ERE5.6

EDI
Antimony and associated elements: from mineralisation to the environment.

Antimony is a critical element for European Union, due to its high interest and low availavility in Europe. However, it has been intensively mined in Europe during the 19th and 20th Centuries, leaving in many cases a legacy of unsolved affection to the environment.
The present session will focus in the present-day possibilities of antimony as an element to be properly exploited and processed. Possible contributions to this session will include research works related with the geological origin of Sb deposits and associated metals (Hg, As, Se, Au), metallogenetical models, mineralogy and geochemistry of Sb-ore deposits, typology of these, as well as environmental studies aimed to assess the possible affections of the mining of Sb deposits to the environment.

Co-organized by GMPV5
Convener: Pablo Higueras | Co-conveners: Antonia Cepedal, Eric Gloaguen, Alexandre Lima
vPICO presentations
| Fri, 30 Apr, 09:00–10:30 (CEST)

vPICO presentations: Fri, 30 Apr

Chairpersons: Eric Gloaguen, Alexandre Lima, Pablo Higueras
09:00–09:05
Mineralizing processes related to antimony deposits
09:05–09:07
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EGU21-144
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ECS
Björn Fritzke, Thomas Seifert, Elmar Linhardt, and Christin Kehrer

The Brandholz/Goldkronach district is situated in the southeastern part of Germany in the Bavarian Fichtelgebirge. Previous literature of the mineralogy of the district is rather descriptive and modern geochemical analysis are entirely missing. In this contribution, we combine petrography, bulk rock-geochemical analysis, SEM-MLA as well as EPMA to infer on precipitation mechanism and ore-forming processes. The quartz-polymetallic-sulfide veins are hosted in Ordovician shists, called “Phycodenschiefer”, which were intruded by upper Devonian meta-basalts. Antimony-sulfides are the main ore mineralization inside of the quartz-veins, accompanied by minor auriferous arsenopyrite and pyrite. Petrographic observations suggest a precipitation of an early stibnite phase (stage I). Sb-Pb-sulfides/sulfosalts (stage II) precipitated in fractures and fissures of stage I stibnite with a slightly change to Pb-rich Sb-phases. The antimony-mineralization event evolved from stibnite (Sb2S3), over fülöppite (Pb3Sb8S15), zinkenite (Pb9Sb22S42), plagionite (Pb5Sb8S17) to boulangerite (Pb5Sb4S11). Chemical analyses corroborate the petrographic observations and indicate a change in the hydrothermal environment from a Sb- to Sb-Pb dominated system with a distinct geochemical change from Pb-free to Pb-containing Sb-phases. A characterization of the precipitation sequence can be used to improve the understanding of the hydrothermal evolution of the whole Sb-Au-ore system in Goldkronach.

How to cite: Fritzke, B., Seifert, T., Linhardt, E., and Kehrer, C.: The Sb-Au-district Brandholz/Goldkronach (Fichtelgebirge, Germany): mineralogical indications for the evolution of hydrothermal Sb-mineralization., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-144, https://doi.org/10.5194/egusphere-egu21-144, 2021.

09:07–09:09
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EGU21-4054
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ECS
Florent Cheval-Garabédian, Eric Marcoux, Jérôme Gouin, Maxime Picault, and Michel Faure

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.

09:09–09:11
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EGU21-12122
Anthony Pochon, Giada Iacono-Marziano, Saskia Erdmann, Eric Gloaguen, and Johann Tuduri

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.

09:11–09:13
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EGU21-12365
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ECS
Valentin Mollé, Giada Iacono-Marziano, Eric Gloaguen, Johann Tuduri, Anthony Pochon, and Héctor Campos

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. BSGFEarth 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.

09:13–09:15
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EGU21-12390
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ECS
Héctor Ricardo Campos Rodríguez, Eric Gloaguen, Anthony Pochon, Pablo Higueras, Saturnino Lorenzo, José María Esbri, Valentin Mollé, and Giada Iacono-Marziano

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.

09:15–09:17
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EGU21-13154
Eric Gloaguen, Héctor Campos, Anthony Pochon, Pablo León Higueras, Saturnino Lorenzo, José-María Esbrí, Giada Iacono-Marziano, and Alexandre Lima

In the Central Iberian Zone (CIZ) and its French counterpart, the Central Armorican Domain (CAD), widespread swarms of mafic dykes with various ages and compositions are known. Indeed, numerous mafic events are recognized in the late Neoproterozoic, in the Cambrian to the Ordovician, in the Ordovician to the Devonian, at the Devonian-Carboniferous boundary, in the Permian and in the Jurassic. Such a succession of mantle partial melting events, localised or generalized, may have strong consequences (i) on the composition and the homogeneity of the mantle below both the CIZ and CAD, and (ii) on the transfert of metals in the overlying crust. Moreover, the mantle below these domains must have been modified also by the subduction of large to small oceanic crusts from the Iapetus, the Rheic, the Galicia-Moldanubian and the Paleo-tethys. Although the occurrences of paleo-subductions below the CIZ and CAD remain discussed, the southern border of the CIZ, the Ossa-Morena Zone (OMZ), is considered as a suture zone resulting from a subduction followed by a collision between 390 and 360 Ma (D1), according to the 2 opposite structural vergences at the CIZ/OMZ boundary, as well as the location of a NE-dipping slab imaged by seismic profiles. In the Armorican massif, the end of subduction is also dated at 360 Ma and associated to a north-directed subduction. The trace of this subduction below the CAD is visible in the tomographic dataset. Interestingly, these two domains (CIZ and CAD) contain the largest number of Palaeozoic antimony deposits, antimony being a volatile element. In these domains, the large clustering of antimony deposits and occurrences is observed within a ca 100km wide bands along their southern parts. In the two domains, the antimony deposits are frequently spatially associated with diabase dykes. Diabase dykes and associated antimony mineralisation have been dated at 360 Ma in the CAD but remain temporally unconstrained in the CIZ. Nevertheless, since these dykes are strongly affected by the Variscan deformation a minimum age of 350 Ma is inferred. Both, the peculiar composition of these diabase dykes, relatively enriched in Cs, Li, Pb and relatively depleted in K and Rb, the spatial association with antimony at the end of a 360Ma subduction, suggest a link between antimony and a ca 360Ma mafic magmatism which could result from the partial melting of a subduction-related metasomatized mantle.

This work was funded by the ANR (ANR-19-MIN2-0002), the AEI (MICIU/AEI/REF.: PCI2019-103779), the FCT (ERA-MIN/0005/2018) and author’s institutions in the framework of the ERA-MIN2 AUREOLE project (https://aureole.brgm.fr).

How to cite: Gloaguen, E., Campos, H., Pochon, A., León Higueras, P., Lorenzo, S., Esbrí, J.-M., Iacono-Marziano, G., and Lima, A.: Origin and significance of the antimony mineralisation associated to mafic intrusions in the Iberian Zone and the Central Armorican Domain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13154, https://doi.org/10.5194/egusphere-egu21-13154, 2021.

Antimony deposits: geological features and mineral exploration
09:17–09:19
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EGU21-2425
Alexandre Lima, Rui Frutuoso, Sara Leal, André Vieira, and Maria Ribeiro

In the Dúrico-Beirão mining district several paragenetic associations have been described in gold mineralizations, including Sb-Au. The objective of this research was the study of the Sb-Au mineralization in the Rates area, from field reconnaissance of the mineralized structures by soil sampling to the petrographic and mineralogical study of the parageneses associated with this gold mineralization, mined by the Romans.

The portable XRF was used to measure Sb and As in farms and forest soils. The observed Au-Sb-As anomalies in the Rates area must be linked to Lagoa Negra mine by the same north-western trend fault. Historical mining works have been identified both in Lagoa Negra and in Rates, where rock-chip sampling returned results up to 30 g/t Au from the Rates prospect.

Some rock samples from Rates were studied by geochemical and petrographic analyses and were analysed in detail by scanning electron microscopy. The results indicate that the paragenetic association in Rates is Sb-Au, with stibnite as primary Sb sulfide mineral, valentinite as alteration mineral, and gold in native and granular form.

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: Lima, A., Frutuoso, R., Leal, S., Vieira, A., and Ribeiro, M.: Antimony-Gold mineralization in Rates (Northern Portugal), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2425, https://doi.org/10.5194/egusphere-egu21-2425, 2021.

09:19–09:21
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EGU21-3039
Jérémie Melleton, Bruno Lemière, Pascal Auger, Virginie Derycke, Eric Gloaguen, and Loïc Bouat

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 18th century at La Ramée, followed at the beginning of the 19th 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.

09:21–09:23
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EGU21-4850
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ECS
Sofía Rivera Jurado, Saturnino Lorenzo, Carmelo Monsuy Minang Eyang, José María Esbrí Víctor, Eric Gloaguen, and Pablo Higueras

The geochemical similarities between Hg and Sb (along with W and As), have produced ore deposits in which both elements are present. In the present work we investigate the relationships between the Sb deposits of the Guadalmez synclinal and the Hg deposits of the Almadén synclinal, separated only 8 kilometres. To accomplish this porpoise a regular sampling grid was used, locating samples in each square (4 km2) according to lithologic criteria. In total, 116 soil samples have been taken at two depths using an Ejkelkamp sampler. The samples have been taken in an area of around 100 m2 around the set point at different depths, sample A at 2-15 cm and sample B at 15-30 cm. Each sample represents a composite sample of 3 subsamples taken at different but close locations, randomly chosen. The preparation of the samples has included drying at room temperature to avoid Hg losses, as well as its disaggregation and homogenization, prior to obtaining an aliquot of 100 grams that was ground in agate mortar until obtaining a grain size of less than 100 microns. The geochemical characterization of the samples included the analysis by energy dispersion X-ray fluorescence (EDXRF) to obtain the concentrations of major and trace elements. Total Hg data has obtained by means of Atomic Absorption Spectrometry using a Lumex equipment with a pyrolysis attachment. The distribution of Sb and Hg contents in the two synclines studied has not shown appreciable similarities. The highest concentrations of Sb have been found in the Guadalmez syncline, where the known mines of La Balanzona and Accesos are located. A particularly anomalous zone has been located in the southeaster zone of the Guadalmez synclinal, in the Ordovician age materials. Elevated Sb contents have also been found in the Almadén syncline, especially in the western zone without an observable predominance by lithology using a 4 km² grid size that could be less sensitive to scarces lithologies (e.g dykes). The Hg distribution, on the other hand, offers its maximum contents, as expected, in the Almadén syncline, particularly at the southeast part. Some anomalous Hg values have been found in Devonian materials of Guadalmez syncline. Concentrations of Cr and Ni are clearly related with the volcanic rocks of Almadén syncline, as well as with the presence of diabase intrusions in the Guadalmez syncline. Considering the age, a higher variability is observed in Hg contents than in Sb, especially in Devonian materials. Sb contents show little variability in general, but this is appreciable in the Ordovician materials of the Gualdamez 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, as well as by Project SBPLY/17/180501/000273, Consejería de Educación, Regional Government of Castilla-La Mancha, Spain.

How to cite: Rivera Jurado, S., Lorenzo, S., Minang Eyang, C. M., Esbrí Víctor, J. M., Gloaguen, E., and Higueras, P.: Regional soil geochemistry for Sb and Hg in Guadalmez and Almadén synclines, South-Central Spain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4850, https://doi.org/10.5194/egusphere-egu21-4850, 2021.

09:23–09:25
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EGU21-7339
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ECS
Julio Alberto López-Gómez, Daniel Carrasco Pardo, Pablo Higueras, Jose María Esbrí, and Saturnino Lorenzo

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.

09:25–09:27
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EGU21-9939
|
ECS
Alex Vella, Charles Gumiaux, Guillaume Bertrand, Bruno Tourlière, Eric Gloaguen, and Stanislas Sizaret

Prospectivity mapping aims at producing favorability maps, outlining areas with the highest likelihood to host mineralization. This process can be done using data-driven approaches, based on statistical and spatial analyses on geological features and known mineral occurences. Besides, such approach contributes to better understand metallogenic processes by highlighting specific and systematic associations between deposits and geological features (structures, lithologies, contacts, geophysical anomalies, etc).

As part of the AUREOLE project, prospectivity maps of Sb throughout the West European Variscan Range are being produced using CBA (“Cell-Based Associations”). CBA is a prospectivity tool developped for mineral prospectivity mapping by the French Geological Survey (BRGM). This method divide at first space into a regular cells grid. Inside each cell, the associations of geological factors, such as lithological, structural, geophysical or geochemical features, are grouped together and define the geological framework in the vicinity of the given cell. This project aims at developing and improving this method by the addition of new machine learning methods and statistical and spatial analysis tools for the automated classification and the calculation of favorability score.

Application of this approach to the Ibero-Armorican Arc, relying heavily on Artificial Intelligence to process the data, will highlight statistical relationships between the Sb deposits and their surrounding geological framework. Computations will be performed at multiple scales and in different areas trough the Arc, in order to observe the influence of scale in the consistency of the results and to bring out general laws from local specificities in the metallogenic models. Results from this almost purely data-driven approach will be compared to the metallogenical models traditionnaly proposed for Sb deposits in the studied areas. We infer this new multiscale and multidomains study  would improve our understanding of the genetic processes resulting in  Sb deposits through the Variscan Range and give new metallotects or specify the common ones, to be used for mineral exploration purpose.

This Phd work is funded by the ERA-MIN2 AUREOLE project (ANR-19-MIN2-0002, https://aureole.brgm.fr).

Keywords: Antimony, Prospective Mapping, Machine Learning, Data-Driven.

How to cite: Vella, A., Gumiaux, C., Bertrand, G., Tourlière, B., Gloaguen, E., and Sizaret, S.: AI oriented prospectivity mapping to study relationships between Sb mineralization and geological framework, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9939, https://doi.org/10.5194/egusphere-egu21-9939, 2021.

09:27–09:29
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EGU21-11102
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ECS
imane baba, Mounsif Ibnoussina, Omar Witam, and Latifa Saadi

Over the last few decades, the construction industry has become interested in materials that are durable, environmentally friendly and easily recyclable. This interest is due to the advantages these materials offer, among others local availability, low carbon footprint, energy efficiency and indoor comfort. The objective of this work is to study the properties of plasters prepared from a mixture of two types of gypsum. We were interested in the evolution of thermal conductivity, mechanical resistance and setting time as a function of the percentage of addition.

Two types of gypsum were studied, the first one belongs to the Safi basin and the second one comes from the High Atlas of Marrakech.

The characterization of the gypsums was necessary to determine its physical and geotechnical properties, its mineralogy, its thermal behavior and its microscopic structure. Several analyses were developed such as density measurement by pycnometer, X-ray diffraction, infrared spectroscopy and scanning electron microscopy.

We have made samples, of standardized dimensions, of mixtures based on both types of plaster. The water/gypsum mass ratio was set at 0.75.

The results revealed that the properties of gypsum as well as the percentage of addition affect the mechanical and thermal properties and the setting time of the composite material. The addition of the High Atlas gypsum of Marrakech allowed improving the material in terms of thermal insulation. The results of the other tests will be communicated later.

How to cite: baba, I., Ibnoussina, M., Witam, O., and Saadi, L.: Thermal and mechanical characterization of a new material based on two gypsums from different localities : High Atlas of Marrakech and Safi Basin, Morocco, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11102, https://doi.org/10.5194/egusphere-egu21-11102, 2021.

09:29–09:31
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EGU21-12933
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ECS
Rui Frutuoso, Maria dos Anjos Ribeiro, Alexandre Lima, and Helena Sant'Ovaia

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 19th 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 behavior in the environment
09:31–09:33
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EGU21-43
Valérie Cappuyns, Axelle Van Campen, and Jillian Helser

While the impact of Sb mining is documented in literature from China, Australia, and Europe, little information is available concerning the environmental impact of Sb mining in Vietnam. This paper presents the results of an exploratory study of mine waste and soil samples from the Mau Due mine (North Vietnam). Besides the chemical and mineralogical composition of soils, waste rock and slag samples, water-soluble and exchangeable/reversibly adsorbed Sb species were also determined, as well as the pH dependent release of Sb. Stibnite and pyrite were found in slag and waste rock samples, with total Sb concentrations in the range of 191–15,699 mg/kg. Soils were characterized by Sb concentrations in the range of 47–95 mg/kg. 
The leaching test show that, when mine waste stored on the Mau Due mining site comes into contact with water, up to 1.7% of its total Sb content is leached. However, because of the high Sb content of some of the waste materials, high dissolved Sb concentrations are found in the leachates. Some of the investigated samples are listed by the EU as absolutely hazardous waste, because of the leaching potential of Sb. Especially in the rainy season, leaching of Sb from the mine waste and slags can contribute to the dispersion of Sb. An increased release of Sb was observed from pH 7.5 to 12.8. Modelling also indicated that the dissolution of stibnite and reprecipitation as Sb(OH)3 is not the only factor that explains Sb solubility. Desorption reactions and the incorporation of Sb in other mineral phases are most likely also important factors determining the retention and release of Sb from the waste materials and slags.
The waste heaps consist of fine-grained material, that can be prone to wind erosion in the dry season. Therefore, measures to prevent the further dispersion of Sb and other potentially hazardous elements, both via leaching and wind erosion, should be put in place. In order to establish regulations for environmental protection, it is necessary to raise governmental and public awareness. The high concentrations of Sb imply an important potential hazard for soils, water bodies, and the food chain, for which appropriate measures are necessary.

 

Reference

Cappuyns, V., Van Campen, A., Helser, J.  (2020). Antimony leaching from soils and mine waste from the Mau Due antimony mine, North-Vietnam. Journal Of Geochemical Exploration, 220, Art.No. 106663, 1-13. doi: 10.1016/j.gexplo.2020.106663 

How to cite: Cappuyns, V., Van Campen, A., and Helser, J.: Antimony leaching from mine waste and soil at a stibnite mine in North-Vietnam, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-43, https://doi.org/10.5194/egusphere-egu21-43, 2021.

09:33–09:35
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EGU21-2781
Fabienne Battaglia-Brunet, Hugues Thouin, José Maria Esbri Victor, Eva Maria Garcia Noguero, Saturnino Lorenzo, Pablo Leon Higueras Higueras, and Eric Gloaguen

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. SbV, 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.

09:35–09:37
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EGU21-12353
Tamara Đorđević, Stefan Uiblein, Uwe Kolitsch, Peter Nagl, Miriam Unterreiner, Goran Tasev, and Todor Serafimovski

We present the results of mineralogical and geochemical investigations of the solid waste dump material from the abandoned Lojane mine in the northern part of North Macedonia. The geologically unusual Lojane deposit was mined for Sb (stibnite), As (realgar) and Cr (chromite) until 1979. Its waste dumps and tailings were left without any proper rehabilitation. Hence, it represents an extensive source of antimony and arsenic pollution.

In April 2018 we took samples from the major waste dump near Vaksince village. This 70 m long and 20 m wide, relatively ore-rich dump lies parallel to the creek bed of the immediately adjacent Suva creek (NW-SE). In 2017 a Turkish exploration company had dug a ~1.6 m deep trench along the middle of the elongate dump. The samples were taken along this trench using a hand-drill tool (ca. 20 cm deep) and laterally along the exposed profiles.

X-ray fluorescence (XRF) spectroscopy analyses showed that the mean concentrations of Sb and As are 9950 ppm and 32004 ppm, respectively, but can locally rise to extreme values of 24 g/kg for Sb and 200 g/kg for As. Besides Sb and As, very high amounts of Ni (up to 4672 ppm) and Cr (up to 5136 ppm) have been measured.

A combination of powder X-ray diffraction, Raman spectroscopy and SEM-EDS analyses (of polished aliquots) showed that the main primary source of antimony is stibnite with up to 2 at.% of As, while the main primary sources of arsenic are realgar, gersdorffite (up to 9 at.% of Sb) and As-rich pyrite (up to. 10 at.% of As). Additionally, minor amounts of Sb and As (up to 1.5 at.%) were detected in violarite (Fe2+Ni3+2S4) and greigite (Fe2+Fe3+2S4). Secondary phases of Sb and As are associated with amorphous iron oxyhydroxides (with up to 2 at.% Sb and up to 11 at.% As) and finely crystalline, porous and chemically inhomogeneous Ca-Fe-Sb-As-oxides/hydroxides belonging to the roméite group, with up to 7 at.% of As. Occasionally, dissolved Sb and As reprecipitated as senarmontite/valentinite, Sb2O3, scorodite, FeAsO4∙H2O (up to 2 at.% of Sb), annabergite, Ni3(AsO4)2∙8H2O, hörnesite, Mg3(AsO4)2∙8H2O, and arseniosiderite, Ca2Fe3(AsO4)3O2∙3H2O. These observations are in good agreement with our prior study focussing on the secondary mineralogy of this and other dumps (Kolitsch et al., 2018).

Further phases confirmed, in approximate order of decreasing abundance are: dolomite, serpentine group-minerals, magnesite, gypsum, quartz, talc, vermiculite, clay minerals, micas (muscovite, phlogopite, annite), plagioclase (albite, anorthite), calcite, siderite, chromite, magnesiochromite, spinel, magnetite, vaesite, clinochlore, tremolite, diopside, fluorapatite, rutile, zircon, monazite-(Ce), hydroxylapatite(?), hydroniumjarosite, chamosite, hematite, manganese oxyhydroxides, bornite, chalcopyrite, cobaltite, galena and baryte.

Financial support of the Austrian Science Fund (FWF) (P 30900-N28) is gratefully acknowledged.

 

Kolitsch, U., Đorđević, T., Tasev, G., Serafimovski, T., Boev, I., Boev, B. (2018): Supergene mineralogy of the Lojane Sb-As-Cr deposit, Republic of Macedonia: Tracing the mobilization of toxic metals. Geol. Maced., 32, 95-117.

How to cite: Đorđević, T., Uiblein, S., Kolitsch, U., Nagl, P., Unterreiner, M., Tasev, G., and Serafimovski, T.: Antimony and arsenic speciation in the major waste dump of the abandoned Lojane Sb-As-Cr mine, North Macedonia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12353, https://doi.org/10.5194/egusphere-egu21-12353, 2021.

09:37–09:39
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EGU21-13392
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ECS
Elisabetta Dore, Dario Fancello, Daniela Medas, Nicola Rigonat, Stefano Naitza, and Giovanni De Giudici

Antimony (Sb) is widely present in the environment as a consequence of both natural processes and human activities. Extremely high Sb concentrations can be found in present and past mine areas and in their surroundings, representing a serious environmental and toxicological threat.

The abandoned Sb mine of Su Suergiu (Sarrabus-Gerrei mining district, SE Sardinia, Italy), has been exploited from 1880 to 1980; the mined ore was dominated by stibnite (Sb2S3), which was processed in the smelter adjacent to the mine. After the closure of the complex, mining and metallurgical residues were dumped without intervention to mitigate their environmental impact. Waters draining Su Suergiu have high Sb concentration (up to 103 - 104 µgL-1) and the contamination extends several km downstream reaching the Flumendosa River, the main river of south-eastern Sardinia, used in agriculture and domestic consumption.

The mineralogy of outcropping rocks, mine wastes and foundry slags from the mine area was investigated by X-Ray Powder Diffraction (XRPD) and Scanning Electron Microscopy - Energy Dispersive Spectroscopy (SEM-EDS) to understand the oxidation pathways and the role of secondary Sb-bearing minerals on Sb dispersion.

At Su Suergiu, the foundry slag heaps are the main contamination sources. Indeed, the residues of metallurgical processes, consisting of metallic Sb (Sb0) and Sb2O3 (valentinite/sénarmontite) together with carbonates and NaAl-silicate hydrate, are exposed to surface environment and subjected to oxidation and weathering processes. The oxidation of Sb0 and Sb3+ phases leads to the formation of Sb5+ that, at the slightly alkaline and oxidizing conditions of surface water draining the Su Suergiu area, is present in solution as dissolved Sb(OH)6.

The local geochemical conditions of waters circulating within the foundry slag heaps, affected by the carbonates and Si-Na-Al phases, promote the precipitation of a rare secondary Sb mineral, namely mopungite NaSb(OH)6. On the slag fragments, mopungite occurs as euhedral crystals (about 100 µm), alteration crusts and micro-aggregates filling the fractures; the different occurrences are likely due to the local availability of Na and water circulation.

Results indicate that mopungite is the last forming mineral in the oxidation paths of Sb phases and derives by a dissolution-precipitation process. Due to its relatively high solubility, mopungite act as a temporary sink, whose effectiveness is conditioned by the hydrological regime and the water physicochemical conditions (T, pH, Eh, etc.).

At Su Suergiu foundry slag heaps the Sb mobility is mainly controlled by mopungite, whereas the role of Fe-bearing compounds, recognized as the main Sb binders in the most part of polluted sites worldwide, is here negligible.

 

The authors acknowledge CESA (E58C16000080003) from RAS and RAS/FBS (F72F16003080002) grants, FP7 ERANETMED2 72094 SUPREME, the Grant of Excellence Departments, MIUR (ARTICOLO 1, COMMI 314 – 337 LEGGE 232/2016), and the CeSAR (Centro Servizi d'Ateneo per la Ricerca) of the University of Cagliari, Italy, for SEM analysis. This work has been supported by the POR FESR Sardegna 2014-2020 (project cluster Top-Down: TESTARE)

How to cite: Dore, E., Fancello, D., Medas, D., Rigonat, N., Naitza, S., and De Giudici, G.: The fate of Sb(V) in the Sb-polluted old mine area of Su Suergiu (SE-Sardinia, Italy): the role of secondary mopungite [NaSb(OH)6], EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13392, https://doi.org/10.5194/egusphere-egu21-13392, 2021.

09:39–09:41
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EGU21-15753
Lenka Mbadugha, Duncan Cowper, Sapar Dossanov, and Graeme Paton

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.

09:41–10:30