Characterization of smectite to NH4-illite conversion series in the fossil hydrothermal system of Harghita Bãi, East Carpathians, Romania
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Iuliu Bobos
Abstract
Ammoniumillite (NH4-I) is one of the alteration products present in a breccia structure in the fossil hydrothermal system from Harghita Bãi (East Carpathians), Romania. A series from smectite (S) via ordered interstratified structures to NH4-I (40 to 5%S) was characterized by Xray diffraction (XRD), Fourier transforminfrared spectroscopy (FTIR), scanning and transmission electron microscopy (SEM and TEM), and chemical analyses. Calculation of one-dimensional Xray patterns was simulated with the NEWMOD code. Transition from two- to one-water smectite interlayer was identified by XRD. Selected samples were saturated with K+, Mg2+, and Li+cations to differentiate low- to high-charge smectite or beidelite layers. X-ray patterns of random powders of K+saturated samples, heated at 300 °C show a transition from 1Md to cis- and trans- vacant 1M polytype. The cell parameters of the cisvacant and transvacant 1M polytype were calculated by oblique texture electron diffraction. The vibration frequencies at 1430 cm-1 of the NH bond were identified in the samples analyzed. Scanning and transmission electron microscopy images show morphological changes from flaky to lathlike shapes. The mean shape ratio of lath crystals ranges from 6 to 5.42 nm and the mean area from 7.8 to 24 × 104 nm2. The mean thickness of the NH4-I layers ranges from 4.62 to 7.89 nm. The calculated structural formula of end-member NH4-I (5%S) is: [(NH4+)0.66K+0.10Na+0.01Sr2+0.02]0.81 (Al3+1.85Fe3+0.01Mg2+0.15)2.01(Si4+3.30 Al3+0.70)4.00O10(OH)2. The fixed NH4+ content quantified ranges from 0.39 to 0.66 atoms per half unit cell [O10(OH)2]. Tetrahedral and octahedral substitutions took place as the %S decreases. The NH4-I-S series formed via direct precipitation from solution at different temperatures.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Dana medal lecture: Tilts and tetrahedra: The origin of the anisotropy of feldspars
- Amorphous Materials: Determination of water content in silicate glasses using Raman spectrometry: Implications for the study of explosive volcanism
- Density functional calculations of the enthalpies of formation of rare-earth orthophosphates
- U-Pb ID-TIMS dating applied to U-rich inclusions in garnet
- Wassonite: A new titanium monosulfide mineral in the Yamato 691 enstatite chondrite
- Determination of Mn valence states in mixed-valent manganates by XANES spectroscopy
- The morphology of the reaction front of the dissolutionprecipitation reaction rutile + wollastonite = titanite in time series experiments at 600 °C/400 MPa
- Precipitation of rutile and ilmenite needles in garnet: Implications for extreme metamorphic conditions in the Acadian Orogen, U.S.A.
- The genesis of mantle-derived sapphirine
- Experimental investigation of smectite interaction with metal iron at 80 °C: Structural characterization of newly formed Fe-rich phyllosilicates
- High-pressure study of a natural cancrinite
- Investigation of cation ordering in triclinic sodium birnessite via 23Na MAS NMR spectroscopy
- The dual behavior of the β-As4S4 altered by light
- Pressure-induced changes in local electronic structures of SiO2 and MgSiO3 polymorphs: Insights from ab initio calculations of O K-edge energy-loss near-edge structure spectroscopy
- Structural stability, cation ordering, and local relaxation along the AlNbO4-Al0.5Cr0.5NbO4 join
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- Determination of Fe3+/Fe using the electron microprobe: A calibration for amphiboles
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- Tsilaisite, NaMn3Al6(Si6O18)(BO3)3(OH)3OH, a new mineral species of the tourmaline supergroup from Grotta d’Oggi, San Pietro in Campo, island of Elba, Italy
- Letter. A nanoscopic approach to the kinetics of anhydrite (100) surface growth in the range of temperatures between 60 and 120 °C
- Letter. High-pressure phase transitions in Ca-Mn carbonates (Ca,Mn)CO3 studied by Raman spectroscopy
- Letter. Actinides in Geology, Energy, and the Environment: Thermally induced transformation of vorlanite to “protovorlanite”: Restoration of cation ordering in self-irradiated CaUO4
