The Ronda ultramafic massif constitutes the Earth’s largest outcrop of peridotites (~ 300 km²) of the subcontinental lithospheric mantle (SCLM). This massif is located in the westernmost part of the Málaga province in SW Spain, and mainly consists of peridotites (lherzolites and harzburgites with lesser amounts of dunites) and mafic pyroxenite layers (usually <10 %). These rocks are arranged in a petrologic and geochemical zoning consisting, from the top to the bottom of the mantle section, of the following domains: (1) spinel (±garnet) tectonite corresponding to the exhumed SCLM roots, (2) granular peridotite formed by thermal erosion of pre-existing spinel (±garnet) tectonite due to upwelling of the asthenosphere during unroofing, and (3) plagioclase tectonite corresponding to shear zones originated shortly before or contemporaneously to the crustal emplacement. The rocks forming these three domains exhibit contrasting degrees of fertility in a wide suite of elements, offering an unequal opportunity to evaluate the impact that different bedrocks have for the distribution of High-Tech Critical Metals in soils.

We performed bulk-rock analyses of around 70 samples from 10 soil profiles above peridotites from the three aforementioned petrological domains. Regardless of the original bedrock, all the analyzed soils show a common trend of progressive enrichment of Fe₂O₃ and Al₂O₃ and depletion of MgO from bedrock to the atop of the profile. Minor elements such as MnO, TiO₂, Na₂O and K₂O overall increase from bottom to top, whereas SiO₂ remains generally unchanged. Interestingly, there is positive correlations between Fe₂O₃ and MnO as well as other transition metals such as Cr (up to ~9000 pm),  Co (up to 310 ppm), V (up to 181 ppm), Zn (up to 136 ppm) and Sc (up to 38 ppm). A general increasing of total REE (up to ~20 ppm) is also observed in most profiles with a significant enrichment of LREE over HREE.

How to cite: González-Jiménez, J. M., Marchesi, C., Yesares, L., Gervilla, F., Villanova, C., and Proenza, J.: Distribution of High-Tech Critical Metals in soils from the Ronda Ultramafic Massif (SW Spain), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1060, https://doi.org/10.5194/egusphere-egu23-1060, 2023.

Epithermal deposits are formed in shallow (< 1 km) crustal environments by precipitation of ore minerals from hydrothermal fluids, associated with magmatic activities. Epithermal deposits are important sources of gold and associated critical metals (e.g., Ag, Bi, Te) used in high-tech industry (e.g., [1]). However, little is known about the controls on their deposit sizes, which range more than two orders of magnitude (<1 to >100 t of contained Au). Since deposit size is a major determining parameter for mine profitability, estimating the governing processes for metal endowment should have important implications for exploration. Here we show that the giant (> 200 t Au) Hishikari epithermal gold deposit in south Kyushu, Japan, is likely to have formed by combination of the following three trans-crustal geological processes: (i) oxidized source mantle of primary magmas, (ii) differentiation of ore-forming magmas without voluminous sulfide saturation and (iii) structural focusing of exsolved ore-forming fluids. These geological processes were recognized by (i) high V/Yb ratio (> 160) of high MgO regional volcanic rocks which reflect the oxidizing [2], high sulfur and gold solubility condition during mantle melting, (ii) minor contribution from reducing crustal rocks [3] and late magnetite saturation which maintained a relatively high fO₂ as well as high sulfur solubility until later stage of differentiation, and (iii) basement uplift or depression detected by geophysical surveys [4] which created effective conduits for hydrothermal fluids. In contrast, representative districts in Japan with previous extensive exploration campaigns (Toyoha, Nansatsu, Iriki, Masaki) failed to meet more than one of the above criteria, which likely explain the smaller or lack of gold mineralization in these districts. Our findings demonstrate the importance of optimally aligned trans-crustal geological processes in the formation of giant gold deposits and the potential utility of the geochemistry of regional volcanic rocks in early stages of epithermal gold exploration.

[1] Goldfarb, R. J., et al. (2016). Reviews in Economic Geology 18: 217-244.
[2] Laubier, M., et al. (2014). Earth and Planetary Science Letters 392: 265-278.
[3] Hosono, T., et al. (2003). Chemical Geology 201: 19-36.
[4] Izawa, E., et al. (1990). Journal of Geochemical Exploration 36: 1-56.

How to cite: Ishida, M., Nakamura, K., Iwamori, H., Hosono, T., and Kato, Y.: Importance of trans-crustal geological processes in understanding the genesis of giant epithermal gold deposits: The case of Hishikari deposit, Japan, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3728, https://doi.org/10.5194/egusphere-egu23-3728, 2023.

Archean and Paleoproterozoic rocks of the Reguibat shied contain main potential Mauritania's mineral deposits. The western Archean terrane includes significant iron deposits in the Tiris and Tasiast gold deposits, while the eastern Birimian rocks have proved mining indices of gold and uranium. Located on the northeastern edge of the Reguibat shield,  the study area of NSOUR, and OUED EL MA prospects represent a complex shear zone of favorable gold mineralization. Through our drill cores and soil samples analysis, the gold mineralization is proved to be hosted within a series of nearly parallel, steeply dipping quartz veins. Our chemical and geophysical results demonstrate a set of indicators of important tonnage and grade of gold in the quartz veins. Results of chemical analyses obtained on all the analyzed samples show gold concentration between 0.33 to 2.12 g/m. Importantly, in the southern part of the prospect, 62% of the wells samples recorded an interception of at least one gram per tonne over more than one meter. Statistical evaluation of these data established large first-level zones delineating areas favorable to gold resources and important potential gold accumulation in these areas. Such first-level identifications nonetheless make it possible to roughly define the potential zones for orogenic gold deposits and encourage the continuation and the intensification of the works of exploration that favor discovery in these Precambrian rocks.

How to cite: Gueimar, N., Abdellahi, M. I., and Benali, H.: Geostatistical study of the gold mineralization of the Nsour region. Reguibat shield, Northern Mauritania, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-219, https://doi.org/10.5194/egusphere-egu23-219, 2023.

The geologic setting of the Kurama mining district is controlled by its assignment to the structures of the eastern part of the extended Beltau–Kurama volcanoplutonic belt in the Middle Tien Shan. This district of Paleozoic age exemplify unique deposits with perfectly preserved characteristic features of Cu-Au-Mo porphyry, epithermal Au–Ag–Te, Ag–Pb–Zn, as well as numerous occurrences of Au, Ag, Cu, Pb, Zn, Bi, and Sn mineralization. Intense magmatic processes occurred in this region throughout the whole Paleozoic, reaching a maximum at its end. The very high concentration of ore occurrences is related to the confinement of the region to the intersection of deep tectonic structures. Another unique feature of this region is that it is a rare example of paleovolcanic areas with well preserved epithermal deposits of Late Paleozoic age. Here we compile published and some new geodynamic, mineralogical and geochemical data, including regional geological features and ore characteristics, sequence of the mineral formation, main mineral assemblages and discuss factors controlling the enrichment mechanism of huge amounts of Cu, Au, Mo, Ag, Re, Pd, Pb, Zn and other elements in the Almalyk ore-field through field and laboratory investigation. We will present summary of the geological, geochronologic and geochemical characteristics of porphyry, scarn and epithermal gold-silver deposits to establish a series of discriminant indicators, which can provide reference for future research on the genetic connection of different deposits in the porphyry copper system. The occurrence of mafic dikes, post-dating the porphyry mineralization and high Re concentrations in the molybdenite may be attributed to a direct involvement of mantle in an arc-subduction environment. But it is becoming more obvious that the problem of sources of ore and rare elements forming cannot be solved only by their introduction with magma. In many specific examples of the formation of the largest and unique concentrations, their confinement to the underlying and enclosing sedimentary rocks, sharply enriched in valuable impurities, is observed. These rocks include organogenic dolomites or dolomitic limestones. During intrusion of igneous bodies, the presence of reactive carbonate rocks (limestone, dolomite, marl) led to the formation of gold-bearing Au-Cu- and Pb-Zn-skarn deposits. The integrated results of this study are used to discuss the metallogenic processes that formed the unique Cu-Au-Mo porphyry, epithermal Au–Ag–Te, Ag–Pb–Zn deposits in the largest porphyry copper-polimetallic ore Almalyk district in the Central Asian Orogenic Belt.

How to cite: Nurtaev, B. and Kurbanova, D.: Metallogenic processes that formed the Cu-Au-Mo porphyry and epithermal Au-Ag-Te deposits in the Almalyk ore district, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1835, https://doi.org/10.5194/egusphere-egu23-1835, 2023.

In recent years mineral sources of Critical Raw Materials (CRMs), whose supply is strategic and irreplaceable in many technological and industrial applications, have become the subject of growing interest throughout Europe. An excellent example is the Silius vein system (SE Sardinia), in which the mining activities, after several years of standby, are going to be resumed to exploit fluorite, galena and LREE minerals. This world-class deposit (2.2 Mt of proven reserves) consists of two main parallel, steeply dipping, ENE-WSW to NE-SW directed veins which coalesce at depth, hosted in Middle Ordovician metavolcanites, Upper Ordovician metasediments and Silurian black shales belonging to the Variscan  Nappe Zone of SE Sardinia. The vein filling displays dominantly banded textures with abundant fluorite, quartz, calcite, galena, barite, and accessory base-metal sulfides (sphalerite, chalcopyrite and pyrite-marcasite), LREE carbonate (synchisite-Ce) and xenotime-Y. Sulfide contents in the ore increase downward. Knowledge about the trace elements content of sulfides in the deposits is still scarce, thus new underground surveys and samplings have been performed in three different levels of the mine. In samples collected from the deepest level (level 100 m a.s.l., Muscadroxiu sector), tiny inclusions of Ni-Co minerals have been found for the first time ever by optical microscopy (reflected light) and SEM-EDS analyses. They consist of very complex intergrowths dispersed in chalcopyrite and the quartz gangue, containing various associations of Ni-Co-Fe arsenides and sulfarsenides such as nickeline, rammelsbergite, gersdorffite, cobaltite and arsenopyrite. Remarkably, this assemblage is very similar to that found in the shallower parts of the nearby “Sarrabus Silver Lode”, a similar, regional-scale vein system exploited in the past for silver. Thus, it may be speculated that it not only could be a general indication of possible Ni-Co enrichments below the 100 level of the mine, but also an exploration tool and a proxy of possible Ag enrichments of the ore at depth. Moreover, the Ni-Co assemblages and LREE minerals found in Silius are similar to those found in the polymetallic (Ni-Co-As-Ag-Bi) veins of Southern Arburèse district (SW Sardinia), the five-element branch of the Montevecchio vein system, in the past a major Pb-Zn source in Italy. In addition to partly similar mineral assemblages, the Silius and Arburèse vein systems share a common derivation from low-temperature and high-saline fluids, supporting their attribution to the unconformity-related group of five-element and fluorite-barite deposits well-known throughout central and western Europe (Erzgebirge, Odenwald, Schwarzwald, French Central Massif, Catalonian Coastal Ranges, Pennidic Alps, etc.). These deposits have been collectively connected to metallogenic events associated with the Late Paleozoic-Mesozoic breakup of the supercontinent Pangea, so Silius, the Arburèse and other similar Sardinian deposits could be related to this regional-scale event. In conclusion, the Silius vein system is a key area to understand the regional events that occurred after the Variscan orogeny in Sardinia; the deposit may represent a relevant source of CRMs and metals in Italy, where besides fluorite, base-metal sulfides and LREE, some concentrations of Ni-Co and, possibly, Ag minerals might be present at depth.

How to cite: Scano, I., Attardi, A., Idini, A., Murroni, A., Zara, F., and Naitza, S.: From a fluorite vein system to a five-element-type polymetallic vein system? The first evidence of Ni-Co minerals from the world-class, CRMs-bearing Silius deposit (SE Sardinia, Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7021, https://doi.org/10.5194/egusphere-egu23-7021, 2023.

The Oumjrane copper deposit in eastern Anti-Atlas is one of the top three major copper producers in North Africa with an annual production exceeding 260,000 tons at an average grade of 1.4% Cu. Current inferred resources are estimated at 5 million metric tons grading 1.5% Cu. Host rocks consist of a succession of Ordovician carbonate-free siliciclastic metasediments comprising sandstone- and quartzite-dominated rocks with cherty beds and phosphate nodules, conformably overlain by Silurian organic-rich black-shales. In the mine area, high-grade ores were recovered from open pits and underground workings of three major roughly continuous, subparallel, and steeply dipping vein systems referred to as Bou N’Hass, Bou Kerzia, and Zagora Graben over a strike length exceeding 10 km. The veins extend vertically for as much as 300 m, and their widths vary from ~2 m to ~15 m averaging 4m. The paragenetic sequence comprises two main stages of alteration and related mineralization. The earliest stage, referred to as the main Cu-rich stage I, is economically the most productive consisting of ore-related quartz together with chalcopyrite and reddish to orange apatite (i.e., Ap-1). The later Pb-Zn-Ba-rich stage II consists of variable proportions of galena and sphalerite enclosed in a matrix of barite as the main gangue minerals. Texturally, this stage ends with the development of well-developed green apatite crystals (i.e., Ap-2) up to 12 cm across. In addition to its potential for U–Pb dating, the REE+Y chemistry of the paragenetically well-constrained ore-related apatite (i.e., Ap-1, Ap-2) could provide insights into fluid chemistry, fluid-rock conditions, and fluid-rock interaction processes that prevailed during ore deposition of both ore stages. In this respect, EMPA analyses show that Ap-1 is almost pure hydroxyapatite, (X_F=0.198-0.334, X_Cl=0.001-0.078, X_OH=0.642-0.795), whereas Ap-2 is fluorapatite (X_F=0.190-0.227, X_Cl=0.066-0.101, X_OH=0.672-0.743). More importantly, LA-ICP-MS analyses indicate that Ap-1 is characterized by ∑REE+Y contents ranging from 962 to 2435 ppm and shows bell-shaped PAAS-normalized patterns with prominent negative Y anomaly Conversely, Ap-2 yields on average the highest ΣREE+Y concentrations at 8473 ppm, and shows negative sloped pattern with no Eu anomaly. The Y/Ho values are variable, but are generally distributed between 15 and 18 for Ap-1, and 23 and 26 for Ap-2. Overall, these geochemical characteristics indicate that there are two temporally distinct mineralizing events. The earlier Zn-rich stage is thought to have occurred in response to hydrothermal circulation of basinal brines and extensive fluid-rock interaction with the phosphate-rich lithologies. Conversely, the late Pb-Zn-Ba stage is linked to mixing between basinal brines and mantle-derived fluids, likely derived from the synchronous Middle Jurassic–Lower Cretaceous alkaline magmatic series. Ongoing U-Pb geochronology of both apatite types is performed to constrain the timing of mineralization and to trace back the ore-forming source(s) and processe(s).

How to cite: Idbaroud, M., Bouabdellah, M., Levresse, G., Mouguina, E. M., Yans, J., and Maacha, L.: Two mineralizing events unraveled by trace element geochemistry of ore-related apatite from the polymetallic Cu-(Pb-Zn-Ba) Oumjrane deposit (Eastern Anti-Atlas, Morocco), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8951, https://doi.org/10.5194/egusphere-egu23-8951, 2023.

The recent need of a green-energy transition has sparked even more interest on critical elements such as tungsten and tin, whose genesis in ore deposits is linked to fluids exsolving from granitic plutons, but some mechanisms of formation remain unclear. Most authors in the past have proposed the mixing with meteoric, metamorphic or basinal fluids to be critical, while others believe that these deposits can form by simple cooling of magmatic fluids.

Given the modern advances in analytical techniques, it is nowadays possible to characterize fluid inclusions in-situ also for trace elements such as bromine and especially iodine with the LA-ICP-MS. This study aims to apply a novel technique of measuring Br/Cl and I/Cl in individual fluid inclusions and bring some new insights on the Sn-W ore deposits genesis from a different perspective. In fact, halogens are well known to be highly incompatible in most minerals, retaining the fluid source reservoir signature, and to behave conservatively in fluid-rock interaction, therefore they can be regarded as suitable tracers for fluid evolution. These characteristics make heavy halogen studies particularly suitable for tackling the open question on the formation of Sn-W mineralized systems.

The study area is the well-studied Cornubian batholith, in south-west England, which has been extensively mined in the past mostly for tin, copper and tungsten. It consists of 5 types of granites, divided into two main fractionation series, and cross-cut by mineralized veins rich in cassiterite, Cu-sulphides and W-oxides (among others), outcropping mainly in proximity of the contacts with the country rock.

Despite significant mineralogical variation across the samples, representing different stages of the transition from magmatic to hydrothermal environments, halogen ratios are relatively homogeneous, especially under the hydrothermal regime, with magmatic fractionation as the only candidate process for a shift to higher Br/Cl and I/Cl values. On the other hand, alkalis and metals in fluid inclusions display variations of several orders of magnitude, with Li and B peaking in pegmatites and base metals being particularly abundant in the magmatic stage.

These results suggest that even moderate changes in P-T conditions (from granitic stage to low-T mineralisation) do not affect significantly the halogen signature of the evolving fluids in the Cornubian batholith. Additionally, given the linear relation between fluid salinity and alkali/metal content, it can be postulated that meteoric water is the main diluting agent throughout the evolution of the system, as mixing with metamorphic fluids or basinal brines would also significantly change the halogen signatures. 

How to cite: Bongiovanni, M., Fusswinkel, T., and Marks, M.: The signature of heavy halogens across the evolution of a Sn-W-Cu mineralized system: a fluid inclusion study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12079, https://doi.org/10.5194/egusphere-egu23-12079, 2023.

Vanadium (V), is primarily used in the production of metal alloys (in addition to high strength low alloy properties) and reinforcing titanium alloys, take notice in the current critical element list by organizations such as the European Union and USGS. There is no detailed study on the exploration of vanadium resources in Turkey. Recently, vanadium can be extracted from several different types of mineral deposits and from fossil fuels. Black shales can be considered as one of the vanadium resources recently. Black shales are fine-grained sedimentary rocks containing not only in organic matter but also in specific trace elements, like V, Mo, Cu, Zn, Ni, Cd, Se, Pb and U.

The study area is located in the Karabük – Kastamonu in Black Sea region of Turkey and primarily consist of Silurian aged black shales. These black shales can be described as a Hercynian continental sliver, which represents the northernmost part of the Western Pontides . This study focuses on revealing the content and major controlling factor of V of Late Silurian-Early Devonian aged black shales in the northwestern Black Sea Region of Turkey. In the end, the depositional model was established. Studied black shales have a wide range of vanadium content, varying from 74 to 400 μg/g. It can be stated that authigenic enrichments in modern suboxic settings, and likely represent the removal of dissolved V as V(IV). V(IV) was adsorped by organic matter. This result is also supported by several redox indicators such as V systematics (V/Sc, V/Ni) as well as ratios of Ni/Co, Th/U, and Mo/Mn. The reducing of V(III), is mainly associated with the excessive H₂S accumulation in sediments and bottom waters and strong reducing conditions is also a key factor. In this circumstance, the decoupling mechanism of V changes from surface adsorption to ionic substitution forming solid solution series with Al in clays. In addition, the Al−Fe−Mn discriminant diagram of siliceous rocks, show that the genesis of siliceous rocks are close to the biogenic origin. The moderate positive correlation of V vs. TOC (R²=0.52) crossplot and the lack of correlation of V vs. clay-forming elements (Al₂O₃, K₂O, Na₂O, and CaO) mean that the organic matter rather than clay minerals can play a role in V enrichments. Also, it means that water conditions were controlled by elevated organic matter flux and consequent oxygen drawdown. Nevertheless, the discreteness of data in cross-plot diagrams may imply that a portion of the V in the samples occurs in other forms in addition to occurring in relation to organic matter. More detailed investigations are necessary.

Keywords: Vanadium potential; Black shales; Depositional model; Northwestern Black Sea; Turkey

How to cite: Sutcu, N. M., Doner, Z., Unluer, A. T., and Kumral, M.: Vanadium Potentiality of Late Silurian-Early Devonian Black Shales in Northwestern Black Sea Region, Turkey, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-402, https://doi.org/10.5194/egusphere-egu23-402, 2023.

A slurry pipeline is a specially designed pipeline used to transport the tailings, wastes from the mining, ores like iron or coal to long distances. A commercially tested solution for the transport of iron ore slurry over the farthest distances in a pipeline includes various parametric checks. For the slurry to move without any hassle in the pipe maintaining the required velocity, it is important to keep some parameters in the desired limits, the most important of which is the rheological characteristics of the slurry. The rheological characteristics gives us an idea about the viscous properties, stress strain behavior of the iron ore exhibiting in its surrounding. The rheological parameters of the iron ore slurry were measured using a high precision Anton paar RheoloabQC Rheometer. At different concentrations the samples were tested keeping the particle size to be same for all the observations. While the method has been kept the same for the experiments, different rotating tools are used in the rheometer to check the accuracy of the data as well as to draw a comparison on the data obtained from them for each level of concentration. Our study majorly deals with a comparative assessment of the performance of the various rotating tools to study the rheology of the iron ore slurry.

How to cite: Mishra, S. and Kaushal, D. R.: Analyzing the rheological behavior of medium fine iron ore slurry., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3821, https://doi.org/10.5194/egusphere-egu23-3821, 2023.

The carbonatite complexes are famous for being hosts for various critical elements including Rare Metals (REE) Thorium (Th), and Uranium (U). Turkey hosts a number of carbonatite-related Light Rare Earth Element (LREE) deposits such as the Ozvatan nepheline syenite - carbonatite complex in Central Turkey.  The Upper Cretaceous Ozvatan complex is composed of nepheline syenites, multi-stage calcio-carbonatite dikes, and a metasomatic aureole around carbonatite dikes. The carbonatites of the complex are mainly sövites (coarse-grained calcites) with fluorites and relict silicate minerals such as nephelines. The Sövite dikes of the Özvatan complex are mainly enriched in terms of LREE (up to 2134 ppm). La, Ce, and Nd constitute most of the LREE values in Sövites. The repetitive emplacement of carbonatite emplacement also caused a wide alteration zone with euhedral nephelines, secondary K-feldspars, and garnets. The alteration zones around carbonatite dikes were identified as potassic fenites due to the enrichment of K and incompatible elements including REE, Ba, and Sr. The REE values of K- fenites in the study area are similar to sövite dikes and determined up to 1445 ppm. However, the brecciated K-fenites contain significantly higher values (up to 3596 ppm) than carbonatites and non-brecciated K-fenites. Other incompatible elements such as Th, U, and Nb are also enriched in brecciated K-fenite zones. Carbonatite veinlets in K-fenites are also observed, therefore it can be concluded that the brecciation and metasomatism processes are closely related to multistage carbonatite emplacements.

Keywords: Carbonatite, REE- Enrichments, Alkali-Potassic Rocks

How to cite: Unluer, A. T. and Budakoglu, M.: Geochemical Features of Ozvatan (Central Anatolia, Turkey) Carbonatites and Potassic Fenite Zones ., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3920, https://doi.org/10.5194/egusphere-egu23-3920, 2023.