ERE5.6

Shear zones hosted antimony (Sb) quartz vein-type deposits are the most important sources of Sb worldwide. They have been recognized and mined since the Antiquity in the European Variscan belt, and particularly in the French Variscan Massifs, as the Armorican Massif. Among this type of deposit two subtypes are identified, i) the Sb and gold (Au) quartz vein-type (Sb-Au) as the La Lucette deposit located in the North Armorican Domain, and ii) the Sb-As quartz vein-type as those from the la Bellière district in the Ligerian domain.

The recent advances in the understanding of the Sb mineralizations in the European Variscan Belt are typically focused on the Sb ore-genesis and its regional implications, ignoring its potential valuable co-products as gold. In this study, detailed textural-mineralogical investigations coupled with geochemical analyses in rock-samples with in-situ EPMA and LA-ICPMS ore-minerals trace element analyses, were carried out for the first time in the Late-Variscan mineralizations from the La Bellière Sb-As occurrences, and the La Lucette Sb-Au deposit, to ascertain the distribution and amount of Au in the ore-minerals and provide new data on ore deposition conditions.

In the La Bellière Sb-As occurrences, no visible gold has been observed, but low-grade gold, ranging between 0.2 to 1 g/t Au, are correlated with high-grade As in rock sample. In the La Lucette Sb-Au deposit, historical assays have shown high-grade gold with an average at 40 g/t Au. EPMA and LA-ICP-MS analyses have demonstrated that gold is already present during the early time of the mineralization as invisible gold, trapped in the lattice of the Sb-rich arsenopyrites, with an average grade of 70 ppm Au in La Bellière, and at higher average grade of 223 ppm Au for La Lucette. For both type of mineralization, the early invisible gold is concentrated preferentially in the borders of the arsenopyrite crystals, and is correlated with an increase of the As content, and a decrease of the Sb and Fe. We argue that gold could be added in the arsenopyrite by substitution with the Fe and Sb at high temperature > 300 °C.

Visible gold corresponds to the economic gold ore of the Sb-Au mineralizations. In the La Lucette ore, it is emplaced in the late stages, as discrete electrum grains spatially associated with the arsenopyrites, as native gold inclusions within the stibnite, and associated with rare aurostibite. Remobilization processes of the gold-bearing arsenopyrite at lower temperature, coupled with a minor initial enrichment of the Sb-bearing ore-fluid might be responsible of the late high-grade gold ore, and the visible expression of this element. In the absence of such remobilization process with late ore-fluid-enrichment, only low-grade gold is present, under the form of invisible gold in auriferous-arsenopyrites.

The presence of a valuable gold co-product, also present in the Sb-As mineralizations, unknown until now in the French Variscan Massifs, will improve its economic attractivity. Gold potential in the huge French Sb-districts as the Vendée or the Brioude-Massiac districts must be reassessed.

How to cite: Cheval-Garabédian, F., Marcoux, E., Gouin, J., Picault, M., and Faure, M.: The genesis of gold in Sb-As and Sb-Au ore veins, new constraints from the study of the La Bellière and La Lucette districts (Armorican Massif, France), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4054, https://doi.org/10.5194/egusphere-egu21-4054, 2021.

A possible genetic link between Sb-W-Hg mineralisation (vein-type and stratabound) and mafic magmatism has been proposed for the Variscan belt during the early Carboniferous, but this hypothesis remains to be rigorously assessed. The metal enrichment of the fluids producing Variscan Sb-W-Hg deposits may be ascribed to (i) crystallization of metal-rich primary mafic magma, and/or (ii) exsolution of metal-rich magmatic fluids and their local concentration, and/or (iii) an efficient hydrothermal leaching of surroundings sedimentary rocks by fluid release due to contact metamorphism. The aim of this project is thus to estimate the contribution of mafic magmas as the metal source of Sb-W-Hg deposits. Our case study focuses on the Saint-Jean-du-Doigt gabbro from the Variscan Armorican belt, Brittany, France. We have characterized the Sb-, W-, and Hg-carrier minerals (e.g. Fe-Ti oxides) and volatile-bearing minerals (e.g. apatite) to quantify the metal content and volatile inventory during purely magmatic and magmatic-hydrothermal processes. Abundant primary amphibole and biotite, and the presence of pegmatoids indicate that the melt was likely to be enriched in volatile. An alteration gradient is observed from the base of the intrusion towards its roof. Moreover, high temperature replacement mineral reactions (e.g. saussuritization) mainly occur in the upper part of the intrusion, suggesting that magmatic fluids were accumulated toward the top of the intrusion. Cathodoluminescence and apatite compositions are taken to record the magmatic-hydrothermal transition and hydrothermal alteration. Apatite ranges in composition between fluorapatite and fluor-hydroxyapatite, but the latter is largely more frequent. A high volatile content of the silicate melt is suggested by the high proportion of negative-shaped fluid inclusions into ilmenite (up to 15 % crystal volume), which hint at a primary magmatic origin. SEM, EPMA and LA-ICP-MS investigations show that magmatic fluid inclusions contain significant amounts of Sb and W. Our results highlight that metals (i.e. Sb, W) were partly partitioned into the fluid phase during magma crystallization and degassing. In addition, trace element content of ilmenite also records metal enrichment from the base to the intrusion roof, probably due to magma degassing and deuteric/metasomatic processes. We therefore propose that mafic magmatism is a potential metal source of the early Carboniferous Sb-W-Hg mineralization event and should be considered as possible sources for other Sb-W-Hg province worldwide. This work was funded by the ANR (ANR-19-MIN2-0002) and author’s institutions in the framework of the ERA-MIN2 AUREOLE project (https://aureole.brgm.fr).

How to cite: Pochon, A., Iacono-Marziano, G., Erdmann, S., Gloaguen, E., and Tuduri, J.: Mafic magma as metal source for Sb-W-Hg mineralisation? A case study of the early Carboniferous mafic magmatic event from the French Armorican Variscan belt, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12122, https://doi.org/10.5194/egusphere-egu21-12122, 2021.

Magmatic heat sources allow hydrothermal fluids to transport and deposit various types of metals and metalloids. For instance, antimony (Sb) is frequently spatially associated with mafic intrusions, and may be associated with various amounts of other elements, such as Hg, As, W, Au and Ag. However, source-sink relationships in those settings remain poorly constrained. Whether mafic magmas contribute fluids, metals and metalloids to hydrothermal systems at the origin of Sb mineralisation remains uncertain. Spatial and chronological correlations between Sb ore deposits and mafic magmatism have been acknowledged in Variscan settings (i.e. the Armorican Massif and the Central Iberian Zone), but no causal processes have been established yet (Pochon et al., 2019).

We herein investigated the Sb, As and W contents of magmatic rocks available in the literature, to assess mafic magmas as a potential source for metals and metalloids. The GEOROC database covers most of the rock types occurring in a TAS diagram (n = 7215, whole rock), whereas the Jenner and O’Neill (2012) database focuses on MORBs (n = 601, glass).

Sb, As and W are highly covariant, suggesting a common behaviour during magmatic processes. Sb, As and W concentrations in oceanic magmatic rocks increase with increasing K₂O content. This increase is up to two orders of magnitude in mafic compositions, and one order of magnitude through intermediate and differentiated compositions. Differentiated alkaline magmas therefore generally yield higher Sb, As and W concentrations. Variations in Sb, As and W with major and trace elements composition suggest a major role of mantle source processes, and a minor contribution from fractional crystallisation. In particular, Sb, As and W contents in mafic compositions show a good correlation with the La/Sm ratio, and an absence of correlation with the ⁸⁷Sr/⁸⁶Sr and the ¹⁴³Nd/¹⁴⁴Nd isotopic ratios, suggesting a crucial control of partial melting processes.

Continental magmatic rocks show a strong Sb, As and W variability, with values up to 3 orders of magnitude higher than oceanic rocks, suggesting the occurrence of crustal contamination. Post-magmatic alteration does not seem to have any effect on Sb, As and W concentrations.

We finally investigate mafic rocks spatially and temporally associated with Sb-Hg ± As-W-Au-Ag ore deposits, and discuss the possible processes at the origin of their enrichment.

GEOROC, 2020. Geochemical rock database. , accessed: 02/10/2020.

Jenner F. E., O’Neill H. St. C., 2012. Analysis of 60 elements in 616 ocean floor basaltic glasses: TECHNICAL BRIEF. Geochemistry, Geophysics, Geosystems 13 (2), 11 p.

Pochon A., Branquet Y., Gloaguen E., Ruffet G., Poujol M., Boulvais P., Gumiaux C., Cagnard F., Baele J.-M., Kéré I., Gapais D., 2019. A Sb ± Au mineralizing peak at 360 Ma in the Variscan belt. BSGF – Earth Sciences Bulletin 190 (4), 12 p.

How to cite: Mollé, V., Iacono-Marziano, G., Gloaguen, E., Tuduri, J., Pochon, A., and Campos, H.: Sb, As and W contents of magmas: insights from geochemical databases, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12365, https://doi.org/10.5194/egusphere-egu21-12365, 2021.

This work presents the preliminary results of geochemistry of mafic intrusions (diabase dykes) and their relationship with antimony mineralization in the Central-Iberian Zone (Variscan Belt). Two different areas were studied, the Almadén (Al) and the San Antonio (SA) areas.

Both macroscopic and microscopic observations show that mafic dykes are mainly composed by clinopyroxene, plagioclase, Fe-Ti oxides and to a lesser extent of calcite and sulphides (pyrite, chalcopyrite and pyrrhotite). These samples are altered presenting chlorite and epidote as alteration minerals. Pyroxene is sometimes altered to amphibole.

Whole rock geochemistry analyses from 20 samples show a difference between SA and Al dolerites. The first fall into the classical basalt field whereas the second fall into the alkali basalt field according to the Zr/TiO2 vs Nb/Y diagram. The tectonic setting for the SA samples coincides with the volcanic arc setting whereas the samples from Al fall into the within plate magmatism. 

Primitive mantle normalized diagrams display high negative anomalies in Rb, K, with small negative anomalies in Nb and Ta for both SA and Al. High positive anomalies for both areas in Cs, Pb (especially for SA) and Li accompanied by small positive anomalies in P and Ti can be observed. Dolerites from Al are more enriched in Ba, Th, U, Nb, Ba, La, Ce, Sr, P, Nd, Sn, Zr, Hf than SA. All samples are depleted in HREE and enriched in LREE. Anomalies in Rb, Nb, Ta and Li may be related with crustal contamination. Pb anomalies could be associated with assimilation of country rocks, especially marine sediments, this anomaly is also related to subduction processes. Positive P and Ti anomalies of some samples is due to the apatite and ilmenite enrichment respectively. Negative anomalies in K could be associated with presence of phlogopite in the source. Rare Earth Elements contents are compatible with the presence of garnet in the source and low degree of partial melting, this is consistent with the correlation between La/Sm vs Gd/Yb and La/Sm vs Rb. Trace element ratios such as Th/La (0,10 for SA) and (0,09 for Al) suggest an enriched mantle source.

Some of these mafic intrusions were collected near antimony mineralization whereas the other are located at distance but in the same swarm of mafic dykes. A spatial and genetic link between Sb mineralization and mafic magmatism has been proposed in other parts of the Variscan Belt, especially in the Armorican Massif.

The source of these Sb mineralization could be related to an enriched mantle with crustal contamination. The geochemical link between mafic magmatism and Sb mineralization and their source in the Central Iberian Zone is still a matter of study.

Acknowledgments

This work was funded by the ANR (ANR-19-MIN2-0002-01), the AEI (MICIU/AEI/REF.: PCI2019-103779) and author’s institutions in the framework of the ERA-MIN2 AUREOLE project, as well as by Project SBPLY/17/180501/000273, Consejería de Educación, Regional Government of Castilla-La Mancha, Spain.

How to cite: Campos Rodríguez, H. R., Gloaguen, E., Pochon, A., Higueras, P., Lorenzo, S., Esbri, J. M., Mollé, V., and Iacono-Marziano, G.: Unravelling the relationship between mafic magmatism and Sb mineralization through dolerite geochemistry (Central Iberian Zone, Spain), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12390, https://doi.org/10.5194/egusphere-egu21-12390, 2021.

Competitiveness of mineral exploration for companies is based on reducing costs and capital intensity, improving dynamics and shortening delays between target testing and feasibility analysis. As the use of in situ analyses increases, pXRF (portable X-ray fluorescence) represents a good perspective for a fast and reliable low-footprint exploration approach. This study was carried out as part of the European EIT Raw Materials project UpDeep, which aimed at the demonstration of the applicability of modern geochemical methods for the discovery of new critical metals ore deposits.

We revisited a historic Vendean Sb district, located in western France and southeast of Brittany. First mining activities on antimony ore deposits took place during the 18^th century at La Ramée, followed at the beginning of the 19^th century, by the discovery of a rich vein at Rochetrejoux, which led to new activities until 1925. The French Geological Survey (BRGM) conducted large-scale survey during the 1970-1980s by stream-sediment followed by soil sampling focusing on sediment anomalies, which led to discovery of around 20 new prospects distributed on a 50x20 km area, in particular at Les Brouzils, La Télachère and La Copechagnière. Mining operations started again until the mid-1990s at Les Brouzils mine. The area is characterized by extensive agricultural practices.

The geological framework of the area is Variscan metamorphic rocks (gneiss and amphibolites) and slightly metamorphised sedimentary rocks, locally crosscut by dolerite dykes. Variscan thrust and shear-zones generated a network of conjugated tension fractures, controlling Sb mineralisations emplacement. The Les Brouzils ore deposits consists of a principal lode system dipping at 70°  and extending over at least 800 m horizontally and recognized up to 100 m vertically. The principal characteristic of this ore deposit is the presence of large blades of stibnite. Berthierite, pyrite and arsenopyrite complete the paragenesis. In the La Télachère prospects, trenches and drill holes on the two principal anomalies determined the presence of a quartz lode system with associated stibnite. Paragenesis comprises stibnite, arsenopyrite, galena, sphalerite, berthierite, chalcopyrite, tetrahedrite, pyrrhotite and gold in a quartz gangue. At La Copechanière, known deposits correspond to subvertical quartz NW-SE veins with stibnite, with thickness of 0.2 – 0.3 m. All the area is partially covered by plateaux silts and gravels of mixed allochtonous (eolian) and autochtonous origin. Thickness of the plateau loess can be comprised in the range 0.5 – 2 m.

For this study, we performed shallow-soil sampling (Ah and B horizons) along profiles across known veins to capture the endogenic geochemical anomaly signals. Despite an expected bias with laboratory analyses, pXRF measurements effectively located the Sb veins, with Sb and associated pathfinder elements (As, Mn) patterns, especially when using the pXRF multi-element capabilities enhanced by compositional data processing methods. Similar geochemical patterns obtained for both studied horizons suggest that application of on-site approach to humic horizon can increase efficiency of the survey and decrease its impacts.   

How to cite: Melleton, J., Lemière, B., Auger, P., Derycke, V., Gloaguen, E., and Bouat, L.: Antimony deposit exploration of antimony by pXRF measurements: example from the Vendean Antimony District (France), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3039, https://doi.org/10.5194/egusphere-egu21-3039, 2021.

Traditionally, prospectivity models were designed using approaches mainly based on expert judgement. These models have been widely applied and they are also known as knowledge-driven prospectivity models (see Harris et al. (2015)). Currently, artificial intelligence approaches, especially machine learning models, are being applied to build prospectivity models since they have been proven to be successful in many other domains (see Sun et al., 2019 and Guerra Prado et al., 2020). They are also known as data-driven prospectivity models. Machine learning models allow to learn from data repositories in order to extract and detect relationships from the data to predict new instances.

In this work, a geological dataset was collected by a team of expert geologists. The data collected includes the geographical coordinates as well as several geological features of points belonged to seventy-seven different mercury deposits in the Almadén mining district. The resulting dataset is composed by a total of 24798 points and 24 attributes for each point. In particular, we have collected geological and mining-related data regarding the Almadén mercury (Hg) mining district; these data include the location of the several Hg mineralizations, including their typology, size, mineralogy, and stratigraphic position, as well as other information associated to the metallogenetic model set up by Hernández et al. (1999).

Later, few machine learning models are built to select the one which offers the best results. The aim of this work is twofold: on the one hand, it is intended to build a machine learning model capable of, given the geological features of a data point, to determine the mercury deposit to which it belongs. On the other hand, the aim is to build a machine learning model capable of, given the geological features of a data point, to identify the kind of deposit to which it belongs. The experiments conducted in this work have been properly designed, validating the results obtained using statistical techniques.

Finally, the models built in this work will allow to generate mercury prospectivity maps. The final aim of this process is to get and train a system able to perform antimony prospection in the nearby Guadalmez syncline.

This work was funded by the ANR (ANR-19-MIN2-0002-01), the AEI (MICIU/AEI/REF.: PCI2019-103779) and author’s institutions in the framework of the ERA-MIN2 AUREOLE project.

References

Guerra Prado E.M.; de Souza Filho C.R.; Carranza E.M.; Motta J.G. (2020). Modeling of Cu-Au prospectivity in the Carajás mineral province (Brasil) through machine learning: Dealing with embalanced training data.

Harris, J.R.; Grunsky, E.; Corrigan, D. (2015). Data- and knowledge-driven mineral prospectivity maps for Canda’s North.

Hernández, A.; Jébrak, M.; Higueras, P.; Oyarzun, R.; Morata, D.; Munhá, J. (1999). The Almadén mercury mining district, Spain. Mineralium Deposita, 34: 539-548.

Sun, T.; Chen, F.; Zhong, L.; Liu, W.; Wang, Y. (2019). GIS-based mineral prospectivity mapping using machine learning methods: A case study from Tongling ore district, eastern China.

How to cite: López-Gómez, J. A., Carrasco Pardo, D., Higueras, P., Esbrí, J. M., and Lorenzo, S.: Machine learning models for Hg prospecting in the Almadén mining district, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7339, https://doi.org/10.5194/egusphere-egu21-7339, 2021.

In the Dúrico-Beirão mining district, several occurrences of Sb-Au are known, which were exploited since the Roman occupation in Iberia until mid-last century. This region is located in the Central Iberian Zone of the Iberian Massif, part of the Ibero-Armorican Arc. The country rocks in the area consist of folded metasedimentary rocks from Cambrian to Carboniferous surrounded by syn- to post-orogenic Variscan granites. The Ribeiro da Serra Sb-Au mine, intensively exploited in the 19^th century, occurs west of the western limb of the Valongo Anticline, a major ante-Stephanian structure with NW-SE trend. This Sb-Au deposit consist mainly of stibnite-bearing quartz veins hosted by slates, quartzites and conglomerates of the Schist-Greywacke Complex in a possible spatial relationship with dolerite dykes. These mafic dykes are emplaced in sub-parallel shear zones to the sinistral Douro Shear Zone and their presence may suggest the existence of mafic/ultramafic bodies at depth, which contributed to the occurrence of Sb-Au deposits.

This study aims to describe the dolerite dykes present through the region (petrographic composition, weathering, distribution, and dimension) considering a possible contribution for the Sb-Au occurrence. Dolerites are greyish-green colored and are intensely weathered. The samples surface shows a few millimeters of brownish supergenic alteration. The petrographic study highlighted an intense chloritization and saussuritization of plagioclase, whose tabular form and twinning are still preserved. The primary igneous texture is better preserved than the primary mineralogy. The texture is ophitic to sub-ophitic although the interstitial mass of the pyroxene is totally altered.  Chlorites occur as fresh, green-colored patches, sometimes with radiated fibrous textures. Frequent polycrystalline quartz lenses and veins occur, also as consequence of the hydrothermal/metamorphic alteration. The opaques, not yet identified, occur in a great modal percentage, and are frequently associated with titanite. They do not seem to have a special concentration related to quartz veins and lenses. Apatite is a frequent accessory phase and appears to be preferentially associated with opaque minerals.

The knowledge of the petrographic characteristics of these dolerite dykes, associated with geochemical data, can be a great contribution to the understanding of the distribution of Sb mineralization and corroborate the hypothesis of non-outcropping mafic/ultramafic bodies.

Acknowledgment

The work was financial supported within the compass of the ERA-MIN/0005/2018—AUREOLE project, FEDER through operation POCI-01-0145-FEDER-007690 funded by the Programa Operacional Competitividade Internacionalização—COMPETE2020 and by National Funds through FCT within the ICT (reference UIDB/04683/2020).

How to cite: Frutuoso, R., Ribeiro, M. D. A., Lima, A., and Sant'Ovaia, H.: Preliminary petrographic study of dolerites related to Sb-Au mineralizations: example of Ribeiro da Serra mine (Dúrico-Beirão mining district, NW Portugal), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12933, https://doi.org/10.5194/egusphere-egu21-12933, 2021.

Antimony (Sb) is a valuable element, exploited for diverse applications including flame retardants, munitions, batteries, glasses, and industry for diodes. However Sb is also a toxic metalloid, often associated with other harmful elements (arsenic, lead, mercury…) in mining sites. The biogeochemical behavior of Sb remains poorly documented, and data must be acquired in order to elaborate solid environmental studies related with Sb mining. Here, the mobility of Sb from solid phases present in former mining sites was assessed through leaching experiments performed in oxidizing or reducing conditions. Five Sb mines located in South-Central Spain were considered: La Nazarena, Accesos, Balanzona, Pilar, and Susana mines. Rock samples were analysed by X-ray diffraction, confirming that the main Sb carrier was stibnite (Sb₂S₃), present in all mines. Surface soils and mine wastes were sampled, together with sediments when ponds or galleries were present. The total Sb concentrations of 18 samples varied from 28 to 221 000 mg kg^-1. However, stibnite was only detected in a soil sample from Balanzona mine and tetrahedrite ((Cu,Fe)₁₂Sb₄S₁₃)in a sediment from the Balanzona mine. The most common Sb secondary minerals were bindheimite (Pb₂Sb₂O₆O), senarmontite (Sb₂O₃), valentinite (Sb₂O₃) and stenhuggarite (CaFeSb(AsO₃)₂O). These materials were incubated in slurries at 10 % solids, at 25°C under agitation, either in presence of air or under N₂/H₂ atmosphere. Sb was generally more mobile in oxidizing conditions; however, for 2 samples, mobility was higher in reducing conditions. The highest Sb concentrations in water were in the range 20 to 30 mg L^-1. The final percentage of solubilized Sb exceeded 1 % (between 1 and 12 %) for 10 samples. For one sediment sampled in Balanzola mine, final Sb concentrations were close to 20 mg L^-1 in oxidizing conditions and 10 mg L^-1 in reducing conditions. Acidification was observed with several samples; however, Sb release was not systematically related with the evolution of pH. The mobility of Sb during leaching might be driven by diverse mechanisms: release of sorbed Sb, abiotic or biotic dissolution of Sb-bearing minerals, including oxidation of Sb sulfides in aerobic conditions, or reductive dissolution of Sb-bearing iron or manganese oxides, and finally release of soluble thio-Sb complexes in anaerobic conditions. Supporting the occurrence of these last mechanisms, final analyses indicated solubilization of Fe and Mn and traces of dissolved sulfide in reducing conditions. Our results, that showed a higher mobility of Sb in oxidizing conditions, are globally consistent with previous works indicating a higher occurrence of the oxidized form of Sb, i.e. Sb^V, in water streams impacted by mining sites. However, we also observed that non negligible release of Sb can be linked to mechanisms occurring in reducing conditions. Perspectives of this work include the elucidation of the biological processes, directly or indirectly involved in Sb release or immobilisation, in order to better predict the evolution of environmental quality on mining sites and propose remediation strategies.

This work was funded by the ANR (ANR-19-MIN2-0002-01), the AEI (MICIU/AEI/REF.: PCI2019-103779) and author’s institutions in the framework of the ERA-MIN2 AUREOLE project.

How to cite: Battaglia-Brunet, F., Thouin, H., Esbri Victor, J. M., Garcia Noguero, E. M., Lorenzo, S., Higueras Higueras, P. L., and Gloaguen, E.: Mobility of antimony in samples from diverse environmental compartments of Sb mines in Spain: leaching experiments in oxidizing and reducing conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2781, https://doi.org/10.5194/egusphere-egu21-2781, 2021.

Mining activities are acknowledged to introduce contaminants into localised environments and cause wider spread diffuse pollution. The concentration, distribution and fate of arsenic (As) and antimony (Sb) were studied at the former metalliferous Louisa Mine at Glendinning, Scotland. The associated deposit is one of very few able to produce Sb in the UK and was mined for three brief periods between 1793 and 1922.  

The remnants of the mine consist of the ore processing area and two spoils. Soils withing these zones as well as around the mine were sampled and complemented by water samples from the adjacent stream, the Glennshanna Burn. All samples were subsequently analysed to map the distribution of contamination and identify pollution sources. The maximum concentrations of As and Sb, 15490 and 1504.2 mg kg⁻¹ respectively, were determined in soils associated with the ore processing area and spoil heaps. Anthropogenic activities also redistributed As and Sb within these mine zones and altered their relative ratios. The fractions of dissolved As and Sb in soils were < 1 and < 5% of total soil content, respectively, confirming findings of previous studies that As and Sb are relatively immobile. Yet, the concentrations of As and Sb released by soils exceeded regulatory limits.

Concentrations of As and Sb in surface water in the immediate vicinity of the mine were impacted by a gully discharge, but rapidly diluted. While the concentrations affected by the run-off waters did not exceed EU environmental standards for freshwater, the concentrations of As and Sb sharply increased to 11.43 ± 3.43 and 9.28 ± 0.59 μg l⁻¹, respectively, approximately 100 m downstream of the mine site. The unaltered As to Sb ratios in water samples suggested a geogenic source of contamination.

While there is a justifiable concern about the soil pollution caused by the historic mining in the studied area, the Glenshanna Burn is affected more by indigenous geochemical processes than the derelict mine.

How to cite: Mbadugha, L., Cowper, D., Dossanov, S., and Paton, G.: Antimony and arsenic distribution and impacts at a derelict antimony mine in Scotland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15753, https://doi.org/10.5194/egusphere-egu21-15753, 2021.