摘要:

Numerical calculations for the structure of convection cells within a self‐gravitating, fluid sphere are used to determine the temperature distribution within the moon. The distribution of surface heat flux is also given. The results are compared with the temperatures deduced from magnetic induction within the moon and with the surface heat flow measurement carried out on Apollo 1

ISSN:0148-0227    

DOI:10.1029/JB077i035p06931

年代:1972

数据来源: WILEY

摘要:

We have used metallographic and X‐ray diffraction techniques to study the shock histories of 119 iron and stony‐iron meteorites and have measured the hardness of kamacite in these specimens and in artificially shocked unannealed and annealed meteorite specimens. Shock increases kamacite hardness, but complications introduced by other physical and chemical properties of meteorites limit its utility as a shock indicator. About 50% of the meteorites studied show evidence for preterrestrial shock loading to pressures of ≥130 kb, and 40% have not been shocked to such high pressures. The remaining meteorites have been heat altered in such a way that their shock histories cannot be determined explicitly. These results, together with those obtained previously, indicate that the plurality, if not the majority, of all iron and stony‐iron meteorites sampled by the earth were shocked to pressures of ≥ 130 kb during preterrestrial collisions between asteroidal‐si

ISSN:0148-0227    

DOI:10.1029/JB077i035p06940

年代:1972

数据来源: WILEY

摘要:

Compressional and shear wave velocities in 13 directions at pressures to 10 kb were measured in dunite from the Twin Sisters peaks, Washington, and in bronzitite from the Stillwater Complex, Montana. Dunite is characterized by a strong preferred orientation of olivine grains, leading to anisotropy of velocity of 15% at 10 kb. The bronzitite is more nearly isotropic, the greatest difference ofPwave velocities reaching 6%. The comparison of elasticity diagrams, obtained at pressures of 0.5 kb and 10 kb, shows that the system of pores, more open at low pressure, is of minor influence; anisotropy is controlled mainly by the preferred orientation of olivine and bronzite in both rocks. Most of the compressional and shear wave velocities, calculated according to Voigt's scheme on the basis of petrofabric determinations and published single‐crystal data for olivine and bronzitite, are in good agreement with the ultrasonic velocities measured at 10 kb. The results confirm the possibility of using this procedure to determine anisotropic elasticity of simple aggregates and suggest a possibility of using ultrasonic measurements in petrostructural analysi

ISSN:0148-0227    

DOI:10.1029/JB077i035p06955

年代:1972

数据来源: WILEY

摘要:

The total thermal conductivity (lattice plus radiative) of several important earth materials is measured in the temperature range 500°–1900°K. A new technique is used in which a CO2laser generates a low‐frequency temperature wave at one face of a small disk‐shaped sample, and an infrared detector views the opposite face to detect the phase of the emerging radiation. Phase data at several frequencies yield the simultaneous determination of the thermal diffusivity and the mean extinction coefficient of the material. The lattice, radiative, and total thermal conductivities are then calculated. Results for single‐crystal and polycrystalline forsterite‐rich olivines and an enstatite indicate that, even in relatively pure large‐grained material, the radiative conductivity does not increase rapidly with temperature. The predicted maximum total thermal conductivity at a depth of 400 km in an olivine mantle is 0.020 cal/cm sec °C, which is less than twice the

ISSN:0148-0227    

DOI:10.1029/JB077i035p06966

年代:1972

数据来源: WILEY

摘要:

The effect of pressure on the temperature of the eutectic minimums of the two systems NaF‐NaCl and CsCl‐NaCl has been studied to 60 kb. These systems behave in a way completely analogous to the behavior of the previously studied Na‐K system. The depth of the eutectic trough, i.e., the difference in melting temperature between the highest melting component and the eutectic minimums, continuously deepens with pressure at high pressures. We believe this continuous deepening to be a general phenomenon and, because of it, we believe the temperature of the beginning of melting in the mantle of the earth has largely been overesti

ISSN:0148-0227    

DOI:10.1029/JB077i035p06984

年代:1972

数据来源: WILEY

摘要:

Experiments to reveal the influence of water concentration in obsidian upon the annealing rate of fission tracks showed that a 2.2% H2O obsidian would lose 70% of its tracks in 1 m.y. if held at 30°C. Data obtained at three temperatures (227°, 253°, and 282°C) give the possibility of extrapolations to geologically significant times. Care must be taken in choosing the proper samples for fission‐track analysis of gl

ISSN:0148-0227    

DOI:10.1029/JB077i035p06990

年代:1972

数据来源: WILEY

摘要:

The most recent version of a microwave‐modulated two‐laser distance‐measuring instrument has completed several months of field tests. This instrument was operated almost continuously for about a month over a 5.9‐km base line just north of Boulder, Colorado. During the tests the optical path lengths for red and blue varied over 3 cm for the base line, and the corrected distance typically has a σ of<3 mm. The preliminary results of these tests clearly show that this type of instrument can correct a distance measurement taken in 10 sec to better than five parts in 10

ISSN:0148-0227    

DOI:10.1029/JB077i035p06994

年代:1972

数据来源: WILEY

摘要:

A method is presented for calculating the gravitational attraction of three‐dimensional bodies of arbitrary shape within a spherical or ellipsoidal earth. The sphericity of the earth is treated exactly by developing the formulas in a spherical coordinate system and the ellipticity is treated approximately by including only first‐order terms in the flattening of the earth. The three‐dimensional body is specified by giving its shape and density at a number of successive depths. The method is well suited for evaluation on a digital computer, and calculations are presented for a couple of examples that demonstrate in a quantitative manner the relative effects of sphericity and ellipt

ISSN:0148-0227    

DOI:10.1029/JB077i035p06999

年代:1972

数据来源: WILEY

摘要:

Trains of seismic waves with periods between 25 and 12 sec commence at Bermuda 17 min after lift‐off of Apollo (Saturn 5) rockets from Cape Kennedy, Florida. The signal, which is identified as Rayleigh mode and first shear mode waves, persists for as long as 7 min. Generation of the entire train is shown to be possible by resonant coupling to the rocket shock cone as it travels across the sea surface at phase velocities appropriate to the different wave periods observed. Arrival time for each phase can be accounted for by the time required for the rocket to reach resonant speed plus the time required for the shock to reach the surface from a height of about 175 km plus the seismic travel time at the appropriate group velocity. The long duration of the signal results from the fact that successively later arrivals have been generated earlier along the rocket trajector

ISSN:0148-0227    

DOI:10.1029/JB077i035p07010

年代:1972

数据来源: WILEY

摘要:

On the basis of the size, the abundance, and the petrographic character of xenoliths in the Moses Rock dike, a model for the vertical stratigraphy of crystalline rocks beneath the dike is proposed extending from near the surface to a depth of about 200 km. Sedimentary clasts, whose original position in the undisturbed vent walls is known but which are now within the intrusive breccia of the Moses Rock dike, show a decrease in size with distance of upward transport from their original position in the vent walls. This inverse relationship between fragment size and known depth of origin provides an empirical basis for a reconstructed model for the distribution of rocks on the basis of the particle size of fragments in the intrusive breccia. Metabasalt, granite, and granite gneiss are abundant in the upper part of the crust along the dike walls; diorite, gabbro, and amphibole schists of basic composition constitute intermediate layers, and garnet‐bearing metagabbro (basic granulite gneiss) and serpentine schist are present in the lower crust. The crustal rock suite is predominantly metavolcanic and metaplutonic and basic in composition. Dense ultramafic rocks, possibly derived from the mantle, constitute about 0.3% of the breccia filling the dike and include jadeite‐rich clinopyroxenite, eclogite, spinel‐websterite, spinel‐lherzolite, and garnet‐lherzolite. The M discontinuity appraently occurs within a petrologically complex region and may coincide with phase and compositional transitions, which include hydration. A compositional transition within the upper mantle between spinel‐ and garnet‐peridotite (lherzolite) is inferred. The variety and the abundance of ultramafic and dense types, together with the complexity of their textures, suggest that the mantle may be as complicated as the crust in compositio

ISSN:0148-0227    

DOI:10.1029/JB077i035p07022

年代:1972

数据来源: WILEY