Arthur N. Thorpe

Influence of an igneous intrusion on the inorganic geochemistry of a bituminous coal from Pitkin County, Colorado

Abstract Although the effects of igneous dikes on the organic matter in coal have been observed at many localities there is virtually no information on the effects of the intrusions on the inorganic constituents in the coal. Such a study may help to elucidate the behavior of trace elements during in situ gasification of coal and may provide insights into the resource potential of coal and coke affected by the intrusion. To determine the effects of an igneous intrusion on the inorganic chemistry of a coal we used a series of 11 samples of coal and natural coke that had been collected at intervals from 3 to 106 cm from a dike that intruded the bituminous Dutch Creek coal in Pitkin, CO. The samples were chemically analyzed for 66 elements. SEM-EDX and X-ray diffraction analysis were performed on selected samples. Volatile elements such as F, Cl, Hg, and Se are not depleted in the samples (coke and coal) nearest the dike that were exposed to the highest temperatures. Their presence in these samples is likely due to secondary enrichment following volatilization of the elements inherent in the coal. Equilibration with ground water may account for the uniform distribution of Na, B, and Cl. High concentrations of Ca, Mg, Fe, Mn, Sr, and CO2 in the coke region are attributed to the reaction of CO and CO2 generated during the coking of the coal with fluids from the intrusion, resulting in the precipitation of carbonates. Similarly, precipitation of sulfide minerals in the coke zone may account for the relatively high concentrations of Ag, Hg, Cu, Zn, and Fe. Most elements are concentrated at the juncture of the fluidized coke and the thermally metamorphosed coal. Many of the elements enriched in this region (for example, Ga, Ge, Mo, Rb, U, La, Ce, Al, K, and Si) may have been adsorbed on either the clays or the organic matter or on both.

Levitation Forces, Relaxation and Magnetic Stiffness of Melt-Quenched YBa2Cu3Ox

Measurements of levitation forces on melt-quenched and free sintered YBa2Cu3Ox superconductors show that melt-quenched samples produce forces from 96-170% higher than sintered specimens. The force increases are correlated with higher magnetization values for the melt-quenched material. Similar increases in the magnetic stiffness were also measured. Vertical levitation force relaxation showed less than 5% decrease in one hour. These results have important favorable implications for application to superconducting bearings.

A study of the natural α-recoil damage in zircon by infrared spectra

Abstract Natural α-recoil damage of 30 natural zircon specimens from Ceylon have been examined by studying the infrared absorption spectra from 1 to 15 μm. Two synthetic zircon specimens were also studied as undamaged reference specimens. The ir absorption coefficient at 6 μm (1666 cm−1) was found to be a function of radiation damage. The ir data can be explained by a dual damage mechanism. The initial damage process produces degradation of the v 3 vibrational mode in the ir spectra which can be explained by deformation of SiO4 tetrahedra, whereas the predominant effect of the advanced stage of radiation damage is the breakdown of the zircon lattice into SiO2 and ZrO2 which causes a skewing of the v 3 absorption band. These data substantiate the model of Pellas and clarify the dualistic nature of the radiation damage mechanism.

Absolute Method of Measuring Magnetic Susceptibility

An absolute method of standardization and measurement of the magnetic susceptibility of small samples is presented which can be applied to most techniques based on the Faraday method. The fact that the susceptibility is a function of the area under the curve of sample displacement versus distance of the magnet from the sample, offers a simple method of measuring the susceptibility without recourse to a standard sample. Typical results on a few substances are compared with reported values, and an error of less than 2% can be achieved.

Oxidation of pyrite in coal to magnetite

Abstract When bituminous coal is heated in an inert atmosphere (He) containing small amounts of oxygen at 393–455 °C, pyrite (FeS2) in coal is partially converted to magnetite (Fe304). The maximum amount of Fe304 formed during the time of heating corresponds to 5–20% of the total pyrite present, depending on the coal sample. The magnetite forms as an outer crust on the pyrite grains. The fact that the magnetic properties of the pyrite grains are substantially increased by the magnetite crust suggests that pyrite can be separated from coal by use of a low magnetic field. In a laboratory test, 75% removal is obtained by means of a 500 Oe magnet on three samples, and 60% on a fourth sample.

A comparative study of sintered and melt-grown recrystallized YBa 2 Cu 3 O x

This paper compares the properties of yttrium barium cuprate bulk specimens prepared by means of solid-state sintering on one hand and of growth from a largely molten state on the other. The current paper focuses on magnetization measurements at 77 K which show specimens made by the latter method to have high remanence magnetization values.

A Muong Nong-type Georgia tektite

Abstract A large (130 g), layered tektite was found just south of Riddleville, Georgia, USA, in July 1993. The specimen has a bulk composition similar to that of splash-form Georgia tektites, but with a much wider range in composition (e.g., the silica content ranges from 69–99 wt%) and it contains numerous white opaque inclusions. Portions of the specimen were studied to determine the petrography, major and minor element, and strontium and neodymium isotopic composition, water content, magnetic properties, ferric/ferrous ratio, and 40 Ar/ 39 Ar age. The white opaque inclusions were found to be zircon crystals, many of which had partly or completely decomposed to baddeleyite plus SiO 2 glass. The trace element, strontium and neodymium isotopic ratios, water content, age (∼34.5 Ma), and magnetic properties are all similar to normal Georgia tektites. Mo¨ssbauer data indicate Fe 3+ /Fe 2+ ratios between 0.07 and 0.16. This specimen has all the characteristics of a Muong Nong-type tektite, except that it is not as strongly enriched in volatile elements, including water, as are the Australasian Muong Nong-type tektites. The lack of a strong enrichment in volatile elements, plus the fact that many of the included relict zircons have partly or completely broken down to baddeleyite plus SiO 2 glass, indicates that this specimen was heated more intensely than most zircon-bearing Australasian Muong Nong-type tektites. The occurrence in the northeastern corner of the Georgia strewn field is consistent with a proposed source crater near Deep Sea Drilling Project Site 612 off the coast of New Jersey.

Change in the magnetic properties of bituminous coal intruded by an igneous dike, Dutch Creek Mine, Pitkin County, Colorado

Abstract Magnetization measurements have been made on natural coke–coal samples collected at various distances from a felsic porphyry dike in a coal seam in Dutch Creek Mine, Colorado to help characterize the nature and distribution of the iron-bearing phases. The magnetization passes through a maximum at the coke-to-coal transition about 31 cm from the dike contact. The magnetic measurements support the geochemical data indicating that magmatic fluids along with a high-temperature gas pulse moved into the coal bed. Interaction of the magmatic fluids with the coal diminished the reducing power of the thermal gas pulse from the dike to a point about 24 cm into the coal. The hot reducing gas penetrated further and produced a high temperature (∼400–525°C) zone (at about 31 cm) just ahead of the magmatic fluids. Metallic iron found in this zone is the principal cause of the observed high magnetization. Beyond this zone, the temperature was too low to alter the coal significantly.

Oxidation of pyrite in an anoxic atmosphere

Abstract Pyrite (FeS2) inclusions in coal, when heated in an oxygen deficient atmosphere (approximately 1% oxygen), become coated with magnetic Fe3O4 due to oxidation. Most of the FeS2 can thus be removed from the coal by magnetic separation to reduce the sulphur concentration. The oxidation products have been studied in greater detail by measuring the SO2 and O2 in the effluent gas during the heating process and by performing further magnetic measurements. At 582 K, the pyrite surface was oxidized to FeSO4. Significant oxidation of FeSO4 and FeS2 to Fe3O4 was observed starting at 677 K. At about 681 K, the Fe3O4 is further oxidized to α-Fe2O3. At 681 K, under isothermal conditions, the oxidation is impeded by the α-Fe2O3 formed on the surfaces of the grains. If the temperature is rapidly increased, the oxygen penetrates the α-Fe2O3 veneer to the FeS2 core of the pyrite grains and oxidizes essentially the whole pyrite mass to Fe3O4 before α-Fe2O3 can be formed.

Yttrium enrichment and improved magnetic properties in partially melted Y-Ba-Cu-O materials

Samples of Y-Ba-Cu-O materials with the formulation Y:Ba:Cu = x :2:3 and values of x ranging between 1 and 3 were prepared by partial melting at a maximum temperature of 1045 °C. Measurements of magnetic susceptibility and maximum (low-field) as well as remanent magnetization show highest values for x = 2. XRD and SEM/EDX analyses show that the corresponding structure involves numerous small crystals of Y 2 BaCuO 5 (211) embedded in highly ordered assemblages of continuous YBa 2 Cu 3 O 7− y (123) layers. The presence of these impurity sites is correlated with flux pinning capacity. Other impurity phases include CuO, a minor phase which shows an increase in amount when x increases, BaCuO 3 , a possibly detrimental minor phase which vanishes when x is raised from 1 to 2, and zones of intermediate composition between the 211 grains and the 123 layers, which are formed from the residual liquid upon cooling. These intermediate regions, like the 211 grains themselves, become gradually more important when x is increased from 1 to 3.