Plagioclase buoyancy in oceanic basalts: Chemical effects

Certain petrological features of oceanic volcanic and plutonic rocks are not completely consistent with previously proposed models of crystal fractionation or magma mixing. For example, Sr is often higher in the differentiated basalts of a suite of aphyric rocks than in the relatively primitive basalts even though the differentiated basalts have apparently been produced by crystallization of large amounts of plagioclase with olivine and clinopyroxene. Additionally, oceanic basalts and gabbroic rocks often contain plagioclase crystals in excess of the appropriate cotectic proportions. Certain differentiated oceanic basaltic glasses and aphyric rocks crystallize plagioclase as the liquidus mineral, which would seem inconsistent with the strongly cotectic nature of the olivine + plagioclase + liquid surface.It is proposed here that plagioclase in mid-ocean ridge magma chambers separates from the basaltic liquid that it crystallizes in at a slower rate than does co-crystallizing olivine or pyroxene. Magma mixing in which a portion of the plagioclase remains suspended in the liquid during crystallization results in much more complex liquid lines of descent in mixed magmas and appears to resolve the apparent discrepancies noted above.     

恒山中元古代早期基性岩墙群的单颗粒锆石U—Pb年龄及其克拉通构造演化意义

华北克拉通中北部变质基底发育大规模的前寒武纪基性岩墙群,由于基性岩墙同位素定年技术存在问题,因此一直未获得岩墙群的确切年龄数据。本文利用单颗粒锆石U-Pb化学法,首次获得恒山地区北西向基性岩墙群的U-Pb年龄为1769.1±2.5Ma,并证明它代表基性岩墙群的侵位年龄,这一年龄数据也是华北克拉通大规模分布的未变质基性岩墙群已知的最古老年龄。综合分析同期岩浆活动的同位素年龄记录,本文提出中元古代早期华北的岩浆侵位发生于伸展构造背景下。     

多道面波分析方法在测量土壤压实度方面的应用研究

在农业和工程领域，土壤压实度是一个重要问题。虽然采用钻孔方法可以探测土壤压实度情况，但费用较高。本文采用多道面波分析方(MASW)研究了土壤压实度的问题，并将试验结果同电阻率测井数据、岩心数据、测井速度做了对比，结果表明该方法可以用于土壤压实度的探测，而且速度快、费用低、结果准确可信。     

On the effect of line current width and relative position on the multi-spacecraft curlometer technique

The response of the multi-spacecraft curlometer technique to variations in the size and relative position of infinitely long line currents with radially varying current density is systematically investigated for spacecraft in a regular tetrahedral formation. It is shown that, for line currents with a width less than the spacecraft separation, there is significant variation in the returned current with position of that current within the tetrahedron. For infinitely thin line currents, the curlometer tends to detect approximately 20% of the input current. For increasingly wide line currents there is less variation of the curlometer results with position of the current and the percentage of current magnitude detected increases. When the width of the current system is half the spacecraft separation, the curlometer tends to detect approximately 80% of the input current. These results are discussed in the context of multi-scale, multi-spacecraft missions.     

Jovian chromophore characteristics from multispectral HST images

The chromophores responsible for coloring the jovian atmosphere are embedded within Jupiter’s vertical aerosol structure. Sunlight propagates through this vertical distribution of aerosol particles, whose colors are defined by ?₀(λ), and we remotely observe the culmination of the radiative transfer as I/F(λ). In this study, we employed a radiative transfer code to retrieve ?₀(λ) for particles in Jupiter’s tropospheric haze at seven wavelengths in the near-UV and visible regimes. The data consisted of images of the 2008 passage of Oval BA to the south of the Great Red Spot obtained by the Wide Field Planetary Camera 2 on-board the Hubble Space Telescope. We present derived particle colors for locations that were selected from 14 weather regions, which spanned a large range of observed colors. All ?₀(λ) curves were absorbing in the blue, and ?₀(λ) increased monotonically to approximately unity as wavelength increased. We found accurate fits to all ?₀(λ) curves using an empirically derived functional form: ?₀(λ) = 1 − A exp(−Bλ). The best-fit parameters for the mean ?₀(λ) curve were A = 25.4 and B = 0.0149 for λ in units of nm. We performed a principal component analysis (PCA) on our ?₀(λ) results and found that one or two independent chromophores were sufficient to produce the variations in ?₀(λ). A PCA of I/F(λ) for the same jovian locations resulted in principal components (PCs) with roughly the same variances as the ?₀(λ) PCA, but they did not result in a one-to-one mapping of PC amplitudes between the ?₀(λ) PCA and I/F(λ) PCA. We suggest that statistical analyses performed on I/F(λ) image cubes have limited applicability to the characterization of chromophores in the jovian atmosphere due to the sensitivity of I/F(λ) to horizontal variations in the vertical aerosol distribution.     

Diverse forms of primordial organic matter identified in interplanetary dust particles

Abstract– Coordinated in situ transmission electron microscopy and isotopic measurements of carbonaceous phases in interplanetary dust particles were performed to determine their origins. Five different types of carbonaceous materials were identified based on their morphology and texture, observed by transmission electron microscopy: globular, vesicular, dirty, spongy, and smooth. Flash heating experiments were performed to explore whether some of these morphologies are the result of atmospheric entry processes. Each of these morphologies was found to have isotopically anomalous H and N. Rare C isotopic anomalies were also observed. The isotopic and morphological properties of several of these phases, particularly the organic globules, are remarkably similar to those observed in other extraterrestrial materials including carbonaceous chondrites, comet 81P/Wild 2 particles collected by the Stardust spacecraft, and Antarctic micrometeorites, indicating that they were widespread in the early solar system. The ubiquitous nature and the isotopic anomalies of the nanoglobules and some other morphologies strongly suggest that these are very primitive phases. Given that some of the isotopic anomalies (D and ¹⁵N excesses) are indicative of mass fractionation chemical reactions in a very cold environment, and some others (¹³C and ¹⁵N depletions) have other origins, these carbonaceous phases come from different reservoirs. Whatever their origins, these materials probably reflect the first stages of the evolution of solar system organic matter, having originated in the outermost regions of the protosolar disk and/or interstellar cold molecular clouds.     

Anomalies in video transmissions from Venera-13 are probably not life forms

Some anomalies in the video images from Venera-13 are explained as possible artifacts of the telemetry system. One anomaly may be a shadow caused by a change in the distribution of illumination.