SSP3.5

EDI
The formation of sedimentary minerals

Minerals are formed in great diversity under Earth surface conditions, as skeletons, microbialites, speleothems, or authigenic cements, and they preserve a wealth of geochemical, biological, mineralogical, and isotopic information, providing valuable archives of past environmental conditions. Interpreting these archives requires fundamental understanding of mineral formation processes, but also insights from the geological record.

In this session we welcome oral and poster presentations from a wide range of research of topics, including process-oriented studies in modern systems, the ancient rock record, experiments, computer simulations, and high-resolution microscopy and spectroscopy techniques. We intend to reach a wide community of researchers sharing the common goal of improving our understanding of the fundamental processes underlying mineral formation, which is essential to read our Earth’s geological archive.

Co-organized by BG5/GMPV5
Convener: Patrick Meister | Co-conveners: Sally Potter-McIntyre, Patricia RoeserECSECS, Michael E. Böttcher
Presentations
| Thu, 26 May, 15:10–16:40 (CEST)
 
Room -2.32/33

Presentations: Thu, 26 May | Room -2.32/33

Chairpersons: Patrick Meister, Patricia Roeser, Michael E. Böttcher
15:10–15:15
Mineral reactions and morphogenesis
15:15–15:25
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EGU22-6310
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solicited
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Highlight
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On-site presentation
Andreas Lüttge

How do we connect the results generated at the molecular scale with meso- and large scale processes?  Or, in other words how do we make frontier research results accessible for the multitude of applications that our daily work demands?

During the last couple of decades the combined effort of field and experimental studies, sophisticated analytical methods and computational models has generated fast and important progress in our fundamental understanding of mineral reactions. Here, we will briefly present and highlight some of these exciting results. Results that are highly appreciated in light of the ever increasing number of applications that demand a better in-depth and quantitative understanding of mineral reactions and their often critical role in large scale processes such as the prediction of long-term behavior of geo-reservoir rocks, ocean acidification, hazardous (nuclear) waste safety, and – of course – global climate change.

Surprisingly enough, our main challenge is often to make the cutting-edge achievements of mineralogical and (geo)chemical research accessible to a broad audience in sedimentology, geochemistry, and geobiology. To highlight just one example, we recognize that crystal dissolution, corrosion and weathering rates are not correctly described by a rate constant but by a multitude of rates, a rate spectrum. However, this insight is difficult to implement in reactive-transport models and is met with significant skepticism.

We will have to focus on new strategies that will not only provide better (and easier) accessibility of cutting-edge research results but address also the even greater challenge of up-scaling our results, i.e., how do we utilize the fast increasing results at the molecular scale with the meso- and large scale problems. It looks like that we need the interfaces that connect the results both in length scale as well as in time. 

How to cite: Lüttge, A.: Latest developments in research on mineral reactions: Accessibility of results and progress versus convenience, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6310, https://doi.org/10.5194/egusphere-egu22-6310, 2022.

15:25–15:30
15:30–15:35
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EGU22-4342
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Presentation form not yet defined
Mike Rogerson, Ramon Mercedes-Martín, Timothy Prior, Alexander Brasier, John Reijmer, Ian Billing, Anna Matthews, Tracy Love, Scott Lepley, and Martyn Pedley

Ancient and recent terrestrial carbonate-precipitating systems are characterised by a heterogeneous array of deposits volumetrically dominated by calcite. In these environments, calcite precipitates display an extraordinary morphological diversity, from single crystal rhombohedral prisms, to blocky crystalline encrustations, or spherulitic to dendritic aggregates. Despite many decades of thorough descriptive and interpretative work on these fabrics, relating calcite micro-morphology with sedimentary hydrogeochemical conditions remains a challenge. Environmental interpretations have been hampered by the fact that calcite morphogenesis results from the complex interaction between different physico-chemical parameters which often act simultaneously (e.g., carbonate mineral supersaturation, Mg/Ca ratio of the parental fluid, organic and inorganic additives). To try to experimentally address the sedimentological causes of calcite morphogenesis, an experimental approach yielding a first attempt at a calcite growth-form phase diagram is presented here. The initial aim was to account for the carbonate products experimentally nucleated in alkaline, saline lake settings. These are the result of at least two competing calcite precipitation ‘driving forces’ that affect morphogenesis: the calcite supersaturation level of the parental fluid, and the concentration of microbial-derived organic molecules (alginic acid). A key finding of this study is that common naturally-occurring calcite products such as calcite floating rafts, rhombohedral prismatic forms, di-pyramid calcite crystals, spherulitic calcite grains, or vertically stacked spheroidal calcite aggregates, can be related to specific hydrogeochemical contexts, and their physical transitions pinpointed in a phase diagram. By exploring binary or ternary responses to forcing in morphological phase-space, links between calcite growth forms and (palaeo)environmental conditions can be determined. This provides a truly process-oriented means of navigating questions around carbonate precipitate morphogenesis for the future.

How to cite: Rogerson, M., Mercedes-Martín, R., Prior, T., Brasier, A., Reijmer, J., Billing, I., Matthews, A., Love, T., Lepley, S., and Pedley, M.: Towards a morphology diagram for terrestrial carbonates: Evaluating the impact of carbonate supersaturation and alginic acid in calcite precipitate morphology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4342, https://doi.org/10.5194/egusphere-egu22-4342, 2022.

15:35–15:40
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EGU22-9860
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Virtual presentation
Maciej Bojanowski, Beata Marciniak-Maliszewska, Milena Matyszczak, and Jan Środoń

Dolomite and magnesite are particularly abundant in the Precambrian strata, which is often explained by abnormal ocean chemistry favoring formation of these minerals in oceanic basins over other carbonates and Ca-sulfates. However, interpretation of the depositional setting is challenging in the Precambrian sequences, mainly due to the scarcity of biotic proxies and commonly significant post-depositional alteration. Therefore, combined sedimentological, mineralogical and geochemical investigations of weakly altered Precambrian sedimentary rocks emerge as the best approach to contribute to our understanding of the climatic and chemical evolution of early Earth. This study deals with the Lapichi Fm. from the East European Craton, which consists of a mixed dolomite-siliciclastic series recently dated at 710 Ma, thus deposited during the Sturtian panglaciation. What is essential, these rocks are exceptionally well preserved and have not experienced any significant alteration. They were previously interpreted to have formed in a saline marine lagoon, so they appeared to represent an ideal target for a palaeoceanographic study. Here, we present results of re-evaluation of the Lapichi Fm. using sedimentology, petrography, SEM, XRD, C, O and Sr isotopes.

Diamictites and rythmites observed in the siliciclastics of the Lapichi Fm., given that the area was positioned around 40°S during the Lapichi deposition, provide sedimentological evidence of cold climate and periglacial conditions on Baltica at low latitudes. The intercalating dolostones contain some siliciclastic material with the same characteristics, so the cold conditions continued during dolomite formation as well. Two types of dolostones are distinguished: pristine dolomicrites representing penecontemporaneous precipitates and coarser-crystalline dolomites with peculiar fabrics apparently exotic to the sedimentary dolomite, which include stellate dolomite with pyramidal terminations. We believe that these dolomites are pseudomorphic and that the precursors might have been magnesite, Ca-sulfates, aragonite, or glendonite/ikaite. Both dolomite types contain numerous micrometer-scale magnesite inclusions; in some samples authigenic K feldspars and traces of artinite were also identified, but neither CaCO3 nor CaSO4 minerals were found. Such mineral paragenesis confirms high salinity, Mg-rich parent fluid. Presence of hematite and goethite attests for strong seasonal fluctuations of temperature and humidity. Radiogenic Sr isotope composition, even in the case of pure dolomicrites, indicates that the rocks did not precipitate from seawater. δ13C and δ18O vary, but 18O enrichment is not observed. δ13C cluster around 0‰, whereas δ18O values are always negative, which suggests predominance of a meteoric water source, possibly meltwater. The covariance between δ13C and δ18O in dolomicrites supports the meteoric source and suggests a closed lake. In summary, the data contradict previous interpretation of the Lapichi Fm. depositional setting and indicate that it formed in a perennial, ice-covered, hypersaline, high-alkaline lake in an arid, periglacial setting. Although recent global climate may be far from that of the Cryogenian, we speculate that the closest possible modern analogs of the Lapichi depositional setting may be lakes in the Antarctic dry valleys, northern Great Plains of Canada, or high-altitude Tibetan or Andean playas.

This work was supported by the Polish National Science Centre MAESTRO grant 2013/10/A/ST10/00050.

How to cite: Bojanowski, M., Marciniak-Maliszewska, B., Matyszczak, M., and Środoń, J.: Peculiar micromorphologies of the middle Neoproterozoic dolomite-magnesite association formed in a hypersaline-alkaline periglacial lake, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9860, https://doi.org/10.5194/egusphere-egu22-9860, 2022.

Trace elements and isotopes in carbonates
15:40–15:45
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EGU22-5027
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ECS
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Presentation form not yet defined
Jean-Michel Brazier and Vasileios Mavromatis

The chemical and isotopic compositions of carbonates minerals allow to reconstruct the composition of the reactive solutions at the time of their formations and are thus of first importance for paleoenvironmental reconstruction over geological time. In this regard, a huge effort was addressed during the last five decades to study the incorporation, and the associated mechanisms, of traces elements in carbonates minerals. Deciphering the effect of particular physical or chemical parameters on the incorporation of traces in natural CaCO3 is not straightforward and in this respect, experimental studies under highly controlled conditions can provide important insight into our understanding of the chemical signatures of natural samples. In this study, we experimentally investigated the incorporation of Ni and Co in aragonite as a function of mineral growth rate using the constant addition technique at 25°C and 1 bar pCO2. Our results show a linear correlation between the distribution coefficients of Ni and Co and the mineral growth rate suggesting that the latter is likely an important parameter controlling the Ni and Co incorporation in aragonite. In both cases, the distribution coefficients of Ni and Co (i.e., DNi and DCo, respectively) between aragonite and the reactive solution are always lower than unity and increase with increasing growth rate following the trend of incorporation of elements incompatible with the host mineral structure. Based on the dependency of DNi and DCo with the saturation indices (SI) of the reactive solution with respect to aragonite, it was possible to estimate a distribution coefficient at equilibrium for both Ni and Co. These experimental values are several orders of magnitude lower than the theoretically estimated ones in the literature. Furthermore, as for other incompatibles elements the correlation between SI and DNi and DCo point toward the importance of the defect sites in the incorporation of these two elements in aragonite. Finally, our results suggest that DNi and DCoin aragonite could be used to rebuild the saturation state of the reactive solution.

How to cite: Brazier, J.-M. and Mavromatis, V.: Nickel and Cobalt incorporation in aragonite as a function of mineral growth rate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5027, https://doi.org/10.5194/egusphere-egu22-5027, 2022.

15:45–15:50
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EGU22-2618
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ECS
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On-site presentation
Rolando E. Clavijo-Arcos, Matthew O. Clarkson, Derek Vance, Stefano Bernasconi, Marcel Guillong, Alcides N. Sial, Marius N. Müller, Nathan Looser, Yana Kirichenko, and Netta Shalev

Global seawater isotope reconstructions from Precambrian marine carbonates must overcome particular difficulties on two fronts: i) accurate age constraints for global stratigraphic correlations and interpretations, and ii) the relative timing of syn- to post-depositional processes. Neoproterozoic cap dolomites have emerged as promising archives for seawater isotope reconstructions, in the context of major geochemical disturbances in the Earth system, including the evolution of complex life, significant shifts in the carbon cycle, Cryogenian glaciations, all in the tectonic framework of continental breakup. However, absolute age constraints are required to set the chronological context of such isotope reconstructions. The direct dating of carbonates by laser ablation ICP-MS U-Pb is an increasingly applied tool, which may help to overcome age uncertainties. Here, we investigate a suite of petrographic sections from the base of the Jacoca Formation cap dolomite, at the Capitão Farm section, Sergipano belt, Brazil, overlying the glacially influenced Sturtian Jacarecica Formation diamictite. The goals of our study are to: i) provide chronological constraints on the timing of the Sturtian deglaciation and ii) to reconstruct the diagenetic history of this unit after carbonate deposition. To this end, in-situ U-Pb geochronology was combined with X-ray diffraction (XRD), and selected element geochemistry data on two cogenetic dolomite phases (D1: finely crystalline dolomite and D2: coarsely rhombic dolomite texture) recognized by optical microscopy- and CL-imagery. Powder XRD patterns, Mg/(Mg+Ca) molar ratios for both D1 and D2 dolomite phases (0.43 to 0.50), as well as petrographic observations, demonstrate a dolomite-dominated mineralogy. Laser ablation U-Pb analyses of the D2 phase yield an isochron in Tera-Wasserburg space, with a lower intercept age of 670±16 Myr and an upper intercept common Pb 207Pb/206Pb value of 0.8805±0.0012. This, therefore, suggests an early dolomitization stage that is consistent with an expected ca. of 660 Myr for post-Sturtian cap dolomites. In contrast, data from an area of the D1 phase defines an isochron age of 555±30 Myr and a more radiogenic common initial 207Pb/206Pb value of 0.8375±0.0026, implying that the U-Pb system was reset long after carbonate dolomitization. The timing of this resetting overlaps with the known Pan-African/Brasiliano tectono-metamorphic event, which folded these geological units, and suggests a post-depositional overprint. Our preliminary data indicates that: i) a reasonable Sturtian dolomitization age is recorded in the Jacoca Formation cap dolomite and that ii) a significant later diagenetic event appears to have reset the U-Pb carbonate system during an episode of crustal deformation. Therefore, U-Pb dating of ancient post-glacial cap dolomites can provide absolute age records of syn- to late-diagenetic geological processes that operated in the aftermath of Cryogenian glaciations. Consequently, these data can help both to anchor isotope and element geochemistry data interpretations, and to highlight potential complexities associated with the subsequent geological evolution of marine carbonate archives.

How to cite: Clavijo-Arcos, R. E., Clarkson, M. O., Vance, D., Bernasconi, S., Guillong, M., Sial, A. N., Müller, M. N., Looser, N., Kirichenko, Y., and Shalev, N.: Using Precambrian carbonates for seawater isotope reconstructions: constraints from LA-ICP-MS U-Pb geochronology of a post-Sturtian cap dolomite, Brazil, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2618, https://doi.org/10.5194/egusphere-egu22-2618, 2022.

15:50–15:55
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EGU22-6856
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ECS
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Virtual presentation
Marjorie Cantine and Axel Gerdes

Carbonates make up about one-quarter of Earth’s sedimentary record, and contain valuable biogeochemical records used to reconstruct Earth history. In situ U-Pb dating of carbonates using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) offers the possibility of dating these records directly, as well as deposition, diagenesis, and deformation. To fully assess the potential of this technique, laser ablation ages must be compared with other geochronological constraints. Geochemical (e.g., stable isotopes or trace elements) and petrographic context provide further guidance in the measurement and interpretation of carbonate-derived dates. This contribution presents case studies from our ongoing work, spanning Proterozoic and Phanerozoic samples from the marine realm, including the Neoproterozoic of Oman and Svalbard and the Cambro-Ordovician of North America. We highlight measured dates and with special focus on dating deposition and early diagenesis and integrating petrographic and geochemical data. We highlight the role of microbial mats and early marine cements in creating “datable” carbonates and discuss implications for sampling.    

How to cite: Cantine, M. and Gerdes, A.: Facies and environmental controls on dating carbonates using LA-ICP-MS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6856, https://doi.org/10.5194/egusphere-egu22-6856, 2022.

Marine and lacustrine authigenesis
15:55–16:00
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EGU22-12842
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Virtual presentation
Francisca Martinez-Ruiz, Adina Paytan, Maria Teresa Gonzalez-Muñoz, Fadwa Jroundi, Maria del Mar Abad, Phoebe J. Lam, Tristan J. Horner, and Miriam Kastner

Despite decades of research, barite formation in the ocean water column has been widely discussed since most of the world´s ocean mesopelagic zone, in which barite forms, is generally undersaturated with respect to this mineral. Recent evidence from experimental work and also from observations in microenvironments of intense organic matter mineralization in the ocean support that barite forms via transient amorphous precursor phases that evolve to barite crystals. This crystallization pathway is further supported by the close association of barite particles with extracellular polymeric substances (EPS) at depths of higher bacterial production. Barite particles association with exopolymers demonstrates that microbial processes and exopolymer production play a major role in promoting locally high concentrations of Ba and barite precipitation. Scanning and high-resolution transmission electron microscopy analyses from particulate samples collected using multiple-unit large volume in-situ filtration systems have shown how these amorphous precursor phase nucleate, demonstrating that phosphate groups in EPS and bacterial cells are the sites for binding Ba. EDX maps have shown the nature of these P-rich nanometer-sized amorphous particles that evolve to poorly crystallized barite and to micrometer-sized barite crystals. The strong link between organo-mineralization and microbial processes further supports the role that such processes play in biomineralization in the ocean. The distribution of particulate Ba and Ba isotopes in the water column is also consistent with such precipitation mechanisms. Hence, processes involved in barite precipitation including primary production, export production, organic matter degradation, bacterial respiration, EPS formation, aggregation, and sinking, need to be taken into account when interpreting temporal and spatial variability in the Ba:Corg ratios and barite accumulation in marine sediments.

How to cite: Martinez-Ruiz, F., Paytan, A., Gonzalez-Muñoz, M. T., Jroundi, F., Abad, M. M., Lam, P. J., Horner, T. J., and Kastner, M.: Barite Precipitation on Suspended Organic Matter in the Ocean Water Column, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12842, https://doi.org/10.5194/egusphere-egu22-12842, 2022.

16:00–16:05
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EGU22-5051
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ECS
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Presentation form not yet defined
Patricia Roeser, Mary A. Zeller, Peter Feldens, Jens Kallmeyer, David Clemens, Jurjen Rooze, Hagen Radtke, Mischa Schönke, Iris Schmiedinger, Stefan Forster, Stefan Sommer, and Michael E. Böttcher

The research project MGF-Ostsee deals with the consequences of the exclusion of mobile bottom-contact fishing in the southern Baltic Sea, specifically to assess its effects on the biogeochemistry of surface sediments and across the benthic-pelagic food chain. In Summer 2021, an in-situ monitored experiment was conducted at a coastal site in the region of Warnemünde/Rostock to investigate the short-term impacts of bottom trawling. Herein, we present first results on how this anthropogenic intervention affects biogeochemical processes and associated elemental cycling, as well as the resulting changes in geochemical mineral tracers. We analyzed porewater and sediment, as well as the water column for major, minor and trace elements, and the stable isotope composition (C, S, O) of dissolved and solid carbon and sulfur species. Porewater gradients are combined with lander-based oxygen-consumption- and radiotracer-based microbial sulfate reduction rates to elucidate how the disturbances by the fishing gear affect element (C, P, Mn, Fe, S) and mineral (re)distribution.

The controlled trawling experiment generated a re-suspension plume that reached up to 2 m above the sea floor, with 4 NTU in the lowermost portion. In the central trawled area, short cores were taken with a MUC prior and one to two hours after the experiment, and on the following day. In addition, sediment cores were recovered by divers from furrows and mounds of recent trawl marks. First results suggest that in the trawled area, the coupled Fe-Mn-P cycle reacts most sensitively, as expressed by altered porewater gradients and element diffusion. In the trawl marks, pore waters are affected differently whether sediments are removed, as in trawl furrows (erosion), or added/topped, as in trawl mounds (burial). In general, the tentative results point towards a Mn loss in the trawling area and in the furrows, whereas in the mounds Mn becomes enriched. The observed short-term changes in geochemical patterns from the experiment in the Warnemünde region are compared to data from a monitored region in the Fehmarn Belt. There, the observed patterns are tentatively associated to meso-scale areas with a history of low or high trawling impact.

How to cite: Roeser, P., Zeller, M. A., Feldens, P., Kallmeyer, J., Clemens, D., Rooze, J., Radtke, H., Schönke, M., Schmiedinger, I., Forster, S., Sommer, S., and Böttcher, M. E.: Short-term anthropogenic impact of mobile bottom-contact fishing on the biogeochemistry of coastal sediments and its long-term effects on mineral distribution, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5051, https://doi.org/10.5194/egusphere-egu22-5051, 2022.

16:05–16:10
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EGU22-10360
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Presentation form not yet defined
Victoria Ershova, Mikhail Rogov, Carmen Gaina, Oleg Vereshchagin, Kseniia Vasileva, Kseniia Mikhailova, and Aleksei Krylov

Glendonites are carbonate (mainly calcite) pseudomorphs after metastable ikaite (CaCO3·6H2O); Glendonites have been found worldwide in Paleoproterozoic to Quaternary sediments.  Modern ikaite are mostly found in regions that experienced low temperatures, thus glendonites are considered to be an indicator of near-freezing temperatures in the past (e.g. Kaplan, 1978; Shearman and Smith, 1985; Last et al., 2013). Indeed, glendonites have been found in association with glaciomarine sediments (Johnston, 1995; James et al., 2005; Thomas et al., 2005; Spielhagen and Tripati, 2009), and they have also been associated with upwelling of near-freezing waters onto relatively shallow shelves (Brandley and Krause, 1994; Jones et al., 2006, Mikhailova et al, 2019). Despite the general association with cold conditions, the relevance of glendonites as a paleotemperature indicator is still questioned (Shearman and Smith, 1985; Teichert and Luppold, 2013). To test the geographical distribution of glendonites through time, and attempt an understanding of the paleoenvironment that facilitated their occurrences we have compiled a global database of Phanerozoic glendonites (Rogov et al., 2021).  This dataset has been reconstructed for key Mesozoic and Palaeozoic time intervals by using a global kinematic model. Our reconstructions indicate that most glendonites occurrences in Mesozoic and Palaeozoic times were originally formed in the polar or close to polar regions. The Cenozoic and especially recent glendonites formed close to polar seas (mainly Arctic wide shelves) or on deep-water continental margins (ex.  Zaire deep fan, Nankai Trough, Sakhalin Island slope). The preservation potential of deep-water sediments in geological record are lower than epicontinental and marginal seas. Based on our global Phanerozoic reconstructions we suggest that documented glendonites found in Phanerozoic deposits could be used as a paleoclimatic indicators of cold-water environments. 

How to cite: Ershova, V., Rogov, M., Gaina, C., Vereshchagin, O., Vasileva, K., Mikhailova, K., and Krylov, A.: The global dataset of Phanerozoic glendonites and paleogeographic reconstructions , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10360, https://doi.org/10.5194/egusphere-egu22-10360, 2022.

16:10–16:15
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EGU22-8146
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ECS
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Presentation form not yet defined
Alejandro Gil-Delgado, Edgar Botero, Jordi Ibàñez-Insa, Ramon Mercedes-Martín, Albert Sellés, Xavier Delclòs, Àngel Galobart, and Oriol Oms

La Pedrera de Meià (LPM) fossil site, discovered in the 19th century, is an important Barremian Konservat-Lagerstätte located at the southern slope of the Montsec range (Lleida province, Spain). LPM is comparable in fossil preservation with other European lithographic limestones lagerstätten sites such as Solnhofen (Germany), Cerin (France) or Las Hoyas (Spain). The LPM site stands out by the conservation of soft tissues of different groups of plants and animals such as arthropods, osteichthyes, frogs or feathered dinosaurs. The high biodiversity recorded in fossil pieces there are up to 50 holotypes and paratypes described, including the first flowered plants or social insects in the history of life. Such a unique fossil record is widespread throughout the most significant collections all over Europe.

Geologically, the outcrop records the deepest part of a coastal lake after a succession of 50 m of laminated mudstones, with restricted lateral continuity. These mudstones produce slabs from metric to millimetric thickness and appear very monotonous. Overall, no conspicuous vertical textural changes can be recognized in outcrop

The main objective of this study is to gain insights on the paleoenvironmental and paleoclimatic conditions concurring to lake formation where the LPM outcrop is located. For this purpose, a detailed stratigraphic study has been performed together with petrographical and geochemical analyses on rock samples collected across a 50m-thick sedimentary log to precisely locate all the samples of a multiproxy study. Our analysis includes X- Ray fluorescence (XRF), throughout all the stratigraphic log. Other analytical measurements have been carried out in a shorter control interval to obtain more accurate data that can be extrapolated to the whole column by using the XRF results. These include X-Ray diffraction (XRD), C and O stable isotopes, loss on ignition of organic matter, pyrite framboid petrography, and laminae counting. Comparison of the complete XRF record with the results of laminae counting suggests that cycles could be orbitally forced. It is concluded that the multiproxy dataset along the shorter interval allows one to characterize the paleoenvironmental evolution of this exceptional site.

The present LPM geochemical data is also being used to test whether lithographic limestone localities have distinctive compositional fingerprint. Worldwide lithographic limestone’s localities are thus compared. The goal is to attain a pattern that may enable one to identify the original site of any specimen in a museum which may have no associated information. In other words, our objective is to assess whether a fossil belongs to the LPM and/or even to determine the specific stratigraphic interval from which it was obtained.

How to cite: Gil-Delgado, A., Botero, E., Ibàñez-Insa, J., Mercedes-Martín, R., Sellés, A., Delclòs, X., Galobart, À., and Oms, O.: Cretaceous coastal lake carbonate geochemistry of La Pedrera de Meià fossil site (southern Pyrenees), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8146, https://doi.org/10.5194/egusphere-egu22-8146, 2022.

Marine diagenesis
16:15–16:20
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EGU22-2002
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On-site presentation
Patrick Meister, Gerhard Herda, Elena Petrishcheva, Susanne Gier, Gerald R. Dickens, Christian Bauer, and Bo Liu

Diagenetic carbonates in marine sediments contribute to the global burial of carbonates (Schrag et al., 2013; Sun & Turchyn, 2014). The carbonates often form in zones of enhanced anaerobic microbial activity, where the consumption and release of metabolites leads to supersaturation of the porewater with respect to carbonate minerals.

Some diagenetic carbonates occur in zones of methanogenesis, where methane concentrations can be very high and reach gas hydrate stability. So far, it has not been clarified how carbonate formation is induced in methanogenic zones. The production of methane by both fermentation of acetate and reduction of carbonate by H2 is stoichiometrically linked to release of excess CO2 and, therefore, should lower carbonate supersaturation in the porewater.

Nevertheless, porewater extracted from drill-cores across methanogenic zones, as at ODP Site 1230 in the Peru-Chile Trench, shows very high total alkalinity of 150 mmol/l, buffering the acidification imposed by the CO2. Based on full-speciation reaction-transport modelling (Meister et al., 2022), it is possible to reproduce alkalinity production as a result of the combined effects of dissimilatory release of ammonia and dissolution/alteration of clay minerals under high pCO2 conditions. Hence, acidification of the fluid is buffered by mineral reactions. In this way, silicate alteration in marine sediments may represent a significant CO2 buffer that contributes to the formation and burial of diagenetic carbonates.

Schrag, D.P., Higgins, J.A., Macdonald, F.A., Johnston, D.T. (2013) Authigenic carbonate and the history of the global carbon cycle. Science 339, 540–3.

Sun, X., Turchyn A.V. (2014) Significant contribution of authigenic carbonate to marine carbon burial. Nature Geoscience 7, 201.

Meister, P., Herda, G., Petrishcheva, E., Gier, S., Dickens, G.R., Bauer, C., Liu, B. (2022) Microbial alkalinity production and silicate alteration in methane charged marine sediments: implications for porewater chemistry and diagenetic carbonate formation. Frontiers in Earth Science 9, 756591, 1-18. https://doi.org/10.3389/feart.2021.756591

How to cite: Meister, P., Herda, G., Petrishcheva, E., Gier, S., Dickens, G. R., Bauer, C., and Liu, B.: Insights on carbonate diagenesis in methanogenic zones from full-speciation reaction-transport modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2002, https://doi.org/10.5194/egusphere-egu22-2002, 2022.

16:20–16:25
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EGU22-6557
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On-site presentation
Jolanta Dopieralska, Mateusz Zieliński, Zdzislaw Belka, Aleksandra Walczak, Marcin Górka, Anna Wysocka, and Andriy Poberezhskyy

Middle Miocene crystals of sabre gypsum and subcrystal of giant gypsum intergrowth cropping out in southern Poland near Busko have been analysed for their Sr isotope composition. The new isotopic data revealed fluctuations in 87Sr/86Sr values within the primary gypsum crystals providing new insight into paleohydrological conditions during the Badenian salinity crisis in the Polish part of the Carpathian Foredeep Basin. The isotopic composition of a glassy gypsum subcrystal decreased progressively with the subcrystal growth, ranging from 0.70892 to 0.70884 near the crystal apex. The 87Sr/86Sr ratios of the sabre gypsum crystals are in the range of 0.70887–0.70934 and there are significant fluctuations within each gypsum layer tested. Similar intra-layer fluctuation patterns observed in various sections provide a strong argument for the synchronous origin of the investigated portions of the sulphate successions.  

The studied primary gypsum has a more radiogenic composition than the Badenian seawater. Its isotope signatures reflect spatial and temporal changes in the supply of continental derived radiogenic Sr to the Carpathian Foredeep Basin. Contrary to previous studies, the Palaeozoic clastic rocks of the Holy Cross Mountains are suggested as potential sources of radiogenic strontium. The new Sr isotope data support a salina model for the evaporitic basin of the Carpathian Foredeep.

This study was supported by the Polish National Science Centre, grant No. 2017/27/B/ST10/00493.

How to cite: Dopieralska, J., Zieliński, M., Belka, Z., Walczak, A., Górka, M., Wysocka, A., and Poberezhskyy, A.: The origin of parent brine of the Badenian (Middle Miocene) primary gypsum deposits in the western part of the Carpathian Foredeep Basin: insights from strontium isotopes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6557, https://doi.org/10.5194/egusphere-egu22-6557, 2022.

Phosphates
16:25–16:30
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EGU22-887
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ECS
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Virtual presentation
Mustapha Hdoufane, Mustapha Mouflih, Hamza Skikra, Khalid Amrouch, and Abderrahmane Soulaimani

The Ouled Abdoun sedimentary basin in Morocco contains the largest phosphate reserves in the world. In the southeastern parts of the basin, the phosphorite deposits lay from the Maastrichtian to the Lutetian sediments of the Tadla Plain. This section has a thickness of ~ 30 m and generally protected from erosion by a relatively strong Turritella slab cover. The phosphorite deposits are distributed in horizontal strata interbedded with levels of limestone, marl and clay, that present various silicifications from the Ypresian. This work aims to study and determine their petrographic, granulometric and mineralogical compositions. A multidisciplinary approach was adopted to achieve these objectives. First, the use of sedimentology and the application of sequence stratigraphy allowed the definition of three depositional sequences in this deposit. Second, the granulometric analysis of the phosphate facies reflects a dominance of well classified medium grains. Furthermore, the analysis of the Visher curves revealed up to three major modes of transport: traction, saltation and suspension. Based on their mineral composition, the microfacies are classified into two phosphate families (or types): Coprolite Intraphospharenite type and Granular Pelphosphalrenite type. Finally, the mineral parageneses recognized by the XRD analyses revealed that phosphorits consist mainly of carbonate, silica and apatitic phases in the section of Tadla.

Keywords: Phosphorite deposit, Tadla plain, Maastrichtian-Lutetian.

How to cite: Hdoufane, M., Mouflih, M., Skikra, H., Amrouch, K., and Soulaimani, A.: Phosphorite series from Maastrichtian to the Lutetian cover of Tadla Plain, Morocco: New insights from lithofacies analysis, granulometric and mineralogical compositions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-887, https://doi.org/10.5194/egusphere-egu22-887, 2022.

16:30–16:35
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EGU22-1454
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ECS
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On-site presentation
Potential REE resources in shallow marine sedimentary phosphorite
(withdrawn)
Jingya Wang and Xiaoyu Zhang
16:35–16:40
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EGU22-6613
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On-site presentation
Pierre-Yves Meslin, Olivier Forni, Matteo Loche, Sébastien Fabre, Nina Lanza, Patrick Gasda, Allan Treiman, Jeff Berger, Agnès Cousin, Olivier Gasnault, William Rapin, Jérémie Lasue, Nicolas Mangold, Erwin Dehouck, Gilles Dromart, Sylvestre Maurice, and Roger C. Wiens

Phosphorus was essential to the development of life on Earth because it enters into the composition of molecules important for biology. Since the development of organisms is often limited by phosphorus supply, secondary phosphate facies are often controlled by biological activity, especially in lacustrine and marine environments. Understanding the formation of phosphate minerals on Mars is therefore interesting not only from an astrobiological standpoint, but also to understand the phosphorus cycle in a presumably abiotic world.  Here, we provide an overview of the different secondary P-rich facies that have been observed by the ChemCam instrument.      

Since 2012, Curiosity has been exploring geological records of a paleo-lacustrine environment in Gale crater. After encountering fluvio-deltaic and lacustrine deposits in the lowermost unit, Bradbury, it explored ~300m of stratigraphy through the Murray formation, composed predominantly of laminated clay-rich mudstones and fine-grained sandstones deposited in an extended lacustrine environment. While crossing the Sutton Island member of this formation (an heterolithic unit composed of mudstones and sandstones), a series of subhorizontal dark laminae enriched in Fe and P were found, progressively giving way to mm-size dark nodules enriched in Mn, Mg and P in the overlying Blunts Point member, growing in size with elevation [1], and to Mn-rich sandstones [1,2,3]. These laminae and nodules were interpreted as syndepositional or early diagenetic features formed in a shallow lake or lake margin environment [1,2,3]. An initial interpretation of their mineralogy, based on chemical measurements, suggested they could be hydrous Fe- and Mn-oxides formed under oxidizing conditions (with Eh increasing along the stratigraphy) at the water-sediment interface, having sorbed (MgHPO4) complexes [1], with nodules’ growth possibly controlled by reworking and winnowing. Dark nodules enriched in (Fe,Mg,P) were also observed in Ca-sulfate-filled fractures across all these units [1]. These dark features suddenly disappeared when the rover reached the Vera Rubin ridge, where only isolated and detached nodules enriched in (Mn,Fe,P), probably eroded from overlying strata, and dark-toned rock patina enriched in (Fe,P) were observed. None of these facies were then observed during the first ~500 Sols of the traverse through the Glen Torridon region, including the base of an unconformity with an overlying Aeolian sandstone unit. In the Groken area of the Glen Torridon region, dark mm-sized nodules arranged in thin layers were again discovered. A rock sample was analyzed by X-ray diffraction by CheMin, which did not detect any crystalline forms of oxides nor phosphates [4]. Meanwhile, the phosphorus and manganese abundances measured by ChemCam have been quantified, which led us to revise prior interpretations. The constant P/Mn ratio in the Groken nodules and their P abundance (too large to be explained by P-sorption to oxides) suggest they are composed of nano-crystalline or amorphous hydrous (Mn,Mg)-phosphates. Previous occurrences are now interpreted as hydrous (Fe,Mn,Mg)-phosphates with varying (Fe,Mn,Mg) proportions. Several formation scenarios are being explored by geochemical modeling [5].  

[1] Meslin et al., LPSC, 2018

[2] Gasda et al., LPSC, 2018

[3] Lanza et al., LPSC, 2018

[4] Treiman et al., LPSC, 2022

[5] Loche et al., LPSC, 2022

How to cite: Meslin, P.-Y., Forni, O., Loche, M., Fabre, S., Lanza, N., Gasda, P., Treiman, A., Berger, J., Cousin, A., Gasnault, O., Rapin, W., Lasue, J., Mangold, N., Dehouck, E., Dromart, G., Maurice, S., and Wiens, R. C.: Overview of Secondary Phosphate Facies observed by Chemcam in Gale Crater, Mars, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6613, https://doi.org/10.5194/egusphere-egu22-6613, 2022.