Middle to late Triassic mélange exhumation along a pre-Andean transpressional fault system: coastal Chile (26°–42° S)

Mélanges occur as discontinuous, mappable, units along an extensive N–S-trending, steeply dipping zone of distributed shear in metamorphic complexes along the coast of central Chile. Large mélange zones, from north to south, near Chañaral, Los Vilos, Pichilemu, and Chiloé Island, contain variations in lithologic and structural detail, but are consistent in exhibiting cross-cutting fabric features indicating a progressive transition from earlier ductile to more brittle deformation. In the Infiernillo mélange near Pichilemu, Permian to Early Triassic, sub-horizontal schistosity planes of the Western Series schist are disrupted, incorporated into, and uplifted along high-angle, N–S- to NNE–SSW-trending brittle–ductile shears. Mylonitic and cataclastic zones within the mélange matrix indicate active lateral shear during cumulative exhumation from depths exceeding 12 km in some areas. Exotic lithologies, such as Carboniferous mafic amphibolite and blueschist, formed during earlier Gondwanide subduction, match well with similar rocks in the Bahia Mansa to Los Pabilos region 750 km to the south, suggesting possible dextral offset. The development of the Middle to Late Triassic, N–S=trending, near-vertical shear zones formed weaknesses in the crust facilitating later fault localization, gravitational collapse, and subduction erosion along the continental margin. The length and linearity of this zone of lateral movement, coincident with a general hiatus of regional arc magmatism during the Middle to Late Triassic, is consistent with large-scale dextral transpression, or possible transform movement, during highly oblique NNE–SSW convergence along the pre-Andean (Gondwana) margin. The resultant margin parallel N–S-trending shear planes may be exploited by seismically active faults along the present coastal area of Chile. The palaeo-tectonic setting during the transitional period between earlier Gondwanide (Devonian to Permian) and later Andean (Late Jurassic to present) subduction may have had some similarity to the presently active San Andreas transform system of California.     

Observation of cosmic soft X-rays

Cosmic X-rays in the energy range between 0.210 keV were observed with polypropylene window proportional counters on board a sounding rocket. The field of view crossed the galactic plane in the Sgr region and reached galactic latitudes of 50° and –90°. A new soft X-ray source was found in the Aries-Taurus region. The soft X-ray flux from the direction of NGC 1275 was conspicuous, whereas that of Sgr region source were very weak. The distribution of the intensity of diffuse soft X-rays over the scanned region indicates the galactic emission of soft X-rays.     

Shock metamorphism on the moon

Shock metamorphism of the lunar samples is discussed. All types of lunar glasses formed by various-size collision-type impact are found as impact glass, ropy glass and agglutinates. The agglutinates bonded by crystal and glassy materials contain hydrogen and helium from the solar wind components. Lunar shocked minerals of plagioclase and silica show anomalous compositions and densities. There are typical two formation processes on planetary materials formed by shock events; that is (1) shocked quartz formed by silica-rich target rocks (esp. on evolved planets of the Earth and Mars), and (2) shocked silica with minor Al contents formed from plagioclase-rich primordial crusts of the Moon. The both shocked silica grows to coarse-grain normal crystals after high-temperature metamorphism which cannot distinguish the original main formation event of impact process.     

Excitation of non-spherical waves in solar atmosphere in the presence of toroidal magnetic field

It has been shown that non-spherical waves could be excited in rotating stellar convective envelopes. In this paper, the manner of excitation of such waves is examined in the presence of toroidal magnetic field. The result shows that one of these waves might be considered to induce the formation of the observed magnetic unipolar regions of the sun.Visiting Scientist to the High Altitude Observatory on leave of absence from the Department of Astronomy, University of Tokyo, Japan.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Distribution of the diffuse component of cosmic soft X-rays

The celestial distribution of the intensity of diffuse soft X-rays is mapped by reference to a critical review of observations available. The soft X-rays of extragalactic origin are subtracted, taking the interstellar absorption into account. The distribution of the galactic component thus obtained shows irregularities, but the general behaviour can be accounted for in terms of a cylindrical distribution of the X-ray emissivity with the scale height of 100300 pc in the direction perpendicular to the galactic plane. Correlations with various celestial objects, such as supernova remnants, radio spurs, flaring stars, and so forth, are discussed.     

针对IPCC评估报告中海洋碳循环的疑问——δ13C收支平衡法的验证

 通过对比IPCC历次评估报告中全球碳循环的收支发现,尽管评估报告在估算各主要碳库及其间的通量时差别不大,但表层至中深层海水间溶解无机碳通量却存在巨大差异。利用δ¹³C的收支平衡检验了这一通量的适用范围,结果表明：IPCC 1996年和2007年评估报告对此通量估计过大,而1990年和2001年评估报告估计偏小。     

An empirical model for transient crater growth in granular targets based on direct observations

The present paper describes observations of crater growth up to the time of transient crater formation and presents a new empirical model for transient crater growth as a function of time. Polycarbonate projectiles were impacted vertically into soda-lime glass sphere targets using a single-stage light-gas gun. Using a new technique with a laser sheet illuminating the target [Barnouin-Jha, O.S., Yamamoto, S., Toriumi, T., Sugita, S., Matsui, T., 2007. Non-intrusive measurements of the crater growth. Icarus, 188, 506-521], we measured the temporal change in diameter of crater cavities (diameter growth). The rate of increase in diameter at early times follows a power law relation, but the data at later times (before the end of transient crater formation) deviates from the power law relation. In addition, the power law exponent at early times and the degree of deviation from a power law at later times depend on the target. In order to interpret these features, we proposed to modify Maxwell’s Z-model under the assumption that the strength of the excavation flow field decreases exponentially with time. We also derived a diameter growth model as: d(t)∝[1-exp(-βt)]^γ, where d(t) is the apparent diameter of the crater cavity at time t after impact, and β and γ are constants. We demonstrated that the diameter growth model could represent well the experimental data for various targets with different target material properties, such as porosity or angle of repose. We also investigated the diameter growth for a dry sand target, which has been used to formulate previous scaling relations. The obtained results showed that the dry sand target has larger degree of deviation from a power law, indicating that the target material properties of the dry sand target have a significant effect on diameter growth, especially at later times. This may suggest that the previously reported scaling relations should be reexamined in order to account for the late-stage behavior with the effect of target material properties.