Thermal decomposition of NH4-analcime

The thermal decomposition of ammonium-exchanged natural analcime is characterized by gas chromatography, IR spectroscopy and X-ray diffraction. The de-ammoniation and dehydroxylation proceed in parallel throughout the decomposition, which evidences the instability of the protonated analcime framework. The mechanism of degassing of NH₄-analcime changes throughout its decomposition. At the initial step, the mechanism of de-ammoniation consists in thermal dissociation of NH₄⁺ molecule onto NH₃ and proton (framework OH group) and diffusion of NH₃ out of the structure. Subsequent decomposition and removal of the OH groups lead to a progressive loss of crystallinity. At this step, an apparent activation energy for NH₃ desorption is estimated to be 145(±13) kJ mol^–1. This value is within the upper limit of the activation energy characteristic for the NH₃ desorption from proton centres in large-pore zeolites. At the final step, the adsorption of NH₃ and protons onto the defect centres in the amorphosed aluminosilicate framework results in a significant increase of an apparent activation energy for the de-ammoniation and dehydroxylation up to 270(±20) kJ mol^–1.     

Statistical relations of the run-up height of Tsunami waves to the distance and energy of the source

A statistical analysis of the relation between the run-up height of historical tsunami events and the distance and magnitude of the source was performed on the basis of the known Historical Tsunami Data Base [5]. The sample from the database used for the analysis comprises 5638 run-ups caused by 628 seismic events. This analysis, together with the dimensionality theory, shows that the statistical average of the run-up height is inversely proportional to the distance from the source to a power close to 1/2 (that is characteristic of the cylindrically symmetrical case) and directly proportional to the 3/8 power of the earthquake energy.     

Experimental study of natrolite and scolecite saturation with ammonium, methane, and propane

The incorporation of the molecular species of C-H-N fluid (ammonium, methane, and propane) into the structural cavities of natrolite and scolecite was experimentally studied at t = 200°C, P = 20 MPa, and an experiment duration of 192 h. The zeolites were modified without ion exchange by the exposure of a preliminarily dehydrated mineral to the appropriate gas. The presence of ammonium and light hydrocarbons in the crystal matrix of zeolites was confirmed by IR and Raman spectroscopy and gas chromatography. The data of differential thermogravimetry revealed differences in the behavior of CH₄- and NH₃-zeolites during heating. The X-ray diffraction patterns and IR and Raman spectra of zeolites in the region of framework vibration indicate deformations in the matrix structure after the experiments. The interaction of dehydrated scolecite with “dry” propane resulted in amorphization under the experimental parameters. The maximum methane contents in the freshly synthesized zeolites determined by gas chromatography are 4.12 wt % for CH₄-scolecite and 8.96 wt % for CH₄-natrolite. The synthetic C₃H₈-natrolite contains 4.45 wt % C₃H₈. In the zeolites saturated with respect to dry ammonium, the highest NH₃ contents were observed in the 0.4–0.25 mm scolecite fraction (12.86 wt %), 0.25–0.05 mm scolecite fraction (11.43 wt %), and NH₃-natrolite (9.28 wt %).     

New data about tsunami evidence on Russia’s Pacific coast based on instrumental measurements for 2009–2010

Doklady Earth Sciences -     

The first results of long wave registration in the range of tsunami periods in the region of Kurilsk ridge on a distributed station network corresponding member of the RAS

Doklady Earth Sciences -     

IR spectroscopic characterization of NH4-analcime

 The IR spectrum of ammonium-exchanged natural analcime (basalt, Nidym River, Siberian platform) exhibits several features that suggest a lowered symmetry for the NH₄ ⁺ ion and that this is influenced by hydrogen bonding within the framework. These features are: the pronounced splitting into three components and high-frequency shift of the ν₄-bending mode; appearance of the ν₁-stretching mode which is predicted to become IR-active when the ideal T _d symmetry of NH₄ ⁺ ion is violated, and the low-frequency shift of the ν₁- and ν₃-stretching modes. The absence of absorption lines in the 1800–2400-cm⁻¹ region indicates that hydrogen bonding between the framework and the NH⁺ ₄ ion is very weak. The three-component splitting of the ν₄-bending mode indicates that the symmetry of NH⁺ ₄ ion is lower than C_3v. This implies that at least two N–H bonds of the NH⁺ ₄ ion are disturbed by hydrogen bonding. Computer analysis of the normal vibrations of the NH⁺ ₄ molecule for different symmetry types (using harmonic approximation) indicates that the best fit to the observed ν₄ triplet frequencies for C₁ symmetry implies a deviation of the valent angle ∠H–N–H from ideal T _d symmetry of around ±2.5°. The factors governing the behaviour of the NH⁺ ₄ ion in the analcime structure are discussed. The geometry of the nearest environment of the NH⁺ ₄ ion in the analcime structure is analyzed with respect to the present IR data. Received: 2 January 2002 / Accepted: 26 June 2002 Acknowledgements We thank Dr. D. Harlov and an anonymous reviewer for their helpful comments, as well as Dr. I.A. Belitsky and Dr. S.V. Goryainov for discussion of the material. This work is supported by RFBR grants 01-05-65414, 00-05-65305 and 02-05-65313.     

Variability in the thermal structure of ocean waters in periods of strong seismic activity

An integrated database is prepared. This database includes vertical profiles of oceanographic observations in the world ocean (more than seven million stations) and seismic catalogs (more than 200000 events) and makes it possible to analyze the variability in the thermal structure of ocean waters in seismically active zones. Examples of observations off Japan’s coasts are presented. These examples demonstrate the development of temperature anomalies up to 6°C at depths exceeding 200 m.     

Compressibility and structure behaviour of maruyamaite (K-tourmaline) from the Kokchetav massif at high pressure up to 20 GPa

Mineralogy and Petrology - The structural behaviour of maruyamaite (K-dominant tourmaline) X(K0.54Na0.28Ca0.19)Y(Mg1.3Al1.17Fe0.39Ti0.14)Z(Al5Mg)[Si5.95Al0.05O18](BO3)3V,W[O1.69(OH)2.31] from the...