °C. Such a time gap can be explained by fluxing of hot magmatic fluids from deeper magmatic sources.

The Torud-Chahshirin Magmatic Belt in northern Iran is defined by Tertiary porphyry, IOCG, Skarn, Manto, MVT, and Au, Ag and base metal-rich epithermal systems, and it is a part of the eastern Alborz Orogenic Belt of Iran. Mineralization in the Torud-Chahshirin Magmatic Belt occurs as veins, veinlet, and disseminated mineralization hosted by the Eocene-Oligocene volcanic, subvolcanic, and volcanoclastic rocks. Mineralization prospects of the Torud-Chahshirin Mgmatic Belt are spatially and temporally accompanied with magmatic rocks of early to middle Eocene (∼55–37 Ma.) calc-alkaline and early to late Oligocene (∼34–24 Ma.) alkaline rocks that have continually evolved through assimilation and fractional crystallization (AFC) processes at shallow crustal levels. The Robaie area is located in the Torud-Chahshirin Magmatic Belt. The dominant stratigraphic unit is composed of Eocene volcanic rocks (trachyandesitic to andesitic in composition), which are intruded by subvolcanic rocks. The subvolcanic rocks have features typical of shoshonitic affinity and are metaluminous to weakly peraluminous. These rocks are characterized by enrichment in large-ion-lithophile elements (LILEs) and light rare-earth-elements (LREEs), depletion of heavy rare-earth-elements (REEs, LaN/YbN ≈ 9.65–24.34), and high-field-strength-elements (HFSEs). Values of eNd(i) commonly show a small variation between +0.2 and +0.7, whilst 86Sr/87Sr (i) goes from 0.7056 to 0.7063. The whole set of evidence agrees with derivation of intrusive rocks of Robaie from primitive magma resulting from partial melting in a mantle wedge above a subduction zone. A sample from a dyke of biotite-hornblende diorite porphyry, with a negative eNd(i) value (−1.7), probably corresponds to a magma that underwent assimilation of crustal material. U-Pb data of zircons from dioritic stock and dyke show ages of 49.99 Ma and 50.43 Ma, respectively. Mineralization in Robaie is related to the biotite-hornblende diorite intrusions and is associated with hydrothermal alterations including argillic, argillic-silicification, argillic-sericitic, and propylitic alteration. The ore-bearing veins, veinlets, and disseminated mineralization are controlled by structures. There are two types of veins and veinlets mineralization in the Robaie area including: 1) quartz-chalcopyrite-pyrite-specularite ± gold veins, and 2) quartz-chalcopyrite-pyrite-specularite-magnetite ± gold veinlets. The highest amount of copper (>1%) and gold (>5 g/t) is associated with quartz-chalcopyrite-pyrite-specularite ± gold veins. Microthermometric study of fluid inclusions shows that homogenization temperatures are 181–422 °C and salinities of ore-forming fluids ranged from 11.1 to 17 wt% NaCl equivalent. The temperature and salinity of ore-forming fluids were lower in the formation of the quartz-chalcopyrite-pyrite-specularite ± gold veins than in the quartz-chalcopyrite-pyrite-specularite-magnetite ± gold veinlets, and fluid mixing was the most important mechanism for mineralization in the area. The mineralogy, alteration, geochemistry, fluid inclusion studies, and petrogenesis of subvolcanic rocks of the Robaie area indicate that the Robaie deposit could be classified as a member of the Iron Oxide-Copper-Gold (IOCG) deposits.

The nature of sub-volcanic alteration is usually only observable after erosion and exhumation at old inactive volcanoes, via geochemical changes in hydrothermal fluids sampled at the surface, via relatively low-resolution geophysical methods or can be inferred from erupted products. These methods are spatially or temporally removed from the real subsurface and thus provide only indirect information. In contrast, the ICDP deep drilling of the Mt Unzen volcano subsurface affords a snapshot into the in situ interaction between the dacitic dykes that fed dome-forming eruptions and the sub-volcanic hydrothermal system, where the most recent lava dome eruption occurred between 1990 and 1995. Here, we analyse drill core samples from hole USDP-4, constraining their degree and type of alteration. We identify and characterize two clay alteration stages: (1) an unusual argillic alteration infill of fractured or partially dissolved plagioclase and hornblende phenocryst domains with kaolinite and Reichweite 1 illite (70)-smectite and (2) propylitic alteration of amphibole and biotite phenocrysts with the fracture-hosted precipitation of chlorite, sulfide and carbonate minerals. These observations imply that the early clay-forming fluid was acidic and probably had a magmatic component, which is indicated for the fluids related to the second chlorite-carbonate stage by our stable carbon and oxygen isotope data. The porosity in the dyke samples is dominantly fracture-hosted, and fracture-filling mineralization is common, suggesting that the dykes were fractured during magma transport, emplacement and cooling, and that subsequent permeable circulation of hydrothermal fluids led to pore clogging and potential partial sealing of the pore network on a timescale of ~ 9 years from cessation of the last eruption. These observations, in concert with evidence that intermediate, crystal-bearing magmas are susceptible to fracturing during ascent and emplacement, lead us to suggest that arc volcanoes enclosed in highly fractured country rock are susceptible to rapid hydrothermal circulation and alteration, with implications for the development of fluid flow, mineralization, stress regime and volcanic edifice structural stability. We explore these possibilities in the context of alteration at other similar volcanoes., info:eu-repo/semantics/published

The Busang mineral prospect in Kalimantan, Indonesia, was reported to host a large Au resource until 1997 when it was revealed that drill core samples had been deliberately and systematically contaminated (&ldquo, salted&rdquo, ) with extraneous Au to falsify resource estimates. One month before the fraud was uncovered, Dr. G. Milligan, then professor emeritus of geology, visited the site to collect a suite of core samples for academic study that was deemed representative of the host rocks, alteration, and mineralization of the Busang Southeast Zone. These samples were re-examined here by optical microscopy, electron microprobe (EMPA), whole-rock geochemistry, and fluid inclusion microthermometry to characterize the subsurface geology and hydrothermal mineralization, and to assess reasons why the system is of uneconomic character. The host rocks were variably altered calc-alkaline porphyritic subvolcanic diorites, typical of the lithological units along the mineralized trend in the Kalimantan Gold Belt. Early hydrothermal mineralization with quartz-sulfide (pyrite, chalcopyrite, Cu-sulfosalts) stockwork veinlets associated with pervasive phyllic and propylitic alteration was overprinted by crudely banded quartz-carbonate-sulfide/sulfosalt (pyrite, sphalerite, chalcopyrite, galena, tennantite-tetrahedrite, bournonite-seligmannite) veins. The stockwork veins were associated with up to 140 ppb bulk rock Au, some of which was hosted by Cu-sulfosalts. Microthermometry on quartz-hosted aqueous fluid inclusion assemblages (FIA, n = 13) and single inclusions (non-FIA, n = 20) in quartz-carbonate-sulfide/sulfosalt veins yielded an overall range in homogenization temperatures (Th) between 179 &deg, C and 366 &deg, C and bulk salinities between 1.1 wt.% to 8.6 wt.% NaCl equivalent, with much smaller data ranges for individual FIA (e.g., FIA 3, 239.1 &deg, C to 240.5 &deg, C and 0.5 wt.% to 1.4 wt.% NaCl equivalent). Primary FIA along growth zones in quartz were identified, providing constraints on fluid characteristics at the time of quartz growth. Carbonate-hosted FIA (n = 3) and single inclusions (non-FIA, n = 3) in the same veins yielded Th between 254 &deg, C and 343 &deg, C and bulk salinities of 1.1 wt.% to 11.6 wt.% NaCl equivalent. Likewise, data ranges for individual FIA were much smaller. Many of the geological characteristics of the Busang Southeast Zone were compatible with a telescoped, intermediate-sulfidation epithermal system, having formed from diluted magmatic fluids that precipitated weak base metal mineralization. However, the system was unproductive with respect to Au and Ag, at least within the studied area. Of note, vein textures and fluid inclusion characteristics indicative of boiling or efficient fluid mixing&mdash, processes both considered critical for the formation of economic lode gold deposits&mdash, were absent in the samples.

The Collahuasi district of northern Chile hosts several late Eocene-early Oligocene world-class porphyry Cu-Mo deposits, including Rosario, Ujina, and Quebrada Blanca deposits, and associated high-sulfidation epithermal mineralization at La Grande. Mineralization is hosted by intermediate to felsic intrusive and volcanic rocks of the upper Paleozoic to Lower Triassic Collahuasi Group, which experienced lower greenschist facies regional metamorphism prior to mineralization. Extensive hydrothermal alteration zones surround the porphyry and epithermal deposits, associated with hypogene ore-forming processes. However, outside of the observed sulfide halo the limits of geochemical anomalism associated with mineralization are difficult to define due to mineralogical similarities between weak, distal propylitic alteration and regional metamorphism affecting the host rocks.Recent advancements in laser ablation-inductively coupled plasma-mass spectrometry analysis of epidote from hydrothermal alteration zones around porphyry and skarn deposits have shown that low-level hypogene geochemical anomalies can be detected at distances farther from the center of mineralization than by conventional rock chip sampling. Selective analysis of propylitic epidote from the Collahuasi district indicates that anomalous concentrations of distal pathfinder elements in epidote, including As (>50 ppm), Sb (>25 ppm), Pb (>100 ppm), and Mn (>5,000 ppm), were detectable 1.5 to 4.0 km from deposit centers. Significantly, the concentrations of these trace elements in epidote were obtained from samples that contained whole-rock concentrations of

The chemical composition, textures and mineral associations of pyrite provide key information that help elucidate the evolution of hydrothermal systems. However, linking the compositional and micro-textural features of pyrite with a specific physico-chemical process, e.g., boiling versus non-boiling, remains elusive and challenging. In this study we examine pyrite geochemical and micro-textural features and relate these results to pyrite-forming processes at the active Cerro Pabellon Geothermal System (CPGS) in the Altiplano of the northern Chile. We integrate electron microprobe analysis (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) data with micro-textural observations of pyrite and associated gangue minerals recovered from a ∼500 m long drill core that crosscuts the argillic, sub-propylitic and propylitic alteration zones of the CPGS. Additionally, we carried out a Principal Component Analysis (PCA) in order to inspect and understand the main data structure of the pyrite geochemical dataset. The concentrations of precious metals (Au and Ag), metalloids (As, Sb, Se, Bi and Tl), and base and heavy metals (Cu, Co, Ni and Pb) in pyrite from the CPGS are significant. Among the elements analyzed, As, Cu and Pb are the most abundant with concentrations that vary from a few parts per million (ppm) to wt% levels (up to 4.4 wt% of As, 0.5 wt% of Cu and 0.2 wt% of Pb). Based on contemporaneous gangue mineral associations and textures, the mechanisms of pyrite precipitation in the CPGS were inferred. Pyrite formed during vigorous boiling is characterized by relatively high concentrations of As, Cu, Pb, Ag and Au and lower concentrations of Co and Ni compared to pyrite formed under different conditions. These anhedral to euhedral pyrite grains display zones with a porous texture and abundant mineral micro- to nano-inclusions (mainly galena and chalcopyrite) indicating a formation by rapid crystallization. In contrast, pyrite formed under gentle boiling (more gradual cooling and less abrupt physico-chemical variations than in vigorous boiling) to non-boiling conditions is characterized by a higher concentration of Co and Ni, and relatively low concentrations of As, Cu, Pb, Ag and Au. Texturally, these pyrites form aggregates of euhedral and pristine pyrite crystals with scarce pores and mineral inclusions suggesting formation under steadier physico-chemical conditions. Our results show that pyrite can not only record the chemical evolution of hydrothermal fluids, but can also provide critical information related to physico-chemical process such as boiling and phase separation. Since boiling of aqueous fluids is a common phenomenon occurring in a variety of pyrite-forming environments, e.g., active continental and seafloor hydrothermal systems, and porphyry Cu-epithermal Au-Ag deposits, pyrite compositional and textural features are a valuable complement for discriminating and tracking boiling events in modern and fossil hydrothermal systems.

The paper presents a quantitative modeling for delineating alteration zones in hypogene zone of Miduk porphyry copper deposit (SE Iran) based on drill core data. The main goal of this study is applying Sequential Gaussian Simulation (SGS) and Concentration-Volume (C-V) fractal model based on Cu grades to separate different alteration zones. In this study, 10 realizations were generated using the SGS modeling and C-V log-log plots were created for them to determine Cu threshold values which delineate alteration zones. Correlation derived from log ratio matrix, which was used to compare between geological and C-V fractal results, shows that Cu values less than 0.575% from simulation number 9 (sim 9) has more overlapped voxels with phyllic alteration zone by overall accuracy (OA) of 0.75. Furthermore, the comparison revealed that sim 9 with Cu values between 0.575% and 0.933% and OA of 0.88 can determine propylitic alteration. Spatial correlation between the potassic alteration zone resulted from 3D geological modeling and high concentration zones for the C-V fractal model shows that the alteration zone has Cu values between 0.955% and 1.380% (sims 2, 3 and 4) with OA of 0.71. Finally, based on correlation between classes in the geological and the fractal models of hypogene zone, this research resulted that potassic alteration, which is the richest zone, has a strong overlap with sims 2, 3 and 4 while phyllic and propylitic alterations, with lower grades, have an appropriate overlap with sim 9.

The Duolong district is located in the south Qiangtang terrane of Tibet and is the most significant ore cluster within the Bangongco-Nujiang metallogenic belt. Duolong contains one giant, three large and two medium to small-sized porphyry (±epithermal ± breccia) copper deposits and several other mineralized porphyry bodies. All deposits are closely associated with early Cretaceous (123–115 Ma) intermediate-felsic intrusions. Naruo is a poorly studied porphyry-breccia copper deposit in the north of the Duolong district. Hydrothermal alteration surrounding the ore-bearing granodiorite at Naruo is characterized by an inner potassic zone and an outer propylitic zone, overlapped locally by minor phyllic and argillic alteration assemblages. A detailed paragenetic study has identified five distinct hydrothermal veins (M, A, B, C, D) within the porphyry system. Hydrothermal B veins are strongly related to copper mineralization. Strong propylitic alteration is also observed throughout the hydrothermal breccias identified at Naruo. Sandstone breccia, diorite-bearing breccia and granodiorite-bearing breccia were identified according to the distribution and composition of clasts. U-Pb zircon dating has determined the ages of the ore-bearing granodiorite (121.6 ± 1.3 Ma) and a barren intrusion (115.5 ± 1.1 Ma) within the porphyry system, diorite clasts (122.3 ± 0.9 Ma) and later diorite matrix (120.5 ± 1.0 Ma) in the hydrothermal breccia system, suggesting that with the exception of the late barren intrusion, they all belong to the same mineralizing event at Duolong. The geological and geochemical evidence presented in this study suggest that the porphyry and breccia systems may have originated from the same magma source, but are now spatially independent.

An orogenic assemblage composed of volcanic conglomerates and basalts of the (?)Lower to Middle Triassic Neara Volcanics, and a basic-intermediate pluton, outcrop within the thesis area, located 6 km southeast of Elgin Vale within the Esk Trough of South-eastern Queensland. The oldest unit within the area , conglomerate, is the most widespread lithology and is interpreted to be of debris flow origin. The conglomerates are typically massive, poorly sorted, clast-supported, non-imbricated, and polymictic. The clasts are predominantly porphyritic andesites (> 95 %) with minor sandstone and plutonic types. The andesitic source that initiated the debris flows was probably located several tens of kilometres from the thesis area and within a separate and distinct eruptive province from that which produced the coeval basalts of the thesis area. These basalts are high-K tholeiites. Minor basaltic andesites also occur within the area. The pluton within the thesis area is a composite body of three petrogenetically unrelated phases: microgabbro; microdiorite; and diorite. The microgabbro phase is minor and is hypersthene-richi The microdiorite is probably a uniform body, geochemically. It consists of andesine, augite, biotite, quartz, magnetite, and apatite, and is completely devoid of hornblende. The diorite phase of the pluton is a fractionated body ranging from true diorite (51 % SiOj) to tonalite (66 % Si02),with minor granitic veins. It contains mainly andesine, hornblende, biotite, quartz, magnetite, and minor relict augite. Metalliferous and barren veins of hydrothermal origin occur within the pluton, in the area where the microdiorite and diorite phases coexist. Their localization was structurally controlled. The main ore mineral within the veins is chalcopyrite. The veins carry microscopic gold. Regional propylitic alteration is widespread within the conglomerates and basalts of the area. An inner propylitic zone dominated by secondary actinolite grades outward from the main pluton into chlorite-calcite assemblages and further into chlorite-epidote assemblages. The strata within the area form an antiform, and faulting (probably normal) is widespread.

Gold and base metal mineralization of Onzon-Kabani area is located at the western part of Mogok Metamorphic Belt in central Myanmar, where the well-known Sagaing Fault serves as its western boundary. Artisanal and small-scale gold operations started here three decades ago on gold mineralization hosted in marble and gneiss. Mineralization occurs as fracture-filling veins of several types: gold-bearing quartz vein, base metal quartz-carbonate vein, and carbonate base metal sulfides vein. Three types of hydrothermal alteration zones develop from the proximal to distal zone of hydrothermal conduit: silicic, sericite-illite and propylitic alteration. Alteration mineral assemblages consist of quartz, calcite, sericite, adularia, epidote, chlorite, illite and smectite which are typical of neutral pH hydrothermal fluid. The presence of adularia and calcite within veins indicate boiling event of near-neutral pH condition. Common vein textures of quartz and calcite are banded, crustiform, bladed calcite, lattice, mosaic or jigsaw, cockade, comb and zonal. Boiling-related mineral textures (e.g. banded, bladed and lattice) and fluid inclusion characteristics of coexisting liquid-rich and vapor-rich fluid inclusions have been identified in mineralized samples. Common ore minerals are pyrite, sphalerite, galena, chalcopyrite and minor marcasite, electrum and native gold. Gold is mostly associated with quartz gangue, pyrite, sphalerite and galena. Fluid-inclusion study suggests the presence of liquid-rich and vapor-rich fluid inclusions which were trapped in boiling fluid at homogenization temperature of 159 to 315°C and moderate salinity of 0.88 to 12.51 wt.% NaCl equivalent. It is concluded that despite mesothermal gold system is more typical style of gold mineralization in the Mogok Metamorphic Belt, it is not the type of mineralization in the Onzon-Kanbani area. Instead, a low-sulfidation epithermal system is more characteristic to be present here. The knowledge generated from this study can serve as a guide in understanding new deposit type as well as mineral exploration in the region.

In the Qarachilar Cu-Mo-Au deposit of the Ahar-Arasbaran metallogenic zone (AAMZ), northwest Iran, mineralization occurs as three quartz-sulfide veins that cut granodiorite-quartz monzodiorite rocks of the Qaradagh batholith (QDB). Ore formation can be divided into three stages, with chalcopyrite, molybdenite, and gold bearing pyrite appearing mainly in the first two stages. The main wall-rock alteration is silicification, and intermediate argillic, carbonate, and propylitic alteration. Fluid inclusion microthermometry indicates trapping of medium- to high-salinity (9.2-55 wt% NaCl equiv.) fluids at Qarachilar. Fluid inclusion trapping conditions are estimated to be 190 degrees C-530 degrees C and 0.1-3 kbar. The variable phase ratios as well as spatial coexisting of liquid and vapor-rich two-phase and halite-bearing multiphase fluid inclusions homogenizing over the same temperatures are consistent with fluid boiling during ore formation. Obtained delta O-18(H2O) values of quartz from ore stage veins are +5.7 parts per thousand to +9.7 parts per thousand, signifying that the ore-fluid system was predominantly magmatic water. The average calculated delta S-34(H2S) values are 1 +/- 1 parts per thousand for pyrite, chalcopyrite and molybdenite, consistent with a magmatic source for sulfur. Combined, the fluid inclusion and stable isotope data indicate that the ore-forming fluids at Qarachilar were magmatic in origin and were subsequently cooled and diluted by meteoric water. Fluid boiling and mixing facilitated hydrothermal alteration and mineralization. Molybdenite Re-Os dating shows that mineralization occurred at 42.35 +/- 0.16 Ma, coincident with formation of porphyry Cu-Mo mineralization at Agarak deposit, and Hanqasar, Aygedzor and Dastakert prospects in the Lesser Caucasus. However, Qarachilar is older than all porphyry Cu-Mo mineralization in the AAMZ and Urumieh-Dokhtar magmatic arc (UDMA), which suggests that collision between Arabia and Eurasia were oblique and thus diachronous. Our data suggest that mineralization at Qarachilar is related to collisional Eocene magmatic-hydrothermal activity related to Neo-Tethys subduction, and shares a number of similarities with the vein-type Cu-Mo-Au mineralization related to Cu-Mo porphyries.

The Tuwu porphyry copper deposit is located in the Eastern Tianshan Mountains, Xinjiang, China. Lentiform-like ore bodies are hosted in the Early Carboniferous Qi'eshan group, and Cu mineralization shows a close association with tonalite porphyry. Porphyry and country rocks have undergone extensive potassic, chlorite-sericite, phyllic and propylitic alteration. The mineralized veins in the Tuwu deposit can be divided into: earlier quartz–biotite ± magnetite ± chalcopyrite veins (stage I), quartz–chalcopyrite ± bornite ± pyrite veins (stage II) and quartz ± molybdenite ± chalcopyrite ± pyrite ± calcite veins (stage III), and later calcite ± quartz veins (stage IV). The Stage II and III are the main Cu mineralization stages. At the Tuwu deposit, three types of fluid inclusions have been distinguished: liquid-rich (L-type), vapor-rich (V-type) and halite-bearing (S-type), respectively. Laser Raman spectra identified magnetite, hematite, chalcopyrite, and pyrite at S-type inclusions. The quartz veins in stage I and II contain all inclusion types. L-type and V-type inclusions are recognized in stage III quartz minerals, but only L-type inclusions are present in stage IV quartz minerals. Fluid inclusions in quartz of stage I, II, III and IV are characterized by homogenization temperature vary of 275–492 °C, 232–477 °C, 199–287 °C and 133–227 °C, with corresponding NaCl equiv. salinities of 2.2–58.7 wt% NaCl equiv., 1.4–58.3 wt% NaCl equiv., 1.1–6.0 wt% NaCl equiv., and 1.1–4.2 wt% NaCl equiv., respectively. Initial ore-forming fluids of the Tuwu deposit belong to relatively oxidized H2O-NaCl system with moderate-high temperature and salinity. Sulfur isotope data from chalcopyrite and pyrite suggest a magmatic source. Two types of chlorite (type 1 and type 2) are recognized based on the relationship with metal sulfides. Electron microprobe analysis shows that chlorites are plotted in ripidolite and pycnochlorite. Decreasing Fe/(Fe + Mg) ratios of chlorites indicate that the meteoric water was involved in the magmatic water, combined with the positive correlation with AlIV, implying that the chlorite formed in a relatively reduced and acidic environment. The hydrothermal fluids in type 1 chlorite bring large quantities of reduced metallic minerals compared to the barren fluids in type 2 chlorite. The formation temperatures of chlorite are roughly coincident with the results that obtained from fluid inclusion studies, which show a decrease trend. Changes in temperature, redox, pH, and fluid-rock interaction likely play an important role in the transportation and precipitation of metal sulfides of the Tuwu deposit.

The Aktogai Group (more than 12.5Mt of Cu and 80t of Au) is located in the western part of the Central Asian Orogenic Belt (CAOB). The mineralization of the Aktogai deposit is associated with the Early Carboniferous tonalite porphyry which intruded into the Koldar complex. The ore-forming tonalite porphyry has higher oxygen fugacity and sulfur contents than those of wall rocks based on results of mineralogical chemistry analyses. Hydrothermal fluid activities result in the potassic, sericite(-chlorite) and propylitic alteration, and are associated with disseminated and/or vein mineralization. The alteration and mineralization include three stages. Potassic stage is characterized by hydrothermal K-feldspar, biotite, magnetite, “A” veins and disseminated mineralization. Sericite(-chlorite) stage that partly overprinted on potassic stage is characterized by sericite, chlorite, “C” veins and disseminated mineralization. Propylitic stage is characterized by chlorite, epidote and “C” veins, and develops in the tonalite porphyry and wall rocks. Five types of fluid inclusions have been recognized in the Aktogai deposit, including liquid-rich (L-type), vapor-rich (V-type), daughter mineral-bearing (S-type), CO2-bearing (C-type) and minor SO2-bearing fluid inclusions. In the potassic stage, ore-forming fluid belongs to H2O-NaCl-CO2 system with four types fluid inclusions, homogeneous temperatures and salinities of fluid inclusions are 320 °C to 448 °C and 0.35 wt% to 51.08 wt%, respectively. In the sericite(-chlorite) stage, the fluid belongs to H2O-NaCl-CO2 system with L-type, V-type and C-type fluid inclusions, homogeneous temperatures and salinities of fluid inclusions are 243 °C to 315 °C and 1.22 wt% to 13.27 wt%, respectively. In the propylitic stage, the fluid belongs to H2O-NaCl system with L-type and V-type fluid inclusions, homogeneous temperatures and salinities of fluid inclusions are 211 °C to 328 °C and 0.35 wt% to 11.46 wt%, respectively. A relatively negative δ34S‰ values (−4.61‰ to −3.18‰) indicate that the sulfur derived from a high oxygen fugacity magma. Decreases of the temperature, pressure and oxygen fugacity of the ore-forming fluid result in metal precipitation in the Aktogai deposit.

The Early Cretaceous Tongshankou Cu-Mo deposit is located in the eastern Yangtze craton and comprises both porphyry and skarn mineralization. The porphyry ore is hosted in a granodiorite porphyry with the skarn mineralization found along the contacts with the carbonate host rocks. Alteration in the porphyry mineralization can be divided into three stages: potassic alteration, phyllic alteration and a carbonate stage, with phyllic alteration associated with the main porphyry mineralization. No propylitic alteration is present at Tongshankou. The skarn-type alteration comprises five stages: early skarn stage, late skarn stage, oxide stage, quartz-sulfide stage and late vein stage. Short wave-length infrared (SWIR) analysis identified 15 hydrothermal minerals in the Tongshankou deposit, including illite, dickite, halloysite, phengite, talc, muscovite, saponite, gypsum, chlorite, prehnite, montmorillonite, serpentine, phlogopite, actinolite, kaolinite, with montmorillonite, illite and chlorite being the most common. SWIR parameters and the electron microprobe results of chlorites show that chlorites close to the mineralization center tend to be iron-rich and have high FeOH absorption position (Pos 2250 > 2251 nm). Consequently, chlorite may be a useful indicator mineral for mineralization in the Tongshankou deposit. Pos 2250 is not correlated to temperature as calculated using a chlorite geothermometer but does correlate with the iron contents of the chlorites. Our results show that the ore-forming fluids are Fe-rich in the proximity to the mineralization but Mg-rich towards the distal area. Unlike in other porphyry deposits the white mica show no consistent variation in the Tongshankou deposit and cannot be used as vectors towards mineralization. The Fe-Mg-Al poor carbonate host rocks of the Tongshankou deposit restrict the development of a propylitic alteration zone. The Fe-Mg-Al host rocks also prevent Tschermak exchange in white mica ((Siiv(Mg,Fe)vi ↔ AlivAlvi)), making white mica Pos 2200 and Illite crystallinity (IC) randomly distributed. Our results show that SWIR spectroscopy of chlorite may be an applicable exploration tool in skarn-related hydrothermal systems.

Western Tianshan along the southwestern margin of the Central Asian Orogenic Belt is well-endowed with epithermal and porphyry Au deposits. The Kuruer Cu-Au deposit, recently discovered in the eastern part of Western Tianshan, was considered as a high sulfidation epithermal deposit. However, our geological, fluid inclusion and stable isotopic studies indicate that it actually formed in transition from high sulfidation to porphyry. The host rocks include the Dahalajunshan Formation volcanic and volcano-sedimentary rocks such as andesite, rhyolite, ignimbrite and tuff. Cu-Au mineralization mainly occurs as quartz-dominated stockworks or disseminations, with abundant pyrite and chalcopyrite and minor galena and sphalerite. Gold occurs as invisible phase in sulfides. Hydrothermal alteration includes a silicic core, surrounded by phyllic alteration and peripheral propylitic alteration. Based on field observations, paragenetic and crosscutting relationship, the mineralization process can be roughly divided into three stages. The early stage is characterized by the assemblage of quartz + pyrite + chalcopyrite while the middle stage contains quartz and chalcopyrite at absence of pyrite. The late stage is characterized by calcite ± quartz ± chlorite ± chalcopyrite veins. Fluid inclusions at the early stage are mainly liquid-rich aqueous and CO2-rich inclusions and minor vapor-rich aqueous and solid-bearing inclusions. Their homogenization temperatures and salinities can be up to 420 °C and 39 wt.% NaCl eq., respectively, indicating that the initial ore-forming fluids are high temperature, high salinity, H2O-CO2-NaCl systems. In the middle stage, there are only liquid-rich aqueous inclusions, with homogenization temperatures and salinities of 130–190 °C and 0.18 to 10.7 wt.% NaCl eq., respectively. Liquid-rich aqueous inclusions in the late stage display much lower temperatures and salinities, ranging from 110 to 130 °C and 0.18–2.7 wt.% NaCl eq., respectively. Obtained δDH2O and δ18OH2O values of quartz from the middle stage are −98 to −107‰ and −2.1 to 0.74‰, respectively. The δ34S values of 9 chalcopyrite samples range from −10.2 to −2.4‰, with an average of −4.1‰. We conclude that the initial ore-forming fluids are magmatic in origin, and further cooled and diluted by mixing with meteoric water. Intensive fluid boiling and mixing facilitated hydrothermal alteration and mineralization.

The Honghai VMS Cu-Zn deposit is located in the Dananhu-Tousuquan arc, Eastern Tianshan, northwestern China. Orebodies of the Honghai deposit are buried 300 m underground and hosted by the Middle Ordovician-Upper Silurian Daliugou Formation felsic to intermediate volcanic-sedimentary rocks. At the footwall and hanging wall of the massive sulfide lens, intensive and pervasive phyllic alterations were found. Detailed drill core logging, petrographic study and electron microprobe analyses had delineated six alteration/mineralization zones, namely (from top to bottom) Zone I (chlorite-albite-white mica-carbonate), II (epidote-chlorite-albite-white mica-carbonate), III (quartz-white mica-pyrite), IV (massive sulfide), V (chlorite-pyrite ± white mica) and VI (chlorite-quartz-white mica). Our new data supported the sub-seafloor replacement influence for the Honghai VMS deposit, as evidenced by the presence of (1) sulfide breccias in the immediate host rocks; (2) rapid emplacement of host rocks; (3) strong phyllic alteration in the immediate hanging wall; (4) replacement textures of the massive sulfides; (5) barite as gangue minerals. Moreover, intensive chlorite and epidote alterations and vein mineralization are present in the hanging wall, which are comparable with porphyry-related propylitic alteration. Besides, different mineralogy and mineral chemistry are present between chlorites from the hanging wall and footwall at Honghai, which probably suggested porphyry-style alteration and mineralization overprinting at Honghai. Short wavelength infrared (SWIR) spectral analysis had identified mainly white mica, chlorite and epidote, and minor montmorillonite, calcite, gypsum, kaolinite and prehnite. The wavelengths of the AlOH absorption feature for white mica range from 2194 to 2221 nm, suggesting compositions from paragonite, through muscovite to phengite. The wavelengths of FeOH absorption feature for chlorite range from 2249 to 2261 nm, indicating compositions from Mg-rich to Fe-rich chlorite. According to SWIR measurements and electron microprobe analyses (EMPA), areas proximal to the massive sulfides are characterized by short wavelength of the AlOH absorption feature and high Alvi content of white mica. Petrography and EMPA showed that chlorite in the ore proximal zones are more Mg-rich than that in ore distal zones. These findings indicated high temperature for the white mica formation and more seawater influx during the chlorite formation in areas near the massive sulfides. This study suggested that SWIR analysis, supported by petrographic study and EMPA, can serve as an effective tool in alteration mapping, and mineral geochemical variations are potential deposit-scale exploration vectoring tools.

The Yandong porphyry Cu deposit in the Eastern Tianshan terrane is the largest in Xinjiang, NW China (metal reserve: 2.3 Mt Cu @ 0.67%). Three periods and six alteration and mineralization stages were identified in this study, i.e., Porphyry period (including Stage I: propylitic alteration; II: quartz-magnetite alteration; III: phyllic alteration and early mineralization); overprinting period (including Stage IV: overprinting mineralization and Stage V: late vein) and supergene period (Stage VI: supergene mineralization). Stage IV was the main Cu mineralization stage at the Yandong Cu deposit, which is characterized by the mineral assemblage of chalcopyrite + chlorite + anhydrite + calcite. Electron microprobe analysis (EMPA) data indicate that Stage IV chlorite contains lower SiO2 and MgO, but higher FeO, Al2O3 and Fe/(Fe + Mg) than Stage I chlorite. LA-ICP-MS analyses indicate that Stage IV chlorite contains lower Cr, Ni, Co, B, Ca and Sr, but higher Sc, Ga, Sn, Ti, Zn and Mn than Stage I chlorite. Stage IV epidote contains lower B, Zr, Ba and Ti, but higher Sn, Y, Ga, Ag, U, Y, Cu and Sr than Stage I epidote. Concentrations of Ti, Zn, As, V, Sc and Cu are highest near the orebody for both Stage I and IV chlorite, and Au and Sn in Stage IV chlorite are highest near the orebody. Titanium content of Stage I epidote is highest near the orebody, but V, Sc and Zr are lowest there. Stage I chlorite at Yandong is geochemically similar to the giant Batu Hijau porphyry Cu-Au deposit (Indonesia), but Stage IV chlorite contains higher Fe, Al and As, lower Mg and Sn than the latter. Stage I epidote at Yandong is geochemically similar to the porphyry and skarn deposits in the central Baguio district (Philippines), but Stage IV epidote has higher Sn, Ga and U, but lower Zr, Ti and Ba than the latter. Ore deposit geology and alteration mineral chemistry indicate that the Yandong Cu deposit is an atypical porphyry deposit. The adakitic tonalite porphyry and quartz albite porphyry (granitic) may have formed the early and overprinting Cu mineralization, respectively. Chlorite Ti and V, and epidote Sb show similar spatial variation patterns in Cenozoic and Paleozoic porphyry deposits, which may be used for exploration targeting for ancient porphyry deposits, such as the Yandong Cu deposit.

The Halasu III deposit, an important Cu deposit in the southernmost part of the Halasu porphyry Cu belt, is situated in the East Junggar block in NW China. Copper and Mo sulfide mineralization commonly occurs as disseminations or veinlets, and is mainly associated with Devonian granodiorite porphyry. Our detailed field geological investigation identified late-stage high grade Cu sulfide-bearing veining superimposed on the earlier porphyry Cu–Mo mineralization. Four hydrothermal alteration and mineralization stages were identified, namely the early epidote alteration (Stage I), porphyry-style alterations (Stage II comprising II-A potassic, II-B propylitic and II-C phyllic alteration sub-stages), late veining (Stage III) and supergene processes (Stage IV) in the northern- and southern mineralization zones at Halasu III. Multiphase granodiorite- and alkali granite dykes intruded the Beitashan Formation volcanic rocks, generating the early epidote alteration. Potassic alteration (Stage II-A) occurred in and around the NNW-treading granodiorite dykes, while the propylitic alteration (Stage II-B) occurred in the intrusions or volcanic wall rocks around the potassic zone. These early alteration assemblages were overprinted by the subsequent, structurally-controlled phyllic alteration (Stage II-C) confined within the granodiorite porphyry. Late veins (Stage III) include sulfide-bearing (Stage III-A) and sulfide-barren (Stage III-B) ones. Supergene process (Stage IV), represented by hematite and jarosite replacing primary sulfides, extends tens of meters down depth and is commonly fracture-controlled. Three fluid inclusion (FI) types were recognized, namely Type A (single-phase), B (liquid–vapor two-phase) and C (liquid–vapor–solid three-phase). For Type B FIs, those of potassic alteration homogenized at 183–347 °C, with corresponding salinities of 6.2–17.8 wt.% NaCl equiv. The propylitic and phyllic FIs homogenized at 172–425 °C and 231–352 °C, respectively, with the corresponding salinities of 0.9–14.0 wt.% NaCl equiv. and 0.4–10.5 wt.% NaCl equiv. The sulfide-bearing vein FIs homogenized at 243–410 °C (Stage III-A-1), 260–362 °C (Stage III-A-2) and 117–235 °C (Stage III-A-3), along with the corresponding salinities of 1.9–9.2 wt.% NaCl equiv., 1.1–6.7 wt.% NaCl equiv. and 6.5–17.1 wt.% NaCl equiv., respectively. The sulfide-barren vein FIs yielded homogenization temperatures of 260–380 °C (Stage III-B-1) and 114–297 °C (Stage III-B-2), with corresponding salinities of 1.7–9.8 wt.% NaCl equiv. and 0.2–13.6 wt.% NaCl equiv., respectively. We suggest that hydrothermal veins at Halasu III may have undergone complex and superimposing alteration due to the episodic reopening of the preexisting veins, with Stage III-A-3 veining overprinting the phyllic alteration and Stage III-A-2 veining. Stage III-B-2 veining superimposed on the potassic alteration, as well as on Stages III-A-1 and III-B-1 veining. Paragenetic sequence and fluid evolution at Halasu III indicate that these complex hydrothermal alteration stages were formed in accordance with the regional tectonic evolution. These various alteration and mineralization stages at Halasu III deposit reveal a prolonged history of magmatic and hydrothermal processes extending episodically from the Middle Devonian to Middle Permian, wherein early mineralization was overprinted by late hydrothermal events. Such superimposed mineralization may occur commonly in the Paleozoic Central Asia Orogenic Belt.

The Dengjitun Cu deposit, located in the central Xing’an Block, represents a key target for medium- to large-sized porphyry Cu deposit exploration. The mineralization in this area is closely associated with silicification and propylitic alteration and occurs in a distinctive sequence of quartz-bearing veinlets as well as in a disseminated form within an altered porphyritic granodiorite. In this paper, we present new precise laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) U–Pb zircon age data, geochemical data and Hf isotopic data on the porphyritic granodiorite at Dengjitun and use these data to improve our understanding of the Jurassic tectonic evolution of this region. Zircon U–Pb dating of two samples from the porphyritic granodiorite yield Early Jurassic ages of 174.2 ± 1.1 Ma and 173.9 ± 1.1 Ma, which are concordant within error. The Dengjitun porphyritic granodiorite is a high-K calc-alkaline and slightly peraluminous I-type granite. It is enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs; e.g., K, Rb, and Ba), depleted in heavy rare earth elements (HREEs; LREE/HREE = 6.43–13.34) and high field strength elements (HFSE; e.g., Nb, Ti, P), and has weak positive Ce anomalies (δCe = 1.15–1.25) and negligible Eu anomalies (δEu = 0.85–0.99). The zircons from the porphyritic granodiorite have positive eHf(t) values (+ 8.7 to +11.7) and elevated 176Hf/177Hf ratios (0.282912–0.283000) that yield young TDM2 ages (428–602 Ma). Collectively, these data indicate that the porphyritic granodiorite formed from primitive magma that was generated by the partial melting of juvenile thickened mafic lower crust, which in turn was originally derived from depleted mantle during the Neoproterozoic. The thickened lower crustal material was metamorphosed under amphibolite- to eclogite-facies conditions at depths of >45 km during the subduction of the Mongol–Okhotsk Ocean, with the resulting magmas assimilating some mantle-derived material prior to emplacement. Combining these data with the tectonic history of this area, we suggest that the Dengjitun porphyritic granodiorite formed in a post-collisional extensional tectonic setting after the Early Jurassic final closure of the Mongol–Okhotsk Ocean.

The southern section of the Cenozoic Urumieh-Dokhtar Magmatic Arc (UDMA) of Iran, known as Kerman Magmatic Arc (KMA) or Kerman copper belt, is a major host to porphyry Cu ± Mo ± Au deposits, collectively known as PCDs. In this study, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and spectral angle mapper (SAM) method, combined with field data, mineralogical studies, and spectral analysis are used to determine hydrothermal alteration patterns related to PCDs in the KMA. Gossans developed over some of these porphyry type deposits were mapped using Landsat 8 data. In the NKMA gossans are more developed than in the SKMA due to comparatively lower rate of erosion. The hydrothermal alteration pattern mapped by ASTER data were evaluated using mineralogical and spectral data. ASTER data proved to be useful for mapping the hydrothermal alteration in this semi-arid type of climate. Also Landsat 8 was useful for mapping the iron oxide minerals in the gossans that are associated with the porphyry copper deposits. Our multidisciplinary approach indicates that unlike the PCDs in the northern KMA that are associated with distinct and widespread propylitic alteration, those in the granitoid country rocks lack propylitic alteration or the alteration is only weakly and irregularly developed. The porphyry systems in southern KMA are further distinguished by development of quartz-rich phyllic alteration zones in the outer parts of the PCDs that could be mapped using remote sensing data. Consideration of variations in alteration patterns and specific alteration assemblages are critical in regional exploration for PCDs.

The quartz-monzonitic intrusion of ‘Botro ai Marmi’ in Tuscany, Italy, can be considered to be a typical example of an intrusion-centred magmatic hydrothermal system. The evolution of hydrothermal fluids in the ‘Botro ai Marmi’ intrusion was investigated using fluid-inclusion analyses to provide suitable physico-chemical constraints on the fluids involved in the late- to post-magmatic hydrothermal activity that affected the intrusion, providing inferences on their origin and variations of temperature and pressure with time.This work demonstrates that the earliest fluids circulating in the ‘Botro ai Marmi’ intrusion were high-temperature brines exsolved directly from the crystallizing magma. This fluid circulated in the intrusion under lithostatic conditions (P > 90 MPa, T > 540°C). A second evolutionary stage of the magmatic hydrothermal system is marked by the transition from lithostatic (>90 MPa) to hydrostatic dominated conditions (50 to 10 MPa). In this stage the fluids are also interpreted to be mainly orthomagmatic in origin but unmixed in a high-salinity brine and in a low-salinity vapour aqueous phase, at a temperature ranging from ~500 to 300°C. These fluids were responsible for the potassic alteration facies. At a later stage of hydrothermal evolution, abundant meteoric dominated fluids entered the system and are associated with propylitic alteration. This event marks the transition from a magmatic-hydrothermal system to a typical hydrothermal (‘geothermal’) system, which can be assumed to be similar to some extent to the nearby active high-enthalpy geothermal system of Larderello. Low-temperature and low-salinity meteoric water-dominated fluids characterize the latest stage of the ‘Botro ai Marmi’ hydrothermal system.