Abstract
The EPR spectrum of Mn2+ in microcrystalline calcite geomaterials (e.g., marbles, travertines) possesses exceptional diagnostic characteristics, allowing to relate samples to their origin (natural/synthetic, inorganic, organogenic, …) and to evaluate the details of impurities clustering. This information, beyond their mineralogical and geochemical interest, is of paramount importance for environmental, palaeoclimatic, and cultural heritage studies.
Accessing the information hidden in the Mn2+ EPR spectrum relies on disentangling spurious self-correlation among spin Hamiltonian parameters in the powder spectrum. In the present study, this goal is achieved through a systematic comparison of the temperature dependencies of four different microcrystalline calcite geomaterials. Accordingly, an assessment of the internal correlation structure of the spin Hamiltonian parameters is provided and the most sensitive discriminating parameters, which are able to mark samples, are identified.
It has been found that the spin Hamiltonian parameters useful for discrimination purposes are those which are dependent on the ligand field interaction, whereas the Fermi contact interaction, as well as the spin-spin, spin-phonon, and spin-lattice interactions, are not able to “store” information related to formation processes, nor post-depositional events. This characteristic behavior is ascribed to the occurrence of mosaic structure and to the clustering among Mn2+ and other impurity ions, which are able to induce a strong and variable ligand field interaction.
In particular, the proposed method appears fully able to reveal the biogenic origin of microcrystalline calcites and to trace post-depositional events.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- MSA Roebling medal lecture. Mineralogy, petrology, U-Pb geochronology, and geologic evolution of the Dabie-Sulu classic ultrahigh-pressure metamorphic terrane, East-Central China
- Brittle-ductile microfabrics in naturally deformed zircon: Deformation mechanisms and consequences for U-Pb dating
- In situ hot-stage AFM study of the dissolution of the barite (001) surface in water at 30–55 °C
- A multi-domain gem-grade Brazilian apatite
- High-temperature structural behaviors of anhydrous wadsleyite and forsterite
- Rates and mechanism of Y, REE, and Cr diffusion in garnet
- EPR discrimination of microcrystalline calcite geomaterials
- Crystal chemistry of Bi- and Mn-bearing vesuvianite from Långban, Sweden
- Cation ordering in Pb2+-bearing, Mn3+-rich pargasite from Långban, Sweden
- Long-term solid-phase fate of co-precipitated U(VI)-Fe(III) following biological iron reduction by Thermoanaerobacter
- The sulfur speciation in S-bearing minerals: New constraints by a combination of electron microprobe analysis and DFT calculations with special reference to sodalite-group minerals
- Simultaneous sound velocity and density measurements of NaCl at high temperatures and pressures: Application as a primary pressure standard
- The temperature and compositional dependence of disordering in Fe-bearing dolomites
- Quantifying crystallization and devitrification of rhyolites by means of X-ray diffraction and electron microprobe analysis
- Reactions of strontium anorthite with H2O+CaCl2 fluids at 500 °C and high pressure: Kinetic information from in situ synchrotron-radiation XRF analyses of the fluid
- Solubility of xenotime in a 2 M HCl aqueous fluid from 1.2 to 2.6 GPa and 300 to 500 °C
- Elastic and anelastic anomalies due to spin-state transitions in orthorhombic perovskite from isoelectronic behavior of Co3+ and Fe2+
- Accurate determination of ferric iron in garnets by bulk Mössbauer spectroscopy and synchrotron micro-XANES
- Re-investigation of the crystal structure of enstatite under high-pressure conditions
- Second-order P6̄c2-P31c transition and structural crystallography of the cyclosilicate benitoite, BaTiSi3O9, at high pressure
- High-pressure structural studies of eskolaite by means of single-crystal X-ray diffraction
- Almandine: Lattice and non-lattice heat capacity behavior and standard thermodynamic properties
- Witzkeite: A new rare nitrate-sulphate mineral from a guano deposit at Punta de Lobos, Chile
- Krasheninnikovite, KNa2CaMg(SO4)3F, a new mineral from the Tolbachik volcano, Kamchatka, Russia
- Crystal structure of pseudojohannite, with a revised formula, Cu3(OH)2[(UO2)4O4(SO4)2](H2O)12
- Letter. A natural photoelectrochemical cell for water splitting: Implications for early Earth and Mars
- Letter. In situ observation of the breakdown of magnetite (Fe3O4) to Fe4O5 and hematite at high pressures and temperatures
- Letter. The crystal structure of bartelkeite, with a revised chemical formula, PbFeGeVI(Ge2IVO7) (OH)2·H2O, isotypic with high-pressure P21/m lawsonite