Petrogenesis of the new lherzolitic shergottite Grove Mountains 99027: Constraints of petrography,mineral chemistry,and rare earth elements

Abstract— We report petrography, mineral chemistry, and microdistribution of rare earth elements (REE) in a new lherzolitic shergottite, Grove Mountains (GRV) 99027. The textural relationship and REE patterns of minerals suggest precipitation of cumulus olivine and chromite, followed by equilibrium crystallization of a closed system with a bulk composition of the inferred intercumulus melt. Subsolidus equilibrium temperatures of pyroxenes and olivine range from 1100 to 1210 °C, based on a two‐pyroxene thermometry and Ca partitioning between augite and olivine. Oxygen fugacity of the parent magma is 1.5–2.5 (av. 2.0 ± 0.4) log units below the quartz‐fayalite‐magnetite (QFM) buffer at 960–1360 °C, according to the olivine‐orthopyroxene‐chromite barometer. The ilmenite‐chromite barometer and thermometer show much wider ranges of oxygen fugacity (1.0–7.0 log unit below QFM) and temperature (1130–480 °C), suggesting subsolidus equilibration of the oxides at low temperatures, probably due to deep burial of GRV 99027 on Mars. The low oxygen fugacity and LREE depletion of the parent magma of GRV 99027 suggest low contamination by martian crust. Characteristics of GRV 99027 demonstrate similarity of lherzolitic shergottites, suggesting a high possibility of launch pairing or a homogeneous upper mantle of Mars if they were ejected by individual impact events. However, GRV 99027 probably experienced severe post‐shock thermal metamorphism in comparison with other lherzolitic shergottites, based on the re‐crystallization of maskelynite, the homogeneity of minerals, and the low subsolidus equilibrium temperatures between chromite and ilmenite.     

Interactions between hot Jupiters and their host stars

A young hot Jupiter might have been tidally inflated beyond its Roche radius when its orbit was being circularized. This scenario has the potential to explain a couple of solid or tentative observations such as a pile‐up of hot Jupiters around 0.04‐0.05 AU, the mass‐period correlation of transiting planets, as well as the existence of hot Neptunes. Other scenarios such as tidal dissipation in a planet‐host star as well as the magnetic interaction will be also discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Presolar grains in the CM2 chondrite Sutter's Mill

The Sutter's Mill (SM) carbonaceous chondrite is a regolith breccia, composed predominantly of CM2 clasts with varying degrees of aqueous alteration and thermal metamorphism. An investigation of presolar grains in four Sutter's Mill sections, SM43, SM51, SM2‐4, and SM18, was carried out using NanoSIMS ion mapping technique. A total of 37 C‐anomalous grains and one O‐anomalous grain have been identified, indicating an abundance of 63 ppm for presolar C‐anomalous grains and 2 ppm for presolar oxides. Thirty‐one silicon carbide (SiC), five carbonaceous grains, and one Al‐oxide (Al₂O₃) were confirmed based on their elemental compositions determined by C‐N‐Si and O‐Si‐Mg‐Al isotopic measurements. The overall abundance of SiC grains in Sutter's Mill (55 ppm) is consistent with those in other CM chondrites. The absence of presolar silicates in Sutter's Mill suggests that they were destroyed by aqueous alteration on the parent asteroid. Furthermore, SM2‐4 shows heterogeneous distributions of presolar SiC grains (12–54 ppm) in different matrix areas, indicating that the fine‐grained matrix clasts come from different sources, with various thermal histories, in the solar nebula.     

NanoSIMS analysis of organic carbon from the Tissint Martian meteorite: Evidence for the past existence of subsurface organic‐bearing fluids on Mars

Two petrographic settings of carbonaceous components, mainly filling open fractures and occasionally enclosed in shock‐melt veins, were found in the recently fallen Tissint Martian meteorite. The presence in shock‐melt veins and the deuterium enrichments (δD up to +1183‰) of these components clearly indicate a pristine Martian origin. The carbonaceous components are kerogen‐like, based on micro‐Raman spectra and multielemental ratios, and were probably deposited from fluids in shock‐induced fractures in the parent rock of Tissint. After precipitation of the organic matter, the rock experienced another severe shock event, producing the melt veins that encapsulated a part of the organic matter. The C isotopic compositions of the organic matter (δ¹³C = ?12.8 to ?33.1‰) are significantly lighter than Martian atmospheric CO₂ and carbonate, providing a tantalizing hint for a possible biotic process. Alternatively, the organic matter could be derived from carbonaceous chondrites, as insoluble organic matter from the latter has similar chemical and isotopic compositions. The presence of organic‐rich fluids that infiltrated rocks near the surface of Mars has significant implications for the study of Martian paleoenvironment and perhaps to search for possible ancient biological activities on Mars.     

HD 82943行星系统的2:1共振与稳定性

用直接数值积分方法通过模拟不同的行星构型探讨了HD82943行星系统(由两颗共振的巨行星组成)的长期动力演化,同时,还研究了在相空间的轨道运动.在对系统长达107年数值积分中,发现所有的稳定轨道均与2:1共振相关联.典型地,在相同的时标内,两个共振幅角θ1和θ2同时(或其中之一)存在秤动.由于共振幅角在一定范围内的秤动,因而使两颗行星轨道半长径被约束而表现为规则运动模式.另外,利用分析模型(包含了外行星偏心率e2的因素),还讨论了对于不同取值的e2和相对近星点经度θ时,内行星在相空间的运动,并发现2:1轨道共振对于相对较小的e2以及当θ=0°时易于保持.此外,适中的e2将导致系统的两颗行星进入深度共振状态.再者,分析模型和数值计算的结果吻合得很好,两者都揭示了行星系统的2:1共振结构.     

卫星轨道预报的一种分析方法

人造地球卫星的轨道预报是空间环境监测和实时跟踪测量中一个重要环节，由于监测对象众多，要求精度也不太高，通常采用分析法预报．在已有分析法得到t时刻平均根数的基础上给出一种轨道预报方法，由t时刻的平均根数给出该时刻卫星的位置和速度，在此基础上将地球非球形引力摄动的周期项直接用卫星直角坐标的位置和速度分量表示，这样可以避免在计算轨道根数变化的周期项时出现的奇点问题，从而对根数的选择无特殊要求，可适用于各种轨道，简化预报程序和相应的软件，提高预报效率。     

Comparison of linear and nonlinear shallow wave water equations applied to tsunami waves over the China Sea

This paper discusses the applications of linear and nonlinear shallow water wave equations in practical tsunami simulations. We verify which hydrodynamic theory would be most appropriate for different ocean depths. The linear and nonlinear shallow water wave equations in describing tsunami wave propagation are compared for the China Sea. There is a critical zone between 400 and 500 m depth for employing linear and nonlinear models. Furthermore, the bottom frictional term exerts a noticeable influence on the propagation of the nonlinear waves in shallow water. We also apply different models based on these characteristics for forecasting potential seismogenic tsunamis along the Chinese coast. Our results indicate that tsunami waves can be modeled with linear theory with enough accuracy in South China Sea, but the nonlinear terms should not be neglected in the eastern China Sea region.     

SIMS U-Pb dating of micro-zircons in the lunar meteorites Dhofar 1528 and Dhofar 1627

About half of the lunar meteorites in our collections are feldspathic breccias. Acquiring geochronologic information from these breccias is challenging due to their low radioactive-element contents and their often polymict nature. We used high-spatial-resolution (5 μm) NanoSIMS (nanoscale secondary ion mass spectrometry) U-Pb dating technique to date micro-zircons in the lunar feldspathic meteorites Dhofar 1528 and Dhofar 1627. Three NanoSIMS dating spots of two zircon grains from Dhofar 1528 show a discordia with an upper intercept at 4354 ± 76 Ma and a lower intercept at 332 ± 1407 Ma (2σ, MSWD = 0.01, p = 0.91). Three spots of two zircon grains in Dhofar 1627 define a discordia with an upper intercept at 3948 ± 30 Ma and a lower intercept at 691 ± 831 Ma (2σ, MSWD = 0.40, p = 0.53). Both samples likely experienced shock metamorphism caused by impacts. Based on the clastic nature, lack of recrystallization and the consistent U-Pb and Pb-Pb dates of the zircons in Dhofar 1528, the U-Pb date of 4354 Ma is interpreted as the crystallization age of its Mg-suite igneous precursor. Some of the Dhofar 1627 zircons show poikilitic texture, a crystallization from the matrix impact melt, so the U-Pb date of 3948 Ma corresponds to an impact event, likely the Imbrium basin-forming event. These data are the first radiometric ages for these two meteorites and demonstrate that in situ (high spatial resolution) U-Pb dating has potential for extracting geochronological information about igneous activities and impact events from lunar feldspathic and polymict breccias.     

Solar flare injection and propagation of low-energy protons and electrons in the event of 7–9 July, 1966

Simultaneous observations of the 7–9 July 1966 solar particle event by energetic particle detectors on three satellites, IMP-III, OGO-III and Explorer 33 are utilized to show that large spatial gradients are present in the fluxes of 0.5–20 meV protons and 45 keV electrons. The event is divided into three parts: the ordinary diffusive component, the halo, and the core. The core corotates with the interplanetary field, and therefore it and the surrounding halo are interpreted as spatial features which are connected by the interplanetary magnetic field lines to the vicinity of the flare region. Upper limits to the interplanetary transverse diffusion coefficient for 4–20 meV protons at 1 AU are derived from the width of the halo. These are at least two orders of magnitude less than the parallel diffusion coefficient for the same energy particles.It is argued that the observed flux variations cannot be explained by an impulsive point source injection for any physically reasonable diffusion model. Instead, since the interplanetary transverse-diffusion coefficient is small for these low-energy particles, the observed spatial features are interpreted as the projection to 1 AU by the interplanetary field lines of an extensive injection profile at the sun. The geometry of the injection mechanism is discussed and it is suggested that some temporary storage of the flare particles occurs near the sun.Now at NASA, Goddard Space Flight Center, Greenbelt, Md., U.S.A.     

陕西青山金矿床黄铁矿的标型特征研究及矿床成因探讨

陕西青山微细浸染型金矿床中的主要矿石矿物黄铁矿具有标型意义,研究表明,富金矿段的黄铁矿具有颜色暗黄-灰黄、颗粒细小破碎、晶形差,为五角十二面体和复杂聚形、亏硫与铁的特点。矿区矿源层为含炭热水沉积岩层组成的黑色岩系,具有热水沉积成矿预富集-韧脆性构造叠加-大气降水为主的含矿热液改造的类卡林型金矿床的成矿特点,富金细粒黄铁矿是地下热卤水与大气降水热液两种流体混合与沸腾使物理化学条件瞬变的产物。