GMPV5.1 | Mineral deposits: systems, settings, processes
EDI
Mineral deposits: systems, settings, processes
Convener: David Dolejs | Co-conveners: Katarzyna Derkowska, Matteo Luca DeiddaECSECS
Orals
| Wed, 17 Apr, 14:00–17:55 (CEST)
 
Room -2.47/48
Posters on site
| Attendance Thu, 18 Apr, 10:45–12:30 (CEST) | Display Thu, 18 Apr, 08:30–12:30
 
Hall X1
Posters virtual
| Attendance Thu, 18 Apr, 14:00–15:45 (CEST) | Display Thu, 18 Apr, 08:30–18:00
 
vHall X1
Orals |
Wed, 14:00
Thu, 10:45
Thu, 14:00
Mineral deposits represent principal sources of metallic and non-metallic raw materials for our society. The implementation of new climate policies and the rise of green energy production and use will trigger an unprecedented demand increase for such resources. Formation of economic commodities requires component sequestration from source region, transport and focusing to structural or chemical barriers. These enrichment processes typically involve magmatic, hydrothermal, weathering or metamorphic events, which operate in diverse geodynamic settings and over various time scales. The scope of this session is to collect insights from diverse areas of mineral exploration, field, analytical or experimental studies of mineral deposits as well as resource characterization and extraction. We invite contributions from fields of economic geology, mineralogy and geochemistry in order to advance our understanding of ore-forming systems.

Orals: Wed, 17 Apr | Room -2.47/48

Chairpersons: David Dolejs, Katarzyna Derkowska, Matteo Luca Deidda
14:00–14:10
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EGU24-716
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ECS
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Virtual presentation
Naside Merve Sutcu, Zeynep Doner, Ali Tugcan Unluer, and Mustafa Kumral

Especially in the context of renewable energy, vanadium (V) is an important component of energy storage technology. Gabbroic rocks in crustal environments may host a considerable amount of V-bearing minerals such as magnetite, and ilmenite. This study focuses on primary V occurrences in Precambrian-Cambrian aged meta-gabbroic rocks of the Alaşehir-Manisa area in the central part of the Menderes Massif (Türkiye). The primary purpose of the study is twofold; 1) to determine the V potentiality of meta-gabbro and 2) to reveal the enrichment mechanism by determining the mineralogical and geochemical properties of gabbroic formations. The meta-gabbroic rocks in the study area can be divided into three subgroups based on the size distribution (fine, medium, and coarse) of the minerals. The ore-bearing minerals observed in the meta-gabbroic rocks are construed by magnetite, ilmenite, titanomagnetite, rutile, pyrite, and hematite. The high-grade metamorphism of Menderes Massif progressively affected the gabbroic rocks resulting in the partial and complete transition of ilmenite minerals to rutile. However, the effect of metamorphism gradually decreases from outward to inward zones of the intrusion allowing an intact vanadiferous ilmenite-rich core in the entire gabbro body. 

The V enrichments are both hosted by oxide and sulphide-bearing phases. While the oxide phases are constituted by ilmenite and Ti-magnetite exsolutions, the sulphide minerals are pyrite and minor chalcopyrite. The V content of the studied meta-gabbro range from 281 to 628 ppm, with an average of 514 ppm. Contents of SiO2, Al2O3, Fe2O3, MgO, TiO2, and P2O5 are between 68.8-38.9%, 7.93-15.4%, 6.87-17.8%, 3.21-8.86%, 1.24-5.64%, 0.19-1.13%, respectively. V shows moderate to strong correlation with Ti, Zn, and Ga (R2= 0.51, 0.86, and 0.87, respectively) and there is a lack of correlation with Fe, Ni, and Cu indicating V3+ ion substituted Fe3+ in magnetite and Ti3+ in ilmenite. The other meta-gabbro intrusions of Menderes Massif generally lacked Ti-V enrichments, therefore Alaşehir meta-gabbro intrusion may gain economic importance in case of a tighter supply trend of these critical elements.

Keywords: Vanadiferous gabbro; Magnetite; Ilmenite; Menderes Massif; Alaşehir-Manisa (Türkiye)

How to cite: Sutcu, N. M., Doner, Z., Unluer, A. T., and Kumral, M.: Vanadium Enrichments of Meta-Gabbroic Rocks in central part of the Menderes Massif (Türkiye): The Incremental Effect of Magmatism and Metamorphism in Highly Siderophile Environments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-716, https://doi.org/10.5194/egusphere-egu24-716, 2024.

14:10–14:20
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EGU24-127
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ECS
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On-site presentation
Smruti Prakash Mallick, Amit Mondal, and Kamal Lochan Pruseth
  • Uranium is generally mobilized in solutions in U6+-complexes and gets precipitated as compounds containing the U4+ ion. Here we report hydrothermal remobilization of U, and the simultaneous precipitation of U6+ and U4+ in the Paleoproterozoic quartz-pebble conglomerate (QPC) from the Mankarchua basin, Singhbhum Craton, India. Uranium occurs associated with vein pyrite in the basal QPC of the Mankarchua basin, suggesting a clear hydrothermal origin of the mineralization. The pyrites occur linearly in veins and are replaced U-bearing minerals. Detrital monazites are the source of U. Newly formed fine-grained U-free monazites are observed along with crandallite series minerals (Ca,Ba,Sr,Pb)Al3(PO3.5(OH)0.5)(OH)6., suggesting alteration of detrital monazite by moderately oxidising acidic fluids. The remobilized U precipitates when it encounters pyrite and apatite. Brannerite (UTi2O6, containing U4+) forms concomitantly with the oxidation of pyrite, while autunite (Ca(UO₂)₂(PO₄)₂·10–12H₂O, containing U6+) forms by replacement of apatite. Thus, detrital or hydrothermal apatite enriched zones with or without pyrite may serve as U-traps for potential mineralization.

How to cite: Mallick, S. P., Mondal, A., and Lochan Pruseth, K.: Simultaneous precipitation of U4+ and U6+ in quartz-pebble conglomerate in the Singhbhum Craton, India., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-127, https://doi.org/10.5194/egusphere-egu24-127, 2024.

14:20–14:30
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EGU24-661
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On-site presentation
Majid Ghasemi Siani and Franz Neubauer

The Sangan mining district consists of 14 iron ore deposits at the contact of Eocene granitoids to Mesozoic sedimentary rocks. Syenite, syenogranite and granite represent the fertile Sarnowsar intrusion and monzogranite to syenogranite barren Sarkhar and Bermani intrusions. LA-ICP-MS U-Pb zircon ages of fertile syenogranite samples are between 39.6 ± 0.7 and 39.1 ± 0.4 Ma corresponding to lithospheric thinning by Eocene flare-up magmatism. Barren Sarkhar and Bermani intrusions (monzogranites at 41.7 ± 0.6 and 41.9 ± 0.3 Ma; syenogranites between 37.4 ± 1.8 and 37.9 ± 1.7 Ma were emplaced contemporaneous with flare-up magmatism.

Plots of Nb vs. Ta, Y vs. Yb/Sm and Y vs. Ce/Ce* classify studied zircons as granitoid-type as parental magma. Uniformly high Hf contents of zircons indicate crystallization from a more evolved felsic magma, especially the Sarkhar and Bermani intrusions. In the U/Yb versus Hf and U versus Yb discrimination diagrams, all data plot in the continental-series and are clearly distinguishable from ocean crust zircons. In the U/Yb versus Nb/Yb diagram, both the whole-rock and zircon compositions show the characteristics of a magmatic-arc array. The Nb content of arc magmas is depleted relative to within-plate settings. As such, arc zircons possess lower Nb/Hf and higher Th/Nb ratios with a similar degree of magmatic fractionation. Bivariate discrimination diagrams such as Th/U versus Nb/Hf and Th/Nb versus Hf/Th indicate that most zircons plot in the orogenic field, signifying a magmatic arc or orogenic setting and a calc-alkaline parent magma. Fertile intrusions are characterized by a higher zircon Eu (>0.3) and Ce (>100) anomalies, 10,000*(Eu/Eu*)/Y (>1), (Ce/Nd)/Y (>0.001), and slightly lower Dy/Yb ratios (0.21 to 0.38) than zircons in barren intrusions with Dy/Yb ratios (0.2 to 0.51) and lower Eu and Ce anomalies. The chondrite normalized zircon Eu/Eu* ratio correlates with whole rock La/Yb and has been used to estimate the crustal thickness. Our results reveal that fertile Sarnowsar granitoids formed in thicker crust (48 to 66 km) than barren Sarkhar and Bermani (25 to 38 km) granitoids. As the granitoids formed in adjacent areas, these differences in crustal thickness imply either a heterogeneously composed crust, or the iuxaposition of units across a major fault, or hitherto unknown complications with the method. The zircon/rock partition coefficients of REEs, and Y, Nb, Ta, Th, and U contents indicate that the trace element patterns of the studied granitoids are controlled by the liquid composition at the magmatic crystallization. Compared to Sarkhar and Bermani magmatism, Sarnowsar magmatism has a higher temperature (736 to 915 °C), higher zircon/rock partition coefficient of REEs, Y and Th (up to 2770 for Zr), and it was formed in higher oxidant conditions (△FMQ values between -0.06 to 17.01). This indicates that the fertile intrusions are interpreted to indicate extremely high magmatic water content and oxidized like fertile porphyry systems. We suggest that oxidized and I-type magmas are more favorable to porphyry-skarn mineralization under arc tectonic settings. Such a conclusion could be used in regional exploration for porphyry-skarn mineralizations in the Cenozoic arc-related magmatism of Iran and elsewhere.

How to cite: Ghasemi Siani, M. and Neubauer, F.: Discrimination of fertile and barren skarn-related magmatism from Sangan Fe Skarn, NE Iran: Constrains from whole-rock geochemistry, zircon chemistry and crustal thickness, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-661, https://doi.org/10.5194/egusphere-egu24-661, 2024.

14:30–14:40
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EGU24-805
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ECS
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On-site presentation
Links between volcanogenic massive sulfide endowment and volcanic rock geochemistry: comparing two assemblages from the Archean Abitibi greenstone belt, Canada
(withdrawn)
Octavio Vite Sanchez, Pierre-Simon Ross, and Patrick Mercier-Langevin
14:40–14:50
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EGU24-1579
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On-site presentation
Antje Fuchs, Guillaume Jacques, Torsten Graupner, Yoseph Swamidharma, Andhi Cahyadi, Yudhi Krisnanto, Ernowo Ernowo, Arifudin Idrus, and Agata Vanessa

Critical raw materials (e.g., Co, Ni, Pt, Sc…) are very important resources for high technology applications (e.g., renewable energies, modern electronic devices, e-mobility, medical). Most of these minor and trace elements are produced as by-products of base metal mining. Magmatic Ni-Cu sulphide ore deposits are of great economic relevance worldwide. The BMBF-funded project “StratOre” (FKZ 033R278) aims to study the high-tech element potential of newly found sulphide deposits in ophiolite sequences in Indonesia, a country, which is well known for its large number of mineral deposits. Here we present the first results of our study addressing the nature of the Sebuku Island Fe-Ni-Co-Cu sulphide ore and the distribution of base and precious metals in different minerals.

Sebuku Island (SE-Kalimantan) is part of the Cretaceous accretionary Meratus collision complex and represents an obducted ophiolite at the convergent boundary of Sundaland in the NW and the compressing Paternoster microcontinent in the SE. This ophiolite complex consists of mafic-ultramafic layers and rocks of the upper mantle of Permian to Jurassic age. Cretaceous intrusions, meta-sediments and mafic-intermediate intrusions are overlain by Tertiary and Quaternary sediments. Serpentinization started prior to obduction and became affected by cretaceous magmatism and alteration. One of the Early Cretaceous intrusions is supposed to represent a mantle wedge and is marked by high-temperature serpentine (Sulistyohariyanto and Soesilo, 2017, Cahyadi et al., 2017, Imani et al., 2020).

Massive Fe-Ni laterite (mined since 2000 by PT SILO) is overlying a recently observed Fe-Ni-Co-Cu sulphide mineralization, which is hosted by high-temperature serpentinite in the cumulus zone of the ultramafic ophiolite complex. Our sample material is taken from 14 drill cores within depths of 22 m to 109 m. The studied mineralization occurs as massive, erratic and disseminated sulphides. Formation of the ore body is probably resulted from subsequent magmatic and hydrothermal processes. The base metal sulphide-ore mineralogy is represented mainly by pentlandite, pyrrhotite, pyrite, chalcopyrite and cobaltite; a large number of further sulphides and arsenides are observed as well. We highlight the extraordinary enrichment of Co in Fe-S, Fe-Ni-S and Ni-S minerals, as well as the extraordinary enrichment of Ni in pyrrhotite and pyrite. Platinum-group elements are not enriched in any of the ore types.

How to cite: Fuchs, A., Jacques, G., Graupner, T., Swamidharma, Y., Cahyadi, A., Krisnanto, Y., Ernowo, E., Idrus, A., and Vanessa, A.: Mineralogical characteristics of a Fe-Ni-Co-Cu sulphide mineralization in Sebuku Island, Indonesia., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1579, https://doi.org/10.5194/egusphere-egu24-1579, 2024.

14:50–15:00
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EGU24-1668
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ECS
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On-site presentation
Steven Kahou, Michel Cathelineau, and Marie-Christine Boiron

The albite-lepidolite-topaz granite of Beauvoir is the last intrusion in a peraluminous granitic complex of Variscan age composed of three successively emplaced units: the hidden granite of La Bosse, the two-micas granite of Colettes, and the Beauvoir granite consisting of 3 units B1 to B3. Compared to similar Li-F-rich igneous bodies, the Beauvoir granite is highly enriched in Sn (200-1400 ppm), Ta (20-400 ppm) and Be (20-300 ppm). The B1 unit is composed of abundant albite and lepidolite laths forming a framework filled with globular quartz, K-feldspar, and rare crystals of topaz, Li-phosphates and Sn-Nb-Ta oxides. This work presents a quantitative mineralogical study of the Beauvoir granite (B1 unit) and detailed textural and chemical characterization of the Li-bearing micas from the cores from the PER and EMILI drilling campaigns. The first approcah of this work consisted in estimating the proportion of minerals, and thus determine their abundance by comparing estimates from in situ thin section mapping from micro-XRF and the calculation of mineral phase proportion from whole rock geochemistry on drill cores. The main trend is a "mix", for the fresh rocks, between an albite pole (> 35 %), and a quartz (~25 %) - lepidolite (~15-25 %) pole. The micas are represented, in the fresh facies, by trioctahedral lepidolite while the altered facies shows i) dioctahedral muscovite replacing the feldspars and lepidolite, and ii) lepidolite replaced partially or totallly by muscovite. Trace element composition of the lepidolite show high Li content with average 28000 ppm for lepidolite from the fresh facies and 24000 ppm for those from the altered facies. Compared to lepidolite, muscovite is not a Li-bearing but Sn-rich mineral. Our study shows that hydrothermal greisen alteration has almost no impact on the lithium content of the lepidolite but decrease the population of the lepidolite. The results obtained, combining to drilling data, will lead to a mineralogical model block of the Beauvoir quarry and better understand the magmatic-hydrothermal evolution of the deposit.

How to cite: Kahou, S., Cathelineau, M., and Boiron, M.-C.: Quantitative mineralogy and lithium distribution in the upper part of the Beauvoir granite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1668, https://doi.org/10.5194/egusphere-egu24-1668, 2024.

15:00–15:10
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EGU24-2829
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On-site presentation
Xiang-Chong Liu and De-Hui Zhang

The granites associated with large-scale W and Sn deposits generally have high concentrations of U, Th, and K, including but not limited to the Cornubian Batholith in Southwest England, the Krušné hory/Erzgebirge Batholith in Central Europe, the Sardinian Batholith in Italy, and the Gejiu Batholith and the Qianlishan granitic complex in South China. These granites can be classified as high heat producing (HHP) granites (>5 μW m-3) because of high radiogenic heat production. However, how long radiogenic heat can prolong the suprasolidus lifetime of magmas and whether radiogenic heat exerts an influence on later W and Sn mineralization is poorly understood.

To answer these questions, finite element numerical modeling was established to link magma cooling by heat conduction with diffusion of W, Sn, and H2O from silicate melts to coexisting aqueous fluids before the solidus is reached. The magma size (vertical thickness of 4–5 km and horizontal length of 20 km) is constrained by the granites associated with large-scale W and Sn deposits. The modeling results suggest that the suprasolidus lifetimes of HHP magmas are positively correlated with the heat production and magma thickness and negatively correlated with the solidus temperatures and the thermal conductivity of host rocks. Average radiogenic heat of 5–10 μW m-3, together with decreased solidus temperatures due to magmatic differentiation and a moderate thermal conductivity of host rocks, can prolong the suprasolidus lifetime of HHP magmas by 49–427 ka (1 Ma = 1000 ka), corresponding to 11–85 % of the suprasolidus lifetime of equally sized magmas with normal radiogenic heat (2 μW m-3). From the available gravity modeling data, over half of the granites associated with large-scale W and Sn deposits are at least 1 km thicker than the values calculated from the empirical power–law equation, and the modeling results indicate that an increase of 500–1000 m in magma thickness prolongs the suprasolidus lifetimes of HHP magmas (5 μW m-3) by 50–74 %. During magma cooling before solidus is reached, the diffusion of W and Sn is at least several orders of magnitude slower than that of H2O in hydrous melts; thus, the equilibrium partitioning of these two metals between silicate melts and coexisting aqueous fluids is not reached, and the metal diffusion from melts is a rate-limiting step. The prolongation of the suprasolidus lifetimes by radiogenic heat and decreased solidus temperatures can allow extraction of 17–95 % more W and Sn from silicate melts before the solidus is reached and increase the possibility of producing W and Sn mineralization at later stages. Therefore, the coexistence of HHP granites and large-scale W and Sn deposits is not accidental.

How to cite: Liu, X.-C. and Zhang, D.-H.: The links between high heat producing granites and large-scale W-Sn deposits: insight from numerical modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2829, https://doi.org/10.5194/egusphere-egu24-2829, 2024.

15:10–15:20
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EGU24-3046
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Virtual presentation
Nikolai Nekrylov, Samvel Hovakimyan, Robert Moritz, Christian Bergemann, Karen Hambaryan, and Khachatur Meliksetian

The Abovyan deposit in Armenia represents a unique example of relatively young, Late Miocene age Kiruna-type apatite-magnetite mineralization in the region. Initially identified in 1947 by a team of Armenian geologists, based on the well-pronounced magnetic anomaly, it remains largely obscure outside the confines of Soviet-era scholarly literature. This deposit resides within a magmatic formation predominantly of intermediate composition, comprising andesites and dacites, and characterized by disseminated and massive magnetite ores and transitional varieties between them. The deposit is fully covered by several dozens of meters of younger, Pliocene-Quaternary volcanic rocks, so the samples for our study were collected from drill cores. These specimens, encompassing both host rocks and ores, retain critical insights into the processes governing ore segregation and accumulation, despite having a large influence of the autometasomatic alteration. The young age (~6-7 Ma, K-Ar, Sarukhanyan, 1969) and, consequently, the absence of later metamorphic events in the area is the main advantage of the Abovyan deposit over the majority of Kiruna-type deposits around the world in terms of preservation of the initial textures and other mineralogical and petrological features. Several generations of the magnetite-apatite ores could be clearly distinguished in the ores, which include (1) magnetite melt-like droplets in the host-rocks, (2) massive magnetite apatite ores, (3) magnetite-hosted breccias of the altered host-rocks and (4) several generations of late hydrothermal veins. Notably, the apatite within these ores exhibits a remarkable enrichment in light rare earth elements (REEs), reaching concentrations as high as 4 wt.%. This level of enrichment is notably higher than that observed in other Kiruna-type deposits (Frietsch, Perdahl, 1995) and is accompanied by the other critical metals’ mineralization (e.g., Th). Ongoing research on the geochemistry and geochronology of the Abovyan deposit may be a key to understanding the formation of the Kiruna-type deposits and their REE potential, in particular.

This study was funded by the Science Committee of RA (Research projects №23PostDoc-1E001 and  № 22IRF‐08), and by the Swiss National Science Foundation (grant 200021_188714).

Frietsch, R., Perdahl, J. A., 1995. Rare earth elements in apatite and magnetite in Kiruna-type iron ores and some other iron ore types. Ore Geology Reviews, 9, 6, 489-510.

Sarukhanyan, L.B., 1969. Some questions about the genesis of the Abovyan apatite-magnetite deposit. Proceedings of the Armenian SSR Academy of Science, Earth Sciences, 3, 40-49 (in Russian)

How to cite: Nekrylov, N., Hovakimyan, S., Moritz, R., Bergemann, C., Hambaryan, K., and Meliksetian, K.: Abovyan – an enigmatic Kiruna-type apatite-magnetite deposit in Armenia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3046, https://doi.org/10.5194/egusphere-egu24-3046, 2024.

15:20–15:30
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EGU24-3657
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ECS
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On-site presentation
Antonio Ciccolella, Vincenzo Festa, Giovanni Ruggieri, Emanuela Schingaro, Fabrizio Tursi, Gennaro Ventruti, and Rosa Anna Fregola

The occurrence of Zn-Pb(-Cu-Fe) mineralization in the northern Sila Massif (Calabria), primarily in Longobucco (LGB) and Fonte Argentila (FAR) areas, is not a novelty (e.g., Fregola et al., 2023). However, the genesis of this mineralization and its relation to the geological evolution of the Sila Massif are still unknown. These issues are addressed in the present study. Detailed mineralogical and geochemical analyses were carried out on ore-samples collected from mineralized faulted bodies within the granodiorite of the Sila batholith. The mineral association, common to both areas, consists of sphalerite (Sp), as main ore-mineral, galena (Gn), quartz (Qz) and calcite (Cal). Samples from the FAR site also contain chalcopyrite (Ccp), pyrite (Py), and fluorite (Flr). Mineral composition and microstructures were characterized using SEM, EPMA and m-Raman spectroscopy techniques. In addition, trace element distribution in sphalerite and chalcopyrite were determined with LA-ICP-MS. The sphalerite is Fe-poor (Fe up to 11.3 wt%; 0.21 mol% FeS) and shows the associated color and chemical zonings mainly due to variations in Fe concentrations. The following trace elements have been identified in sphalerite: Mn, Co, Cu, Ga, Ge, Ag, Cd, In, Sn, Sb, Hg, Tl, Pb, Bi. The reconstructed paragenetic sequence comprises five growth stages for both areas. During stage-1, precipitation of massive, light-colored and Fe-poorer Sp1 occurred, whereas in stage-2 a darker, Fe-richer Sp2 formed in association with euhedral Qz1. The latter shows color and chemical zonings related to variations in Al, Na, K, Ca content. Fracturing characterized stage-3, along with precipitation of massive Cal (in LGB) and Flr (in FAR). The calcite in LGB hosts synchysite, with grain sizes between 20 and 60 µm, and ΣREE (Ce, La, Y, Nd, Sm, Pr, Gd, Dy) ranging from 2.40 to 42.6 wt%. Stage-4 was characterized by diffuse recrystallization of colorless Sp3 and Qz2. During the stage-5 an almost pure Gn, Ccp and Py formed at the expense of the previous minerals. Formation temperatures ranging between 150 and 200°C were derived for Sp1 and Sp2 using the GGIMFis sphalerite geothermometer (Frenzel et al., 2016). These predicted values will be compared with those obtained from ongoing fluid inclusion analyses. Anyway, such low formation temperatures are also supported by the Zn/Cd (195–267), Ga/In (190–596), and In/Ge (0.24–1.20) average ratios in the sphalerite, indicative of a low-temperature ore-forming fluid. Our mineralogical and geochemical results are comparable with those of either the vein-type or the MVT deposits, although the examined mineralization in the northern Sila Massif occur in a different geological context and registers slightly higher temperatures than those typical of the MVT deposits (that is, 100–150°C).

How to cite: Ciccolella, A., Festa, V., Ruggieri, G., Schingaro, E., Tursi, F., Ventruti, G., and Fregola, R. A.: The Zn-Pb(-Cu-Fe) mineralization in the northern Sila Massif (Calabria, southern Italy): Genetic constrains from trace element concentrations in sphalerite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3657, https://doi.org/10.5194/egusphere-egu24-3657, 2024.

15:30–15:40
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EGU24-5713
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ECS
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On-site presentation
Abouttarouk Ayoub, Alikouss Saida, Morsli Yousra, Ennabir Mohamed, Abidi Mohamed, Ouhoussa Lhoussayn, Tahar Rachid, Zerhouni Youssef, Samir Mohamed, and Baroudi Zouhir

The Western Anti-Atlas belt is globally renowned for hosting metallic ore deposits, including large copper-silver deposits. The Ouarmdaz-Chikh Imi Nrfi area is located southwest of the Precambrian Ighrem inlier, approximately 168 km east of the city of Agadir. This area is known for its stratiform copper-silver mineralization along the contact between the Precambrian basement and the infracambrian cover. This level is of particular interest on a regional scale because of its spatial extension.

The Igherm inlier comprises Precambrian basement formations, including polygenic conglomerates, red sandstones, and andesitic lava. The cover consists of a siltstone-sandstone series capped by Tamjout dolomites and lower limestones. These terrains are cross-cut by the Ighrem doleritic dyke and are affected by extremely discrete brittle deformation and very pronounced ductile deformation, indicating highly mineralized zones.

This area is characterized by polymetallic mineralization with copper, silver, lead sulfides, and iron oxides. These mineralizations are hosted in the infracambrian cover. Paragenesis is stratiform, vein-type, or in geodic cavities. The mineralized structures are mainly oriented NE–SW, with a dip of 30° to 50° toward the southwest.

The paragenetic study of mineralization has enabled us to identify the different metallic phases and propose a paragenetic succession. The primary paragenesis comprises pyrite, chalcopyrite, bornite, and galena. The primary mineral phases underwent metasomatism, giving rise to secondary parageneses represented by chalcocite, covellite, malachite, azurite, and iron oxides, including hematite and goethite. This mineralization features complex textures (myrmekitic, collomorphic, carrie, and continent).

The analytical data by (ICP) indicated relatively high levels of copper and copper oxide (<25.4%). Silver with concentrations ranging from 7 to 176 g/t, demonstrates a positive correlation with copper.

Scanning electron microscopy (SEM) analysis revealed that the highest copper concentrations were recorded in the malachite-rich zones. Iron and copper oxides of the delafossite type have also been identified in association with dolomite.

Keywords: Western Anti-Atlas, Ighrem, Ouarmdaz-Chikh Imi Nrfi, Mineralization, stratiform, Copper-silver deposits, ICP, SEM.

How to cite: Ayoub, A., Saida, A., Yousra, M., Mohamed, E., Mohamed, A., Lhoussayn, O., Rachid, T., Youssef, Z., Mohamed, S., and Zouhir, B.: The Ouarmdaz region: A new copper-silver potential of the Igherm inlier (Western Anti-Atlas, Morocco)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5713, https://doi.org/10.5194/egusphere-egu24-5713, 2024.

Coffee break
Chairpersons: David Dolejs, Katarzyna Derkowska, Matteo Luca Deidda
16:15–16:25
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EGU24-8251
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ECS
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On-site presentation
Erwin Schettino, Igór González-Pérez, Claudio Marchesi, José María González-Jiménez, Michel Grégoire, Fernando Gervilla, Idael Blanco-Quintero, Alexandre Corgne, and Manuel Schilling

The geological factors controlling Li abundances in the mantle and mantle-derived magmas rising through the continental lithosphere, as well as their implications for Li ore genesis in the shallow crust, are still under debate. Here, we look from the mantle source perspective at those mechanisms that may boost the Li inventory in continental arc magmas, by characterizing a set of sub-arc mantle xenoliths from the southern Andes (Coyhaique volcanic field, western Patagonia). The mineral trace element signatures and oxygen fugacity estimates (FMQ > +3) in these peridotite xenoliths are consistent with those expected for a mantle wedge fluxed by oxidizing, subduction-related silicate melts rich in slab-derived volatile components. However, our data support that subduction-related metasomatism did not enhance significantly the Li inventory of the sub-arc lithospheric mantle, at odds with the generally claimed major role of slab-derived fluids in enriching Li in the supra-subduction mantle wedge. Major and trace element compositions of minerals also record transient thermal and chemical anomalies fingerprinting the interaction with OIB-type alkaline melts, which percolated through the shallow (7.2-16.8 kbar) and hot (952-1054 °C) mantle wedge in response to the opening of an asthenosphere slab window and ridge collision. This alkaline metasomatism produced exceptionally high Li abundances (6-15 ppm) in metasomatic clinopyroxene, promoting the generation of a Li-rich and fertile lithospheric mantle wedge. A numerical model suggests that low degrees (< 10%) of partial melting of this alkaline-metasomatized sub-arc lithospheric mantle generates primitive melts having Li abundances (⁓13 ppm) much higher than average subduction-zone basalts. Extreme differentiation by fractional crystallization of these Li-rich magmas may provide an effective pathway for enhancing the fold enrichment process required for a magmatic rock to effectively source ore deposition in the shallow arc crust.

How to cite: Schettino, E., González-Pérez, I., Marchesi, C., González-Jiménez, J. M., Grégoire, M., Gervilla, F., Blanco-Quintero, I., Corgne, A., and Schilling, M.: A metasomatized lithospheric mantle contribution to the genesis of Li-rich magmas in slab-window settings, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8251, https://doi.org/10.5194/egusphere-egu24-8251, 2024.

16:25–16:35
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EGU24-9186
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On-site presentation
Alexis Plunder, Benjamin Le Bayon, Florence Cagnard, Marc Poujol, Nathan Cogné, and Laurent Bailly

The Otjosondu area contains one of the most important Manganese deposit of Namibia. An exploration campaign in the late 2000’s acquired an extensive dataset (fieldwork, drillholes, geophysics and petrological data) to improve our knowledge of the deposit. The geological history is however, ill-studied and the deposit is classically attributed to banded iron formation of the Sturtian Chuos formation from the Damara sequence.

Using samples from drillholes, we here provide Pressure-Temeprature-time constrain using thermodynamic modelling and LA-ICP-MS U-Pb ages on zircon, monazite and apatite to decipher the regional metamorphic evolution. Our petrological study concludes that the Otjosondu Mn deposit is affected by a HT-MP metamorphic event, estimated at ~670°C and 0.6. This HT-MP metamorphism is associated to a strong ductile deformation with development of shear zones, and multiple-scale intense folding. These metamorphic and structural features totally preclude the description of a typical sedimentary sequence, on which the previous authors had based their classical lithostratigraphic comparison. We date this HT metamorphic event at ca. 525Ma using U-Pb ages on monazite in paragneisses and in a granite, and U/Pb ages on zircon in the same granite.

Detrital U-Pb ages on zircon reveal that the maximum deposition age is at ca. 540Ma. This excludes the attribution of the gneisses surrounding the Mn deposit to the Sturtian Chuos Formation challenging the prevailing interpretation of this ore deposit. Detrital U-Pb ages on zircon also record older magmatic events at ca. 620 and 585 Ma, which are well-known regionally, but were not previously documented in the Otjosundu area. Finally, U-Pb ages on apatite (490+/-3Ma) highlight a late thermal event (hydrothermal or static metamorphism). Results of this study illustrates the importance of characterizing the entire geological history of an ore deposit, to improve the future exploration.

How to cite: Plunder, A., Le Bayon, B., Cagnard, F., Poujol, M., Cogné, N., and Bailly, L.: Back to the Otjosondu manganese deposit: an integrated structural, petrological and geochronological study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9186, https://doi.org/10.5194/egusphere-egu24-9186, 2024.

16:35–16:45
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EGU24-10027
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ECS
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On-site presentation
Andreas Kaufmann, Marina Lazarov, Ingo Horn, Juraj Majzlan, and Stefan Weyer

Antimony is an incompatible chalcophile element. Its concentration in the Earth’s mantle was estimated to ~0.14 μg g-1 Sb [3], while the Sb estimates for the upper continental crust scatter between 0.2 to 0.8 μg g-1 [4]. Recent analytical advances in the precision and accuracy of stable Sb isotope analyses allowed to assess the potential of δ123SbNIST3102a as a proxy for ore forming [1] and oxidation/weathering [2] processes. Application of this proxy, however, is limited by the lack of knowledge of the Sb isotope composition of the Earth and its fractionation during high-temperature cycling.

Here, we present bulk rock Sb isotopic compositions of a range of basic and ultrabasic USGS reference materials (n = 12) from different settings and a suite of basic rocks (n = 3) from Hawaii, aiming to estimate the Sb isotopic composition of the bulk silicate Earth (BSE).  The sample suite shows an isotopic range (all values expressed hereafter as δ123SbNIST3102a) from -0.10 to +0.27 ‰. Two of the fifteen samples display an isotopic composition of > +0.24 ‰ which are, however, marked by low Nb/U, Ce/Pb, and elevated Zr/Nb, indicating crustal contamination in the magmatic source [5]. Excluding these two samples our analyzed sample suite shows an average δ123SbNIST3102a value of +0.01 ± 0.08‰ that we suggest as a preliminary reference value for the Sb isotope composition of the bulk Earth. Our findings furthermore provide first insights for Sb isotope variations in high-temperature rocks that may be related to recycling processes in the mantle.

[1] Zhai et al. (2021), GCA. 3016, 84-97.

[2] Ferrari et al. (2023), Chem. Geol. 641, 121788.

[3] McDonough and Sun (1995), Chem. Geol. 120, 223-253.

[4] Majzlan and Filella (2023), Geochem. In press, 126072.

[5] Hofmann et al. (1986), EPSL. 79(1-2), 33-45.

How to cite: Kaufmann, A., Lazarov, M., Horn, I., Majzlan, J., and Weyer, S.: Antimony isotope composition of the bulk silicate Earth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10027, https://doi.org/10.5194/egusphere-egu24-10027, 2024.

16:45–16:55
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EGU24-10634
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On-site presentation
Joseph Magnall, Yang Liu, Sarah Gleeson, and Alexander Rocholl

The European Kupferschiefer Province contains multiple sediment-hosted stratiform copper (SSC) deposits and has been mined for many centuries. The mineralized rocks of the Kupferschiefer are stratabound and hosted by a stratigraphic succession of Late Permian terrestrial sandstones (Rotliegend Formation) and transgressive marine mudstones and limestones (Zechstein Formation). The formation of the Kupferschiefer deposits has been described by various genetic models, which primarily differ in terms of the timing of ore stage sulfide formation relative to host rock deposition (i.e. syn-genetic vs. epigenetic). In this study, samples from two drill cores in the Spremberg-Graustein Kupferschiefer deposit (eastern Germany) are described. Reflected light and scanning electron microscope (SEM) petrography has been used to determine key paragenetic relationships and in situ sulfur isotope values of pyrite and chalcopyrite (secondary ion mass spectrometry; SIMS) have been generated to determine pathways of sulfide formation. The extensive replacement of carbonate and feldspar by ore stage sulfides provides evidence that hydrothermal activity post-dated the formation of diagenetic phases in all units. The highly negative δ34S values of pyrite (–41.9‰ to –35.7‰) and chalcopyrite (–38.9‰ to –34.5‰) indicate that reduced sulfur was generated via open system organoclastic sulfate reduction (OSR). The indistinguishable δ34Schalcopyrite values preserved in the Rotliegend sandstones and Zechstein mudstones suggest a common origin of sulfides in distinct lithologies. To reconcile the petrographic evidence of host rock replacement with the isotopic evidence of open system sulfate reduction requires an external source of bacteriogenic sulfur, most likely in the form of a low temperature sulfur rich brine. The infiltration of low temperature brines transporting bacteriogenic sulfur is a key feature of genetic models in other sediment hosted systems (e.g., Irish Zn Ore Field). If this model is applied to the Kupferschiefer district, exploration programs should target subbasins with evidence of low temperature brine circulation from marginal sedimentary facies.

How to cite: Magnall, J., Liu, Y., Gleeson, S., and Rocholl, A.: The origin of the Kupferschiefer mineralization (eastern Germany): constraints from petrography and analysis of stable sulfur isotopes of pyrite and chalcopyrite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10634, https://doi.org/10.5194/egusphere-egu24-10634, 2024.

16:55–17:05
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EGU24-11597
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ECS
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On-site presentation
Alon Elhadad, Elisha Bar, Yevgeny Vapnik, Itai Haviv, Andrew Kylander-Clark, Tzahi Golan, and Yaron Katzir

The absence of primary sulfides challenges the interpretation of metal ore genesis, particularly where ore is hosted within several separate stratigraphic horizons. In the Timna Valley, S Israel, copper ore bodies occur mostly in Cambrian and Cretaceous sandstones and rarely in the underlying late Neoproterozoic Timna igneous complex (TIC), as secondary Cu-sulfides in veins and nodules and more abundantly as Cu-hydroxides. The timing and setting of copper mineralization in the TIC and its relation to the sedimentary ore are unknown. Quartz phenocryst-hosted fluid inclusion assemblages (FIA) in quartz porphyry (QP) stock and dykes are associated with sulfide inclusions of pyrite, chalcocite, and chalcopyrite, indicating a magmatic-hydrothermal genetic relationship. Mineralization-associated fluid inclusion assemblages (FIAs) in QP are: (FIA.a) <12 wt% NaCl eq., CO2 vapor-rich arrays with and homogenization temperatures (Ths) of 270­­­­­­­­­­­­–500°C; ­­­­­(FIA.b) immiscible 30–35 wt%. NaCl eq. aqueous liquid and a CO2 vapor-rich fluid trapped at 193–266°C; (FIA.c) secondary H2O liquid-rich arrays (0-11 wt% NaCl eq.), Th of 115–256 ⁰C. Mineralization-associated zircon and rutile in QP yielded U–Pb ages of ~595 Ma, overlapping alkaline felsic dykes in S Israel. Rapid cooling below 220°C is evident by average rutile (U–Th)/He age of 595 ± 46 Ma found in QP and adjacent quartz monzonite and porphyritic granite. Zircon (U–Th)/He ages record Carboniferous heating at 180 ⁰C ≤ T ≤ 220 ⁰C and hydrothermal alteration. This indicates temperatures in the TIC did not exceed ~180 ⁰C after the Carboniferous. Primary copper mineralization in the TIC is attributed to QP emplacement, during A-type granite intrusions, possibly scavenging copper and other metals from earlier calc-alkaline crust. This was followed by lower temperature (<220°C) hydrothermal events.

How to cite: Elhadad, A., Bar, E., Vapnik, Y., Haviv, I., Kylander-Clark, A., Golan, T., and Katzir, Y.: The Setting and Timing of Copper Mineralization in the Timna Igneous Complex, southern Israel., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11597, https://doi.org/10.5194/egusphere-egu24-11597, 2024.

17:05–17:15
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EGU24-15044
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ECS
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On-site presentation
Henri Höytiä, Petri Peltonen, Tapio Halkoaho, Juha Karhu, and Pertti Lamberg

The Paleoproterozoic (c. 2054 Ma) Sakatti Cu-Ni-PGE deposit is one of the most significant metal discoveries in Europe during the 21st century with the resource of 44.4 Mt @ 1.9 wt.% Cu, 0.96 wt.% Ni, 0.05 wt.% Co, 0.64 g/t Pt, 0.49 g/t Pd and 0.33 g/t Au. The deposit lies in the municipality of Sodankylä, northern Finland, that is emerging as a Ni-Cu-PGE mining camp, already including the Kevitsa Ni-Cu-PGE mine (Boliden) and several subeconomic magmatic sulfide deposits. The Sakatti ore mainly consists of massive Ni- and Cu-dominated ore lenses (Cu/Ni < 0.5, Pd/Pt ≈ 4, and Cu/Ni ≈ 9, Pd/Pt ≈ 1, respectively). These massive ore shoots are surrounded by a veil of Cu-rich disseminated sulfides (Cu/Ni ≈ 7, Pd/Pt < 1) hosted by olivine cumulates and coarse-grained gabbronorites. In the upper parts of the deposit, massive ore lenses grade into Cu-rich stockwork vein ore (Cu/Ni > 100, Pd/Pt ≈ 2) that partly sits in olivine cumulates and partly in flanking komatiitic lavas. The sulfide deposit is underlain by tens of meters thick anhydrite-carbonate rock unit that represent a Paleoproterozoic meta-evaporite based on carbon and sulfur isotope values. Sulfate-bearing sediments are a legitimate source of sulfur for magmatic Ni-Cu-PGE deposits, as demonstrated by major Ni-Cu(-PGE) deposits, e.g., Noril‘sk-Talnakh (RUS), Bushveld and Uitkomst Complexes (RSA), Munali in Zambesi belt (ZMB) and Quill Creek Intrusive Complex in Slave Craton (CAN).

The ore and host rocks in Sakatti exhibit chaotic magma-sulfate interaction textures, salt crystal pseudomorphs, and crustal contamination trends that are evident in major and trace element geochemistry as well as in isotope geochemistry. The Sakatti deposit contains typical indicator minerals such as marialitic scapolite, albite, chlorapatite, pargasite and phlogopite-biotite resulting from the interaction of magma with sulfate evaporites and/or saline brines derived after dissolution of evaporites. Sulfur isotope ratio from different ore types is rather uniform (δ34SCDT c. 3-4 ‰) suggesting a mainly non-mantle source for sulfur and isotopically homogeneous sulfide phase, either due to homogeneous source composition or complete mixing of sulfur from multiple sources before its precipitation as sulfide. Assimilation of sulfate and conversion to a sulfide ore is a complex process likely facilitated by a co-existing fluid phase due to the degassing caused by assimilation. Recent melting experiments using Noril’sk picrite and sedimentary rocks have demonstrated how sulfate incorporation into mafic-ultramafic magmas by diffusion does not unequivocally lead to precipitation of sulfides but instead to a sulfate-rich magma, that further requires interaction with a reductant such as carbon-rich sediments, before sulfides may precipitate. Recognizing the role of sulfates in formation of a magmatic sulfide ores is detective work, as pristine sulfate evaporites tend to vanish from the geological record in structurally complex Precambrian metamorphic terrains, leaving only cryptic marks to the mineral deposits, including skarns, Cl-alterations, pseudomorphs, breccias and heat-resistant sulfates (e.g., anhydrite).

How to cite: Höytiä, H., Peltonen, P., Halkoaho, T., Karhu, J., and Lamberg, P.: Role of sedimentary sulfates in the genesis of massive Ni-Cu-PGE deposits - constraints from the Sakatti Cu-Ni-PGE deposit, Northern Finland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15044, https://doi.org/10.5194/egusphere-egu24-15044, 2024.

17:15–17:25
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EGU24-15759
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ECS
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On-site presentation
Judit Mészárosné Turi

The Börzsöny mountain is part of the neogene Inner Carpathian volcanic belt and located in north of Hungary, close to the Central Slovakian Volcanic Field. The andesitic-dioritic rocks of the mountain host ore deposits of a porphyry hydrothermal system, but most of these ore bodies are barely known.

The complex volcanic history of the Börzsöny took place in the middle miocene. According to the K/Ar dating of the host and overlapping volcanic rocks, the ore formation is related to the first, mostly explosive and finally intrusive stage of the volcanic activity (15.2 – 14.8 Ma) (Korpás et. al, 1998). The elevated position of the crystalline basement in the central part of the Börzsöny showed by different geophysical measurements and endomagmatic rock inclusions suggest the presence of a large dioritic intrusive body at a depth of about 2.5 km from the surface (Csillagné Teplánszky et. al., 1980). The ore deposits discovered until now fall on a ring-shaped structure left over from the uplift (Korpás et. al, 1998).

The best investigated part of the ore complex is the central epithermal ore deposit called Rózsabánya. During geological research of two decades, a weak porphyry copper deposit was discovered below Rózsabánya at a depth of about 1.2 km (Csillagné Teplánszky et. al., 1980).

Based on ore petrography and SEM measurements, the multistage paragenesis of Rózsabánya started with the mineralization of arsenopyrite with some cobalt content, native gold and bismuth. This first stage was followed by a Zn-Cu-Pb-Ag-Sn-In mineral association mostly related to galena, sphalerite and chalcopyrite, that could be found as remnants in later minerals in almost all cases. In the third stage, the former minerals were partly consumed by a large amounts of pyrrhotite, which altered to different degrees to pyrite±marcasite. The next stage is characterised by galena, chalcopyrite and sphalerite mineralization, without Sn and In. The mentioned minerals are often replaced by pyrite±marcasite, Bi-sulphides and –sulphosalts, occasionaly arsenopyrite (with some cobalt and nikkel content) and finally by siderite. In some cases, where the alteration of pyrrhotite to pyrite and marcasite was intensive, the mineralization is associated with chloritization.

Based on the observed textures and paragenesis of Rózsabánya, some of the important thermodynamic parameters of the system could be estimated. After the mineralization of a low sulphidation state epithermal mineral assemblage, increasing temperature (around 400 – 450 °C according to the mol fraction of FeS of the pyrrhotite) and/or decreasing sulphur and oxigene fugacity caused the pyrrhotite mineralization. With cooling and elevation of sulphur and oxigene fugacity, the system crossed the pyrrhotite-pyrite reaction line, the sulphidation state of the system changed to intermediate and native gold and bismuth were partly dissolved during this process. While the bismuth re-precipitated as native bismuth, bismuth-sulphide and –sulphosalts (at slightly acidic-neutral pH), gold was carried to longer distances.

The presence of geochemical barriers where gold could be precipitated, the cause of the mentioned changes in the hydrothermal system and the relation of these processes to the deep level and the surrounding epithermal deposits are the subjects of further research.

How to cite: Mészárosné Turi, J.: Geological and geochemical investigation of ore bearing deposits in the Börzsöny mountains, N-Hungary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15759, https://doi.org/10.5194/egusphere-egu24-15759, 2024.

17:25–17:35
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EGU24-19743
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ECS
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On-site presentation
Giulia Consuma, Anthony Kemp, Laure Martin, Brian Tattich, Steffen Hagemann, and Marco Fiorentini

Volatiles, such as H2O, S, Cl and CO2, play a crucial role in regulating volcanic emissions and contribute significantly to the genesis of ore deposits. However, a comprehensive understanding of their role presents a significant challenge due to the intricate task of quantifying the volatile budget and assessing the timeframe linked to magma ascent and volatile exsolution in ore systems.

Apatite, Ca5(PO4)3(F,Cl,OH), stands out as a well-established repository of various volatile species (H2O, CO2, S, halogens) in addition to numerous trace elements, making it an excellent mineral to study the volatile budget of magmas. When encapsulated in zircon, apatite inclusions can preserve a unique record of the abundance of volatile ore-forming constituents, eliminating potential influences from diffusion, degassing, and alteration effects associated with late-stage melts and/or hydrothermal fluids.

Our investigation focuses on thoroughly examining such inclusions, alongside groundmass apatite from the Escondida porphyry Cu-Mo±Au district in Northern Chile, which represents one of the most significant high-grade porphyry copper districts in the world. The ore-forming magmatism of the Escondida district took place in the framework of the protracted late Eocene-Oligocene arc magmatic activity, favouring the emplacement of multiphase porphyry stocks.

To resolve the volatile budget of the melt/fluid responsible for the Cu-Mo±Au mineralization in Escondida, we selected a suit of minimally altered samples from mineralized felsic-intermediate igneous intrusions as well as barren counterparts that are spatially associated with the copper mineralization but do not contain metals in sufficient quantity to be extracted and sold at a profit.

The employed multi-microanalytical approach on apatite (SEM-BSE-CL imaging, EPMA, δ34S by SIMS) and the host zircon (Ti-in-zircon geothermometry, U-Pb geochronology), allowed us to determine:
a) the concentrations of halogens in the melt, which contribute to our understanding of the initial, optimal volatile composition for high-grade copper mineralization; b) the pathway and relative timing of volatile exsolution during the magmatic-hydrothermal stage; c) the hydrothermal volatile record of apatite associated with the mineralization stage.

Our work provides new insights into the role of volatiles in arc magmatic settings, demonstrating their potential in shaping economically viable deposits, a crucial cornerstone for a sustainable and environmentally conscious future.  

 

 

How to cite: Consuma, G., Kemp, A., Martin, L., Tattich, B., Hagemann, S., and Fiorentini, M.: The role of volatiles in forming high-grade porphyry Cu deposits: learnings from apatite inclusions in zircon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19743, https://doi.org/10.5194/egusphere-egu24-19743, 2024.

17:35–17:45
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EGU24-20409
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ECS
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On-site presentation
Xiao-Dong Chen and Bin Chen

Single-stage partial melting modeling of meta-sediments or extreme fractional crystallization is inadequate for producing melts with the required Li content (>5000 ppm) for spodumene saturation. Therefore, multi-stage partial melting or fractional crystallization processes have been simulated to achieve the necessary Li content. However, these modeling approaches have overlooked the phenomenon of liquid immiscibility, which has been widely observed in the formation of spodumene-rich granitic pegmatites through studies of melt/fluid inclusions. In this study, we investigate the contribution of liquid immiscibility to the enrichment of lithium in granitic pegmatites by conducting elemental micro-analysis and melt inclusion Raman mapping on multi-stage apatite (Ap) samples from the Dangba large spodumene pegmatite deposit (NW China). The apatite samples are categorized into magmatic Ap1, transitional Ap2, hydrothermal Ap3a, and Ap3b based on the presence of exclusive melt, coexisting melt/fluid, liquid-rich, and vapor-rich fluid inclusions, respectively. The observed increase in Li content from Ap1 (median 43.4 ppm) to Ap2 (median 92.1 ppm) can be attributed to melt-melt immiscibility and subsequent fluid exsolution, as evidenced by the occurrence of coexisting water-rich/-poor melt and fluid inclusions. Furthermore, the significant surge in Li content from Ap2 to Ap3a (median 364 ppm) may result from fluid-fluid immiscibility, supported by the presence of coexisting liquid- and vapor-rich fluid inclusions, complementary negative (Ap3a) and positive (Ap3b) Eu anomalies in the chondrite-normalized rare earth element (REE) patterns, and the lowest Li contents found in Ap3b (median 12.3 ppm) among all apatite types. Considering the partition coefficients of Ap-melt (DLiAp/melt < 0.05) and Ap-fluid (DLiAp/fluid << 0.05), both the melts and fluids associated with Ap2 and Ap3a contain sufficient Li content for spodumene saturation. In conclusion, our findings highlight the significant role of liquid immiscibility in the extreme enrichment of lithium during the formation of granitic pegmatites.

How to cite: Chen, X.-D. and Chen, B.: Extreme enrichment of lithium in granitic pegmatite by liquid immiscibility, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20409, https://doi.org/10.5194/egusphere-egu24-20409, 2024.

17:45–17:55
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EGU24-16622
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ECS
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Virtual presentation
Francesca Corrado, Germano Solomita, Giuseppina Balassone, Angela Mormone, Barbara Marchesini, Stefano Tavani, Eugenio Carminati, Monica Piochi, and Nicola Mondillo

The Allumiere-Tolfa district is located approximately 60 kilometers northwest of Rome (Italy) and has been characterized by a long mining history for base metals (Pb, Fe), alunite and kaolinite mineralizations dating from prehistoric times (Field & Lombardi, 1972).

These deposits are genetically associated with the emplacement in arc setting of a Plio-Pleistocene volcanic dome consisting of latites and rhyolites, which intruded sedimentary carbonate and siliciclastic country rocks. The intrusive event first produced contact metasomatism of the limestones, and lately triggered hydrothermal activity, which caused a widespread epithermal alteration of the volcanic rocks, resulting in the alteration of the volcanic rocks and emplacement of polymetallic proximal association of Hg-Sb, Pb-Cu, Fe, Zn, Ag, Ba-Sr, F and distal U, Th, Ce, La, Be, Ba, Sr mineralizations (Masi et al., 1980, Della Ventura & Patanè, 2020).

The present work is part of a bigger project investigating various geological features of the Allumiere-Tolfa district (Marchesini et al., 2023) and aims to deepen previous knowledge and investigate in detail the nature of the polymetallic mineralizations of the area. Samples, collected in old pits and outcrops, were analyzed through various techniques: optical microscopy, X-ray diffraction, SEM-EDS analysis, and chemical analysis.

In the area, it was possible to identify distinct alteration facies, residual silica, advanced argillic and argillic facies, with specific ore minerals. The residual silica facies is commonly sulfide-bearing, containing pyrite, As-pyrite, cinnabar, with sphalerite, galena and chalcopyrite. In the advanced argillic facies, pyrite is disseminated in between the aggregates of planar crystals in veins and cavities. Pyrite is also associated with smectite and dickite in the argillic alteration zone. The metasomatized carbonates contain several sulfides such as pyrite and cinnabar with molybdenite, Sr-sulfates, thorutite, thorianite and fluorite. Supergene alteration affected this epithermal assemblage bringing to the formation of gossans with Fe-oxy-hydroxides and secondary sulfides. Preliminary bulk-rock chemical analyses report trace to ultra-trace concentrations of Au.

The identified alteration zones and ore minerals in outcropping rocks indicate low-temperature ore-forming conditions, similar to those occurring in epithermal ores (Simmons et al., 2005), suggesting that possibly the mineralized system extends in depth.

References

Della Ventura G. & Patanè A., 2020. Le miniere dei Monti della Tolfa-Allumiere. Memorie Descrittive Della Carta Geologica D’Italia 106, 23-32.

Field C. & Lombardi G, 1972. Sulfur Isotopic Evidence for the Supergene Origin of Alunite Deposits, Tolfa District, Italy. Mineral. Deposita (Berl.) 7, 113-125.

Marchesini B., Tavani S., Mercuri M., Mondillo N., Pizzati M., Balsamo F., Aldega L., Carminati E., 2023. Structural control on the alteration and fluid flow in the lithocap of the Allumiere-Tolfa epithermal system. Journal of Structural Geology, 105035.

Masi U., Ferrini V., O’Neil J. R. & Batchelder J.N., 1980. Stable Isotope and Fluid Inclusion Studies of Carbonate Deposits from the Tolfa Mountains Mining District (Latium, Central Italy). Minerl. Deposita (Berl.) 15, 351-359.

Simmons S.F., White N.C. & John D.A., 2005. Geological Characteristics of Epithermal Precious and Base Metal Deposits. Economic Geology 100th Anniversary Volume, 485-522.

 

 

How to cite: Corrado, F., Solomita, G., Balassone, G., Mormone, A., Marchesini, B., Tavani, S., Carminati, E., Piochi, M., and Mondillo, N.: The mineralizations of the Allumiere-Tolfa District (Central Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16622, https://doi.org/10.5194/egusphere-egu24-16622, 2024.

Posters on site: Thu, 18 Apr, 10:45–12:30 | Hall X1

Display time: Thu, 18 Apr 08:30–Thu, 18 Apr 12:30
Chairpersons: Matteo Luca Deidda, Katarzyna Derkowska, David Dolejs
X1.145
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EGU24-2161
Nora K. Foley, Robert A. Ayuso, John C. Jackson, Rani Indela, and Damon P. Bickerstaff

Beryllium (Be) is among the most important rare metals in the world and is used to produce complex alloys and ceramics critical for the telecommunication, aerospace, medical, and defense industries. Global Be supplies are primarily obtained from bertrandite [Be4Si2O7(OH)2] mined from the Spor Mountain deposit, Utah, U.S.A, in a region dominated by Miocene-Oligocene alkaline rhyolitic tuffs and lavas. Ore occurs primarily in lithic-rich, phreatomagmatic, base-surge deposits containing carbonate debris in a basal tuff. The tuff is part of a package of rare-metal-rich rhyolite lava flows, pyroclastic deposits, and discordant fluorite-bearing pipes. Pb-Nd-Sr isotope and trace element data, together with mineral associations (1) map the flux of Be, Li, F, REEs, and U in the magmatic-to-hydrothermal system, (2) reveal the role of fluid-rock interactions and recrystallization processes in concentrating metals, and (3) place constraints on timescales of bertrandite-fluorite-opal precipitation. Geochemical models indicate that high-grade ore formed under pH-buffered conditions when F-rich fluids leached metals from glassy tuff, reacted with carbonate xenoliths, and deposited Be and other rare metals in complexly layered nodules composed of Mn-oxide, Li-smectite, calcite, fluorite, opal, and bertrandite. U-Pb age dates and coupled 29-element analyses of discrete opal layers by the SHRIMP-RG method show an almost continuous record of opal deposition. The results establish timescales of high-grade opaline ore formation with major influxes of Be, F, REEs, and Li from ~16 Ma to 10 Ma and of Mn and U at <6 Ma. The interplay of periodic infusions of Be-rich magma, ash, and gas with shallow-circulating, heated fluids led to large-scale remobilization of Be and concentration of high-grade Be ore in the tuff. Fluid-rock interaction and recrystallization had limited effects on other rare elements (Li, REEs) in tuff and rhyolite. These new data shed light on the magnitude of the metallogenic processes and magmatic-to-hydrothermal system required to form a world-class volcanic-hosted beryllium deposit. Additional Be occurrences in Utah, Nevada, New Mexico, and Texas highlight the potential for additional resources of volcanic-related Be and co-product Li-F-REEs in the western United States and globally.

How to cite: Foley, N. K., Ayuso, R. A., Jackson, J. C., Indela, R., and Bickerstaff, D. P.: Volcanic-hosted Be-(Li-F-REEs-U) mineralization at the world-class Spor Mountain deposit, Utah, USA: Insights into source rocks, geochemical signatures, and macro-to-microscale concentration processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2161, https://doi.org/10.5194/egusphere-egu24-2161, 2024.

X1.146
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EGU24-3013
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ECS
Jie Meng and Li-xing Li

High-grade hematite mineralization is widely developed in banded iron formations (BIFs) worldwide. However, in the North China craton where Neoarchean-Paleoproterozoic BIFs are abundant, economic high-grade hematite ores are scarce. High-grade hematite ores hosted in the Paleoproterozoic Yuanjiacun BIFs represent the largest occurrence of this type of ore in the North China craton. It was once viewed that the lack of high-grade hematite ores in the North China was due to the lack of prolonged epigenetic weathering-leaching conditions, but that could not explain the fault-controlled characteristics of high-grade hematite orebodies in Yuanjiacun. On the basis of field contact relationship, petrological and mineralogy analysis, the in-situ U-Pb dating of monazite and xenotime and the fluid inclusion analysis of quartz intergown with hematite was both carried out. The results show that, the timing of high-grade hematite mineralization was at 1.41 to 1.34 Ga, revealing that the deposition of hematite was probably related to tectonic extension in the North China craton related to the breakup of the Columbia/Nuna supercontinent. Petrography and microthermometry of primary fluid inclusion assemblages indicate that the high-grade hematite ore formed from hot (313°–370°C), CO2-rich, and highly saline (about 20 wt % NaCl equiv) hydrothermal fluids. These fluids channeled along faults, which concentrated iron through interaction with the BIFs—a process similar to typical hematite mineralization elsewhere. By comparing to the typical iron deposits worldwide, and combining with the views of the predecessors, we argue that the high-grade hematite ores formed in lower metamorphic-grade BIFs at shallower depths than magnetite mineralization and was largely eroded during later exhumation and uplift of the craton. The determination of ore genesis of the Yuanjiacun high-grade hematite ores  is of theoretical and practical significance to enriching the mineralization process of high-grade iron ores and futher prospecting exploration for high-grade iron ores in the Yuanjiacun area.

How to cite: Meng, J. and Li, L.: Monazite and xenotime U-Pb geochronology constraints on the genesis of the Paleoproterozoic Yuanjiacun banded iron formation-hosted high-grade hematite ores of the North China craton, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3013, https://doi.org/10.5194/egusphere-egu24-3013, 2024.

X1.147
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EGU24-4062
Anoxic Ocean inhibited the formation of porphyry copper deposits
(withdrawn)
Min Sun, Xiangsong Wang, and Guochun Zhao
X1.148
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EGU24-4167
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ECS
|
Ali Erdem Bakkalbaşı, Tolga Oyman, and Ramazan Sarı

The Güneş Ophiolite is located in Eastern Central Anatolia, contains number of mineralization in different types in different settings. Nickel-Cobalt-Copper mineralization are generally in association with large mantle-derived igneous complexes or basic igneous rocks of the ophiolitic sequences. Relatively high Ni, Co and Cu contents in addition of sulphur from different sources prompted to form sulphide minerals as a result of gravity segragation coupled with fractional crystallization. Since the Late Cretaceous Güneş Ophiolite’s Ni-Co-Cu potential had been confirmed, through the drilling of the first exploration hole, further drilling programs were conducted by different companies for several years. Ophiolitic sequence is composed of tectonites (harzburgite and orthopyroxenite), cumulates (clinopyroxenite, olivine gabbro), and their serpentinized equivalents, pegmatitic gabbro, massive gabbro, sheeted dike complex and basaltic lava from bottom to top. Whole sequence is cut by sub-volcanic diabasic intrusion and younger distal dykes which differs in terms of lithology but with similar strucural condition. Dykes in association with mineralization strikes generally ENE-WSW and dips 50 to 60° NW.  Three settings of mineralization were identified; a) mineralization occurs in the contact zone between the dykes and ultramafic host rocks as massive, semi-massive and net textured b) in fractures of the dyke c) veins and fissure-fillings with disseminations in ultramafic host rock. Alteration minerals are represented by phlogopite-biotite in the proximal (potassic) part of the mineralization, amphibole group actinolite, tremolite and chlorite are observed towards the middle parts as a result of uralitization of pyroxenes. The distal parts are represented by albite, epidote, chlorite and serpentine associated with unmineralized ultramafics. Ni values in the rock samples vary between 500-4700 ppm and the Co values range between 50-1050 ppm, in the soil samples these ranges are 250-4500 ppm and 50-700 ppm, respectively. Pyrrhotite (Fe1-xSx), pyrite (FeS2), pentlandite ((Ni,Fe)9S8) and chalcopyrite (CuFeS2) were identified in core samples as representative of  primary ore mineralization stage. Early stage oxide minerals are represented by magnetite (Fe3O4), rutile (TiO2) and ilmenite (FeTiO3). According to field and drill core observations, it is though that nickel-saturated ultramafic rocks of Güneş Ophiolite were cut by diabasic dykes of a sub-volcanic intrusion and younger acidic dykes from different origin. In this situation nickel in ultramafics were leached by diabasic and more acidic apophyses and remobilized along ENE-WSW trending structures and dykes. Based on geological setting and structural evolutution and spatial distribution, we suggest that mineralization is mostly related to acidic dykes at the upper parts, whereas at the lower parts, it is mostly associated with highly altered diabasic dykes. It seems like that the enrichment of the main ore minerals shows direct relationship with the thickness of the enclosed individual dyke and it also reflects proximity to the main body of subvolcanic intrusion, in addition to the nickel saturation rate of the ultramafic rock.

Keywords: Ni-Co deposits, Ophiolites, Ultramafics, Ore petrography, Eastern Central Anatolia, Turkey.

 

How to cite: Bakkalbaşı, A. E., Oyman, T., and Sarı, R.: Geology, mineralogy and geochemistry of ultramafic-mafic hosted Ni-Co mineralization; Gunes Ophiolite (Eastern Central Anatolia, Türkiye), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4167, https://doi.org/10.5194/egusphere-egu24-4167, 2024.

X1.149
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EGU24-5487
|
ECS
Understanding Critical Mineral Enrichment in the Mineralized Al-Ghurayyah Granite Pluton and Associated Pegmatites, NW Saudi Arabia: Insight on Mineral Exploration in the Arabian Shield
(withdrawn)
Faris Sulistyohariyanto, Scott Whattam, Sabyasachi Chattopadhyay, Simone Pilia, Robert Stern, Jieun Seo, and Keewook Yi
X1.150
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EGU24-8552
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ECS
Mohammad Goudarzi, Hassan Zamanian, Urs Klötzli, and Matee Ullah

Boiling is one of the common processes that lead to the formation and enrichment of precious metal deposits. The investigation of the spatial relations between fluid boiling and deposition of precious metals is a valuable tool in exploration of epithermal deposits. Fluid boiling, isothermal mixing and surface dilution of fluids processes are important factors for the instability of chloride and sulphide complexes, which lead to the simultaneous deposition of Fe-Cu and then deposition of sulphide phases in the final stages of mineralization which are caused by a sudden decrease in pressure in the fractures. To investigate evidence of boiling and its role in mineralization we have studied fluid inclusions and quartz textures in the Mamouniyeh Cu deposite in the middle part of Urumieh-Dokhtar magmatic arc in Iran. Evidence for fluid boiling, such as different liquid-vapor ratios of fluid inclusions, the coexistence of fluid inclusions with different salinities and co-existing liquid single-phase fluid inclusions with vapor single-phase fluid inclusions and breccia, crustiform and colloform textures of quartz indicate that boiling process occurred during the formation and growth of minerals. The study of 138 fluid inclusions in ore-bearing silica veins shows the similar density values from 0.8 to 1 g/cm3 for quartz with pyrite + chalcopyrite, chalcopyrite and chalcopyrite + specularite ± pyrite ± chalcocite mineralization systems. Adjacency of multiphase fluids with vapor-rich fluid inclusions indicates that fluids are trapped at the boiling point, that is, in the state where the vapor is in equilibrium with the liquid. As a result of this boiling part of the Cu in the fluids was deposited as chalcopyrite. Evidence shows this process probably occurred at a depth of about 700 meters below the water table and lithostatic pressure of about 16 MPa. In the case study area, boiling, mixing of magmatic fluids with meteoric fluids and cooling process by oxide and sulphide complexes, that this mixing process has reduced the temperature and salinity in the system and caused oxide-sulphide mineralization include chalcopyrite, pyrite, bornite, specularite, and secondary ore minerals include chalcocite, covellite, azurite, malachite, chrysocolla, goethite, and limonite which related to granodiorite, monzonite and gabbro-diorite intrusive rocks.

How to cite: Goudarzi, M., Zamanian, H., Klötzli, U., and Ullah, M.: Evidence of boiling in ore-forming process based on quartz textures and fluid inclusions studies, a case study in Mamouniyeh Cu deposit, Iran, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8552, https://doi.org/10.5194/egusphere-egu24-8552, 2024.

X1.151
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EGU24-9992
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ECS
CRMs prospecting through comparative ore deposit modelling and the case of SW Sardinia
(withdrawn)
Antonio Attardi, Fabrizio Cocco, Matteo Deidda, Lorenzo Sedda, Antonio Funedda, and Stefano Naitza
X1.152
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EGU24-10804
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ECS
Hatice Nur Bayram, Mustafa Kumral, Amr Abdelnasser, Ali Erdem Bakkalbasi, and Mustafa Kaya

The present study focuses on the mineral chemistry data of hydrothermal alteration and sulfide minerals that are related to gold mineralization in the Şirindere area of the Ödemiş-Kirazlı tectonic unit of the Menderes Massif polymetamorphic complex, located in WestTurkiye. The study area contains paragneiss, orthogneiss, and various types of schists (muscovite-, tremolite-, and actinolite-schists) of the Pan-African basement rocks that constitute the central part of the Menderes Massif complex. Additionally, there are Permian garnet-mica schist and marble lenses, as well as Triassic orthogneiss, which are part of the Paleozoic cover series. The Şirindere gold mineralization occurred as gold-bearing quartz carbonate veins hosted within the garnet-mica schist. The veins exhibit boudinage patterns that run parallel to the schistosity direction within the shear zone, which has a N-S orientation, include two types of quartz crystals.The main types of hydrothermal alteration that occurred adjacent to the auriferous quartz-carbonate veins are silicification, chloritization, and sericitization, with subordinate carbonatization alteration types. The ore mineralogy includes pyrite and chalcopyrite associated with free native gold and native copper. The minerals albite, biotite, calcite, chlorite, garnet, sericite, and quartz have been analyzed using an electron microprobe, together with chalcopyrite, pyrite, and gold. According to the EPMA data, the biotite is categorized as magmatic and re-equilibrium Fe-biotite that originated from both crustal and crust-mantle sources within the peraluminous suites. Chlorite is mostly classified as Fe-chlorite (chamosite), which is formed within a temperature range of 249°C to 355°C with an average temperature of 275°C. Sericite has a larger proportion of muscovite (XMs) ranging from 0.89 to 0.96 (average XMs = 0.94), with a phengite content ranging from 0.35% to 1.55%. The EPMA trace element analyses of the pyrite minerals are plotted in the fields of magmatic-hydrothermal and carlin-type gold deposits. This pertains to sulfur derived from juvenile magmatic and/or upper mantle sources with slightly sedimentary origins. Furthermore, these pyrite minerals serve as the primary source of gold, as they include small mineral inclusions like visible gold and chalcopyrite. The pyrite has high amounts of gold, with maximum values reaching 270 ppm. It is hypothesized that the pyrite undergoes longer-term crystallization and co-precipitates with native gold and chalcopyrite. The Şirindere region has been affected by many metamorphic episodes and deformational events caused by various orogenies, including M1, M2, M3, and M6, as well as D3 and D4. During M6, which was represented by the Main Menderes Metamorphism (MMM) that occurred along the Alpine orogeny, it is believed that the gold mineralization in the study area resulted from the metamorphic fluid that formed due to the hydration and decarbonization of volcano-sedimentary rock. This fluid leached gold from the previously formed mafic rock, specifically the tremolite-actinolite schist (metagabbro) in the study area. The gold then migrated upwards along the N-S extensional shear (D3–D4). Hence, the evolution of gold-sulfide mineralization in the Şirindere area may be attributed to the regional metamorphism and deformation caused by the Alpine orogeny, which affected the pre-existing Pan-African basement units.

Keywords: EPMA data, geochemistry, gold-bearing quartz-carbonate veins, Menderes Massif, Şirindere(Aydın,Turkiye)

How to cite: Bayram, H. N., Kumral, M., Abdelnasser, A., Bakkalbasi, A. E., and Kaya, M.: Microchemical analyses of the alteration and sulfide minerals associated with the Şirindere gold mineralization at the Central Menderes Massif, West Turkiye, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10804, https://doi.org/10.5194/egusphere-egu24-10804, 2024.

X1.153
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EGU24-11484
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ECS
|
Botond Géza Gereczi and Gabriella B. Kiss

Though sphalerite is a common mineral in hydrothermal ore mineralization, there are still several open questions in terms of its mineralogical characterization. Many elements may appear in its structure such as Fe, Mn, Cu, Cd, Co, Hg, Ga, Ge, Ag, In, Tl, Se, etc. and some of them may correlate with the formation conditions (e.g., the amount of Fe strongly depends on formation T). For this reason, it is expected that composition of sphalerite my fingerprint the ore deposit type, although, until now only a few attempts were made to investigate this topic. As even technological/critical metals could be enriched in sphalerite (e.g. Co, Ga, Ge, Mn, In, etc.), this topic should be in the spotlight of modern research.

As a contribution to this field, we selected to study sphalerite from volcanogenic massive sulphide (VMS) deposits. Our investigation areas were chosen from the Neothethyan realm: Xylagani from the Hellenides, Greece; Gjegjan from the Dinarides, Albania and Lasail from the Semail Ophiolite, Oman. While Xylagani and Lasail has been identified as Cyprus-type VMS, the classification of Gjegjan ore deposit is uncertain. Our study supports its VMS related origin (more precise classification would need more detailed studies), but its host basalt formed most likely during the Triassic, advanced rifting stage, rather than during the oceanic stage of the Neotethys.

We performed petrographic microscopic, SEM-EDS and EPMA studies on sphalerite-bearing samples, aiming to characterise their texture, their mineral paragenesis, their mineral precipitation series and the mineral chemistry of sphalerite. It has been found that sphalerite mostly precipitated at the early stage of mineralisation, during the upbuild of the hydrothermal system, though at some places it also formed as a late product, during the waning of the system. Early sphalerite often suffered “chalcopyrite disease”, caused most likely by later Cu-rich fluid impulses. All studied sphalerite precipitated from a 238 °C to app. 60 °C warm fluid, characterised by an intermediate sulphidation state (logfS2). We identified chemical anomalies in sphalerite, like Co in Lasail (up to 1230 ppm in massive suphide lens) and Ga in Gjegjan (up to 840 ppm in distal part of the mineralization). Fe (1,039–3,973 wt.%), Cd (950–3220 ppm), Mn (b.d.l.–2680 ppm) and Pb (b.d.l.–1260 ppm) was also presented in all samples and good correlations (R2 > 0,64) were found between Fe–Zn, Cu–Zn, Fe/Cd–Zn and Fe/S–Zn.  Extreme Co enrichment of sphalerite could have been caused by a sudden change in the fugacity of S2 and/or O2 in the massive sulphide lens, while high Ga content favours low temperature conditions and may be accompanied by Ge anomaly as well. The identified Co and Ga anomalies not only may represent a new source of extractable raw materials for the investigated ore deposits, but understanding the reasons for enrichment of these critical raw materials can help to make mining more economical when exploring other similar ore deposits.

How to cite: Gereczi, B. G. and B. Kiss, G.: Mineral chemistry of sphalerite from volcanogenic massive sulphide deposits: genetical implications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11484, https://doi.org/10.5194/egusphere-egu24-11484, 2024.

X1.154
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EGU24-13247
Christiane Wagner, Omar Boudouma, Nicolas Rividi, Beate Orberger, Ghassem Nabatian, and Maryam Honarmand

Magnetite is common in various iron ore deposits including BIF, Fe-skarn, IOGC (iron oxide-copper-gold), IOA (iron oxide-apatite) and porphyry Cu-Au deposits. Magnetite incorporates a number of trace elements in tetrahedral and octahedral site in its structure. Its trace element composition has been used in numerous studies to fingerprint deposit type and ore genesis and to provide a guide for mineral exploration, based on a series of discriminant diagrams (e.g. [1]). However, the applicability of such diagrams must be carefully evaluated as the composition of magnetite can be modified by various processes. In this study we present textural and compositional data for magnetite from a late Ediacaran BIF in NW Iran[2] to illustrate complex re-equilibration processes.

Three stages of magnetite (Mt) has been identified. Mt1 forms large (≤1 mm) inhomogeneous dark grey grains surrounded and locally invaded by a light grey porous Mt2. The Mt1/Mt2 boundary is irregular and sharp, consistent with replacement textures. Bright Mt3 forms needle-like bands (10-80 µm width) aligned along fracturing planes. Mt3 contains rare hematite relicts and is porous in close proximity to hematite.

Mt1 shows a variable trace element composition and contains the highest Si (average 1.14 wt.%), Al and Ca (0.28 wt.%), Mg (0.13 wt.%) and the lowest Fe (68 wt.%) contents. Both Mt2 and Mt3 show a restricted range of composition. Mt2 has lower Si (0.68 wt.%), Al (0.14 wt.%), Ca (0.15 wt.%) and Mg (0.08 wt.%) contents, while Mt3 is characterized by the lowest Si (0.16 wt.%), Al and Ca (0.05 wt.%) and Mg (0.01 wt.%) and the highest Fe (71.1 wt%) contents. The three magnetite have low Mn (≤0.03 wt.%), and Ti (≤0.02 wt.%), and Ni and Cr are mostly below the detection limit.

The silician dark Mt1 magnetite likely forms in a rather reduced Si-rich environment. The presence of structural silicon is supported by correlations / antithetic correlations with R2+/R3+ cations and the lack of inclusions. The incorporation of Si may cause lattice defects or deformation facilitating fluid alteration. A fluid-assisted coupled dissolution of Mt1 and precipitation of Mt2 (CDR process) is supported by close spatial relationship, sharp compositional boundaries, similar crystallographic structure of MT1 and Mt2 and abundant porosity in Mt2. The increase in porosity promotes the infiltration of hydrothermal fluids and further advances the CDR process. By removing trace elements from the early Mt1 this process increases the iron grade of Mt2.

Micro-fracturing allows the penetration of a more oxidized fluid along cleavage planes and formation of needle-like bands of hematite. Then porous mushketovite Mt3 formed after hematite under a more reduced fluid composition by a redox transformation supported by the volume decrease.

All these processes significantly modified the texture and composition of the magnetite and point to a predominant imprint of hydrothermal fluid, thus causing difficulties in using magnetite as a genetic indicator.

 [1] Dupuy and Beaudoin, 2011; [2] Honarmand et al, in press.

How to cite: Wagner, C., Boudouma, O., Rividi, N., Orberger, B., Nabatian, G., and Honarmand, M.:  Re-equilibration processes in magnetite from an Iranian BIF deposit., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13247, https://doi.org/10.5194/egusphere-egu24-13247, 2024.

X1.155
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EGU24-514
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ECS
Reeya Ghosh and Manoj Kumar Ozha

Kiruna-type Fe-oxide-apatite (IOA) mineralization is a potential source of phosphorous, iron rare earth elements (REEs), and other elements (Ag, Cr, Co, and U) of economic importance. In such deposits, textures associated with ore minerals provide important insights that can aid in characterizing the primary/secondary phases vis-à-vis the process of mineralization. Accordingly, apatite-magnetite veins (associated with calcite-bearing ultramafic rocks) from the Beldih area (South Purulia Shear Zone) of Eastern India were studied to appraise the formation of Fe-oxides and sulfide minerals hosted within these rocks. The present work integrates preliminary Petrological studies (both under microscope and Backscattered electron: BSE imaging) to comprehend the texture/s of Fe-Ti oxides and associated sulfides. The major/dominant phases in the samples comprise magnetite and ilmenite (among the Fe-Ti oxides) and pyrrhotite, pyrite, chalcopyrite, sphalerite, cobaltite, and gersdorffite (as sulfide phases). These rocks in the study area preserve varied textural assemblages/associations of magnetite: (a) Magnetite (Mag1) in the samples is coarse-grained with euhedral/polygonal grain boundaries, in which larger grains preserve two different sets of fine lamellae of ilmenite (in addition to individual grains) exhibiting both Trellis intergrowth and Widmanstatten texture; and (b) medium-sized, discrete grains of magnetite (Mag2) and ilmenite at the boundary of large pyrrhotite grains (associated with pyrite and chalcopyrite). Both these textural types include euhedral grains of apatite embedded on clusters of calcite, associated with minor REEs (allanite and monazite) and silicate phases (amphibole, biotite, muscovite, and titanite). Pyrite grains (exhibiting sharp boundary) in the rock are found both as inclusions and at the grain boundary of large (anhedral) pyrrhotite grains, indicating possible alteration of pyrite to form pyrrhotite. Inclusions of gersdorffite are also seen within a few pyrrhotite grains. Thus, from the afore-discussed textural assemblage of magnetite (Mag1), it stands to reason that high-fO2 environment prevailed during its formation and the possible difference of pressure in the solid solution between magnetite and ilmenite. The formation of Fe-oxides, calcite, apatite, and silicates is consistent with the primary crystallization of these minerals possibly from a silicate melt (by liquid immiscibility process) or from a high-T magmatic-hydrothermal fluid. Subsequently, the formation of secondary discrete magnetite (Mag2) and associated ilmenite grains (in addition to various sulfide phases), indicates possible ingress of a hydrothermal fluid into the system.

How to cite: Ghosh, R. and Kumar Ozha, M.: Textural studies of Magnetite from the rocks of Beldih, Purulia, West Bengal , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-514, https://doi.org/10.5194/egusphere-egu24-514, 2024.

X1.156
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EGU24-19401
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ECS
Katarzyna Derkowska, Piotr Wojtulek, Marina Lazarov, Jakub Kierczak, Jakub Ciążela, and Paweł Derkowski

The Fore-Sudetic Monocline, stretching from southwestern Poland to central Germany, hosts significant sediment-hosted copper deposits associated with the Kupferschiefer formation. While the Kupferschiefer generally displays dispersed mineralization in sandstone, black shale, and dolomite layers, massive mineralization is rare but noteworthy. Our investigation focuses on the Lubin district and aims to enhance understanding of the formation of massive sulfide veins and their setting in the complex stages of Kupferschiefer development.

Four mineralogically distinct types: chalcopyrite-pyrite, chalcopyrite-galena, galena, and chalcocite veins are identified. Each forms complex structures with mineralogical overgrowths, replacements and minor occurrences of bornite, pyrite, sphalerite, tennantite, and tetrahedrite. The diversity extends to geochemistry, with observed variations in bulk trace element concentrations, where strong Hg, Co, and Mo enrichment in the chalcopyrite-galena zone (3500-7000 ppm, >2000 ppm, 25-50 ppm, respectively), Zn, Hg, and Cd in the galena zone (3-5 wt%, 0.5-1.5 wt%, 90-210 ppm, respectively), and Re in the chalcocite zone (200-1000 ppm) is observed. Chalcocite and galena veins show significantly stronger REE depletion, compared to the chalcopyrite-dominated ones. Finally, differences in Cu, As (pyrite), Pb, Ag, Co, Ga (pyrite and chalcopyrite), Zn (chalcopyrite), and Co (galena) concentrations are noted within the minerals from different mineralogical zones.

The complex mineralogy of the veins exhibits isotope variations based on in-situ Cu isotope analyses. The δ65Cu in chalcopyrite, chalcocite, and bornite (chalcopyrite-pyrite and chalcocite veins) spans from approximately -1‰ to +~0.5‰, with lower δ65Cu in chalcopyrite compared to other minerals within a sample. This data suggests complex chalcopyrite formation and its subsequent alteration, mostly to secondary bornite. Relatively small differences between minerals within the sample result from the isotopic equilibration with the ambient fluid responsible for the vein’s origin. However, the disparity between various samples in their Cu isotope composition indicates differences in the ambient fluid origin, i.e. possible time-related separation in veins formation or the isotope fractionation process that took place after sulfides precipitation process.

The study was funded by the National Science Centre grant to KD (2019/35/N/ST10/04524).

How to cite: Derkowska, K., Wojtulek, P., Lazarov, M., Kierczak, J., Ciążela, J., and Derkowski, P.: Origin and geochemical variability of massive sulfide veins in the Permian Kupferschiefer Formation: insights from the Fore-Sudetic Monocline, Poland , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19401, https://doi.org/10.5194/egusphere-egu24-19401, 2024.

X1.157
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EGU24-20021
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ECS
Carla Carvalho, Iuliu Bobos, and Fernando Noronha

The Abraveses massif consists of a syn- to late-D3 two-mica granite which crops out along the core of the NW-SE-trending Porto-Viseu D3 antiform. Multiple W-Sn mineralizations are spatially associated with this granitic massif. From a geochemical standpoint, the Abraveses granite is characterized by a strongly peraluminous signature (A/CNK = 1.25 - 1.51), suggesting it was produced by partial melting of a metasedimentary protolith in mid crustal levels (S-type affinity). The low CaO/Na2O ratio (0.1 - 0.2) and high Rb/Sr (12.2 - 18.5) and Rb/Ba (3.4 - 5.3) ratios indicate that the respective magma was derived from a metapelitic (plagioclase-poor) protolith. The granitic samples present low REE contents (ΣREE = 69.19 - 91.33 ppm). The respective chondrite-normalized pattern is moderately fractionated, showing a relative enrichment in LREE (LaN/YbN = 9.02 - 10.86) and a negative Eu anomaly (Eu/Eu* = 0.32 - 0.39). The LREE fractionation is higher compared to the HREE fractionation (LaN/SmN = 2.75 - 3.30; GdN/YbN = 1.82 - 2.17). The UCC-normalized spidergram shows a strong enrichment in Rb, Cs, U and Ta. A significant depletion in Ba, Sr and Ti is also observed. These geochemical features are consistent with the presence of biotite in the crustal source. The strong ore-forming potential of the Abraveses granite is confirmed by its remarkable enrichment in Sn (51 - 106 ppm), W (4 - 17.8 ppm) and ore-transporting volatiles such as F and B. Specialized peraluminous granites from northern and central Portugal typically contain Sn and W concentrations close to those obtained in our study.

How to cite: Carvalho, C., Bobos, I., and Noronha, F.: Petrogenetic constraints of the W-Sn-bearing Abraveses granite (Viseu, Central Portugal), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20021, https://doi.org/10.5194/egusphere-egu24-20021, 2024.

Posters virtual: Thu, 18 Apr, 14:00–15:45 | vHall X1

Display time: Thu, 18 Apr 08:30–Thu, 18 Apr 18:00
Chairpersons: David Dolejs, Katarzyna Derkowska, Matteo Luca Deidda
vX1.17
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EGU24-2550
Nimet Coskun, Bala Ekinci Sans, and Fahri Esenli

One of the important Neogene basins of Western Anatolia (Turkey) is the NE-SW trending Demirci Basin. The Miocene sequence, consisting of approximately 1000 m thick clastics and volcanics, is unconformably located on the Paleozoic-Menderes Metamorphic Massif (gneiss, schist, marble). The lower part of Miocene sequence contains block–pebble–sand size of clastics. They are continued upward with sandstone, claystone, marl, limestone, mudstone, and shale lithologies laterally transition with pyroclastic rocks at the top. Pyroclastic rocks (Akdere Tuff) are covered by a lacustrine unit consisted of sandstone, mudstone, bituminous shale limestone and tuffite. Akdere tuff, with rhyodacite character, light beige-gray-green color, 10-70 m thickness, is highly zeolitized (heulandite-clinoptilolite). At the bottom of the tuff unit, there are 25-30 m thick, fine-coarse grained, pumiceous, glassy, and glassy-crystalline ash tuffs containing rare lithic fragments. These are overlain by 20-25 m thick glassy dust-ash tuffs. At the top there is a 5 m thick pumicite level with lateral transitions. Zeolitic Akdere tuff petrographically contains small and rare amounts of mineral and lithic fragments in a matrix consisting of glass fragments with concave, sharp straight or curvilinear edges and rarely pumice fragments. Mineral fragments (2-25 %) are feldspars (albite-oligoclase type of plagioclases and K-feldspar) quartz, biotite, muscovite, amphibole, and opaque minerals. According to the X-ray diffraction (XRD) results, the mineralogical composition throughout the samples is 'heulandite-clinoptilolite (hul-cpt) + opal-CT + opal-A + smectite + illite-mica + quartz + feldspar’. The heulandite-clinoptilolite ratio in the samples examined varies between 0-95 percent. The glassy groundmass of the tuffs is almost completely zeolitized. Heulandite-clinoptilolite grains, formed by the transformation of volcanic glass, are in the form of monoclinic plates, shorter than 15 µm according to the results obtained from scanning electrone microscope (SEM) studies. SEM studies also showed that devitrification of volcanic glass formed firstly a gel-like phase before the formation of heulandites-clinoptilolites. Cationic values ​​(Si/Al and Na+K/Ca+Mg ratios) taken from heulandite-clinoptilolite grains by Energy dispersive X-ray spectroscopy (SEM-EDX) gave the composition of both heulandite and clinoptilolite. However, thermal stability results indicated clinoptilolite, and clinoptilolite did not deteriorate at 550 oC. Whole-rock chemical values ​​and some chemical parameters of the zeolitic Akdere Tuff are as follows. SiO2: 68.45-76.50 %, Al2O3: 10.10-14.30 %, SİO2/Al2O3: 4.82-7.19, K2O: 1.34-4.46 %, Na2O: 0.13-2.92 %, CaO: 0.70-2.92 %, MgO: 0.59-4.85 %, Fe2O3: 0.68-1.82 % and (Na2O+K2O)/(CaO+MgO): 0.33-5.63. The chemical composition of zeolitized tuffs in the Demirci region is a function of selectivity of zeolite minerals additionally to the primary composition of the volcanism. Tuff samples containing high amounts of hul/cpt have higher values ​​for CaO, H2O, and most trace elements and REEs than the samples containing little or no zeolite.

 

Key words: Clinoptilolite, Demirci, Geochemistry, Turkey, Zeolitization.

 

How to cite: Coskun, N., Ekinci Sans, B., and Esenli, F.: Petrographical And Geochemical Characteristics of The Zeolitic Akdere Tuff (Demirci, Western Anatolia), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2550, https://doi.org/10.5194/egusphere-egu24-2550, 2024.

vX1.18
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EGU24-7622
Vivek Prakash Malviya, Harel Thomas, Sanjeet Kumar Verma, Mahendra Shukla, Muduru Lachhana Dora, and Alok Kumar

The depositional environment of the Banded Iron Formations (BIFs) is highly controversial. The BIFs are type of chemical precipitates characterized by presence of alternating layers of iron and silica-rich. Paleo-Mesoarchean BIFs of the Central Bundelkhand Greenstone Belt (Babina-Mauranipur-Mahoba) occur along with the E–W trending of the Bundelkhand Tectonic Zone (BTZ) gives us opportunity to study the depositional environment during Archean Eon. The lithological association of BIFs in the Babina and Mauranipur areas consists of pillowed basic–ultrabasic volcanics and metasediments whereas the Mahoba´s BIFs and quartzite occur within basic volcanics. The bulk geochemical composition of BIFs shows the high content of FeOt with an average of 51.57 wt. %. The Babina´s BIFs show relatively lower concentration of V, Cr and Co in comparison to the Mauranipur and Mahoba. The significant negative Ce anomaly implies the signature of a deep marine source of the Bundelkhand BIFs. The samples from Babina show less Y/Ho ratios, along with lack of relativelyhigh Zr, Th, and Hf suggest that terrestrial material input was insignificantor very less during BIFs precipitation. Most of the BIFs from the Mauranipur and Mahoba show intermediate Y/Ho ratio suggesting chemical precipitation of BIFs from a mixture of seawater and high-temperature hydrothermal fluids generated from a back-arc spreading centre. The geochemical characteristics indicate that these BIFs are formed by volcanogenic hydrothermal activity in aback-arc tectonic setting. The Rare Earth Elements (REE) patterns suggest the role of high-T hydrothermal fluid for the deposition of BIFs in the Babina and Mauranipur greenstone belts whereas low-T hydrothermal fluid is responsible for the Mahoba greenstone belt deposition. Their geochemical variation also suggests the shallowing of the proto-basin from the Babina (west) to Mahoba (east).

How to cite: Malviya, V. P., Thomas, H., Verma, S. K., Shukla, M., Dora, M. L., and Kumar, A.: Geochemistry of Banded Iron Formations (BIFs) from the Central Bundelkhand Craton, India: Implication for depositional setting, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7622, https://doi.org/10.5194/egusphere-egu24-7622, 2024.

vX1.19
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EGU24-4292
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ECS
Manju Sati, Rajagopal Krishnamurthi, and Sakthi Saravanan Chinnasamy

Paramanahalli gold prospect lies in the Chitrdurga greenstone belt, India; the mineralization found in altered rocks characterized by the mineral assemblage of chamosite (Fe-rich chlorite) + annite (Fe-biotite) + ankerite + quartz + pyrite + gold ± chalcopyrite ± pyrrhotite ± magnetite. Strain fringes are developed with the pyrite and magnetite of the Banded Iron Formation and phyllite of the study area. Strain fringes are indicators of the low-pressure zones parallel to the least compressive stress. These features are massive and monomineralic adjacent to a rigid object (pyrite, magnetite) and are usually composed of a different material than the rigid object. Pyrite and magnetite are euhedral in shape and medium-coarse-grained (20-80 µm) in size. Fringes contain information on flow and style of deformation in their internal and external shape and are helpful kinematic indicators in the mineralized zone. The Hiriyur Formation rocks metamorphosed up to greenschist facies that can retain the pre-deformed shapes. This study illustrates the variety of strain fringes, studied in detail to understand deformation patterns and gold-sulfide mineralization in the research area. Fringe-1 is face-controlled, uneven, made up of fibrous quartz, and associated with rigid magnetite. The uneven nature of extended fringes infers simple shear. Fringe-2 is a face-controlled, variable extended fiber made up of quartz. Fringe-3 is a displacement-controlled fringe consisting of quartz that is similar on both sides and shows typical wing-type features. These stain fringes indicate a sense of rotation after the hydrothermal fluid precipitates ore minerals (pyrite/ magnetite). The presence of strain fringes with pyrite (± gold) infers the remobilization and recrystallization of sulfides during/after a deformation event at Paramanahalli prospect, Karnataka. The current work points toward a strong link between the development of microstructures and ore formation. Based on petrological and microstructural evidence, it is proposed that there was a syn-ore formation / main mineralization event responsible for the precipitation of sulfides, later affected with deformation that leads to the formation of such features.

How to cite: Sati, M., Krishnamurthi, R., and Chinnasamy, S. S.: Strain fringes in Hiriyur Formation of rocks, Chitradurga greenstone belt, Karnataka: Implications with ore formation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4292, https://doi.org/10.5194/egusphere-egu24-4292, 2024.