Barite Veins Research Articles

Paragenetic and geological setting of the Starra iron oxide copper–gold deposits, Mount Isa Inlier, Queensland, Australia: constraints on IOCG deposit models

The five Starra iron oxide copper–gold (IOCG) deposits, which are located in the Cloncurry district of the Mount Isa Inlier, NW Queensland, are hosted in a N-trending zone of deformed iron-rich metasedimentary rocks that are underlain by two mineralogically distinct mafic–intermediate meta-igneous rocks. Copper–Au mineralisation is subdivided into two stages—an early main stage that transitioned from a magnetite-dominated Cu substage comprising chalcopyrite, pyrite, biotite and chlorite, to a hematite–muscovite-bearing Cu–Au substage with chalcopyrite, bornite and rare chalcocite, as well as Au–Ag-tellurides and native Au. This second stage was followed by a subordinate but nonetheless important carbonate–quartz–barite vein stage with minor but locally high-grade Cu–Au mineralisation characterised by abundant chalcocite and bornite, minor native bismuth and wittichenite (Cu3BiS3), together with minor Au–Ag telluride minerals. Bornite in these carbonate–quartz–barite veins contains considerable amounts of Au (>10 ppm), which appears to be deported either as lattice substitution in the bornite crystal structure or as homogeneously distributed Au0 nanoparticles. An earlier, coarse-grained mafic intrusion was affected by early Na–Ca alteration, whereas a second mafic intrusion lacks evidence of Na–Ca alteration but was exposed to K–Fe alteration and subsequent mineralisation at Starra 222. Mushketovite (magnetite after specular hematite) is only observed in ironstone lodes proximal to the mafic–intermediate rocks. The close spatial and mineralogical associations of the mafic–intermediate bodies and the ironstone lodes point to a stronger link between magmatic activity and IOCG mineralisation than has previously been recognised at Starra. Remobilisation of gold by late-stage hydrothermal fluids aided by the relatively low fluid temperatures during the main pulse of Cu–Au mineralisation refined gold grades at Starra, making it a relatively gold-rich IOCG deposit. We show that the Cu–Au deposits of the Starra trend feature mineralogical and geochemical elements common to both Cloncurry IOCG deposits (e.g. abundant magnetite) and IOCG deposits of the Tennant Creek district (e.g. Au–Cu–Bi mineralisation; hematite–bornite–chalcocite assemblages), making them a unique and important member of this complex family of deposits.

Integration of Whole-Rock Geochemistry and Mineral Chemistry Data for the Petrogenesis of A-Type Ring Complex from Gebel El Bakriyah Area, Egypt

El Bakriyah Ring Complex (BRC) is a prominent Neoproterozoic post-collisional granite suite in the southern part of the Central Eastern Desert of Egypt. The BRC bears critical materials (F, B, Nb, and Ta) in appreciable amounts either in the form of rare-metals dissemination or in the form of fluorite and barite vein mineralization. The complex consists of inner syenogranite and outer alkali feldspar granite that have been emplaced in a Pan-African assemblage made up of granitic country rocks (granodiorite and monzogranite), in addition to post-collisional fresh gabbro as a part of the Arabian-Nubian Shield (ANS) in northeast Africa. Granites of the BRC are characterized by enrichment in silica, alkalis, Rb, Y, Ga, Nb, Ta, Th, and U and depletion in Sr, Ba, and Ti. Geochemical characterization of the BRC indicates that the magma is a crustal melt, which originated from the partial melting of metasedimentary sources. Concentrations of rare-earth elements (REEs) differ in magnitude from the ring complex and its granitic country rocks but they have similar patterns, which are sub-parallel and show LREEs enrichment compared to HREEs. The presence of a negative Eu anomaly in these rocks is related to plagioclase fractionation. The abundance of fluorine (F) in the different granite varieties plays an important role in the existence of a tetrad influence on the behavior of REEs (TE1, 3 = up to 1.15). Geochemical parameters suggest the crystallization of the BRC granite varieties by fractional crystallization and limited assimilation. Mn-columbite and Mn-tantalite are the most abundant rare-metals dissemination in the BRC granite varieties. We present combined field, mineralogical and geochemical data that are in favor of magma originating from a metasedimentary source for the BRC with typical characteristics of A-type granites. Our geodynamic model suggests that the Gebel El Bakriyah area witnessed the Neoproterozoic post-collisional stage of the ANS during its late phase of formation. This stage was characterized by the emplacement of fresh gabbros followed by the syenogranite and alkali-feldspar granite of the BRC into an arc-related assemblage (granodiorite and monzogranite). It is believed that the mantle-derived magma was interplated and then moved upward in the extensional environment to a shallower level in the crust owing to events of lithospheric delamination. This presumably accelerated the processes of partial melting and differentiation of the metasedimentary dominated source (Tonian-Cryogenian) to produce the A-type granites building up the BRC (Ediacaran).

Multistage fluorite mineralization in the southern Black Forest, Germany: evidence from rare earth element (REE) geochemistry

Abstract. The Black Forest hosts a wide range of hydrothermal mineralization, including fluorite–barite vein deposits. In a detailed investigation of the Finstergrund and Tannenboden deposits in the Wieden mining district (southern Black Forest), the diversity, geochemical evolution and relative chronology of multistage fluorite precipitation is tracked on the basis of rare earth element (REE) geochemistry, geologic field relationships and crystal zoning. Geochemical discrimination and mathematical λ coefficients suggest a total of seven fluorite REE groups, at least three distinguishable post-Variscan fluid mobilization events and independent formation histories for the deposits despite their spatial proximity. Fluorite vein mineralization at the Finstergrund deposit evolved over three fluid generations, was derived from gneissic source aquifers and comprises five distinct fluorite REE groups: the first fluid generation is characterized by fluorite precipitation above 200 ∘C (“group III”), below 200 ∘C (“group I”) and after fractional crystallization (“group IV”); the second generation comprises remobilized fluorite (“group II”); and the third generation revealed fluorite precipitation by meteoric water mixing (“group V”). Fluorite vein formation at the Tannenboden deposit is associated with two distinct fluorite REE patterns derived from the same fluid generation: fluorite precipitation above 200 ∘C (“group VII”) and after cooling below 200 ∘C (“group VI”). Its fluid source aquifer lithology best matches migmatites contrary to previous models that suggest either gneissic or granitic aquifer rocks for fluorite vein precipitation in the Black Forest. The decoupled formation history between the deposits is tectonically controlled as suggested by a new genetic model for the Wieden mining district. The model argues for a change in the local fluid percolation network and the termination of hydrothermal activity at the Tannenboden deposit after the first fluid mobilization event. The geochemical evolution of multistage fluorite mineralization, as exemplified by the Tannenboden and Finstergrund deposits in combination with other fluorite mineralizations in the Black Forest, provides unique insights into the lithospheric origin and precipitation behaviour of fluorite by various fluid–rock interaction processes occurring in large hydrothermal systems. The local diversity of REE patterns emphasizes the need for detailed investigations of individual hydrothermal vein deposits.

Fault-controlled barite veins of the eastern Anti-Atlas (Ougnat, Morocco), a far-field effect of the Central Atlantic opening? Structural analysis and metallogenic implications

Tectonic and micro-tectonic studies at different scales are of primary importance in a modern metallogenic investigation. In the Ougnat massif of the eastern Anti-Atlas belt (Morocco), the barite ore deposit is hosted within mafic to felsic rocks of the Ediacaran Saghro and Ouarzazate groups together with their folded Paleozoic cover. Here, we provide for the first time new field-based data on the tectonic control of barite mineralization, and their relation with regional tectonic events. The mineralization occurs in brittle-ductile structures as a vein-type system, mainly hosted within NE-SW to E-W and NW-SE strike-slip-normal faults. Economic orebodies spread frequently along the Precambrian-Cambrian contact zone thus acting as open conduits for mineralized fluid flow. The geometry of hosted barite sigmoidal lenses corresponds to “pull-apart” or “tension gashes” openings, commonly arranged en echelon arrays along the bearing transcrustal faults. The occurrence of predominant massive and breccia internal texture implies a tectonic-mineralizing collapse process in an extensional tectonic context. Kinematic pattern, directional distribution and host-rock age relationship point to a syntectonic barite control probably occurred during the NW-SE Atlantic rifting, as already attributed to similar deposits in the neighboring Ougarta and Atlas-Meseta domains.The barite ore is quantitatively and qualitatively more preserved in competent host rocks than those with ductile behavior, thus offering a useful hint for further barite exploration in this part of the Anti-Atlas fold and thrust belt.

Žune Ba-F epithermal deposit Part 2: Geophysical characterization and exploration perspective

The Žune barite-fluorite ore body in northwestern Bosnia and Herzegovina has been explored in order to determine spatial distribution of the ore body. At the Žune site, barite mineralization occurs in the form of veins and is hosted by dolostone. A geophysical survey was carried out with the aim to detect anomalies associated with the barite-fluorite deposit and to characterize the abandoned old deposit. Therefore, 2D electrical resistivity tomography (ERT) was measured along four profiles. Prior to surface geophysical measurements, detailed geological field mapping of the ore body and host rocks was undertaken. The geometry of the abandoned mining cut with steep walls and complex structural setting with barite that incorporates coarse fragments of host rock and fluorite makes interpretation of the results challenging. The collected geological data were used to calibrate the geophysical models. Forward modelling in addition to inversion of the ERT data helped to reduce the ambiguity of geophysical data interpretation. The results revealed that the barite vein in the area of mining cut is limited to a depth of about 10 m and length is about 40 m. There is no indication for barite mineralization in the area south of the mining cut, while anomalies that may be associated with ore bodies are present in the northern and northeastern part.

Anglesite, Cerussite, Gypsum, Langite, Malachite, and Posnjakite: New Occurrences in the Calabria Region (Southern Italy)

This study undertook the mineralogical and chemical analysis of anglesite (PbSO4), cerussite (PbCO3), gypsum (CaSO4∙2H2O), langite (Cu4(SO4)(OH)6∙2H2O), malachite (Cu2CO3(OH)2), and posnjakite (Cu4(SO4)(OH)6·H2O) detected for the first time in the abandoned Mastricarro Barite Mine (Catanzaro, Calabria, southern Italy). Geological conditions make this one of the few well-preserved, partly accessible mines in the Calabria region. Numerous mineralogical species, some beautifully crystallized, have been discovered among the alteration products of the sulfides present within the barite veins. The newly identified crystals occur as secondary minerals in the oxidized portions of deposits originally containing lead and copper sulfides; they are widely distributed and are almost always detected as microcrystals. The anglesite, cerussite, gypsum, langite, malachite, and posnjakite crystals were identified and characterized using optical microscopy (OM), micro-Raman spectroscopy (µR), and scanning electron microscopy, combined with energy dispersive spectrometry (SEM/EDS). The new mineral occurrences can be useful for scientific and didactic purposes; further, for langite, malachite, and posnjakite crystals, new Raman bands, which have not been mentioned before in the literature, were identified.

The mobilization of boron and lithium in the hydrothermal system of the ∼3.48 Ga Dresser caldera: A stable isotope perspective

Voluminous hydrothermal circulation in the ∼3.48 Ga Dresser caldera produced zoned alteration haloes around major fluid pathways. Specifically, in the North Star Basalt (the footwall) hydrothermal alteration decreases with increasing distance from the margins of hydrothermal silica±barite veins, changing from argillic (i.e., kaolinite-quartz) to phyllic (i.e., illite-quartz), and then to either propylitic (i.e., chlorite-albite-epidote) or actinolitic (i.e., actinolite-albite-chlorite-epidote) assemblages at distal positions. This alteration series developed through hydrolysis reactions at decreasing acidic conditions, which promoted variable degrees of mobilization of major and trace elements in the hydrothermal fluids.In this study, we characterize the B and Li concentrations and the relative stable isotope ratios of the altered North Star Basalt to provide new insights into the hydrothermal processes that generated these complex alteration patterns. In particular, we focus on the magnitude and timing of the inputs from different fluid reservoirs, the mobilization of B and Li in the hydrothermal system of the Dresser caldera and their influence on the near-surface environment where ancient stromatolites were forming.Actinolitic and propylitic samples have homogeneous δ11B and δ7Li values (−17 to −15‰ and +1 to +3‰, respectively) that are associated with lower B and Li concentrations in actinolitic (4 to 11 ppm and 46 to 128 ppm, respectively) relative to propylitic samples (9 to 25 ppm and 176 to 305 ppm for B and Li, respectively). This pattern suggests that at least the propylitic assemblage interacted with alteration fluids of largely magmatic origin, thus excluding the possibility of an early seawater contributions to the hydrothermal system. Conversely, phyllic samples have distinctly higher B contents (57 to 99 ppm) and δ7Li values (+7 to +8‰), but have much lower δ11B values (−19 to −28‰) and Li contents (5 to 6 ppm) relative to actinolitic and propylitic samples. We argue that these striking differences are attributable to mineralogical and temperature controls that promoted the preferential removal of 6Li during chlorite dissolution and incorporation of 10B into illite. Furthermore, the highly negative δ11B values in phyllic samples suggest that the additional B incorporated into the altered North Star Basalt originated from the magma chamber underlying the Dresser caldera rather than from seawater or other crustal sources. The most intensely altered (argillic) samples have moderate B and Li contents (2 to 43 ppm and 41 to 71 ppm, respectively) and highly variable δ11B and δ7Li values (−24 to −0.4‰ and −10 to +11‰, respectively). These signatures are interpreted to represent the input of ‘external’ fluids into the upper portions of the hydrothermal system during periodic crack-seal events that allowed the influx of restricted amounts of seawater and, possibly, meteoric fluids.Overall, this study provides a novel non-traditional stable isotope perspective on the evolution of the hydrothermal system of the Dresser caldera that adds richness to our understanding of this complex environment. Both B and Li stable isotopes support a prominent magmatic contribution to the hydrothermal fluid budget, reinforcing the interpretation of a hot-spring origin of the tourmaline-bearing layers associated with the stromatolites of the North Pole Chert.

Rift-induced structurally controlled hydrothermal barite veins in 1.6 Ga granite, Western Bastar Craton, Central India: Constraints from fluid inclusions, REE geochemistry, sulfur and strontium isotopes studies

Expressive granitic magmatism and a complex system of fault and shear zones are the main features associated with the crustal evolution and metallogeny in the Western Bastar Craton (WBC), Central India. The barite mineralization in WBC, Central India, occurs as veins and fracture fillings along faults are activated or reactivated as a consequence of rifting of – 1.5–1.6 Ga Pranhita-Godavari (PG) basin. The barite mineralization is hosted in ca. 1.6 Ga Mul granite of WBC. We present the first comprehensive, integrated field and laboratory studies approach using structural mapping, fluid inclusion, Sulfur, and Sr-Isotope geochemistry, mineral, and REE geochemistry to characterize barite mineralization ore-forming processes, a fluid source, and structural control. The host granite is intensely altered with evidence of hydrothermal mineralization in the form of silicification and hematitisation. Both sulfide-free (Brt-I) and sulfide-bearing (Brt-II) barites occur in the study area. Besides, barites with fluorite (Brt-III) were also observed in minor concentrations. The mineralization is associated with quartz-calcite vein, and the barite is accompanied by galena, pyrite, and chalcopyrite. Petrographic observations, fluid inclusion, and isotope data suggest a bimodal evolution of the mother brine viz. the oxidative source forms sulfide-free high-salinity brine and reductive low-salinity sulfide-bearing aqueous fluid formed by interaction with reducing agent causing hydrothermal barite mineralization in the study area. The source for the hydrotherms responsible for the formation of barite and galena in association with the quartz-barite vein is, in all probability, granitic magma. Incompatible elements like Ba, Pb and volatiles like S, preferentially concentrated in late magmatic hydrothermal fluids, got emplaced along the structurally weak zones in the interior of the granite pluton. The combined 87Sr/86Sr and δ34S‰ data suggest mixing fluids from diverse sources, including magmatic, marine, and crustal fluids. Low 87Sr/86Sr (<0.707) and high δ34S(>10‰) are indicative of alteration products of granite that were subsequently mixed with submarine hydrothermal fluid mobilized through the Mesoproterozoic PG rift system. This regional rifting event provided pathways for fluid flow and ore formation along faults/fracture systems (F2 and F3 fault systems) in the host Mul granite of WBC. The F2 fault system, sympathetic to the PG rift, is deep-seated and contains mainly barites of magmatic origin besides the minor marine signature. The F3 cross faults, developed across the gneissic foliation of TTG gneisses and charnockites, can be traced to the PG basin's younger marine sediments, host barites of dominantly marine signature.The Ba ± F mineralization in the study area is a perspective for regional exploration for REE-Ba-F in central India and elsewhere in a similar geological milieu. The epigenetic-submarine hydrothermal vein-type barite mineralization hosted in granite, WBC differs from Sedex, VMS, Carlin, or Orogenic type barite deposits, which has a great deal of replicability and suitability for future exploration targeting.

Seismic imaging of a near-vertical vein using controlled-source seismic interferometry

New methodologies for narrow-vein mining are making thin, steeply dipping mineralized veins economically viable mining targets. Drilling is the normal method for delineation and resource evaluation prior to mining. However, for the evaluation of narrow veins, significant drilling of barren rock is required. Controlled-source seismic interferometry has the potential to significantly decrease the costs of target delineation by providing high-resolution seismic images of thin, steeply dipping mineralized veins. We present a case study that employs seismic interferometry in conjunction with a walkaway vertical seismic profiling survey to image a thin (0.5–4 m), steeply dipping barite vein. The footprint of the seismic data acquisition is relatively small and compatible with operations in areas with limited access (e.g., mining camps). The technique requires some care with experimental design and data processing, but it is clearly demonstrated to produce a high-resolution seismic image. Furthermore, we demonstrate that inversion of the depth-migrated image can be used to quantify vein thickness and provide direct information for resource evaluation and reserve estimation.

Evaluation of exploiting barite, the critical raw material in Slovakia, and benefits of its mining

Purpose. There are several deposits of critical raw materials in the Slovak Republic, but currently only one is mined. This is a barite deposit in Spiš, which shows an ever-lower volume of exploited raw material year-on-year. However, this area is rich in several confirmed barite veins, which represent potential strategic raw materials. The presented article analyzes in detail and describes the Jaklovce I. deposit, which is located in the Gelnica district in north-east of Slovakia. Despite the fact that Slovakia, as well as most EU countries, is dependent on imports of raw materials, the new deposits represent new potential. Determination of the economic value of these deposits creates a promising potential for the investor, but also, secondarily, a potential for the socio-economic development of regions, as well as for the state. Methods. Based on the evaluation of dynamic economic variables, the article predicts the benefits which mining in this deposit would bring, which are also supported by SWOT analysis of barite exploitation. Findings. According to the methods used during the financial evaluation of the single mined deposit of CRM in Slovakia, which was developed because of CRM criticality in EU, we showed, based on § 14 of the Mining Act no. 44/1988 Coll. the necessity of CRM mining from the view of regions, the state and investors. The present article summarizes impacts of exploiting the barite from Jaklovce I. deposit for the investor, as well as for the state, which is also underlined through SWOT analysis. Originality. This study attempts to point out that mining critical raw materials is economically suitable not only for the state, but also for investors. SWOT analysis also pinpoints most threats, opportunities and some forecasts which should be taken into account while designing the investment project. Practical implications.I nvestment project in mining area is one of the most critical and challenging decisions that experts have to make mainly based on geological, economical and geotechnical properties of the deposit, which are very specific. The same is true for the investment project which represents huge investments and rate of risk

Genesis of the Abbasabad epithermal base metal deposit, NW Iran: Evidences from ore geology, fluid inclusion and O–S isotopes

The Abbasabad epithermal Pb–Zn–Cu deposit is located in the Tarom–Hashtjin Metallogenic Belt (THMB), northwest Iran. Mineralization occurs as quartz-base metal sulfide veins and breccias mainly hosted by Eocene volcanic and volcaniclastic rocks of the Karaj Formation. Four mineralization stages are recognized: (1) quartz-chalcopyrite-pyrite veins and breccias, (2) quartz-calcite I-sphalerite-galena ± chalcopyrite ± pyrite veins and breccias, (3) late stage barite veins and veinlets, and (4) barren post-ore calcite II veinlets. The primary metallic minerals, in order of abundance, are galena, sphalerite, chalcopyrite, and pyrite; gangue minerals are mainly quartz, barite, calcite, sericite/illite, and chlorite. The main wall-rock alteration is silicification, intermediate argillic, carbonatization, and propylitic alteration. Microthermometric measurements of primary LV fluid inclusion assemblages in quartz, sphalerite and barite show that the ore-forming fluids belong to the low- to moderate-temperature (170–315 °C), moderate-salinity (3.6–7.1 wt% NaCl equiv.), low-density H2O–NaCl system. Estimated trapping hydrostatic pressures are 60 to 100 bars, corresponding to entrapment depths of 614 to 1022 m below the paleowater table. Oxygen isotopic data (δ18OH2O of + 7.6 to + 0.6‰) indicate that the ore-forming fluid was derived largely from magmatic fluid, with the addition of meteoric water in the later stage. δ34SH2S values of sulfides vary over a narrow range from –17.4‰ to –15.4‰, (averaging − 16.3‰), indicate that sulfur might be derived from a relatively homogeneous magmatic source which oxidized by meteoric water through fluid mixing. The Abbasabad deposit is interpreted as an intermediate-sulfidation epithermal mineralization derived from a mixed source during a phase change in temperature and pressure interpreted as being related to fluid mixing and boiling. Our data suggest that mineralization at Abbasabad and other epithermal deposits in the THMB are related to late Eocene (~40 to 36 Ma) post-collisional magmatism, which is a useful concept for local and regional epithermal base metal exploration targeting.

Assessing the geochemical and environmental baseline of heavy metals in soils around hydrothermal hematite-barite-galena veins in Baghin area, Kerman, Iran.

To assess the geochemical and environmental baseline as well as the availability of the heavy elements in soils around the hematite-barite-galena veins in the Baghin area, a total of 70 soil samples were collected and analyzed by ICP-OES for 43 heavy metals and metalloids. Compared to the global soil level or crustal abundance, the calcareous soils are 2-26 magnitudes enriched in Ca, Cu, Pb, Zn, Cd, Se, As, Sb and Sr. The ferruginous soils are highly enriched in Fe, Mo, Pb, Zn, Cd, As, Sb, Ba and Sr, almost 2-49 orders higher than the crustal abundance and global soil level. Additionally, the baritic soils are 3-94 times higher than the crustal and global soil values for Ba, Cu, Mo, Pb, Zn, Ni, Co, Cd, Se, As, Sb and Sr. However, the soils developed on the shale layers are moderately enriched in As, Zn, Se, Sb, Ba, Pb and Sr. The high concentrations of heavy metals are possibly related to the presence of minor sulfide minerals in barite-rich soils or adsorption by Fe-oxy-hydroxides formed by oxidation of sulfide minerals. Therefore, the oxidation of minor sulfide minerals in barite veins may be prone to acid mine generation and of environmental concern. The inhalation of silica dusts released by silica-rich barite ores (20% SiO2) during crushing, milling, as well as using in drilling mud may trigger silicosis. Despite the high baseline values of some heavy metals and metalloids, the presence of Fe-oxy-hydroxides and clay minerals in the soils could play significant roles in sequestering the toxic effects of heavy metals contamination in soil, groundwater, plants, wildlife and humans.

Dehydroxylation of Minerals of Gadisunkapur Area with Special Reference to FTIR and Thermal Study

This paper attempts to explain the presence of OH group for micas along with some sulfate, chlorite, quartz and feldspar minerals. These minerals are found to be associated with barite vein, metasediments (quartz-chlorite schist), metarhyolite and varieties of granitic rocks of Gadisunkapur area of Hungund-Kushtagi Schist belt. The samples were collected in and around Gadisunkapur village of Bagalkote district, Karnataka and further processed to determine OH group anion in different minerals present based on FTIR and Thermal studies such as Thermogravimetric analysis (TGA) and Differential Thermal analysis (DTA). The high temperature dehydroxylation is investigated using this analysis. Furthermore, present study indicates the presence of different extra species (CO2, CO32- and OH-). The results show the incorporation of CO2 into the structures due to heating or enhanced by the dehydroxylation process.

Dehydroxylation of Minerals of Gadisunkapur Area with Special Reference to FTIR and Thermal Study

This paper attempts to explain the presence of OH group for micas along with some sulfate, chlorite, quartz and feldspar minerals. These minerals are found to be associated with barite vein, metasediments (quartz-chlorite schist), metarhyolite and varieties of granitic rocks of Gadisunkapur area of Hungund-Kushtagi Schist belt. The samples were collected in and around Gadisunkapur village of Bagalkote district, Karnataka and further processed to determine OH group anion in different minerals present based on FTIR and Thermal studies such as Thermogravimetric analysis (TGA) and Differential Thermal analysis (DTA). The high temperature dehydroxylation is investigated using this analysis. Furthermore, present study indicates the presence of different extra species (CO2, CO32- and OH-). The results show the incorporation of CO2 into the structures due to heating or enhanced by the dehydroxylation process.

Constraints on the genesis of the Proterozoic bornite dominated copper deposit from Nim ka Thana, western India: An IOCG perspective

The copper mineralization at the southeastern fringe of the Khetri copper belt in western India is primarily hosted within the metapelites and dolomite units of the Mesoproterozoic Ajabgarh Group of rocks. The copper mineralization is well exposed along a NE-SW trending basinal part around Nim ka Thana area where a few of the prospects namely Dokan, Baniwala-ki-Dhani, Dariba, and Nanagwas primarily consist of abundant bornite, chalcopyrite, covellite, digenite, and chalcocite as disseminated phases hosted within a wide-ranging litho units and along quartz-calcite-barite veins. An integrated approach has been adopted to understand the metallogenetic evolution of this bornite dominated copper mineralization. δ13CV-PDB and δ18OV-SMOW results of the carbonate veins ranging from 0.57‰ to −3.75‰ and δ18O range from 15.01‰ to 20.74‰ respectively suggest the influx of hydrothermal fluid in shaping up the deposit. δ13C (CO2) of the ore-bearing fluid ranges from −1.67‰ to 2.65‰ and δ18O (H2O) from 7.11‰ to 12.84‰ respectively also suggest the input of hydrothermal source. The S-isotopic values of Cu-mineralized barite samples range between 16‰ and 20‰, which are lower than that of seawater (δ34S‰ = 20–22‰). This provides the evidence that the barite mineralization could have formed from the hydrothermal fluid that is cogenetic with the late-stage mineralization in a phase-wise separation as an associated mineral assemblage in the system progressively enriching the bornite-rich copper deposit.Based on the field data and evidences, petrographic characteristics, mineral chemistry, fluid inclusion, and stable isotopic signatures, a three-stage mineralization event is proposed as 1) syngenetic precipitation of dispersed bornite-pyrite in a euxinic environment; 2) hydrothermal vein-type mineralization dominated by chalcopyrite-bornite phase, and 3) supergene enrichment of the vein filled mineralization with the development of wide-scale chalcocite-digenetite-covellite mineral phases. Fluid inclusion microthermometry suggests a temperature range from 225°-320 °C with moderate salinity fluid representing epithermal mineralization which is coherent with the stable isotope data (C, O and S isotopes) of the mineralized carbonate and barite veins suggesting the involvement of large scale hydrothermal fluid influx. Te content of various Cu-bearing sulfide phases shows a gradual change in the concentration from chalcopyrite (2.21% to 2.31%), bornite (2.31% to 4.50%), chalcocite (2.77% to 2.87%), digenite (2.57% to 3.70%) and covellite (2.53% to 3.13%) suggesting their evolution from hydrothermal to supergene process. The studied area has experienced wide-scale alterations and Na-metasomatism with the development of associated minerals such as scapolite, tremolite, and sericite. Occurrence of primary and secondary copper sulfides in the metasedimentary sequence, alteration assemblages affected by Na-metasomatism, association of magnetite and specularite in the study area is affiliated to the hydrothermal system akin to IOCG clan as noted from the adjoining Khetri Copper Deposit.

Trace element geochemistry of magnetite and pyrite and sulfur isotope geochemistry of pyrite and barite from the Thanewasna Cu-(Au) deposit, western Bastar Craton, central India: Implication for ore genesis

The Thanewasna copper belt in Bastar Craton of central India is well-known for Cu ± Au mineralization. In this study, we use major and trace element chemistry of magnetite, hematite, and pyrite, as well as the sulfur isotope composition of chalcopyrite, pyrite and barite from the deposit to characterize the mineralization and to constrain its petrogenesis. The mineralization is hosted in quartz-chlorite veins associated with 2.5 Ga and 1.6 Ga granitoids. The mineralization is focused along the NW-SE trending Thanewasna brittle-ductile shear zone and comprises disseminated and vein-hosted Cu-sulfides, mainly chalcopyrite and pyrite intergrown with minor magnetite, hematite, and sulfide-free barite. The associated hydrothermal alteration is characterized by pervasive potassic-sodic alteration and chloritization. Calcite and sulfide-bearing barite veins postdate the Fe-oxide and Cu-sulfide ores. At least two generations of magnetite, hematite, and pyrite were identified based on their textural and trace element characteristics.Texturally early magnetite (Mag-I) displays oxy-exsolution of ilmenite and is of magmatic origin, representing the pre-mineralization igneous assemblage of the host rocks. Texturally later magnetite (Mag-II) is of hydrothermal origin and replaces Mag-I. It has high Co and Mg concentrations and shows dissolution and re-precipitation texture as well as evidence for high-temperature annealing. Martitisation of Mag-I and II associated with chloritization and Cu-Au mineralization produced hematite.The δ34SVCDT of syn-mineralization pyrite and chalcopyrite (−0.77‰ to −4.28‰) is suggestive of magmatic sources for the sulfur. Post-mineralization barite veins have δ34SVCDT between +10.31‰ and +17.55‰ which indicate that the sulfur was derived from seawater sulfate without going through an intermediate stage of reduction. Variation in the sulfur isotopic compositions of sulfide and sulfate was the result of dilution and cooling of the metalliferous fluid after interaction with meteoric fluids, which triggered the deposition of Cu ± Au along structural weak planes.The widespread presence of iron-rich breccias, association with crustal-scale shear zone, pervasive K-Na alteration, chloritic and advanced argillic alteration, the involvement of magmatic and non-magmatic fluid and Cu-Fe-Au-Ag-Ba-REE metal association are all suggestive of IOCG-style mineralization at Thanewasna. This supported by the Ti, Al + Mn, Ti + V concentrations and Ti/V, Ni/Cr, Ni/(Cr + Mn) ratios of Mag-II and hematite. The Co/Ni ratios of pyrite further supports a hydrothermal origin of the deposit, unrelated to skarns or copper porphyry, having similarity with known IOCG deposits. The identification of IOCG-type deposits in the Thanewasna region gives a boost to deeper sub-surface exploration in this belt as well as in similar geological setting elsewhere.

Hot fluids, burial metamorphism and thermal histories in the underthrust sediments at IODP 370 site C0023, Nankai Accretionary Complex

Abstract Drilling during International Ocean Discovery Program (IODP) Expedition 370 at Site C0023 encountered instances of hydrothermal mineralization from 775 to 1121 m below seafloor. Fluid inclusion homogenization temperatures measured on barite veins within this interval indicate precipitation from fluids with temperatures up to 220 °C, and salinities ten times higher than interstitial water (16–25 c.f. 2.8–3.6 wt % NaCl). Patches of stratabound mineralization (rhodochrosite, calcite, barite and anhydride) are largely confined to the vicinity of veins and have vertical thicknesses and extents that can be explained by precipitation within the thermal aureoles of veins. Thermal maturities measured on petroleum biomarkers in underthrust sediments record a rise from pre-oil window to early oil window thermal maturities. Basin models show that increases in thermal maturity can be explained by burial metamorphism, and kinetic-based calculations suggest that hot fluids would only have had a minimal effect on hydrocarbon generation. However, the movement of hot fluids still has geochemical implications and creates a complex thermal history where both short-duration, localized heating within fracture zones at hot temperatures (~200 °C for less than 1 yr) and heating during burial over long durations (80–110 °C for 0.5–2 Myrs) need to be considered.

Evaluating of lithological and structural controls on the barite mineralization by using the remote sensing, Fry and fractal methods, Northwest Iran

The most part of barite deposits in the NW Iran have been epigenetically formed in the form of veins, fracture, and/or open-space fillings. For this reason, structural evaluation is the important factor for investigation of the barite mineralization in the host rocks. Fault and fracture are the predominant structures that can be distinguished in the studied area. Two approaches are proposed for analyzing the structures; the first one is visual investigation. This approach produces a fracture density map and a fracture rose diagram. The second one is used to quantify the fracture distribution by using the fractal dimension. The results indicated that the fracture distribution is not only the controlling factor of the barite mineralization, but also the presence of hydrothermal fluids and the lithology of the host rock that are other important factors in the productivity of the fractures as well. For this reason, despite the high fractal dimension (1.92) in the SE of the studied area, the barite indices have not been introduced up until now, whereas several barite indices in the NW of the study area with low value of fractal dimension (1.62) have been found. Fry analysis data can help us to identify the trend of mineralization in barite deposits. Fry analysis results revealed that E-W trending fractures are the most important structures for barite vein emplacement and subsidiary N-S striking fractures also host for the barite veins, but NE-SW trending fractures are almost barren. In this research, pyrite strain firings were used for temporal evolution of ore deposition. Wrapping of barite around the porphyroblasts reveals that coeval growth of fractures and mineralization with deformation of shear zone and exhumation of host rocks are done by a set of thrust faults in the study area.

Fluid inclusion constraints on the hydrothermal evolution of the Dalucao Carbonatite-related REE deposit, Sichuan Province, China

Carbonatite-related rare-earth element (REE) deposits are the most important source of the world’s REE resources. Hydrothermal fluids have been proposed to play a significant role in the transport and precipitation of REEs, but fluid inclusion data on the hydrothermal processes in carbonatitic settings are relatively sparse. The Dalucao deposit, located in the Mianning–Dechang (MD) REE belt, Sichuan, China, is a Cenozoic carbonatite-related REE deposit (c. 12 Ma) that offers an excellent opportunity to investigate the evolution of ore-forming fluids. Brecciated and weathered ores are common in this deposit. The former are characterized by mineral assemblages comprising fluorite + barite + celestite + calcite + quartz + bastnäsite (No. 1 orebody) or fluorite + celestite + pyrite + muscovite + calcite + quartz + bastnäsite (No. 3 orebody), whereas the latter contain REE minerals, clay minerals, and minor gangue minerals. We present a comprehensive study of fluid inclusions from the Dalucao deposit to constrain its hydrothermal evolution.Magmatic, pegmatitic, hydrothermal, and supergene stages have been recognized. During the pegmatitic stage, the main minerals that formed were coarse-grained fluorite, barite, celestite, calcite, and quartz, which host melt inclusions, melt–fluid inclusions, and minor high-salinity fluid inclusions. The presence of melt and melt–fluid inclusions suggests a magmatic origin for the ore-forming fluids. Hydrothermal processes included at least two stages, characterized by hydrothermal veins that are developed in fractures within the carbonatite–syenite complex: (1) Fluid inclusions during the formation of the fluorite–quartz–barite veins in the pre-REE stage were trapped under immiscible conditions, as evidenced by the presence of CO2-bearing inclusions coexisting with aqueous ones. These immiscible CO2-bearing inclusions recorded a range of pressures from 1050 to 1600 bar. All of fluid inclusions in this stage exhibited homogenization temperatures varying from 278 to 442 °C, with salinities ranging from 3.2 to 45.1 wt% NaCl equivalent (equiv.). (2) The REE-stage fluids were represented by abundant aqueous inclusions, characterized by homogenization temperatures ranging from 147 to 323 °C and salinities between 1.1 and 9.5 wt% NaCl equiv. These data suggest that the ore-forming fluids forming the Dalucao deposit evolved from high-temperature, high-pressure, high-salinity, CO2-rich to low-temperature, low-pressure, low-salinity, CO2-poor. Gas- and ion-chromatographic analyses combined with mineralogical features indicate that the initial fluids were rich in REEs, (SO4)2−, Cl−, F−, Na+, K+, Ca2+, and volatile components (e.g., H2O, CO2, N2, CH4, Ar, and C2H6). H–O isotope analyses of quartz suggest that the hydrothermal fluids had a dominantly magmatic signature and were gradually diluted by meteoric waters. Hydrothermal REE transport was probably controlled by F−, (SO4)2−, and Cl− as complexing ligands. We propose that fluid cooling and mixing rather than immiscibility led to the precipitation of bastnäsite during the waning stage of hydrothermal activity. Taken together, the inclusiondata and observations of alteration, paragenesis and mineralization have provided insights into the development of REE mineralization and the further exploration of carbonatite-related REE resources.

Jurassic ore-forming systems during the Tethyan orogeny: constraints from the Shamlugh deposit, Alaverdi district, Armenia, Lesser Caucasus

The Shamlugh polymetallic deposit located in the Alaverdi mining district, Armenia, is hosted by Middle Jurassic magmatic rocks of the Somkheto–Karabakh island arc, Lesser Caucasus. Lithogeochemistry and radiogenic isotope geochemistry indicate a subduction setting with an evolution from tholeitiic to transitional Middle Jurassic magmatism to calc-alkaline to high-K calc-alkaline Late Jurassic magmatism. A progressively more juvenile mantellic input in the magmatic source is noted. Ore consists of stratabound massive sulfide ore bodies, ore-bearing breccia, stockwork-style mineralization, and disseminated ore hosted by a pyroclastic host rock unit below a subvolcanic rhyolitic sill. Towards depth, the stratabound ore is connected to subvertical high-grade sulfide veins hosted by basaltic andesitic, andesitic, and dacitic tuff and lava breccia. Ore minerals include principally pyrite and chalcopyrite with minor sphalerite and hematite. Hydrothermal alteration consists of quartz, chlorite, carbonate, and sericite in the footwall pyroclastic rock, tuff, and lava breccia, which are also crosscut by late-stage carbonate and barite veins. The rhyolitic sill has been altered by silica and sericite and contains rare sulfides. Sulfur isotope values for sulfides range from + 0.7 to + 4.6‰ and suggest an essentially magmatic source for sulfur. Strontium isotopic compositions of hydrothermal carbonates and sulfates (0.70507–0.70660), sulfur isotopes of sulfates (+ 16.8 to + 17.3), and carbon and oxygen isotopic compositions of late-stage carbonates (δ18O VSMOW + 15.9 to + 17.6‰; δ13C VPDB − 1.8 to − 0.8‰) not only are permissive with seawater incursion in the ore-forming hydrothermal system but can also be attributed to fluid–rock interaction with hidden metamorphic basement rocks and Jurassic magmatic rocks. The lead isotopic composition of sulfides (206Pb/204Pb 18.505 to 18.586, 207Pb/204Pb 15.611 to 15.636, 208Pb/204Pb 38.516 to 38.640) implies leaching of the Middle Jurassic host rocks as the main source of Pb. LA-ICP-MS U–Pb zircon dating of the hanging wall rhyolitic sill affected by hydrothermal alteration yielded an age of 155.0 ± 1.0 Ma and provides a maximum age for mineralization. Ore formation at Shamlugh is younger than the immediate Middle Jurassic host rocks and is related to the Late Jurassic calc-alkaline and high-K calc-alkaline magmatic evolution. Late Jurassic magmatism includes a tonalite dated by LA-ICP-MS U–Pb zircon geochronology at 152.9 ± 0.7 Ma that hosts the 146-Ma-old Teghout porphyry deposit. In the absence of other age constraints, the genetic relationship of the polymetallic Shamlugh deposit with the Teghout porphyry deposit remains open to question. Nevertheless, hydrothermal minerals and alteration paragenesis and the lithologically and structurally controlled ore body geometry at Shamlugh are consistent with a low to intermediate sulfidation epithermal model.