Influence of high pressure on the refractive index and density of tholeiite basalt glass

The pressure dependence of the refractive index of tholeiite basalt glass was studied in the range 0–5.0 GPa with an interference-polarization microscope and a diamond anvil cell. The non-linear change of the refractive index of basalt glass, with a kink around 2.0–2.5 GPa, is similar to the behaviour of the refractive index, density and elastic properties of silica glass under pressure. The comparison of data for glasses with continuous silicon-oxygen frameworks shows that the strain-polarizability potential Λ (photoelasticity theory), describing the change of refraction R with increasing density ρ: (Λ=–ΔR ρ/R₀Δρ) is nearly constant. Using the value Λ=0.21 and the refractive index data, the compressibility of the investigated basalt glass under pressure up to 5.0 GPa was calculated by the equation: Δρ/ρ=6nΔn/(n²–1)(n²+2)(1–Λ). The results of the calculation agree with the compressibility of tholeiite basalt glass determined by measurement of the sizes of glass samples under pressure using photographic equipment. The compressibility of basalt glass is higher than that for plagioclases, resulting in the possibility of relative density inversion of deep-seated basalt melts and plagioclase crystals. These data reinforce the model of anorthositec crust generation on the Earth and on the Moon by inverse plagioclase crystal fractionation at high degrees of melting of basic rocks.     

Distribution of regions of emission at different frequencies in pulsar magnetospheres

It is shown that the observed width of the emission profile W ₁₀ and the maximum derivative C of the polarization position angle for the mean profile of a pulsar can be used to calculate the ratio n of the emission-cone radius ?? to the minimum distance between the line of sight and the center of this cone fairly accurately. Estimates of n obtained earlier by eye based on the shape of the emission profiles are close to these more accurate values for pulsars from a catalog at a frequency near 1 GHz. Values of n are calculated for several dozen pulsars using data at 10 and 20 cm. In the standard model, the ratio of n at two frequencies is equal to the ratio of the squares of the distances from the center of the neutron star to the emission levels at the two frequencies. Statistical dependences of the profile width on the pulsar period for these wavelengths and a model assuming emission at the local plasma frequency are used to determine the absolute values of these distances. These estimates display good consistency and yield distances to the emission levels of the order of several tens of neutron-star radii. The calculations take into account possible variation of the dimensions of the polar cap associated with the inclination of the emission cone to the rotational axis of the pulsar; i.e., the influence of the angle ?? between the magnetic moment and rotational axis of the neutron star. Values of ?? calculated earlier for the pulsar sample considered are used for this analysis.     

A spindown mechanism for short-period radio pulsars

It is shown that a model with accretion in a “quasi-propeller” mode can explain the observed spindown of pulsars with periods P<0.1 s. The mean accretion rate for 39 selected objects is \(\dot M = 5.6 \times 10^{ - 11} M_ \odot /year\). If \(\dot M\) is constant during the pulsar’s lifetime, the neutron star will stop rotating after 10⁷ years. The mean magnetic field at the neutron-star surface calculated in this model, \(\bar H_0 = 6.8 \times 10^8 G\), is consistent to an order of magnitude with the values of H₀ for millisecond pulsars from known catalogs. However, the actual value of H₀ for particular objects can differ from the catalog values by appreciable factors, and these quantities must be recalculated using more adequate models. The accretion disk around the neutron star should not impede the escape of the pulsar’s radiation, since this radiation is generated near the light cylinder in pulsars with P<0.1 s. Pulsars such as PSR 0531+21 and PSR 0833-45 have probably spun down due to the effect of magnetic-dipole radiation. If the difference in the braking indices for these objects from n=3 is due to the effect of accretion, the accretion rate must be of the order of 10¹⁸ g/s.     

Modeling the wind of the Be star SS 2883

Observations of eclipses of the radio pulsar B1259-63 by the disk of its Be-star companion SS 2883 provide an excellent opportunity to study the winds of stars of this type. The eclipses lead to variations in the radio flux (due to variations in the free-free absorption), dispersion measure, rotation measure, and linear polarization of the pulsar. We have carried out numerical modeling of the parameters of the Be-star wind and compared the results with observations. The analysis assumes that the Be-star wind has two components: a disk wind in the equatorial plane of the Be star with a power-law fall-off in the electron density n _e with distance from the center of the star \(\rho (n_e \sim \rho ^{ - \beta _o } )\), and a spherical wind above the poles. The parameters for a disk model of the wind are estimated. The disk is thin (opening angle 7.5°) and dense (electron density at the stellar surface n_0e ～ 10¹² cm^?3, β₀ = 2.55). The spherical wind is weak (n_0e ? 10⁹ cm^?3, β₀ = 2). This is the first comparison of calculated and observed fluxes of the pulsating radio emission.     

Re-evaluating Nd/Nd in lunar mare basalts with implications for the early evolution and bulk Sm/Nd of the Moon

The Moon likely accreted from melt and vapor ejected during a cataclysmic collision between Proto-Earth and a Mars-sized impactor very early in solar system history. The identical W, O, K, and Cr isotope compositions between materials from the Earth and Moon require that the material from the two bodies were well-homogenized during the collision process. As such, the ancient isotopic signatures preserved in lunar samples provide constraints on the bulk composition of the Earth. Two recent studies to obtain high-precision ¹⁴²Nd/¹⁴⁴Nd ratios of lunar mare basalts yielded contrasting results. In one study, after correction of neutron fluence effects imparted to the Nd isotope compositions of the samples, the coupled ¹⁴²Nd-¹⁴³Nd systematics were interpreted to be consistent with a bulk Moon having a chondritic Sm/Nd ratio [Rankenburg K., Brandon A. D. and Neal C. R. (2006) Neodymium isotope evidence for a chondritic composition of the Moon. Science312, 1369-1372]. The other study found that their data on the same and similar lunar mare basalts were consistent with a bulk Moon having a superchondritic Sm/Nd ratio [Boyet M. and Carlson R. W. (2007) A highly depleted Moon or a non-magma origin for the lunar crust? Earth Planet. Sci. Lett.262, 505-516]. Delineating between these two potential scenarios has key ramifications for a comprehensive understanding of the formation and early evolution of the Moon and for constraining the types of materials available for accretion into large terrestrial planets such as Earth.To further examine this issue, the same six lunar mare basalt samples measured in Rankenburg et al. [Rankenburg K., Brandon A. D. and Neal C. R. (2006) Neodymium isotope evidence for a chondritic composition of the Moon. Science312, 1369-1372] were re-measured for high-precision Nd isotopes using a multidynamic routine with reproducible internal and external precisions to better than ±3 ppm (2σ) for ¹⁴²Nd/¹⁴⁴Nd ratios. The measurements were repeated in a distinct second analytical campaign to further test their reproducibility. Evaluation of accuracy and neutron fluence corrections indicates that the multidynamic Nd isotope measurements in this study and the 3 in Boyet and Carlson [Boyet M. and Carlson R. W. (2007) A highly depleted Moon or a non-magma origin for the lunar crust? Earth Planet. Sci. Lett.262, 505-516] are reproducible, while static measurements in the previous two studies show analytical artifacts and cannot be used at the resolution of 10 ppm to determine a bulk Moon with either chondritic or superchondritic Sm/Nd ratios. The multidynamic data are best explained by a bulk Moon with a superchondritic Sm/Nd ratio that is similar to the present-day average for depleted MORB. Hafnium isotope data were collected on the same aliquots measured for their ¹⁴²Nd/¹⁴⁴Nd isotope ratios in order to assess if the correlation line for ¹⁴²Nd-¹⁴³Nd systematics reflect mixing processes or times at which lunar mantle sources formed. Based on the combined ¹⁴²Nd-¹⁴³Nd-¹⁷⁶Hf obtained we conclude that the ¹⁴²Nd-¹⁴³Nd correlation line measured in this study is best interpreted as an isochron with an age of 229⁺²⁴₋₂₀Ma after the onset of nebular condensation. The uncertainties in the data permit the sources of these samples to have formed over a 44 Ma time interval. These new results for lunar mare basalts are thus consistent with a later Sm-Nd isotope closure time of their source regions than some recent studies have postulated, and a superchondritic bulk Sm/Nd ratio of the Moon and Earth. The superchondritic Sm/Nd signature was inherited from the materials that accreted to make up the Earth-Moon system. Although collisional erosion of crust from planetesimals is favored here to remove subchondritic Sm/Nd portions and drive the bulk of these bodies to superchondritic in composition, removal of explosive basalt material via gravitational escape from such bodies, or chondrule sorting in the inner solar system, may also explain the compositional features that deviate from average chondrites that make up the Earth-Moon system. This inferred superchondritic nature for the Earth similar to the modern convecting mantle means that there is no reason to invoke a missing, subchondritic reservoir to mass balance the Earth back to chondritic for Sm/Nd ratios. However, to account for the subchondritic Sm/Nd ratios of continental crust, a second superchondritic Sm/Nd mantle reservoir is required.     

The mechanism of surface chemical kinetics of dissolution of minerals

This paper deals with the mechanism of dissolution reaction kinetics of minerals in aqueous solution based on the theory of surface chemistry.Surface chemical catalysis would lead to an obvous decrease in active energy of dissolution reaction of minerals.The dissolution rate of minerals is controlled by suface adsorption,surface exchange reaction and desorption,depending on pH of the solution and is directly proportional to δH^n0 ,When controlled by surface adsorption,i.e.,nθ=1,the dissolution rate will decrease with increasing pH;when controlled by surface exchane reaction,i.e.,nθ=0,the dissolution rate is independent of pH;when controlled by desorption,nθis a positive decimal between 0 and 1 in acidic solution and a negative decimal between-1 and 0 in alkaline solution.Dissolution of many minerals is controlled by surface adsorption and/or surface exchange reactions under acid conditions and by desorption under alkaline conditions.     

A unified model for hydrogen in the Earth and Moon: No one expects the Theia contribution

The Moon is thought to have formed after a planetary embryo, known as Theia, collided with the proto-Earth 4.5 billion years ago. This so-called Giant Impact was the last major event during Earth’s accretion, and its effects on the composition of the Earth and the newly forming Moon would be measureable today. Recent work on lunar samples has revealed that the Moon’s water was not lost as a result of this giant impact. Instead, the Moon appears to contain multiple hydrogen reservoirs with diverse deuterium-to-hydrogen (D/H) ratios. For the first time, we incorporate hydrogen isotopic measurements of lunar samples to help constrain the composition of Theia. We show that the Moon incorporated very low-D/H (δD ≈ -750‰) materials that only could have derived from solar nebula H₂ ingassed into the magma ocean of a large (∼0.4 M_E) planetary embryo that was largely devoid of chondritic water. We infer Theia was a very large body comparable in size to the proto-Earth, and was composed almost entirely of enstatite chondrite-like material. These conclusions limit the type of impact to a “merger” model of similarly-sized bodies, or possibly a “hit-and-run” model, and they rule out models that mix isotopes too effectively.     

The quantification of atmospheric emissions from complex configuration sources using reverse dispersion modelling

Reverse dispersion modelling was employed to quantify sulphur dioxide (SO₂) and nitrogen dioxide (NO₂) emissions from brick firing clamp kilns and spontaneous combustion from a coal discard dump. Reverse dispersion modelling technique integrates ambient monitoring and dispersion simulation to calculate actual emission rates from an assumed rate of 1 g per second (g/s). Emission rates and emission factors were successfully quantified for SO₂, but not for NO₂, due to the influence of external sources and the complexity regarding the varying proportion of nitrogen oxides released from the kiln. Quantified emission factor for clamp kiln firing ranged from 1.91–3.24 g of SO₂ per brick fired and 0.67–1.14 g of SO₂ per kilogram of bricks fired. The variation in SO₂ emission factors was linked to high variability in energy input. The source configuration input to the dispersion model, assumed to represent the kiln, was changed from a volume source to a more effective “bi-point” source situated at the top of the kiln, with buoyancy calculated from the carbon combustion rate. In addition, SO₂ emission rate for spontaneous combustion from the discard dump was quantified as 0.35 g/s. 274 tons of discard material was estimated to burn annually, assuming that the emission rate is consistent over a year. Consequently, the reverse dispersion modelling and the elevated “bi-point” source technique may be considered a novel approach for quantifying emissions from combustion of materials or mixture of materials where knowledge of source parameters is limited.     

Theoretical exploration of the water exchange mechanism of the polyoxocation GaO4Al12(OH)24(H2O)12 in aqueous solution

Reaction pathways, solvent effects and energy barriers have been investigated for the water exchange of the polyoxocation GaO₄Al₁₂(OH)₂₄(H₂O)₁₂⁷⁺ (K-GaAl₁₂) in aqueous solution by means of supermolecule density functional theory calculations. In the proposed reaction pathway, the supermolecular reactant K-GaAl₁₂15H₂O first loses a water ligand to form an intermediate with a five-coordinated aluminum atom, and then the incoming water molecule in the second coordination sphere attacks the intermediate with a five-coordinated aluminum atom to produce the reaction product. Our calculated results indicate that the water exchange of K-GaAl₁₂ proceeds via a dissociative mechanism, and that the reverse reaction of Step II is the most favorable dissociative pathway, with a barrier height of 31.3 kJ mol⁻¹. The calculated transition-state rate for the favorable dissociative pathway is much larger than the experimental rate constant, but is close to the data calculated for Al₃₀ by molecular dynamics. The transmission coefficient was also predicted on the basis of both the calculated transition-state rate and the experimental rate. Our calculated results also indicate that both the explicit solvent effect and the bulk solvent effect have obvious effects on the barrier heights of the water exchange reaction of K-GaAl₁₂. By comparison, the water exchange mechanism for K-GaAl₁₂ was found to be more similar to that for mineral surfaces than that for monomeric aluminum species.     

Use of biomarkers indices in a sediment core to evaluate potential pollution sources in a subtropical reservoir in Brazil

The presence of PAHs, n-alkanes, pristane, and phytanes in core sediment from the Vossoroca reservoir (Parana, southern Brazil) was investigated. The total concentration of the 16 PAHs varied from 15.5 to 1646 μg kg⁻¹. Naphthalene was present in all layers (3.34–74.0 μg kg⁻¹). The most abundant and dominant n-alkanes were n-C₁₅ and n-C₃₆, with average concentrations of 198.1 ± 46.8 and 522.9 ± 167.7 μg kg⁻¹, respectively. Lighter n-alkanes were distributed more evenly through the layers and showed less variation, specially n-C₉, n-C₁₂, and n-C₁₈, with average concentrations of 14.6 ± 3.0, 31.6 ± 1.9, and 95.0 ± 5.2 μg kg⁻¹, respectively; heavier n-alkanes were more unevenly distributed.     

Grain growth in porous olivine aggregates

Grain growth experiments have been performed at 1 atm on fine grain size (<10 μm) synthetic olivine (Fo₉₁) aggregates at various temperatures (1200° to 1400° C), oxygen fugacities (10^-4 to 10^-11 atm) and total anneal times (10, 30, 60, 100 and 200 h). The rate of grain growth increased with increasing temperature and with increasing oxygen fugacity. The presence of a second phase (residual porosity), introduced during sample fabrication, has a significant effect on grain growth, with evolution in grain size paralleled by changes in the size and frequency of the pores. When the grain growth data were fit to a growth law G ⁿ ?G _O ⁿ =κ₀ tf ₀ ^m ₂e^?Q/RT, the growth exponents fall in the range of n=4 to 5, suggesting that grain growth may be controlled by the coalescence of the second phase. The evolution in pore size and frequency may occur either by the transport of the ionic species constituting olivine between the pores or by the movement of the pores themselves along the grain boundaries and edges. Thus, the rate of growth of the pores and grains is probably limited by diffusion of the slowest ionic species constituting olivine (magnesium, iron, silicon, or oxygen) moving along the fastest path for that species (through the lattice, along the grain boundaries, around the surface of the moving pores, or through the vapor phase in the pores). Activation energies for grain growth of Q=290 ± 20 kJ/mol and 345 ± 25 kJ/mol were calculated from our results for n=4 and 5, respectively. These activation energies preclude vapor-phase transport and iron diffusion along grain boundaries but do not otherwise permit a discrimination between the rate limiting species or path. The oxygen fugacity exponent of m ≈0.12 suggests that lattice diffusion does not control the grain growth. However, the lack of data for magnesium, iron, silicon and oxygen surface and grain boundary diffusion in olivine makes definitive determination of the mechanism controlling grain growth difficult.     

A reflected light investigation of ilvaite

Summary The reflectance of oriented crystal faces parallel (100) and (001) of ilvaite was measured in air and in oil at different wavelengths with linearly polarized light. Refractive indices and absorption constants were calculated from the reflectance values. In contrast ton andn ,n has a strong dispersion. For the calculation ofn the absorption constant can be neglected. According to the unit cell ofBelov andMokeeva (1954) with the lattice constantsa ₀=8.82,b ₀=13.07,c ₀=5.86 Å,n vibrates parallel to [001]n parallel to [100] andn parallel to [010]. Ilvaite is optically negative.

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Auflichtuntersuchungen zur Optik des Ilvaits

Zusammenfassung Auf orientiert geschliffenen (100) und (001) Kristallplatten von Ilvait wurde das Reflexionsvermögen in Luft und in Öl mit linear polarisiertem Licht bei verschiedenen Wellenlängen gemessen. Aus den Reflexionswerten wurden die Brechungsindices und Absorptionskonstanten berechnet.n zeigt im Gegensatz zun undn eine auffallend starke Dispersion. Für die Berechnung vonn kann die Absorptionskonstante vernachlässigt werden. Nach der Aufstellung der Elementarzelle vonBelov undMokeeva (1954) mit den Gitterkonstantena ₀=8,82,b ₀=13,07,c ₀=5,86 Å schwingtn parallel [001],n parallel [100] undn parallel [010]. Der Ilvait ist optisch negativ.

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With 2 Figures     

Ab-initio structure, energy and stable Fe isotope equilibrium fractionation of some geochemically relevant H-O-Fe complexes

The hexa-aqua complexes [Fe(H₂O)_6−m−n(OH)_n]⁽²⁻ⁿ⁾⁺n = 0 → 3, m = 0 → 6 − n; [Fe(H₂O)_6−m−n(OH)_n]⁽³⁻ⁿ⁾⁺n = 0 → 4, m = 0 → 6 − n were investigated by ab-initio methods with the aim of determining their ground-state geometries, total energies and vibrational properties by treating their inner solvation shell as part of their gaseous precursor¹ (or “hybrid approach”). After a gas-phase energy optimization within the Density Functional Theory (DFT), the molecules were surrounded by a dielectric representing the Reaction Field through an implicit Polarized Continuum Model (PCM). The exploration of several structural ligand arrangements allowed us to quantify the relative stabilities of the various ionic species and the role of the various forms of energy (solute-solvent electronic interaction, cavitation, dispersion, repulsion, liberation free energy) that contribute to stabilize the aqueous complexes. A comparison with experimental thermochemistries showed that ab-initio gas-phase + solvation energies are quite consistent with experimental evidence and allow the depiction of the most stable form in solution and the eventual configurational disorder of water/hydroxyl species around central cations. A vibrational analysis performed on the ⁵⁴Fe, ⁵⁶Fe, ⁵⁷Fe and ⁵⁸Fe isotopomers indicated important separative effects systematically affected by the extent of deprotonation. The role of the system’s redox state (fO₂) and acidity (pH) on the isotopic imprinting of the aqueous species in solution was investigated by coupling the separative effects with speciation calculations. The observed systematics provided a tool of general utility in the interpretation of the iron isotopic signature of natural waters. Applications to the interpretation of isotopic fractionation in solution dictated by redox equilibria and to the significance of the Fe-isotopic imprinting of Banded Iron Formations are given.     

Composition and origin of lipid biomarkers in the surface sediments from the southern Challenger Deep,Mariana Trench

The surface sediments collected from the southern Mariana Trench at water depths between ca. 4900 m and 7068 m were studied using lipid biomarker analyses to reveal the origin and distribution of organic matters. For all samples, an unresolved complex mixture (UCM) was present in the hydrocarbon fractions, wherein resistant component tricyclic terpanes were detected but C₂₇–C₂₉ regular steranes and hopanes indicative of a higher molecular weight range of petroleum were almost absent. This biomarker distribution patterns suggested that the UCM and tricyclic terpanes may be introduced by contamination of diesel fuels or shipping activities and oil seepage elsewhere. The well-developed faults and strike-slip faults in the Mariana subduction zone may serve as passages for the petroleum hydrocarbons. In addition, the relative high contents of even n-alkanes and low Carbon Preference Indices indicated that the n-alkanes were mainly derived from bacteria or algae. For GDGTs, the predominance of GDGT-0 and crenarchaeol, together with low GDGT-0/Crenarchaeol ratios (ranging from 0.86 to 1.64), suggests that the GDGTs in samples from the southern Mariana Trench were mainly derived from planktic Thaumarchaeota. However, the high GDGT-0/crenarchaeol ratio (10.5) in sample BC07 suggests that the GDGTs probably were introduced by methanogens in a more anoxic environment. Furthermore, the n-alkanes C₁₉–C₂₂ and the n-fatty acids C_20:0–C_22:0 were depleted in ¹³C by 3‰ compared to n-alkanes C₁₆–C₁₈ and the n-fatty acids C_14:0–C_18:0, respectively, which was interpreted to result from the preferential reaction of fatty acid fragments with carbon “lighter” terminal carboxyl groups during carbon chain elongation from the precursors to products. The abundance of total alkanes, carboxylic acids, alcohols and total lipids were generally increased along the down-going seaward plate, suggesting the lateral organic matter inputs play an important role in organic matter accumulation in hadal trenches. The extremely high contents of biomarkers in sample BC11 were most likely related to trench topography and current dynamics, since the lower steepness caused by graben texture and proximity to the trench axis may result in higher sedimentation rate. This paper, for the first time, showed the biomarker patterns in surface sediments of the Mariana Trench and shed light on biogeochemistry of the hardly reached trench environment.     

Thermal evolution of n- and iso-alkanes in oils. Part 1: Pyrolysis model for a mixture of 78 alkanes (C1-C32) including 13,206 free radical reactions

A mechanistic model consisting of 13,206 lumped free radical reactions has been developed to describe the thermal evolution of a mixture of 78 alkanes: all n-alkanes from C₁ to C₃₂ and 46 branched alkane model compounds from C₄ to C₃₂. The mixture was meant to represent the major part of the saturated fraction of petroleum. The rate constants used are available from the literature. The lumping together procedure is described and the model validated on the basis of several experimental results from the literature and relating to pure alkanes. The model is also compared to the saturated fraction obtained from pyrolysis of Elgin oil at 372 °C for up to 1000 h. The cracking global activation energy of n-C₁₅ as well as iso-C₁₅ is close to 69 kcal/mol in the range 200-350 °C. The implications of the model for geological reservoirs will be discussed in a following paper.     

A study on carbon dioxide emissions from bituminous coal in Korea

Consumption of primary energy in Korea increased 5.25 % per year over a 10 years span starting in 1990. Korea ranked 8th in primary energy consumption in 2011; coal consumption increased 35 % from 87,827 million tons in 2006–119,321 tons in 2010. Heavy energy-consuming countries consistently conduct research to develop an emission factor of Tier 2 level, reflecting the characteristics of the fuel that they use. To calculate the emission factor of bituminous coal for fuel, this study developed emission factor and calculated emission amount by implementing fuel analysis on bituminous coal consumed in Korea between 2007 and 2009. CO₂ emission factor calculated by fuel analysis method is 95,315 kg/TJ, which is 0.75 % higher than the default value suggested by IPCC. The emission amount calculated by using the CO₂ emission factor in this study is 231.881 million tons, which has a difference of 1.739 million tons compared to the IPCC default value.     

Volatile production and transport in regional metamorphism

Calculations show that H₂O and CO₂ produced during devolatilization of an average pelite will occupy 12 vol. % of the rock at 500°C and 5 kb. Because the tensional strength of well foliated rock at metamorphic conditions is vanishingly small, such a volume of fluid having any vertical extent will fracture the rock and escape upward owing to its lower density.In a simplified model of a sudden increase of heat flow from 0.8 to 2.5 H.F.U., the average pelitic rock will have a rate of fluid production averaging 9.4×10^–10 g cm² s^–1 between 400°C and 600°C. The escape of this fluid can be accomodated by a single fracture 1 cm long and 0.2 wide per cm² of rock. If the fracture is reduced to 0.02 then 1,000 cm of fracture per cm² would be required. This width is the minimum original width as calculated from the volume of fluid observed in fluid inclusions trapped along annealed fractures within quartz in metamorphic terrains. Fluid flow will be laminar if the fracture is <0.025 cm wide. Additional calculations show that grain boundary diffusion is not an effective means of fluid transport in regional metamorphism.The commonly observed quartz segregations in pelitic terrains appear to mark the site of major channelways for fluid escape. In this case the bulk of escaping fluid is not able to react pervasively with rocks higher in the metamorphisc pile. Regionally metamorphosed rocks will have a discrete fluid phase only when devolatization reactions are actually taking place. At other times only an absorbed surface monolayer of volatiles on the minerals will be present.Died April 2, 1980     

A quantitative study of the degradation of whale bone lipids: Implications for the preservation of fatty acids in marine sediments

The degradation and preservation affecting the biomarker record of ancient metazoa are not fully understood. We report on a five month experiment on the fate of fatty acids (FAs) during the degradation of recent whale vertebrae (Phocoena phocoena). Whale bones were analysed for extractable FAs and macromolecularly bound n-acyl compounds. Fresh bone showed extractable FAs dominated by 16:1ω7c, 16:0, 18:1ω9c and 18:0. Calculated degradation rate constant (k) values showed a rapid decrease in FA concentration, with k values higher for unsaturated than for saturated compounds (0.08/day for 18:1ω9c, 0.05/day for 16:0). The appearance or increased abundance of distinctive methyl branched (e.g. i/ai-15:0 and -17:0, 10Me-16:0) and hydroxy FAs (e.g. 10OH-16:0 and 10OH-18:0) were observed, providing clear evidence for the microbial degradation of bone organic matter and an input of lipids from specialised bacteria. Catalytic hydropyrolysis (HyPy) of demineralised extraction residues released up to 0.13% of the total n-C₁₆ and n-C₁₈ moieties in the degraded bones. This revealed that only a small, yet sizeable, portion of bone-derived fatty acyl units was sequestered into (proto)kerogen during the earliest stages of degradation.