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S. I. Kalogeropoulos 《Mineralium Deposita》1985,20(2):135-142
Tetsusekiei (literally, iron quartz) is in the form of thin, discontinuous beds that occur in the hanging wall of the Kuroko-type massive sulphide ores and at some distance beyond ore, along the uppermost part of the ore horizon tuff. The presence of tetsusekiei within a volcano-sedimentary sequence marks a horizon of fossil hydrothermal activity. Tetsusekiei shows elevated concentrations in trace elements of exhalative input relative to normal pelagic sediments and consists of two components; a clastic and a chemical component. Discriminant analysis applied to the following three groups: chemical component of tetsusekiei, clastic component of tetsusekiei and the upper part of the ore horizon tuff which is stratigraphically equivalent to tetsusekiei, has aided in providing the exploration geologist with a number of statistically significant major and trace elements that may be useful to exploration. The lateral distribution of the statistically significant major elements, expressed in the alteration index $$\operatorname{R} \% = \frac{{\left( {K_2 O + MgO} \right) \times 100}}{{K_2 O + Na_2 O + MgO + CaO}}$$ (Ishikawa et al. 1976) for the clastic component of tetsusekiei along the same stratigraphic horizon, shows an increase from about 50% to 90% approaching the Fukazawa mine from the northwest. The trace elements which are of exhalative origin show a relatively erratic distribution. In addition, the accommodation of barium, which is of exhalative origin, in the sericite constituent of the clastic component, combined with its higher concentration in the clastic relative to that in the chemical component, may indicate the presence of sulphide and/or barite ore lower in the stratigraphy. 相似文献
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The orbits of 12 Trojan asteroids, which have Lyapunov times T
L105 years and were previously classified as ASCs(=asteroids in stable chaos), are integrated for 50 Myrs, along with a group of neighbouring initial conditions for each nominal orbit. About 40% of the orbits present strong instabilities in the inclination, which may be attributed primarily to the action of the 16 secular resonance; two escapes are also recorded. Higher-order secular resonances, involving the nodes of the outer planets, are also found to be responsible for chaotic motion. Orbital stability depends critically on the choice of initial conditions and, thus, these objects can be regarded as being on the edge of strong chaos. 相似文献
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Harry Varvoglis Vasiliki Sgardeli Kleomenis Tsiganis 《Celestial Mechanics and Dynamical Astronomy》2012,113(4):387-402
The recent discovery of free-floating planets and their theoretical interpretation as celestial bodies, either condensed independently or ejected from parent stars in tight clusters, introduced an intriguing possibility. Namely, that some exoplanets are not condensed from the protoplanetary disk of their parent star. In this novel scenario a free-floating planet interacts with an already existing planetary system, created in a tight cluster, and is captured as a new planet. In the present work we study this interaction process by integrating trajectories of planet-sized bodies, which encounter a binary system consisting of a Jupiter-sized planet revolving around a Sun-like star. To simplify the problem we assume coplanar orbits for the bound and the free-floating planet and an initially parabolic orbit for the free-floating planet. By calculating the uncertainty exponent, a quantity that measures the dependence of the final state of the system on small changes of the initial conditions, we show that the interaction process is a fractal classical scattering. The uncertainty exponent is in the range (0.2–0.3) and is a decreasing function of time. In this way we see that the statistical approach we follow to tackle the problem is justified. The possible final outcomes of this interaction are only four, namely flyby, planet exchange, capture or disruption. We give the probability of each outcome as a function of the incoming planet’s mass. We find that the probability of exchange or capture (in prograde as well as retrograde orbits and for very long times) is non-negligible, a fact that might explain the possible future observations of planetary systems with orbits that are either retrograde (see e.g. Queloz et?al. Astron. Astrophys. 417, L1, 2010) or tight and highly eccentric. 相似文献
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Despoina K. Skoulidou Aaron J. Rosengren Kleomenis Tsiganis George Voyatzis 《Celestial Mechanics and Dynamical Astronomy》2018,130(11):77
In this paper, we study the long-term dynamical evolution of highly elliptical orbits in the medium-Earth orbit region around the Earth. The real population consists primarily of Geosynchronous Transfer Orbits (GTOs), launched at specific inclinations, Molniya-type satellites and related debris. We performed a suite of long-term numerical integrations (up to 200 years) within a realistic dynamical model, aimed primarily at recording the dynamical lifetime of such orbits (defined as the time needed for atmospheric reentry) and understanding its dependence on initial conditions and other parameters, such as the area-to-mass ratio (A / m). Our results are presented in the form of 2-D lifetime maps, for different values of inclination, A / m, and drag coefficient. We find that the majority of small debris (\(>70\%\), depending on the inclination) can naturally reenter within 25–90 years, but these numbers are significantly less optimistic for large debris (e.g., upper stages), with the notable exception of those launched from high latitude (Baikonur). We estimate the reentry probability and mean dynamical lifetime for different classes of GTOs and we find that both quantities depend primarily and strongly on initial perigee altitude. Atmospheric drag and higher A / m values extend the reentry zones, especially at low inclinations. For high inclinations, this dependence is weakened, as the primary mechanisms leading to reentry are overlapping lunisolar resonances. This study forms part of the EC-funded (H2020) “ReDSHIFT” project. 相似文献