The metamorphic rocks from the Pohorje Mountains represent parts of the Austroalpine metamorphic units of the Eastern Alps, which are thought to experience the peak P-T in the ultrahigh-pressure zone during the Cretaceous orogeny, mainly near to or in the diamond stability field (Vrabec et al., 2012; Janák et al., 2015 and references therein). Gneisses are the most common occurring lithologies. They host garnet porphyroblasts, which contain numerous fluid and solid inclusions, among which diamonds have also been identified. To better understand their precipitation from COH fluids, thermodynamic modelling was performed and to elucidate the structure of diamond-bearing inclusions, they were investigated at the atomic scale using a plethora of TEM techniques.

The C-O-H fluid system undergoes evolution during metamorphism as a result of variations in pressure and temperature. The saturation of the C-O-H fluid with carbon depends on the P-T-fO₂ conditions. Carbon saturation of the C-O-H fluid can be represented with carbon saturation isopleths. Assuming that the fluids, trapped in the metapelitic rock share common P-T path, the relationship between the carbon saturation isopleths and the P-T path is essential.

P-T diagrams were calculated at various logfO₂ values to determine the threshold at which the system's behaviour changes. The modelling revealed that it is highly sensitive to the change of fO₂. Due to the shape of the P-T path of metapelite, graphite precipitates in all cases up to approximately 700 °C and 2.5 GPa, where the P-T path changes its slope. Up to the fO₂ value of QFM –1.5, the P-T path is parallel to the isopleths; therefore, the carbon doesn’t precipitate. When the fluid is more reduced, reaching QFM –1.6, the P-T path intersects the isopleths throughout its range. If the C-O-H fluid is even more reduced, the P-T path crosses more isopleths, resulting in even more abrupt precipitation of carbon. This means that ~ QFM –1.6 was the maximum fO₂  value at which the diamonds from the Pohorje metapelites could have precipitated.

The behaviour of the COH fluids predicts dissolution of the diamonds during the retrograde metamorphism, which didn’t occur. TEM analysis of the diamond-bearing inclusion revealed the presence of an amorphous phase, which enclosed the diamonds and prevented dissolution processes. Furthermore, the amorphous phase influenced the internal structure of the diamonds, which precipitated after the amorphous solid. Electron diffraction and high-resolution TEM showed that some diamonds are polycrystalline, composed of numerous nanocrystallites. The crystallisation of metamorphic diamonds suggests complex dynamics within the microsized system, which was partially revealed by our study. However, further studies are needed to draw more precise conclusions.

Janák, M., Froitzheim, N., Yoshida, K., Sasinková, V., Nosko, M., Kobayashi, T., Hirajima, T. & Vrabec, M. Diamond in metasedimentary crustal rocks from Pohorje, Eastern Alps: A window to deep continental subduction. J. Metamorph. Geol. 33, 495–512 (2015).

Vrabec, M., Janák, M., Froitzheim, N. & De Hoog, J. C. M. Phase relations during peak metamorphism and decompression of the UHP kyanite eclogites, Pohorje Mountains (Eastern Alps, Slovenia). Lithos 144, 40–55 (2012).

How to cite: Sotelšek, T., Janák, M., Semsari Parapari, S., Šturm, S., and Vrabec, M.: Diamond precipitation from COH fluids: a case study from Pohorje, Eastern Alps, Slovenia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5255, https://doi.org/10.5194/egusphere-egu25-5255, 2025.

Subduction is an efficient process that allows the transfer of elements and interaction between the crust and the mantle. During subduction elements concentrated in the crust, such as volatiles (e.g., H₂O, CO₂, Cl, F, S and N₂) and other incompatible elements, can be released in melts and fluids that then interact with the overlying mantle. The most direct way to investigate crust-mantle interaction is to target melts and fluids responsible for the elements transfer. In this contribution, we report the occurrence of micrometric volatiles-bearing fluid inclusions in clinopyroxene and garnet of a mantle body in Góry Sowie (SW Poland).

In Góry Sowie, migmatitic gneisses with subordinate granulites host bodies of garnet peridotites and metabasites (Kryza and Pin, 2002). The garnet clinopyroxenite hosting the inclusions is associated with other ultramafic rocks and it mainly contains garnet, clinopyroxene, amphibole, and locally orthopyroxene porphyroblasts in a fine-grained matrix.

The inclusions in clinopyroxene are randomly distributed in the inner part of the crystal, thus they are primary, and they were trapped while the host was growing in the presence of a fluid phase. The main phase assemblage in the inclusions was determined with micro-Raman spectroscopy and it includes two carbonates (dolomite and calcite), N₂, cristobalite, CH_4, and pyrophyllite. In garnet, the inclusions are primary/pseudosecondary (i.e., distributed along fractures occurring during garnet growth) and they contain CO₂, dolomite, pyrophyllite, N_2, and CH₄. The presence of carbonates, OH-bearing phases, and N₂ suggests that the trapped fluid is COHN; hence the garnet clinopyroxenite formed in the presence of such fluid.

Further studies will allow us to better constrain the nature of the fluid and quantify the concentration of carbon in the different C-bearing phases and N₂. COH(N) fluids in subduction zones can interact with the mantle metasomatizing it and our data will help to better constrain their importance for volatiles mobilization and transfer to the mantle during subduction.

This research is part of the project No. 2021/43/P/ST10/03202 co-funded by the National Science Centre of Poland and the European Union Framework Programme for Research and Innovation Horizon 2020 under the Marie Skłodowska-Curie grant agreement No. 945339.

Kryza and Pin (2002). Mafic rocks in a deep-crustal segment of the Variscides (the Góry Sowie, SW Poland): evidence for crustal contamination in an extensional setting. Int J Earth Sci (Geol Rundsch), 91, 1017-1029.

How to cite: Borghini, A., Majka, J., Walczak, K., and Włodek, A.: COHN fluid inclusions in garnet clinopyroxenite of Góry Sowie (SW Poland), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18537, https://doi.org/10.5194/egusphere-egu25-18537, 2025.

Carbon represents an essential element for the origin and evolution of life and profoundly contributes to the well-being and sustainability of our planet. Over recent years, understanding carbon cycling on a global scale has become a central objective within the Earth science community, and the study of subduction zone fluids has become a crucial topic, as this geological setting represents the primary carbon input into the mantle. At subsolidus conditions, carbon transfer is mediated by mineral dissolution, triggered by aqueous fluids released from the subducting slab. While carbonate solubility has been extensively investigated, the contribution of reduced carbon forms, such as graphite and amorphous carbon, has been only recently taken into consideration, and their role in the deep carbon cycle is still unconstrained. Several issues remain open, especially whether carbon-rich fluids, generated from reduced carbon dissolution, can be transferred across oxidized conditions in the subduction mélange and eventually reach the mantle wedge.

Here we present in-situ results on the solubility of glass-like carbon, considered a proxy for disordered subducted organic material, in aqueous fluids and in equilibrium with quartz at pressures up to 2 GPa and 800 °C. Experiments were conducted in Hydrothermal Diamond Anvil Cells¹, employing Rhenium gaskets to ensure oxidized conditions² and mimic fluids released by dehydrating slabs in fore to back-arc settings. The solubility in aqueous fluids of glass-like carbon and quartz was determined by in-situ observations of the complete dissolution of samples, while the speciation of the fluids was monitored by Raman spectroscopy. Our results constrain the mutual solubility of carbon and silica in natural slab fluids and provide new constraints for the transfer of carbon operated by aqueous fluids.

[1] Bassett W.A., Shen A.H., Bucknum M. & Chou I.M. Rev. Sci. Instrum. 64, 2340–2345 (1993)

[2] Foustoukos D.I. & Mysen B.O. Am. Mineral. 100, 35–46 (2015)

How to cite: Tiraboschi, C. and Sanchez-Valle, C.: Carbon transfer by slab-fluids: in-situ experimental constraints, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10872, https://doi.org/10.5194/egusphere-egu25-10872, 2025.

In the models of the geological carbon cycle, the contribution from crustal magmas is generally overlooked. However, organic matter that has been transformed to graphite through metamorphism could represent an important source of carbon in the lower crust, which can be re-mobilized during partial melting (Cesare et al., 2005). A COH fluid produced solely by dehydration in the presence of graphite will retain the H/O ratio of H₂O (H/O = 2) and thus maximize the H₂O activity and form of a ternary H₂O-CO₂-CH₄ mixture (Connolly and Cesare, 1993). Previous solubility studies have mainly considered oxidizing conditions (H/O < 2) and cannot be used to interpret graphitic systems, in which conditions are more reducing (Carvalho et al., 2023). Therefore, it is essential to obtain new solubility data for graphite-saturated silicate melt coexisting with a ternary H₂O-CO₂-CH₄ fluid.

In this study, solubility experiments were carried out in a single-stage piston cylinder apparatus at 5 to 10 kbar and in a temperature range of 800-1000°C. To simulate an anatectic melt formed in the mid to lower metasedimentary crust, a haplogranitic glass was synthesized, and the experimental charge was loaded with graphite and H₂O as the source for the COH fluid. To buffer the fluid composition at the condition H/O = 2 during the run, the double-capsule technique was utilized, and graphite and H₂O was added in the outer capsule. The speciation of the experimental fluid was analyzed ex-situ by a capsule-piercing quadrupole mass spectrometer (Tiraboschi et al., 2016). In all experiments H₂O was the major fluid component, in accordance with thermodynamic predictions, followed by variable amounts of CO₂ and CH₄. The relative amount of H₂O to carbonic species in the fluid changes with pressure and temperature, and the experiments cover a range of XH₂O_fluid = 0.67-0.99.

The experimental glasses contain bubbles which have been analyzed by micro-Raman spectroscopy, revealing that they mainly consist of pure CH₄ or binary CH₄-CO₂ mixtures and graphite. The H₂O content of the glasses have been determined by micro attenuated total reflectance Fourier transform infrared spectroscopy. Dissolved H₂O generally increases with pressure, and there is no visible temperature dependence. To quantify the total carbon (CO₂) content of the glasses, secondary ion mass spectrometry will be used. The new solubility data for carbon will complement the existing experimental dataset to allow better interpretation of complex systems where graphite, melts and fluids are present.

References:

Carvalho et al. (2023) Chem Geol 631

Cesare et al. (2005) Contrib Mineral Petrol 149, 129-240

Connolly, J.A.D. & Cesare, B. (1993) J Metamorph Geol 11, 379-388

Tiraboschi et al. (2016) Geofluids 16, 841-855

How to cite: Krona, M., Tumiati, S., Toffolo, L., Bartoli, O., Carvalho, B. B., Sorger, D., Dingwell, D. B., and Cesare, B.: Solubility of CO2 and H2O in graphite-saturated haplogranitic melt, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12413, https://doi.org/10.5194/egusphere-egu25-12413, 2025.

Phlogopite (nominally ^AK^MMg₃^T(AlSi₃)O₁₀^X(OH)₂) is the magnesian trioctahedral endmember of the biotite solid-solution series. This phyllosilicate can accommodate substantial amounts of fluorine, usually up to 5 weight percent (wt%) and up to 8.7 wt% in extreme cases (Gianfagna et al., 2007), which substitutes for hydroxyl (OH) groups at the anionic site. Given that phlogopite is a commonly found hydrous silicate, acting as an important F reservoir in ultramafic and ultrapotassic upper mantle lithologies and an accessory mineral in various igneous and metamorphic rocks, it can contribute to the Earth’s volatile cycles. Therefore, the deeper understanding of the temperature-induced phlogopite breakdown into pyrope and forsterite (Trønnes, 2002) and the role of F in the crystal structure of fluorophlogopite during its structural collapse can provide valuable information in several Earth’s dynamic systems. For instance, in metasomatic processes in the peridotitic mantle wedge of subduction zones, mineral stability at upper mantle conditions, and complex volcanic systems. Additionally, the high-temperature atomic dynamics of complex hydrous silicates containing Fe²⁺, characterized by considerable structural anisotropy, as studied by Raman spectroscopy, can offer valuable information about the thermal activation of charge carriers (delocalized H⁺ and e^-), thus about lithosphere conductivity anomalies (Bernardini et al., 2023).

This study focuses on the temperature-induced changes in the local structure and atomic vibrations of Fe²⁺-containing fluorophlogopite. For this purpose, a fluorophlogopite sample from Cardiff, Ontario in Canada was subjected to in situ Raman spectroscopy in the temperature range of 300-1450 K. The exact chemical formula of this mineral specimen was determined by wavelength-dispersive electron microprobe analysis (EMPA) and it is ^A(K_0.93Na_0.06Ba_0.01)^M(Mg_2.81Fe²⁺_0.15Ti_0.01Mn_0.01)^T(Si_2.99Al_0.99Ti_0.02)O₁₀^X(F_1.60OH_0.40). We show that fluorophlogopite undergoes stepwise structural and chemical changes, which can be monitored by the evolution of the Raman-active phonon modes at ~93 cm^-1 (interlayer vibrations), 195, 279, and 325 cm^-1 (dominated by octahedral vibrations) as well as at 684 and 739 cm^-1 (TO₄-ring mode vibrations). Near 500-600 K an interlayer structural instability occurs, which most probably results in a rearrangement of the layer stacking sequence. This activates the mobility of K⁺ cations in the interlayer space in the temperature range between 600 and 1000 K. Two independent heating-cooling runs to 1100 and 1450 K indicate a partial loss of K⁺ above 1000 K, which was confirmed by subsequent WD-EMPA. Oxidation of ^MFe²⁺ takes place between 900 and 1300 K. A partial thermal decomposition of fluorophlogopite occurs above 1300 K, leading to the formation of a minor amount of nanosized forsterite within the phlogopite matrix, but the overall biotite structure type persists up to 1450 K. 

References

• Bernardini, G. Della Ventura, J. Schlüter, B. Mihailova, Geochem. 2023, 83, 125942.
• Gianfagna, F. Scoradri, S. Mazziotti-Tagliani, G. Ventruti, L. Ottolini, Am Mineral. 2007, 92, 1601.
• R.G. Trønnes, Mineral Petrol. 2002, 74, 129.

How to cite: Aspiotis, S., Reinberg, C., Peters, S., and Mihailova, B.: Temperature-induced structural transformations in fluorophlogopite studied by in situ high-temperature Raman spectroscopy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6307, https://doi.org/10.5194/egusphere-egu25-6307, 2025.

The release and transport of volatiles, including sulfur-bearing species, by subduction related dehydration fluids are some of the key mechanisms of the deep sulfur cycle and link the surface with the crust and mantle sulfur budgets. However, parameters like the speciation of sulfur and the prevailing redox conditions during dehydration-related and fluid-mediated transport are still highly debated. To gain a deeper understanding of sulfur transport, distribution and speciation driven by different fluid migration processes at the blueschist-eclogite facies transition, we investigate samples from the New Caledonian Pouébo eclogite mélange (Taetz et al., 2016). These samples comprise two generations of garnet-quartz-bearing veins with adjacent omphacite-rich reaction halos in a blueschist metabasalt matrix. The veins are interpreted as both internal dehydration veins and external transport veins formed during prograde to peak metamorphism of the oceanic slab (Taetz et al., 2016). Therefore, these samples offer an ideal opportunity to link sulfur transport and speciation with different fluid migration processes at HP/LT subduction conditions.

Using the sulfur mineral distribution within and at varying distance to the veins, combined with in situ sulfur isotope and sulfide trace element compositions, three generations of pyrite formation and two main stages of sulfur mobilization at peak metamorphic conditions are inferred. The first stage of sulfur mobilization is linked to the formation of dehydration veins at low fO₂ conditions, by the breakdown of water-bearing phases. At this stage, the primary wall rock pyrite (δ³⁴S = -3.4‰ to -35.7‰) is partially leached from the wall rock and reprecipitates as fine-grained pyrite aggregates with δ³⁴S values averaging at -12.4‰ in and along the newly forming, small-scale quartz-garnet-bearing dehydration veins. The second stage of sulfur mobilization takes place during the infiltration of an external fluid and formation of the transport vein. Due to a significant decrease of sulfide minerals towards the transport vein and the occurrence of Fe-oxide decomposition rims around the selvage pyrites, we infer an oxidizing character of the external fluid. This causes the development of a redox gradient between more oxidizing vein and more reducing matrix during selvage formation and enables sulfur mobilization and oxidation in the selvage area balanced by the reduction of omphacite Fe³⁺. The absence of sulfur-bearing minerals in the transport vein itself indicates, furthermore, that dissolved sulfate was removed from the investigated vein system by the passing external fluid.

Based on the studied vein systems, we imply that in subduction zones at the blueschist-eclogite facies transition fluid-mediated sulfur mobilization and speciation is mainly controlled by the fluid-rock ratio. While internally-buffered rock dehydration fluids carry sulfur in its reduced form, fluid-dominated transport veins may carry sulfur mostly in its oxidized form.

REFERENCES

Taetz, S., John, T., Brocker, M., & Spandler, C. (2016). Fluid-rock interaction and evolution of a high-pressure/low-temperature vein system in eclogite from New Caledonia: insights into intraslab fluid flow processes. Contributions to Mineralogy and Petrology, 171(11). doi:ARTN 9010.1007/s00410-016-1295-z

How to cite: Scherzer, S., Schwarzenbach, E. M., Pettke, T., and Scicchitano, M. R.: Intraslab sulfur mobilization in different co-occurring redox regimes at HP/LT conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9962, https://doi.org/10.5194/egusphere-egu25-9962, 2025.

How to cite: Willar-Sheehan, S., Llewellin, E., and Sullivan, P.: Disequilibrium Sulfur degassing – a mixed volatile bubble growth model , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18516, https://doi.org/10.5194/egusphere-egu25-18516, 2025.

Mobility of S in subduction zones is complex with far reaching impacts on the formation of large hydrothermal ore deposits in arc environments, volcanic S emissions into the atmosphere potentially impacting the Earth’s climate, S transfer into the mantle via the subducting slab and accompanying potential remodification of the S mantle budget. Sulfur flux and sulfides in subducting slabs have been extensively investigated, but most studies focus on HP metamorphism from the zone de mélanges at the mantle-crust transition, thus lacking a comprehensive overview of the slab perspective. In particular, a knowledge gap exists regarding the early stages of the S cycle within the subduction zone from sub-greenschist to epidote blueschist/eclogite facies. This study  presents new data on the control of pyrite growth during subduction-related prograde metamorphism and the implications on the flux of S as well as related elements (Ag, As, Bi, Co, Cu, Mo, Pb, Sb, Se, Te, Tl, Zn; hereafter referred to as related elements) in subduction zones.

The Cyclades, Greece, are part of the Hellenides subduction system. The Cyclades host the Cycladic Blueschist Unit (CBU), which contains a passive margin and an ophiolitic sequence hosting metasedimentary and metavolcanic rocks metamorphosed from pumpellyite to eclogite facies and are thus particularly well suited to investigate mass transfer in a subducting slab during prograde metamorphism. We selected samples from islands within the CBU to obtain insights into the S mobility along the subducting slab.

Petrological observations show that pyrite growth and abundance increase during prograde metamorphism from the pumpellyite/greenschist (~300°C, ~7 kbar) to the blueschist/ecologite facies (500–600°C, ~22 kbar). Partial resorption and hematisation/magnetisation of pyrite seems to have occurred at the transition of peak HP metamorphism to early exhumation at >500–600°C. In-situ analyses on pyrite (LA-ICP-MS) and trace element maps distribution (EPMA) within prograde pyrite shows complex concentric patterns. Based on geothermobarometric investigations of inclusions in pyrite we observed two main temperature ranges of 350–400°C and 550–600°C where metal mobilisation happenned (Au, Sb, Pb, Te, Bi, Ni, and Co). Following this, pyrite can serve as a new powerful tool to indirectly constrain metal mobility during prograde metamorphism.

How to cite: Peillod, A., Patten, C. G. C., Drüppel, K., Beranoaguirre, A., Hector, S., Kleine-Marshall, B. I., Borchardt, P. M., Majka, J., and Kolb, J.: Pyrite growth during slab subduction: implications for S flux, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12541, https://doi.org/10.5194/egusphere-egu25-12541, 2025.

The dehydration of oceanic crust in subduction zones is a key control on subducting plate interface rheology and global element and fluid budgets. The “lower” grade metamorphic history of dehydration in subducted metabasalts in warm subduction zones is particularly important as these rocks may carry significant volumes of water into subduction zones, some of which may be released in the forearc at depths where deep slow slip and tremor occur in modern subduction zones, helping to generate local high pore fluid pressures. To explore the geologic record of such dehydration reactions, we synthesize petrologic observations, bulk rock and epidote major- and trace-element geochemistry, Sr-isotope data, and thermodynamic modeling of epidote-amphibolite facies metabasalts in the Catalina Schist of CA, USA. These metabasalts represent exhumed slices of oceanic crust that experienced peak P-T conditions of ~550°C and ~1 GPa and were underplated during Cretaceous subduction beneath North America. We focus on using epidote-group minerals in these rocks as a recorder of hydration and dehydration processes because epidote commonly forms during seafloor hydrothermal alteration and is a predicted reaction product in thermodynamic modeling of metabasalts during prograde subduction. Indeed, the Catalina Schist metabasalts include textural and geochemical evidence of seafloor hydration in the form of interpillow epidosite, epidote trace element patterns, and bulk-rock Sr-isotope values. However, these rocks also include metamorphic epidote porphyroblast and vein-like networks that developed during prograde metamorphism. Based on in-situ epidote trace element analyses, we suggest that metamorphic epidote in these rocks grew from pumpellyite breakdown, in some cases resulting in the development of epidote-rich zones that represent loci of dehydration and possible fluid pathways. We suggest these vein-like zones developed as a result of density changes during this reaction. Using thermodynamic models of the bulk rock composition of these metabasalts, we estimate that this pumpellyite to epidote reaction occurred at ~300°C and 0.5–0.7 GPa. The results of our thermodynamic modeling further suggest that the pumpellyite to epidote reaction resulted in a change in the water content of a hydrated Catalina Schist basalt from 5.5 wt. % H₂O to 2.5 wt. % H₂O, or a release of ~90 kg H₂O per cubic meter of basalt.   This corresponds to a flux of water from a 600 m-thick pile of altered basalts on the order of 10⁴–10⁵ kg m^-2 Myr^-1 in the region experiencing dehydration. In modern subduction zones, a dehydration pulse at these conditions would provide significant volumes of fluid at the updip end of the deep slow slip and tremor source region, and may provide a local source for inferred elevated pore fluid pressures. Our petrologic and geochemical observations paired with thermodynamic modeling provide insight into the metamorphic reactions that may deliver water to the plate interface at the conditions of slow slip, and show that epidote-group minerals are a powerful tools for exploring relatively “low” grade metamorphic processes in subduction zones (e.g., lithologies lacking garnet).

How to cite: Lindquist, P., Condit, C., Hoover, W., and Guevara, V.: The geologic record of hydration and dehydration in the subducting slab: Epidote minerals record alteration and metamorphism before and during subduction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12613, https://doi.org/10.5194/egusphere-egu25-12613, 2025.

It is well known that the density of metamorphic reactions occurring in subduction zones, due to intense fluid-melt activity, is very high. One of the minerals resulting from all these reactions, present both in the downgoing slab and in the serpentinized mantle wedge, is magnetite. Its study is therefore crucial to understanding geodynamic processes, as it gives information about oxidized fluids, temperature, trace elements mobility etc... Its applicability encompasses not only metamorphic petrology (sensu lato) but also tectonic processes of accretion, exhumation and obduction (e.g., emplacement of the Samail Ophiolite), as well as ore geology, as it is an ubiquitous mineral in numerous ore deposit types. Being able to date magnetite, providing a temporal framework to all these reactions, is to put in one more piece of this big puzzle.

Advances in analytical techniques and instrumentation, above all regarding the laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), have made that currently, the U-Pb dating reaches far beyond the traditionally dated minerals (zircon, monazite, rutile, etc.). In this context, at the FIERCE laboratory of the Goethe University-Frankfurt, we have investigated the possibility of dating magnetite.

Magnetite from several localities (Greek Islands, Cyprus, Alps) have been studied, resulting in a variety of U and Pb contents (up to a few µg/g in the case of U) as well as a significant spread on the U/Pb ratios. This has allowed us to date the studied samples, with internal precisions as good as 1.5% in the best of the studied cases.

Recognising the possibility of dating such a mineral is only the first step in the implementation of the technique. Ideally, the availability of reference materials for magnetite analyses would be very advantageous. Currently (as of this EGU-abstract deadline), some of the samples dated by LA-ICPMS are being analysed using the U-Th/He method, which will allow us to compare the ages obtained by both methods and eventually, to use those magnetite as reference for future analyses.

How to cite: Beranoaguirre, A., Peillod, A., Patten, C., Dunkl, I., Hector, S., Ring, U., Kolb, J., and Gerdes, A.: First steps of LA-ICPMS U-Pb magnetite geochronology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16826, https://doi.org/10.5194/egusphere-egu25-16826, 2025.