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The Pinavand fluorite deposit is hosted by lower Cretaceous carbonate rocks in the structural-geological transitional zone of Central Iran. The purple and white fluorite occur, respectively, as early replacement masses and late cross-cutting veins. Both fluorites have different and distinct physicochemical characteristics. The purple fluorite has higher homogenization temperatures of fluid inclusions (170–260 °C) and lower ∑REE (1.6 ppm) and Y (1.3 ppm) than the white variety (90–150 °C, 11.12 ppm, and 21.3 ppm, respectively). All fluorite samples show positive Y anomalies (Y/Y*) in the range of 1.15–3.5. The average values of La/Ho in the purple and white fluorites are 23.1 and 3.4, respectively. The purple fluorite samples have lower Y/Ho values (an average of 63.45) than the white fluorite samples (an average of 87.64). The Tb/Ca ratio in the Pinavand fluorites ranges between 0.0000000348 and 0.00000105, and the Tb/La ratio varies between 0.01 and 0.4; these values suggest that both fluorite types are “hydrothermal” in origin. The purple fluorites have a lower Sr and a negative Eu anomaly. These differences in concentrations and ratios of various REE suggest that the physico–chemical conditions of mineralization changed during fluorite deposition at the Pinavand. These changes correspond to an increase in oxygen fugacity and pH, which occurred during white fluorite mineralization at lower temperatures. The δ34S values of the Pinavand barite samples (an average of 23.25‰) are similar to those of seawater sulfate in the upper Proterozoic. The δ34S values of galena range from −0.2‰ to −3.7‰, compatible with bacterial sulfate reduction (BSR). These features are similar to those in the hydrothermal and magmatic deposits.

The Nain ophiolite complex with an extent of > 600 km2 is a part of the Central Iranian ophiolite, which is related to the opening and subsequent closure of the Neo-Tethys Ocean. Dunite and serpentinized harzburgite in the Nain area host podiform chromitites that occur as three (eastern Hajhossein, western Hajhossein, and Soheil Pakuh) schlieren-type tabular and aligned massive lenses with various sizes. The most common chromitite ore textures are massive, nodular, disseminated, and banded, reflecting crystal settling processes. The Cr# [Cr/(Cr + Al)] ranges from 0.43 to 0.81 (average 0.63). The Mg# [Mg/ (Mg + Fe2+)] varies from 0.25 to 0.78 (average 0.62). The Nain ophiolite and hosted chromitite are generally characterized by high Cr#, reflecting crystallization from a very hot boninite magma in a MORB setting. The high Cr# in the Nain chromitite also indicates a high degree of melting (15%–35%) of the depleted peridotite. The average total PGE content in the ophiolitic host rock (harzburgite and dunite) and chromite are 107 and 221 ppb, respectively. The Nain ophiolite and chromitite have high IPGE/PPGE and negative Pt* (Pt/Pt* = 0.6) anomaly, which is a characteristic of high Cr# chromitite. The U-shaped REE pattern of dunite host rock suggests the interaction of depleted mantle peridotite with boninitic melt. Geochemical data suggest that the Nain chromitites are related to the boninitic magma emplacement in a supra-subduction zone.

International audience; The Bou Jaber ore deposit is one of the numerous diapir-related Pb–Zn–F–Ba deposits of the Dome Zone in Northern Tunisia. Its location is controlled by the regional NE-SW Tajerouine Fault.Ore minerals are hosted in the Late Aptian limestones (Serdj Formation) as open space filling and stratabound replacement bodies. According to Bouhlel et al. (2016), the poly-phase mineralization resulted from the successive activity of three mineral systems, a Pb–Zn, then a barite, and eventually a fluorite deposition system. The latter, from the Late Miocene, is demonstrated in the present study.The fluorite system is characterized by the involvement of oil in the hydrothermal fluids. This oil was produced in the local environment of the deposit from the thermal maturation of the Albian Fahdene black shale source-rock at temperature range of~140 °C–~100 °C. Two brines were involved in the fluorite hydrothermal system. The first one (L1) is a Ca-rich brine (≥20 wt % bulk salinity), with Na/Ca ≤ 0.18, which is thought to have long resided in the basement, before its transfer into the Jurassic reservoir (Upper Nara Formation) and its eventual mobilization at the time of ore deposition. The second brine (L2), less saline (≤14 wt % bulk salinity) is more sodic, with Na/Ca up to 0.53, and represents unmodified brine originated from the nearby Triassic salt. The L1 brine was F-bearing, whereas the L2 brine was associated with oil. Fluorite deposition occurred at the estimated shallow depth of 1.7 km from cooling of the L1 brine due to the first isobaric cooling from ~160 °C to 135 °C under sub-lithostatic conditions (36 MPa). This stage is followed by mixing with the newly incoming L2 brines (transporting oil) along a sub-isochoric decompression path (down to the hydrostatic pressure at 17 MPa) and continuously cooling from 135 °C to 125 °C. The cooling and mixing caused fluorite deposition after which a transient heat advection episode (up to 145 °C) caused late calcite deposition prior to the end of hydrothermal circulation.

International audience; The Djebel El Hamra Pb-Zn-Ba-Sr (Hg) deposits in northern Tunisia are hosted in a post-nappe anticline with a core of a Triassicevaporite diapir affected by the NE–SW-trending Ghardimaou-Cap Serrat lineament. Three stages of mineralization occurred inthe Triassic dolostone: stages I and II caused alternating deposition of sulfate (Ba, Sr) and sulfide (sphalerite, galena) minerals;stage III formed late-stage calcite-marcasite-cinnabar. Zebra textures record the syntectonic transition from compression toextension in the Late Tortonian-Messinian interval. Two fluid end-members were involved in sulfate deposition: one lowsalinity(L1, ~3 wt% eq. NaCl) fluid, probably from a meteoric origin, and a Na-Ca-Cl brine (L2, ~22 wt% eq. NaCl) solutionwhich originated from the Triassic diapiric source. A third end-member fluid (L3) with long residence time in the basement wasalso involved in the Pb-Zn deposition. The δ34S values froma cluster of sulfates around +16‰, show a Triassic evaporate source.The sulfur in sphalerite resulted from bacterial sulfate reduction (BSR); however, crystallization in a closed system resulted in arange of δ34S between +1.6 and +26.5‰. The δ34S values in galena (−28.4 to +8.2‰) are consistent with a BSR and thermochemicalsulfate reduction (TSR) origin of the sulfur. Secondary ion mass spectrometry (SIMS) lead isotope data in galena(207Pb/204Pb: 15.595 to 16.193, 206Pb/204Pb: 18.673 to 18.939, 208Pb/204Pb: 38.330 to 40.572) point to local contributions(sedimentary and Cenozoic magmatic rocks) to the main source from the Precambrian basement. Ore deposition occurred at adepth of about 2 km at temperatures between 80 and 250 °C. A shallow magmatic heat source was the cause of these thermalfluctuations.

The field-portable X-ray fluorescence (FPXRF) spectrometer has evolved significantly in the last decade and has become one of the most innovative tools for field geologists. Portability and ease of use of FPXRF systems have opened up new and unique applications for even novice technicians. Application of FPXRF in precious metals exploration and mining appears to be challenging due to their low concentrations (lower than detection limit by FPXRF) in nature and even in most ore deposits. This case study shows the success of FPXRF in identifying anomalous zones of platinum group elements (PGE) and Au (target elements) using pathfinder elements in the Pilanesberg PGE deposit, Bushveld Complex, South Africa. Sixty-three core samples were analysed using both FPXRF and laboratory methods. In these samples, Pt

The Gujiao ore field, located in the middle segment of the L&uuml, liang Mountain in central North China Craton (NCC), is one of iron skarn deposits of western iron belt in China. The U&ndash, Pb dating results of zircon by LA-ICP-MS suggest that the ore-related monzonite from the Guojialiang deposit was formed at 129.7 &plusmn, 1.7 Ma, early Cretaceous, which is consistent with the timing of iron skarn deposits in the Handan&ndash, Xingtai district of western iron belt. The zircons of monzonite present notable positive Ce anomalies (Ce/Ce* = 23.38&ndash, 45.85), high Ce4+/Ce3+ values (154&ndash, 385) and relatively high oxygen fugacity (fO2 = &minus, 13.09 to &minus, 15.36), and yield relatively low Ti-in-zircon temperatures. The physico-chemical conditions of the Guojialiang deposit were quite similar to these of ore-bearing plutons in the Handan-Xingtai district. The ore-bearing magmas are derived from the enriched lithospheric mantle with crustal material contribution, which played key role in oxidation state of the magma and the iron mineralization in the western iron belt.

Conflict minerals are those mined in politically unstable regions of the world and are then sold to finance war or other illegal activities. Industrial manufacturers are required to show that minerals used in their applications are not derived from conflict areas. Several geochemical and geochronological methods have been suggested to fingerprint conflict minerals, however, all these methods require sophisticated and extensive laboratory procedures. Portable X-ray fluorescence data of 108 samples from various location in Democratic Republic of the Congo shows that cassiterite and wolframite ores from all studied regions can be fingerprinted using various discrimination diagrams. Coltan ore samples from several regions can also be discriminated using major and trace elements of these samples. In addition, patterns in chondrite-normalized spider diagrams for each region are unique and can be used as fingerprinting tools.

The Rangraz copper deposit (5 Mt @ 0.83% Cu) is located 20 km north of Saveh city, Markazi Province, Iran, in the central Uromieh-Dokhtar volcano-plutonic belt. Host rocks are mainly composed of Eocene volcanic and volcaniclastic rocks that have been intruded by late Eocene quartz monzodiorites and basaltic-andesitic dikes. The dominant copper-related hydrothermal alteration types include silicification, sericitization, and chloritization-kaolinitization. The ore body takes the form of fault-hosted, NW-SE-striking lodes comprising pyrite, chalcopyrite, bornite, specular hematite and magnetite as the principal hypogene ore minerals. Gold (maximum spot assays of up to ca. 0.37 ppm Au) and silver (up to 20.6 ppm Ag) have also been recorded. The ore minerals are mainly confined to veins or veinlets showing crustiform, colloform, open space-filling, dissemination and replacements characteristics in texture. The principal gangue minerals are quartz, barite and calcite. Most of the fluid inclusions identified in quartz-chalcopyrite ± specular hematite veins contain two liquid and vapour phases at room temperature. The primary and pseudo-secondary fluid inclusions have low to intermediate homogenization temperatures between 134 and 338 °C and salinities between 3.55 and 16.89 wt% NaCl equivalents. The fluid inclusion data are consistent with a two-stage evolution of the mineralizing system with initial metal precipitation at crustal depths of

The geological study of Miocene clays from Gram area, North West of Tunisia shows an important series of clay materials to use them in the faience ceramic. Selected samples were studied with the objective of analyzing their chemical and mineralogical composition, morphology, particle size, plasticity, thermal analysis and their ceramic aptitude to be used in the faience ceramic. Raw materials are mainly composed of illite and kaolinite are the dominant clay minerals with minor quartz and dolomite. The plasticity indexes are lower than 15.40%, suggesting that these clays are not plastic. Technical characterization was carried out on one representative mixture of Miocene clay samples. The firing characteristics (shrinkage and water absorption) were measured. The optimum firing temperature of clay mixture (M) has been established. These clays could be used in the manufacture of ceramic pieces.

A geochemical exploration program was applied to recognize the anomalous geochemical haloes at the Ravanj lead mine, Delijan, Iran. Sampling of unweathered rocks were undertaken across rock exposures on a 10 × 10 meter grid (n = 302) as well as the accessible parts of underground mine A (n = 42). First, the threshold values of all elements were determined using the cut-off values used in the exploratory data analysis (EDA) method. Then, for further studies, elements with lognormal distributions (Pb, Zn, Ag, As, Cd, Co, Cu, Sb, S, Sr, Th, Ba, Bi, Fe, Ni and Mn) were selected. Robustness against outliers is achieved by application of central log ratio transformation to address the closure problems with compositional data prior to principle components analysis (PCA). Results of these analyses show that, in the Ravanj deposit, Pb mineralization is characterized by a Pb-Ba-Ag-Sb ± Zn ± Cd association. The supra-mineralization haloes are characterized by barite and tetrahedrite in a Ba- Th- Ag- Cu- Sb- As- Sr association and sub-mineralization haloes are comprised of pyrite and tetrahedrite, probably reflecting a Fe-Cu-As-Bi-Ni-Co-Mo-Mn association. Using univariate and multivariate geostatistical analyses (e.g., EDA and robust PCA), four anomalies were detected and mapped in Block A of the Ravanj deposit. Anomalies 1 and 2 are around the ancient orebodies. Anomaly 3 is located in a thin bedded limestone-shale intercalation unit that does not show significant mineralization. Drilling of the fourth anomaly suggested a low grade, non-economic Pb mineralization.

The Esfordi iron oxide–apatite deposit is located in the Bafq district, Central Iran. The ore body is hosted by the Lower Cambrian succession of rhyolite, rhyolitic tuff, cherty dolomite, and limestone. Calc-silicate assemblages occur locally in altered host rocks as stratigraphically controlled patches. The main hydrothermal minerals include apatite, magnetite–hematite, actinolite, garnet, clinopyroxene, talc, calcite, and quartz. The prograde calc-silicate mineral paragenesis manifests as garnet (Ad96.7, Gr1.88) and clinopyroxene (Di76.14, Hd22.65, Jo1.21), whereas apatite, magnetite, hematite, tremolite–actinolite, chlorite, talc, epidote, quartz formed during retrograde episode. Microthermometric results yield a temperature range for 222–465 ° C, with a salinity of 8 to 21 wt% NaCl for apatite that coexists with retrograde mineral assemblage. δ18O isotopic variations of apatite (1.23–14.9 ‰), magnetite (6.8–8.3 ‰), and quartz (13.8–15.8 ‰) suggests that mixing of magmatic and meteoric fluids occurred during mineralization. Calc-silicates prograde stage is believed to have formed at T

The Dopolan deposit is a Mediterranean-type bauxite located in the Zagros Fold-Thrust Zone, Iran. This deposit consists of five lithological members including iron-rich, clay-rich, oolitic, pisolitic and organic matter-containing bauxites. The mineralogy of the deposit includes diaspore, boehmite, and kaolinite, nacrite, with minor pyrite, anatase and rutile. Geochemical studies show that light rare earth elements (LREEs) are enriched relative to heavy rare earth elements (HREEs) in all members, supporting an authigenic origin. Mass changes based on Ti as an immobile element indicate that conventionally-immobile elements (Al, Nb, Ta, Zr, Hf) are enriched in situ in the residual units, whereas mobile elements (K, Ca, Si) were depleted during bauxitization. This study shows that the Khaneh–Kat argillitic dolomite is the likely parent rock. The δ18O (7.63‰to 9.35‰) and D values (49.91‰to 66.49‰) for kaolinite in the bauxite samples suggest equilibration with meteoric waters which supports a supergene origin. Bauxitization occurred in a warm climate with relatively constant isotopic composition suggesting climate stability during the development of bauxite horizons and remobilization of Al (with formation of secondary boehmite). The δ13C values of calcite (7.3‰) in the bauxite support the idea that the Khaneh–Kat Formation has experienced post-depositional isotope exchange with meteoric waters during the karstification process.

Airborne radiometric survey and field studies outlined a large, elongate, high-level plutonic suite within the Richardson pluton south of the Contact Lake Belt in the Great Bear Magmatic Zone, Northwest Territories, Canada. In terms of content of radioactive elements, the Richardson pluton is composed of two distinct granite types, low heat production (LHP) and high heat production (HHP). Uranium content in the LHP and HHP granites ranges from 3.0 to 4.9 ppm and 6.5 to 24.6 ppm, respectively, showing similarity of the LHP granite to average granites. Geochemical studies indicate that there is a genetic relationship between these two types of granite; the LHP granite was the early product of magma crystallization, whereas the HHP granite is the result of extensive crystal fractionation of biotite, plagioclase and apatite. The presence of magmatic fluorite in granite suggests that high fluorine content lowered the liquidus temperature of magma causing lower temperature fractionation during ascent to high crustal levels, which increased U and Th concentrations in the resultant HHP granite. Weak U mineralization occurs locally as discontinuous quartz ± hematite ± pitchblende veins and veinlets within the HHP granite. Stronger U mineralization (U ± Ag ± Ni ± Co ± Cu) occurred in the past-producing Contact Lake and Port Radium deposits. It appears that such mineralization may have had a spatial and temporal genetic-paragenetic relationship with the HHP granite.

The Ain Allega Pb–Zn–Sr–Ba ore deposit is located in the flysch zone on the Eastern edge of the Triassic diapir of Jebel Hamra. It is part of the extrusive Triassic evaporate formation along the Ghardimaou–Cape Serrat faults. The ore body consists of argilic–dolomite breccias surrounded by argilo–gypsum Triassic formation, which forms the hanging wall of the deposit, and rimmed by the Paleocene marls. The ore minerals show a cap-rock type mineralization with different styles particularly impregnation in dolomite, cement of breccias, replacement ore and open space filling in the dissolution cavities and fractures. Ore minerals include sphalerite, galena, marcasite and pyrite. Principal gangue minerals are composed of barite, celestite, calcite, dolomite and quartz. The ore minerals are hosted by the Triassic carbonate rocks which show hydrothermal alteration, dissolution and brecciation. X-ray – crystallographic study of barite–celestite mineral series shows that pure barite and celestite are the abundant species, whereas strontianiferous barite (85–96.5% BaSO4) and barian–celestite (95% SrSO4) are minor. Primary and secondary mono-phase (liquid only) fluid inclusions are common in celestite. Microthermometric analyses in two-phases (liquid and vapour) fluid inclusions suggest that gangue and ore minerals were precipitated by a low-temperature (180 °C) saline (16.37 wt.% NaCl equivalent) solution originated possibly from a basinal brine with some input from magmatic or metamorphic fluid. Based on geology, mineralogy, texture and fluid characteristics, the Ain Allega deposit is classified as a carbonate-hosted Mississippi valley-type deposit.

The Mazraeh Cu–Fe skarn deposit, NW Iran is the result of the intrusion of an Oligocene–Miocene granitic pluton into Cretaceous calcareous rocks. The pluton ranges in composition from monzonite to quartz monzonite, monzogranite, tonalite and granodiorite with I-type, calc-alkaline, and weakly peraluminous characteristics. The Mazraeh pluton was emplaced in a volcanic arc setting in an active continental margin at a depth of ~8 km. Pyroxene skarn, garnet skarn, and epidote skarn zones were formed during the intrusive phase. The garnet skarn developed as exoskarn and endoskarn from the calcareous wall rocks and the pluton, respectively, prior to mineralization. Garnet skarn from the exoskarn zone is identified by relict layering inherited from the precursor calcareous lithologies. Mass balance calculation of garnet skarn in the endoskarn zone indicates that hydrothermal fluids originating from the cooling magma introduced Si, Fe, Mn, Ca, Mg, P, Ag, Cu, Zn, La, Pb, Cd, Mo, and Y. The main mass loss in the garnet skarn was due to destruction of feldspars in the Mazraeh plutonic rocks and leaching of K2O and Na2O. Released Ca has been fixed in the andraditic garnet. Garnetization of the Mazraeh pluton was accompanied by mass and volume increase. The magnitude of these changes depends mainly on the degree of alteration and composition of the precursor. The brittle behavior of the endoskarn zone was increased due to formation of massive garnet which subsequently fractured. These fractures not only facilitated movement of hydrothermal fluids but also provided new locations for Cu mineralization. Therefore locating strongly garnetized zones may be a vector to ore in skarn deposits.

The Contact Lake Belt forms the NW-trending flank of a collapsed andesite stratovolcano complex adjacent to a subvolcanic intrusion within the northern, 1.87 to 1.85 Ga, Great Bear magmatic zone, Northwest Territories, Canada. It belongs to the Port Radium-Echo Bay historical district that hosts past producers of U, Ag, Cu (± Ra, Ni, Co, Bi) from polymetallic sulfide and arsenide veins. A re-examination of the belt has revealed widespread IOCG-type polymetallic mineralization exposed in numerous veins, stockworks, breccias, and replacement zones within extensive areas of polyphase hydrothermal alteration. The effects are most visible and intense in andesite, but also affect associated synvolcanic intrusions. A weak, pervasive chlorite-epidote-carbonate-sericite alteration is observed in the least-altered volcanic rocks. Subsequent hydrothermal alteration that is progressively superimposed on earlier facies includes: sericitic (sericite, quartz); phyllic (sericite, quartz, pyrite); potassic (K feldspar); earthy and specular hematite; K feldspar-scapolite-albite-magnetite-actinolite-apatite as veins, stockwork, and pegmatitic recrystallization; K feldspar-tourmaline-Fe-oxide-silica-sulfides; and massive albitites locally laced with amphibole. Hydrothermal breccias and diatremes occur locally throughout the belt. The style, size, overprinting relationship, mineralogy, and chemical composition of alteration zones and mineralization support the current IOCG exploration model for polymetallic mineralization in the Contact Lake Belt, as well as for mineralization elsewhere in the Port Radium-Echo Bay district and the Great Bear magmatic zone overall.

Synvolcanic structures played a fundamental role in the genesis, morphology, and siting of volcanogenic massive sulfide ores and associated hydrothermal alteration in the Archean South Sturgeon Lake caldera complex. The most voluminous and persistent hydrothermal venting and massive sulfide deposition occurred along synvolcanic rifts and grabens associated with faults and tectonic fissures that created permeable fracture zones deep enough to access the underlying hydrothermal reservoir. The type of fracturing is highly variable and changes with the composition, competency, degree of consolidation, and alteration of host rocks. Synvolcanic structures and fracture styles also vary according to the amount and type of tectonic movement, including extension-related collapse, shearing and faulting perpendicular to the principal direction of extension, and orthogonal faulting and shearing. Permeable conduits were created by tension fracturing along fault zones, brittle deformation at the intersections of orthogonal faults, and by extensional fractures in stockworks. In texturally uniform footwall rocks, the distribution of alteration zones was controlled by the morphology of the structural conduit. In rocks with vertical and/or lateral facies, permeability, and competency changes (e.g., Lyon Lake graben), there was an additional stratigraphic control over fluid migration. Some crosscutting synvolcanic structures, alteration zones, and intrusions appear as stratiform units at the present erosion surface due to regional deformation and the present attitude of the volcanic stratigraphy. Hydrothermal mineral assemblages (e.g., quartz, carbonates, chlorite, pyrite, chalcopyrite) infilling structurally induced fractures provide good evidence of fluid migration pathways. However, mineralogy can vary significantly according to the fluid characteristics, host rock geochemistry, and subsequent metamorphic history of the area. Clearly, one of the best methods for locating volcanogenic massive sulfide deposits is to delineate the attitudes of synvolcanic structures, and explore those that show evidence of associated high-temperature hydrothermal mineral assemblages. Excellent exploration targets occur where synvolcanic structures with hydrothermal alteration intersect paleo-seafloor horizons.

The Glen Eden area is located within the New England Orogen (also known as New England Fold Belt). This orogen is one of the major structural elements within the extensive Tasman Orogenic Province which comprises the eastern part of the Australian continent (Hensel, 1982). The present length of this orogen is about 1500 km from Townsville to Newcastle. It is separated from the Thomson and Lachlan fold belts to the west by the Permian and Triassic strata of the Bowen-Gunnedah-Sydney Basin. The Mesozoic ClarenceMoreton and Great Artesian basins separate the northern and southern parts of this orogen. The New England Orogen was the site of the extensive episodic calc-alkaline magmatism related to west-dipping subduction from middle Paleozoic to Early Cretaceous time. The oldest rocks might have formed at least partly in a volcanic island arc, but from the Late Devonian, the orogen developed as a convergent Pacific-type continental margin. During Late Devonian-Carboniferous time, parallel belts representing continental margin, volcanic arc, forearc basin and subduction complex assemblages can be recognized (Murray, 1988). More than one hundred plutons were emplaced from the Late Carboniferous to the Triassic in the southern NEO. These intrusions have been attributed to two major periods of plutonism, the first during Late Carboniferous time and the second during the Late Permian and Triassic. The resulting plutons comprise the New England Batholith. Although volcanogenic massive sulfides and volcanic-hosted epithermal gold-silver ore deposits occur in older rock sequences (Murray, 1988), almost all of the other ore deposits of this region, including the Glen Eden Mo-W-Sn deposit, have a genetic or paragenetic relationship with plutons of the New England Batholith which is one of the largest Paleozoic-Mesozoic batholiths in eastern Australia. It underlies an area of almost 20000 km2 and is composed of more than one hundred N-S-trending plutons which include all of the granitoids in the southern part of the NEO. These granitoids intruded into the tectono-stratigraphic terranes (Flood and Aitchison, 1993a, b) and deformed trench-complex metasedimentary rocks (Shaw and Flood, 1981). The composition of this batholith is 80% monzogranite, 18% granodiorite, 1% diorite and tonalite, 1% quartz-bearing monzonite and

The Ain Allega ore deposit represents one of the most significant Pb-Zn Sr-Ba deposits of the flysch zone in northern Tunisia. The total quantity of sulphide produced is 22,700 metric tons, with 13,300 t of galena and 9,400 t of sphalerite. It is located on the eastern edge of the Triassic diapir of the Jebel Hamra. The main ore minerals include sphalerite, galena, pyrite and marcasite, and gangue minerals including dolomite, calcite, celestite, quartz and barite. The mineralization hosted by carbonate rocks, shows some evidence of dissolution and brecciation characteristic of cap-rock formation. The fluid inclusion study from the celestite suggests that the primary and secondary monophase liquid (L) inclusions are most abundant compared to the other types. The microthermometric analyses of two-phase primary inclusions display homogenization temperatures ranging from 136 to 208°C (average of 180°C) and salinities ranging from 11.34 to 24.38 equivalent weight % NaCl (average of 16.4). The calculated density, pressure and depth are 0.965 g/cm3, 18 bars and 80 m, respectively. The hydrothermal fluid resulted from mixing of basinal brines and magmatic-meteoric solutions. Geological, mineralogical and thermometric data indicate that the Ain Allega ore deposit results of a mixing of basinal fluids (Mississippi valley type deposit) and hydrothermal fluids related to a shallow intrusion.