SSP3.5

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.

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.

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., D_Ni and D_Co, 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 D_Ni and D_Co 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 D_Ni and D_Co point toward the importance of the defect sites in the incorporation of these two elements in aragonite. Finally, our results suggest that D_Ni and D_Coin 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.

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.

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.

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.

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.

La Pedrera de Meià (LPM) fossil site, discovered in the 19^th 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.

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.