摘要:

The γ rays emitted from the moon or any similar body carry information on the chemical composition of the surface layer. The elements most easily measured are K, U, Th, and major elements such as O, Si, Mg, and Fe. The expected fluxes of γ ray lines are calculated for four lunar compositions and one chondritic chemistry from a consideration of the important emission mechanisms: natural radioactivity, inelastic scatter, neutron capture, and induced radioactivity. The models used for cosmic ray interactions are those of Reedy and Arnold (1972) and Lingenfelter et al. (1972). The areal resolution of the experiment is calculated to be around 70–140 km under the conditions of the Apollo 15 and 16 experiments. Finally, a method is described for recovering the chemical information from the observed scintillation spectra obtained in these experime

ISSN:0148-0227    

DOI:10.1029/JB078i026p05847

年代:1973

数据来源: WILEY

摘要:

A few small areas on the moon with extremely low albedo are shown also to have similar spectral reflectivity and radar backscatter characteristics. These lunar ‘black spots’ include the dark mantling material of the Apollo 17 landing site as well as areas of the Sulpicious Gallus formation. Excluded from the black spot group are the dark haloed craters of Alphonsus and the normal dark mare areas such as northern Mare Tranquillitatis. Earth‐based radar and optical measurements indicate that these lunar black spots have rock‐free surfaces with a very low proportion of crystalline material to amorphous material. The glassy soil is rich in iron and titanium, at least to the concentrations found at the Apollo 11 site. Crystalline pyroxene is present also. The data for the black spots are consistent with a mantling material of ash or

ISSN:0148-0227    

DOI:10.1029/JB078i026p05867

年代:1973

数据来源: WILEY

摘要:

Linear chains of active volcanoes are usually associated with oceanic trenches. It is postulated that the active volcanoes lie above the point on the slip zone between the descending lithosphere and the overlying mantle where partial melting of the descending oceanic crust takes place. By assuming that the frictional stress on the slip zone is either constant or proportional to depth, the thermal structure of the descending lithosphere is determined. The alternative theories are used to determine the shear stresses and friction coefficients for various trench‐volcano systems. Values for the shear stress and friction coefficient have standard deviations of 10 and 24%, respectively. We conclude that the shear stress on a slip zone is probably weakly dependent on depth with a value near 1.35kb. Our results are compared with previous calculation

ISSN:0148-0227    

DOI:10.1029/JB078i026p05876

年代:1973

数据来源: WILEY

摘要:

Let the configuration or first‐order design matrixAof a geodetic net be given and let the weight or second‐order design matrixPofmobservations be unknown. For some predetermined choice of the dispersion matrix Σ of thenunknown net coordinates, the unique minimum Euclidean norm solution for the weight matrixPisP= (A′)+Σ−1A+.A′ indicates the transpose andA+the pseudoinverse of the (in general) rectangular matrixA. For a general first‐order design matrixAand a given Σ, there does not exist a solution for a diagonal positive definite weight matrixP. Our solution for P belongs to the first category of an optimal design of C. R. Rao. The designsP=IandP= (A′)+Σ−1A+yield the same best linear unbiased estimator for the unknowns, but the variance covariance matrix for these designs is different. Examples, especially the structure by G. I. Taylor and T. Karman for the homogeneous and isotropic geodetic net, illustrate

ISSN:0148-0227    

DOI:10.1029/JB078i026p05887

年代:1973

数据来源: WILEY

摘要:

Water fugacity and oxygen fugacity can be controlled concomitantly in solid‐media high‐pressure apparatus by using CO2‐H2O vapors and the double‐capsule technique with oxygen buffers. Calculations based on an ideal‐solution model yield values of the fugacities of O2, H2, and H2O in th

ISSN:0148-0227    

DOI:10.1029/JB078i026p05898

年代:1973

数据来源: WILEY

摘要:

Lightning bolts appear to be able to produce neutrons by processes associated with the acceleration of ions to an amount estimated to be about a percent of the cosmic ray neutron production. The corresponding effect on radiocarbon in tree rings can explain the well‐known short‐term secular errors in radiocarbon dates as being caused by climatological fluctuations in frequency of lightning sto

ISSN:0148-0227    

DOI:10.1029/JB078i026p05902

年代:1973

数据来源: WILEY

摘要:

Extraction of geologic information from thermal infrared images requires a suitable mathematical model with which to relate diurnal surface temperatures to incident flux and surface and near‐surface physical properties. Some success has been achieved in discriminating several rock types and mapping thermal inertia differences by assuming a semi‐infinite solid. However, the widespread presence of surface effects caused by soils, lichen cover, and coatings suggests the need to extend current models. Jaeger's technique for treating the periodic heating of a solid has been applied to a layer over a semi‐infinite solid. Numerical examples for limiting cases demonstrate both the influence of surface coating and the ‘effective’ penetration of the ground that can be sensed by observing surface temperatures. A 0.01‐cm ‘lichen’ layer and a 0.1‐cm ‘soil’ layer have a negligible effect, whereas a 1‐cm lichen layer produces a surface temperature similar to that of an infinitely thick soil cover. A 10‐cm thickness of soil or lichen completely

ISSN:0148-0227    

DOI:10.1029/JB078i026p05904

年代:1973

数据来源: WILEY

摘要:

The functional relationship between various difinitions of effective stress, i.e., conventional, Biot‐Willis‐Nur‐Byerlee, and theory of interacting continua (Tinc), is explored both theoretically and experimentally. Stress‐strain data on dry and saturated Weber sandstone demonstrate that the conventional effective stress law grossly overestimates the pore pressure effect, whereas Biot‐Willis‐Nur‐Byerlee and Tinc laws somewhat underestimate this effect. Failure is examined from a microscopic point of view. It is shown that Tinc‐type effective stress laws cannot account for the effect of pore pressure on failure in a simple manner. Failure is one aspect of material response in which the conventional effective stress law is useful. In summary it appears necessary to have two effective stress laws, i.e., one to describe the stress‐strain response and a second to delineate th

ISSN:0148-0227    

DOI:10.1029/JB078i026p05911

年代:1973

数据来源: WILEY

摘要:

The complete stress‐strain equation of state for a granodiorite and two graywacke sandstones has been determined on loading to 20 kb axial stress at room temperature. Data under conditions of hydrostatic, uniaxial stress at various confining pressures and uniaxial strain loading are synthesized to define the behavior of these rocks. For the granodiorite it is observed that the onset of dilatancy as well as intersection of the failure envelope is independent of loading path. No dilatant behavior is observed on uniaxial strain loading to 12 kb axial stress. Both sandstones are observed to load below the hydrostat (increased compressibility) in either uniaxial stress or uniaxial strain loading. This enhanced compaction at relatively low pressures is believed to result from the influence of the additional shear stresses, which facilitate intergranular movements in these porous rocks. Dilatant behavior greatly diminishes at higher mean stresses where the rock undergoes a transition in failure mechanism from throughgoing narrow tensile and shear fractures (predominantly intergranular) to pervasive small‐scale fracturing (predominantly intragranular). Dilatancy again becomes important at the highest stresses, where most of the initial porosity has been removed. The data on both rocks are used to delimit areas of characteristic behavior that are uniquely defined in stress space, independent of loading p

ISSN:0148-0227    

DOI:10.1029/JB078i026p05922

年代:1973

数据来源: WILEY

摘要:

A spectrographic system is described that is capable of measuring optical absorption spectra in solids to shock pressures of several hundred kilobars. The system utilized light from a ‘point’ source at about 60,000°K. Spectra have a resolution of about 40 A and cover the visible range. With a streak camera, time resolution of about 75 nsec can be obtained. The spectrum of MgO is observed to remain featureless at 450 kb and upon unloading from this pressure. The color centers observed in shock‐recovered material must result from either higher pressures or other processes. The optical absorption spectra of ruby under shock compressions of almost 15% have been measured in the range 375–600 nm. Below the elastic limit the large anisotropic strains are evident from the splitting of the4A2→4T2(F) absorption band by 3730 cm−1. Above the elastic limit this splitting is not resolved (but must be less than 800 cm−1), indicating considerable loss of shear strength in such cases. Above the Hugoniot elastic limit up to pressures of 530 kb (15% volume compression) the measured value of the crystal field parameter agrees, within experimental error, with the value calculated from a point charge model (Dq∝r−5) if the local compressibility is equal to the bulk compressibility. This result agrees with Stephens and Prickamer's absorption data up to 150 kb and suggests that the point charge model is useful in predicting crystal field effects in mantle minerals, especially those having similar oxygen anion packing

ISSN:0148-0227    

DOI:10.1029/JB078i026p05942

年代:1973

数据来源: WILEY