Assessing the origin of pisoids within a travertine system in the border of Puna Plateau, Argentina

The origin of pisoids in a diversity of environments has been recently discussed. While traditionally considered physico-chemical sedimentary products developed in turbulent environments, or even grown in situ, new results show that microbes may influence their development. In the Terma Los Hornos travertine system, two types of actively forming pisoids were recognized: (i) laminated pisoids with a concentrically laminated crust surrounding a nucleus; and (ii) dendriform radial pisoids with no distinct nucleus. Laminated pisoids form in turbulent pools at the base of waterfalls, while dendritic pisoids develop within small depressions between terracettes, and they can occur superposed as a result of episodic transport and recycling within the travertine system (for example, dendritic textures as nucleus of laminated pisoids). The laminated pisoids are characterized by laterally constant laminae thickness with high inheritance and low amounts of randomly distributed organic matter and microbial remains, suggesting a predominantly abiogenic origin. In contrast, the dendritic pisoids exhibit an intimate relationship with diatoms and filamentous bacteria suggesting a stronger biotic influence in their formation. Thus, both abiogenic and biogenic carbonate structures can coexist in the same hydrothermal system. Pisoids found in the stratigraphic record of Terma Los Hornos allowed to test the preservation potential of the primary signals and reconstructing early diagenetic overprints.Fil: Mors, Rodolfo Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Gomez, Fernando Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Astini, Ricardo Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Celestian, Aaron J.. Natural History Museum Of Los Angeles County; Estados UnidosFil: Corsetti, Frank A.. University of Southern California; Estados Unido

Structure Determination and Time-Resolved Raman Spectroscopy of Yttrium Ion Exchange into Microporous Titanosilicate ETS‑4

The ion exchange of yttrium, one of the five most critical rare-earth elements as outlined by the U.S. Department of Energy, into ETS-4 is a dynamic, multistep ion exchange process. The ion exchange process was followed using in situ time-resolved Raman spectroscopy, and the crystal structures of the pre-exchange and post-exchange forms were determined by single-crystal X-ray diffraction. In situ Raman spectroscopy is an ideal tool for this type of study, as it measures the spectral changes that are a result of molecular geometry changes at fast time intervals, even where symmetry and unit volume changes are minimally detected by X-ray diffraction. By tracking the stepwise changes in the peak positions and intensities in the spectra, where we focused primarily on the strong spectral features corresponding to titania quantum wires and three-membered-ring bending and breathing modes, we constructed molecular models to explain the changes in the Raman spectrum during ion exchange. The multistep ion exchange process started with rapid absorption of Y into the Na2 site, causing titania quantum wires to kink. After this initial uptake, the exchange process slowed, likely caused by hydration coordination changes within the channels. Next, Y exchange accelerated again, during which time the Y site moved closer to the framework O^2–. Crystal structures of the maximal Y exchanged ETS-4 material were determined and confirmed the splitting of the Y site. Inductively coupled plasma optical emission spectroscopy was also used to quantify the extent of Y exchange and to measure if there were indications of titania leaching from the framework

Agate Analysis by Raman, XRF, and Hyperspectral Imaging Spectroscopy for Provenance Determination

Raman, XRF, and hyperspectral data for the analysis of quartz and moganite ratios in agates from Brazil and Germany

Evidence for benthic oxygen production in Neoarchean lacustrine stromatolites

The evolution of oxygenic photosynthesis fundamentally altered the global environment, but the history of this metabolism prior to the Great Oxidation Event (GOE) at ca. 2.4 Ga remains unclear. Increasing evidence suggests that non-marine microbial mats served as localized ¡°oxygen oases¡± for hundreds of millions of years before the GOE, though direct examination of redox proxies in Archean lacustrine microbial deposits remains relatively limited. We report spatially distinct patterns of positive and negative cerium (Ce) anomalies in lacustrine stromatolites from the 2.74 Ga Ventersdorp Supergroup (Hartbeesfontein Basin, South Africa), which indicate that dynamic redox conditions within ancient microbial communities were driven by oxygenic photosynthesis. Petrographic analyses and rare earth element signatures support a primary origin for Ce anomalies in stromatolite oxides. Oxides surrounding former bubbles entrained in mats (preserved as fenestrae) exhibit positive Ce anomalies, while oxides in stromatolite laminae typically contain strong negative Ce anomalies. The spatial patterns of Ce anomalies in Ventersdorp stromatolites are most parsimoniously explained by localized Ce oxidation and scavenging around oxygen bubbles produced by photosynthesis in microbial mats. Our new data from Ventersdorp stromatolites supports the presence of oxygenic photosynthesis ¡«300 m.y. before the GOE, and add to the growing evidence for early oxygen oases in Archean non-marine deposit

Aragonite Dissolution Kinetics and Calcite/aragonite Ratios in Sinking and Suspended Particles in the North Pacific

The lack of consensus on CaCO3 dissolution rates and calcite to aragonite production and export ratios in the ocean poses a significant barrier for the construction of global carbon budgets. We present here a comparison of aragonite dissolution rates measured in the lab vs. in situ along a transect between Hawaii and Alaska using a 13C labeling technique. Our results show a general agreement of aragonite dissolution rates in the lab versus in the field, and demonstrate that aragonite, like calcite, shows a non-linear response of dissolution rate as a function of saturation state (Ω). Total carbon fluxes along the N. Pacific transect in August 2017, as determined using sediment traps, account for 11∼23 weight % of total mass fluxes in the upper 200 m, with a PIC (particulate inorganic carbon) /POC (particulate organic carbon) mole ratio of 0.2∼0.6. A comparison of fluxes at depths of 100 m and 200 m indicates that 30∼60% PIC dissolves between these depths with 20∼70% attenuation in POC fluxes. The molar ratio of PIC to POC loss is 0.29. The simultaneous loss of PIC and POC in the upper 200 m potentially indicates PIC dissolution driven by organic matter respiration, or metazoan/zooplankton consumption. The calcite/aragonite ratio in trap material is significantly lower in the subtropical gyre than in the subarctic gyre. Aragonite fluxes vary from 0.07 to 0.38 mmol m−2 day−1 at 100 m, and 0.06 to 0.24 mmol m−2 day−1 at 200 m along the North Pacific transect, with no specific trend over latitude. The identification of suspended PIC mineral phases by Raman spectroscopy shows the presence of aragonite below 3000 m in the subtropical gyre, but none in the subpolar gyre. These multiple lines of evidence suggest that predictions based on a strictly thermodynamic view of aragonite dissolution, combined with measured aragonite fluxes, underestimate observed alkalinity excess and measured PIC attenuation in sinking particles. Our measured aragonite flux combined with our inorganic dissolution rate only account for 9% and 0.2% of the excess alkalinity observed in the North Pacific (Feely et al., 2004), assuming aragonite sinking rates of 1 m day−1 and 100 m day−1, respectively. However, respiration-driven dissolution or metazoan/zooplankton consumption, indicated by the simultaneous attenuation of PIC and POC in sediment traps, is able to generate the magnitude of dissolution suggested by observed excess alkalinity

Pieter Boddaert to Carl Linnaeus

Pieter Boddaert to Carl Linnaeu

Synthesis and Characterization of Two- and Three-Dimensional Calcium Coordination Polymers Built with Benzene-1,3,5-tricarboxylate and/or Pyrazine-2-carboxylate

Two new calcium coordination polymers, [Ca₃(btc)₂(H₂O)₁₂] (<b>1</b>) and [Ca₂(btc)­(pzc)­(H₂O)₃] (<b>2</b>) (btc = benzene-1,3,5-tricarboxylate, pzc = pyrazine-2-carboxylate), have been synthesized using the hydro/solvothermal method and have been characterized using X-ray diffraction, IR, UV–vis, thermogravimetric analysis, and fluorescence analysis. The structure of compound <b>1</b> is a three-dimensional framework consisting of helical chains of calcium coordination polymers, while that of compound <b>2</b> is a double layered network in which the inorganic zigzag chains of calcium coordination polyhedra are linked by organic ligands. Both compounds show blue fluorescence when excited with UV light. Density functional theory calculations on electronic absorption spectra of organic ligands and calcium coordination polymers are discussed