Correlation of Néel temperature and vacancy defects in fine-particle goethites

Positron annihilation lifetime spectroscopy (PALS) has been used to study the vacancy-type defects in fine-particle goethites (α-FeOOH). The PALS spectra reveal three components. The intermediate lifetime component (τ₂, I₂) is attributed to positrons trapped at vacancy defects. The relative intensity of the intermediate lifetime component, I₂, increases significantly with decreasing Néel temperature, and this increase is attributed to increasing concentration of vacancy defects. These results support a model of magnetic ordering of clusters arising from a high concentration of iron vacancies which reduces the Néel temperature in these fine-particle goethites.     

Coordination of water molecules with Na+ cations in a beryl channel as determined by polarized IR spectroscopy

Subtle variations of frequencies in the infrared (IR) absorption spectra of beryl have been predicted based on the coordination between extra-framework cations and water molecules in two orientations (referred to as type I and type II) trapped within the channel. In this study, the polarized IR spectra of hydrated synthetic beryl and natural beryl were measured to clarify the relationships between the frequencies of the absorption bands and the coordination states of type II water. Na⁺ was assumed to be the predominant cation coordinated to type II water in our samples, as determined by chemical analyses. These measurements revealed a clear quantitative linear relationship in absorbance between bands at 3,602 and 1,619 and at 3,589 and 1,631 cm⁻¹. On the basis of experimental and theoretical studies, we assigned these pairs of bands to the ν₁ and ν₂ modes of doubly coordinated type II H₂O and to singly coordinated type II H₂O, respectively. These assignments were supported by IR measurements of annealed natural beryl. We also conducted dehydration studies of natural beryl, in which two observed dehydration peaks, at 600 and 750°C, suggested the dehydration of type I and type II water, respectively.     

Optical absorption and electron spin resonance in blue and green natural beryl

A comparative study of blue and green beryl crystals (from the region of Governador Valadares, Minas Gerais, Brazil) using electron paramagnetic resonance (EPR) and optical absorption (OA) spectroscopy is reported. The EPR spectra show that Fe³⁺ in blue beryl occupies a substitutional Al³⁺ site and in green beryl is localized in the structural channels between two O₆ planes. On the other hand the infrared spectra show that the alkali content in the blue beryl is mostly at substitutional and/or interstitial sites and in green beryl is mostly in the structural channels. The OA spectra show two types of Fe²⁺. Thermal treatments above 200° C in green beryl cause the reduction of Fe³⁺ into Fe²⁺ accompanied by a change of color to blue. The blue beryl color does not change on heating. The kinetics of the thermal conversion of Fe³⁺ into Fe²⁺ is composed of two first order processes; the first one has an activation energy ΔE ₁=0.30 eV and the second one has an activation energy ΔE ₂=0.46 eV.     

Alpha-decay damage in minerals of the pyrochlore group

X-ray diffraction analysis and transmission electron microscopy have been used to study the effects of alpha-decay damage in pyrochlore group minerals, characterized by the general formula A _1?m B ₂O₆(O,OH,F)_1?n ·pH₂O. As defined by the XRD intensity ratio I/I ₀ , both the saturation dose (for which I/I ₀ =0.1?0.0) and the dose which signifies the initial loss of crystallinity (for which I/I ₀ =1.0?0.8) increase as a function of geologic age. The increase is attributed to annealing of isolated alpha-recoil tracks back to the original crystalline structure. The tracks have calculated mean lives, τ_a, on the order of 10⁸ years. In contrast, minerals which remain crystalline (e.g., uraninite, UO₂) despite doses of up to 10¹⁸ alpha-events/mg have mean alpha-recoil track lives ≈10⁴ years (Eyal and Fleischer 1985). After correcting the calculated dose for annealing of alpha-recoil damage, I/I ₀ is observed to decrease exponentially to zero over the dose range 0.02–1.0 × 10¹⁶ alpha-events/mg. The relationship between I/I ₀ and “corrected” dose was used to calculate an average alpha-recoil track diameter of 4.6 nm, in which < 2600 atoms are displaced. XRD line broadening due to strain dominates the first half of the crystalline-to-metamict transition, reaching a maximum of 0.003, then decreasing to < 0.001. Line broadening due to decreasing crystallite size dominates the latter half of the transition. Estimated crystallite dimensions decrease from 450 nm to < 15 nm prior to reaching the fully metamict state. With increasing dose HRTEM images of microlites from the Harding pegmatite sequentially exhibit: 1) mottled diffraction contrast, 2) isolated 1–5 nm aperiodic areas, 3) coexisting aperiodic and crystalline areas, 4) relict “islands” of crystalline material in an aperiodic matrix, and 5) complete loss of lattice fringe periodicity. With no consideration given to alpha-recoil track fading, the transition covers a dose range of 0.04–1.7 × 10¹⁷ alpha-events/mg. Using a value of τ_a=10⁸ years, this dose range is corrected down to 0.02–1.2 × 10¹⁶ alpha-events/mg. The metamict state is characterized by a range of M-M and M-O distances which give rise to bands of diffuse scattering centered at 0.30 nm and 0.18 nm, respectively, in x-ray and electron diffraction patterns. Random image contrast shown by HRTEM is consistent with a random network type structure, an interpretation supported by EXAFS/XANES studies (Greegor et al. 1985a, b, 1987). The structure of metamict pyrochlore consists of an aperiodic framework of corner-sharing B-O polyhedra. Compared to the crystalline precursor, the metamict state displays a reduced M-O coordination number and mean bond length, increased distortion of the B-site, and a slight increase in the average M-M distance.     

Matrix corrections in trace-element analysis by X-ray fluorescence: An extension of the Compton scattering technique to long wavelengths

Mass absorption coefficients (A₂) for a series of standard rocks, have been calculated in the wavelength region 0.492–3.03 $\text{a}\text{?}$. Plots of these data against the intensity of the Compton scattered peak [(I) Compton] give an excellent correlation for the wavelengths 0.429 $\text{a}\text{?}$ to the Fe-absorption edge (1.74 $\text{a}\text{?}$); the data confirm the observations of Reynolds. Hence, routine measurement of one peak will give the mass absorption coefficient of a sample in an analytically important region (Sn/1bK_α to Ni/1bK_α). A₂ has also been directly measured on three of the samples and systematic differences between calculated and measured are attributed to the measuring technique. At wavelengths longer than the Fe-absorption edge, (up to 3.03 $\text{a}\text{?}$) A₂ can be estimated using a combination of (I) Compton and Fe/1bK_α c.p.s. This technique enables meaningful matrix corrections to be carried out on the elements Co, Mn, Cr, V, Ti, Sc (K spectra) and Ba (L spectra). Cr and Ba results are presented for some standard rocks.     

Polarized Raman spectra of beryl and bazzite

The polarized Raman spectra of four different beryl crystals were studied at room temperature in the range from 30 to 4000 cm^-1. The spectra show significant differences between the samples studied, and corrections are proposed for the reference Raman spectra of beryl previously reported by Adams and Gardner (1974). Type II water is observed in two crystals; the corresponding symmetric Raman stretching band at 3595 cm^-1 is extremely strong for an impurity (about 20% of the strongest beryl lattice mode). Another, sharper, band of similar intensity at 3605 cm^-1 could possibly originate from a hydroxyl stretching mode. Additional weaker bands are observed around 1600 cm^-1 and 3600–3750 cm^-1. The first polarized Raman spectra of bazzite are presented and discussed.     

Soft X-ray spectroscopy of ferrous silicates

Energy gaps and electrical conductivities in the ferrous silicates, Fe₂SiO₄ and FeSiO₃, depend primarily on Fe-O bonding and may be studied by ultraviolet and soft X-ray spectroscopy. We have measured FeL_II–III X-ray band spectra under conditions of “minimal” (I₄, at 4.0 keV) and “high” (I₁₀, at 10.0 keV) self absorption to determine 3d orbital energy levels, to delineate d states in the valence band, and to construct band gap models. Absorption spectra, I₄/I₁₀, were computed to determine vacant orbital levels in the gap. A difference function (I₄–I₁₀) has been proposed to identify X-radiation at photon energies above the measured L_III absorption edge, including high-energy, double-vacancy satellites and radiative transitions involving the anti-parallel (spin-down) d ⁶ electron in the ground state. The proposed band gap model for Fe₂SiO₄ is consistent with that of Nitsan and Shankland (1976), including an intrinsic transition of 6.5 eV and an energy gap of 7.8 eV. The 3d orbital energy level electronic structures are in general agreement with levels computed by Tossell et al. (1974) for [FeO₆]^10? in FeO using an SCF Xα cluster MO method. A high-energy, double-vacancy satellite was found at ～710.7 eV, and is presumed to originate from an L_IIIM_II,III initial state. The intensity of these satellites for the ferrous silicates and other iron compounds, and corresponding Fe L_II/L_III intensity ratios are correlated with differences in band gap magnitudes and gap structure. Fe L_II/L_III intensity ratios are not well correlated with iron oxidation state.     

The effect of thermal treatment on the 57Fe Mössbauer spectrum of beryl

Mössbauer spectra (MS) of blue, green and yellow beryl (ideally Be₃Al₂Si₆O₁₈) containing approximately 1% of iron were obtained at 295 and 500 K. Room temperature (RT) spectra of both blue and green samples showed the presence of an asymmetric Fe²⁺ doublet (ΔE _Q~2.7 mm/s, δ~1.1 mm/s), with a very broad low-velocity peak. There is no clear evidence for the presence of a ferric component. The MS of the yellow sample at RT consists of an intense central absorption with parameters typical for Fe³⁺ (ΔE _Q~0.4 mm/s, δ~0.29 mm/s), plus an apparently symmetrical Fe²⁺ doublet. This sample acquires a light-blue shade upon heating in air at about 620 K. Thermal treatments at high temperatures caused no significant changes in the MS, but the green and yellow beryl acquire a blue colour. All these results are interpreted in relation to the existence of channel water and the distribution of iron among the available crystallographic sites.     

Vibrational spectroscopy of beryllium aluminosilicates: Heat capacity calculations from band assignments

Far-infrared, mid-IR, and Raman powder spectra were measured on six phases (bromellite, chrysoberyl, phenakite, bertrandite, beryl, and euclase) in the system BeO-Al₂O₃-SiO₂-H₂O. A single-crystal absorption spectrum of IR fundamentals in beryl is also presented, which more closely resembles the powder absorption spectrum than it does absorption spectra calculated from single-crystal reflection data. Assignments of the SiO₄ and BeO₄ internal vibrations are made in accordance with each mineral's symmetry and composition and by comparison to structural analogs. Heat capacities C _v calculated for these partial band assignments agree with C _v derived from experimental C _p for all six phases, provided that Kieffer's (1979c) model is slightly modified to correctly enumerate both Si-O and Be-O stretching modes in the high frequency region (>750 cm^?1). Si-O stretching bands were found to out-number Be-O stretching modes in the high-energy region of the vibrational spectra with two exceptions: (1) For those phases containing oxygen ions not coordinated to silicon, vibrations occurring at v>1,080 cm^?1 that are attributable to Be-O (H) stretching must be treated separately in the model in order to calculate C _v accurately. (2) Minerals consisting entirely of interlocking Si and Be tetrahedra (i.e., phases without Al or OH) can be modeled by one optic continuum representing all optical modes. These results, along with the occurrence of very low energy lattice vibrations for Be-silicates within Al, suggests that although Be-O bonds are generally weaker than neighboring Si-O bonds, Be mimics the network-forming characteristic of Si to a limited extent.     

Simulation of the fluorescence evolution of “live” oils from kerogens in a diamond anvil cell: Application to inclusion oils in terms of maturity and source

The evolution of fluorescence has been measured for “live” oils generated from 14 oil-prone kerogens or coals from varying depositional environments during closed system pyrolysis in a diamond anvil cell at three heating rates (3, 8, and 25 °C/min), and temperatures up to 600 °C. The measured fluorescence intensities of the samples, employing using violet excitation at 405 nm, increases significantly during maturation intervals within the oil window, while the fluorescence spectra of oils generated from all studied kerogens exhibit progressive blue-shift of peak wavelengths (λ_max) and red/green quotients (I₆₅₀/I₅₀₀) upon increasing maturity. The observed trend is consistent with a maturity dependence of the spectral shift, which is widely recognized in natural hydrocarbon inclusions and crude oils using ultraviolet (UV) excitation (365 nm). The data presented herein suggest that the λ_max of spectra for inclusion oils shift in similar direction despite differences in composition or source kerogen. This implies that the reverse or anomalous trends reported for inclusion oils in nature may be attributed to other processes, which significantly alters the fluorescence properties of oils subsequent to their generation. Oils with the similar color (λ_max or I₆₅₀/I₅₀₀) can be derived from diverse kerogens with maturities that vary by ±0.3% Ro, suggesting that the fluorescent colors of crude and inclusion oils are both maturity- and source-dependent, and therefore cannot be used as universal maturity indicators. In addition, the blue-shifts observed for cumulative oils generated from all kerogens approaches similar minima λ_max values around the green-yellow wavelength (564 nm) and at I₆₅₀/I₅₀₀ values around 0.6, at maturities close to the middle or late stage of oil generation. This suggests that most late-stage cumulative oils will exhibit similar colors. Oils generated during late-stage maturity intervals, however, can exhibit colors with shorter wavelengths.     

Characterization of beryl (aquamarine variety) by Mössbauer spectroscopy

The Mössbauer spectra of several blue beryls have been obtained in the temperature range of 4.2–500 K. A common feature observed in all room-temperature spectra is the presence of an asymmetric Fe²⁺ doublet (ΔE _Q ?～?2.7?mm?s^?1, δ?～?1.1?mm?s^?1), with a very broad low-velocity peak. This asymmetry seems to be related to a relaxation process involving ferrous ions and water molecules in the structural channels, as suggested by Price et?al. (1976). Surprisingly, the spectrum at 500?K also shows a broad, but symmetrical, doublet, with a clear splitting of the lines indicating the presence of at least two Fe²⁺ components. The room-temperature spectrum obtained after the 500?K run shows the same features as prior to the heating. At 4.2?K the spectrum of a deep blue beryl was well fitted with four symmetrical doublets, one of which could be related to Fe²⁺ in the structural channels. Ferrous ion was also found to occupy the octahedral and tetrahedral sites, whereas ferric ion is most probably located in the octahedral site. A meaningful fit of the room-temperature spectrum, as well as an explanation for the temperature dependence of the Mössbauer spectra, are discussed. Finally, it is believed that the color in beryl will be dictated by the relative proportions of Fe³⁺ in the octahedral sites and of Fe²⁺ in the channels.     

EPR investigation of NO2 and CO2 − and other radicals in beryl

A number of different impurities are located in the open channels of natural beryl crystals. The rare Maxixe beryl contains an unusual amount of NO₂. The isoelectronic CO₂ ⁻ radical is found in the irradiated Maxixe-type beryl. The NO₂ radicals are distributed in the Be–Al plane of the crystal, with the nitrogen atom close to the oxygens of the beryl cavity wall. These oxygens repel the negative CO₂ ⁻ radical, which is located at the center of the beryl cavity and rotates around its O–O axis, which is parallel to the crystal c-axis. When there is a nearby alkali ion at the center of the beryl channel, it reorients the CO₂ ⁻ radical so that its bisector is parallel to the c-axis and points toward the positive ion. Different signals are analyzed for Li⁺, Na⁺, and another counter-ion, which probably is Cs⁺. The related NO₃ and CO₃ ⁻ radicals are the color centers in the investigated deep blue beryls. The slow decay of the color, which makes these beryls useless as gem stones, is related to the decay of the hydrogen atoms which are present in these crystals. Evidence is given that NO₃ is created in Maxixe beryl by a natural process, while CO₃ ⁻ in Maxixe-type beryl has been created by irradiation. The temperature dependence of the EPR signals of these two radicals was investigated, but a definitive proof that they rotate at the center of the beryl cavity could not be given. EPR signals from some other radicals in beryl have been observed and described.     

Thermal expansion coefficients for indialite,emerald, and beryl

Thermal expansion coefficients ?₁ and ?₃ calculated for the hexagonal minerals indialite, emerald and beryl are, in general, small with ?₃ being negative near room temperature. This unusual behavior leads to low volume coefficients of thermal expansion (β=2?₁+?₃) making these materials ideal ceramic bodies for catalyst carriers in air-pollution control. The temperature at which the c-cell edge length of beryl is a minimum is strongly dependent upon the presence of trace amounts of impurity atoms. This effect is ascribed to changes in the Grüneisen parameters.     

Phase transitions in langbeinites II: Raman spectroscopic investigations of K2Cd2(SO4)3

Polarized single crystal Raman spectra of the langbeinite K₂Cd₂(SO₄)₃ were recorded for different polarisations. With a view to understanding the phase transition mechanism, the lattice vibrational spectra (0–300 cm^?1), as well as the SO₄ symmetric stretching mode v ₁ (1,022 cm^?1), were recorded at different temperatures. No soft modes were observed. From the study of the temperature variation of the integrated intensity I ₀ and band width Γ of the hard mode (1,022 cm^?1), both SO₄ libration and SO₄ order/disorder models were ruled out as possible phase transition models. On the other hand, the model of Speer and Salje (paper I), involving the distortion of the polyhedra around Cd and K ions, explains the observed temperature behaviour of the Raman spectra very well. The consequences of a possible hypothetical high-temperature phase are discussed.     

Blue, complexly zoned, (Na,Mg,Fe,Li)-rich beryl from quartz-calcite veins in low-grade metamorphosed Fe-deposit Sk��ly near Ryma?ov, Czech Republic

Syn-tectonic quartz-calcite veins containing blue beryl are enclosed in hematite > magnetite-rich portions of the low-grade metamorphosed Fe-deposit Skály near Ryma?ov, Czech Republic. Aggregates of pale to deep blue beryl, up to 2?cm in diameter, are associated with euclase, clinochlore, hematite, albite and dravite. Complexly zoned beryl crystals consist of skeletal aggregates of beryl I randomly distributed within volumetrically dominant beryl II with narrow rims of beryl III. All types of beryl have similar contents of Na (0.32?C0.49 apfu) and Mg (0.31?C0.41 apfu) but variable contents of Fe_tot (0.05?C0.34 apfu) and Al (1.20?C1.62 apfu). The LA-ICP-MS study yielded elevated contents of Li, up 1,314?ppm (0.28?wt.% Li₂O) in beryl I. The quartz-calcite veins represent an unusual type of low-T metamorphic-hydrothermal vein related to Fe-ore deposit characterized by single-stage fracturing and mobilization in a closed system at T~200?C300°C and CO ₃ ^2- as a major complexing agent for the mobility of Be.     

The evolution of hydrocarbon dust grains in the interstellar medium and its influence on the infrared spectra of dust

Computations of the evolution of the distributions of the size and degree of aromatization of interstellar dust grains, destruction by radiation and collisions with gas particles, and fragmentation during collisions with other grains are presented. The results of these computations are used to model dust emission spectra. The evolution of an ensemble of dust particles sensitively depends on the initial size distribution of the grains. Radiation in the considered range of fluxes mainly aromatizes grains. With the exception of the smallest grains, it is mainly erosion during collisions with gas particles that leads to the destruction of grains. In the presence of particle velocities above 50 km/s, characteristic for shocks in supernova remnants, grains greater than 20 Å in size are absent. The IR emission spectrum changes appreciably during the evolution of the dust, and depends on the adopted characteristics of the grains, in particular, the energy of their C–Cbonds (E₀). Aromatic bands are not observed in the near-IR (2–15 μm) when E₀ is low, even when the medium characteristics are typical for the average interstellarmedium in our Galaxy; this indicates a preference for high E₀ values. The influence of the characteristics of the medium on the intensity ratios for the dust emission in various photometric bands is considered. The I_3.4/I_11.3 intensity ratio is most sensitive to the degree of aromatization of small grains. The I_3.3/I₇₀₊₁₆₀ ratio is a sensitive indicator of the contribution of aromatic grains to the total mass of dust.     

High-pressure crystal chemistry of chromous orthosilicate, Cr2SiO4. A single-crystal X-ray diffraction and electronic absorption spectroscopy study

The high-pressure behaviour of chromous orthosilicate, Cr₂SiO₄, has been studied by means of single-crystal X-ray diffraction and electronic absorption spectroscopy. X-ray diffraction data show that the structure remains orthorhombic to the highest pressure reached of 9.22?GPa. The compressibility of the unit-cell is strongly anisotropic with the c axis approximately six times more compressible than the a and b axes. A third-order Birch-Murnaghan equation of state fitted to the volume-pressure data yields V ₀?=?610.10(3)?ų, K = 94.7(4)?GPa, K′?=?8.32(14). Cr₂SiO₄ is therefore more compressible than the isostructural Cd analogue, even though its molar volume is smaller. This unusual behaviour can be attributed to the fact that the Cr atom is too small for the six-coordinated site that it occupies, and the site is therefore strongly distorted. Structure refinements indicate that under high pressures the Cr atom remains strongly displaced from the central position of the octahedron. Polarized and unpolarized electronic absorption spectra include a strong absorption band occuring at 18.300 cm^?1 for E//c (which is parallel to the shortest Cr-Cr vector in the structure) which has an unusually large half width (5000?cm^?1), indicative of electronic interaction between metal centres. Deconvolution of unpolarized high-pressure spectra show that the relative integrated intensity of this component increases linearly from 40% at 1?bar to 60% at 11.2?GPa. Both the structural changes and the absorption spectra at high pressures suggest that pairs of adjacent Cr atoms in chromous orthosilicate form chromium dimers with a weak metal-metal bond, which is consistent with the diamagnetic response found at ambient pressure.     

The solubility of iron hydroxide in sodium chloride solutions

The solubility of iron(III) hydroxide as a function of pH was investigated in NaCl solutions at different temperatures (5–50°C) and ionic strengths (0–5 M). Our results at 25°C and 0.7 M in the acidic range are similar to the solubility in seawater. The results between 7.5 to 9 are constant (close to 10⁻¹¹ M) and are lower than those found in seawater (>10⁻¹⁰) in this pH range. The solubility subsequently increases as the pH increases from 9 to 12. The solubility between 6 and 7.5 has a change of slope that cannot be accounted for by changes in the speciation of Fe(III). This effect has been attributed to a solid-state transformation of Fe(OH)₃ to FeOOH. The effect of ionic strength from 0.1 to 5 M at a pH near 8 was quite small. The solubility at 5°C is considerably higher than at 25°C at neutral pH range. The effects of temperature and ionic strength on the solubility at low and high pH have been attributed to the effects on the solubility product and the formation of FeOH²⁺ and Fe(OH)₄⁻. The results have been used to determine the solubility products of Fe(OH)₃, K¹_Fe(OH)3 and hydrolysis constants, β¹₁, β¹₂, β¹₃, and β¹₄ as a function of temperature (T, K) and ionic strength (I):log K¹_Fe(OH)3 = −13.486 − 0.1856 I^0.5 + 0.3073 I + 5254/T (σ = 0.08)log β¹₁ = 2.517 − 0.8885 I^0.5 + 0.2139 I − 1320/T (σ = 0.03)log β¹₂ = 0.4511 − 0.3305 I^0.5 − 1996/T (σ = 0.1)log β¹₃ = −0.2965 − 0.7881 I^0.5 − 4086/T (σ = 0.6)log β¹₄ = 4.4466 − 0.8505 I^0.5 − 7980/T. (σ = 0.2)Both strong ethylenediaminetetraacetic acid and weak (HA) organic ligands greatly affect iron solubility. The additions of ethylenediaminetetraacetic acid and humic material were shown to increase the solubility near pH 8. The higher solubility of Fe(III) in seawater compared to 0.7 M NaCl may be caused by natural organic ligands.     

Bounding relationships between parameters of earthquakes and seismogenic clastic dikes (based on worldwide data)

This paper presents the first boundary equations describing the relationship between earthquake parameters (magnitude M _S and macroseismic intensity I _P at the observation point on the MSK-64 scale) and clastic dikes (having maximal thickness m _cd , visible height h _cd , and the index of manifestation intensity of dikes in the cross section I _cd ). As was expected, the maximal size of dikes grows with an increase in the earthquake magnitude and macroseismic intensity. Analysis of the dependences showed that it is better to use all three parameters for estimation of the minimal threshold M _S or I _P from clastic dikes, and, in the absence of data on seismogenic rupture, the maximal calculated value should be used. Some limitations in application and the advantages of the equations obtained are discussed with respect to characterizing earthquakes of the pre-instrumental period.     

An example of multicomponent magnetization in welded tuffs: a case study of Upper Cretaceous welded tuffs of eastern Russia

Four distinct components of natural remanent magnetization were isolated from a single site in welded tuffs in the Upper Cretaceous Kisin Group of the Sikhote Alin mountain range, Russia. In order to contribute toward a basis for an interpretation of multicomponent magnetization, rock magnetic experiments were performed on the welded tuffs. All four magnetization components essentially reside in magnetite. The lowest-temperature component up to 300 °C (component A: D=349.3°, I=60.9°, α₉₅=7.3°, N=7) is a present day viscous magnetization. The third-removed component (component C: D=41.4°, I=51.8°, α₉₅=3.5°, N=8), isolated over the temperature range of 450–560 °C, is a primary remanence. The second- and fourth-demagnetized components (component B: D=174.7°, I=−53.1°, α₉₅=21.2°, N=3 and component D: D=188.1°, I=−64.5°, α₉₅=4.0°, N=8, respectively) are secondary magnetizations related to a thermal event in Sikhote Alin between 66 and 51 Ma. Components B and D were acquired through different remagnetization processes. Component B is ascribed to a thermoviscous remanent magnetization carried by single-domain magnetite, and component D is a chemical remanent magnetization.