Formation process of pyrite polyframboid based on the heavy-metal analysis by micro-PIXE

Pyrite framboid in sedimentary rocks could be concerned with arsenic contamination in groundwater of acidic environment and has been studied for the formation process of its unique morphology. However, not much has been discussed about the formation process based on the heavy-metal distribution in pyrite framboids and their aggregates. To reveal the formation process of pyrite framboids and their aggregates, mudstone from the Late Cretaceous Hakobuchi Group, central Hokkaido, Japan, are investigated for mode, petrographical, mineralogical, and micro-PIXE (particle-induced X-ray emission) analysis in this study. Spherical and sub-spherical pyrite framboids observed in polyframboids can be divided into two types based on the diameter of framboids (D) and the average diameter of microcrystals (d) within framboids: type 1, ranging from 2 to 9 μm and from 0.4 to 0.9 μm, respectively, and type 2, ranging from 8 to 50 μm and from 0.5 to 1.8 μm, respectively. Based on the quantitative traverse analyses and 2-D elemental mapping results by micro-PIXE, heterogeneities in the concentrations of heavy metals within the analyzed aggregations of pyrite are exhibited. On the basis of the As and Pb zoning patterns, the time range and chronological stages of pyrite-aggregation growth are revealed.     

Coronal Hole Influence on the Observed Structure of Interplanetary CMEs

We report on the coronal hole (CH) influence on the 54 magnetic cloud (MC) and non-MC associated coronal mass ejections (CMEs) selected for studies during the Coordinated Data Analysis Workshops (CDAWs) focusing on the question if all CMEs are flux ropes. All selected CMEs originated from source regions located between longitudes 15E?–?15W. Xie, Gopalswamy, and St. Cyr (2013, Solar Phys., doi: 10.1007/s11207-012-0209-0 ) found that these MC and non-MC associated CMEs are on average deflected towards and away from the Sun–Earth line, respectively. We used a CH influence parameter (CHIP) that depends on the CH area, average magnetic field strength, and distance from the CME source region to describe the influence of all on-disk CHs on the erupting CME. We found that for CHIP values larger than 2.6 G the MC and non-MC events separate into two distinct groups where MCs (non-MCs) are deflected towards (away) from the disk center. Division into two groups was also observed when the distance to the nearest CH was less than 3.2×10⁵ km. At CHIP values less than 2.6 G or at distances of the nearest CH larger than 3.2×10⁵ km the deflection distributions of the MC and non-MCs started to overlap, indicating diminishing CH influence. These results give support to the idea that all CMEs are flux ropes, but those observed to be non-MCs at 1 AU could be deflected away from the Sun–Earth line by nearby CHs, making their flux rope structure unobservable at 1 AU.     

The Solar Connection of Enhanced Heavy Ion Charge States in the Interplanetary Medium: Implications for the Flux-Rope Structure of CMEs

We investigated a set of 54 interplanetary coronal mass ejection (ICME) events whose solar sources are very close to the disk center (within ±?15^° from the central meridian). The ICMEs consisted of 23 magnetic-cloud (MC) events and 31 non-MC events. Our analyses suggest that the MC and non-MC ICMEs have more or less the same eruption characteristics at the Sun in terms of soft X-ray flares and CMEs. Both types have significant enhancements in ion charge states, although the non-MC structures have slightly lower levels of enhancement. The overall duration of charge-state enhancement is also considerably smaller than that in MCs as derived from solar wind plasma and magnetic signatures. We find very good correlation between the Fe and O charge-state measurements and the flare properties such as soft X-ray flare intensity and flare temperature for both MCs and non-MCs. These observations suggest that both MC and non-MC ICMEs are likely to have a flux-rope structure and the unfavorable observational geometry may be responsible for the appearance of non-MC structures at 1 AU. We do not find any evidence for an active region expansion resulting in ICMEs lacking a flux-rope structure because the mechanism of producing high charge states and the flux-rope structure at the Sun is the same for MC and non-MC events.     

Prediction of ground motion in the Osaka sedimentary basin associated with the hypothetical Nankai earthquake

We studied the long-period ground motions in the Osaka sedimentary basin, Japan, which contains a 1- to 3-km thickness of sediments and is the site of many buildings or construction structures with long-natural period. We simulated the broadband ground motions likely to be produced by the hypothetical Nankai earthquake: the earthquake expected to give rise to the most severe long-period ground motion within the basin. For the simulation, we constructed multiscale heterogeneous source models based on the Central Disaster Management Council of Japan (CDMC) source model and adopted a hybrid computation method in which long-period motion and short-period motion are computed using a 3-D finite difference method and the stochastic Green’s function method, respectively. In computing long-period motions, we used a 3-D structure model of the crust and the Osaka sedimentary basin. The ground motions are estimated to have peak velocities of 50–90 cm/s, prolonged durations exceeding 300 s, and long predominant periods of 5–10 s in the area with great thickness of sediments. The predominant periods are in agreement with an approximate evaluation by 4 H/V _s where H and V _s are the thickness of the sediment and the average S wave velocity, respectively.     

The Potential of Eleocharis acicularis for Phytoremediation: Case Study at an Abandoned Mine Site

Phytoremediation, a plant‐based and cost‐effective technology for the cleanup of contaminated soil and water, is receiving increasing attention. In this study, the aquatic macrophyte Eleocharis acicularis was examined for its ability to take up multiple heavy metals and its potential application for phytoremediation at an abandoned mining area in Hokkaido, Japan. Elemental concentrations were measured in samples of E. acicularis, water, and soil collected from areas of mine tailing and drainage. The results reveal that Pb, Fe, Cr, Cu, Ni, and Mn accumulation in the plants increased over the course of the experiment, exceeding their initial concentrations by factors of 930, 430, 60, 25, 10, and 6, respectively. The highest concentrations of Fe, Pb, Zn, Mn, Cr, Cu, and Ni within the plants were 59500, 1120, 964, 388, 265, 235, and 47.4 mg/kg dry wt., respectively, for plants growing in mine drainage after 11 months of the experiment. These results indicate that E. acicularis is a hyperaccumulator of Pb. We also found high Si concentrations in E. acicularis (2.08%). It is likely that heavy metals exist in opal‐A within cells of the plant. The bioconcentration factors (BCF: ratio of metal concentration in the plant shoots to that in the soil) obtained for Cr, Cu, Zn, Ni, Mn, and Pb were 3.27, 1.65, 1.29, 1.26, 1.11, and 0.82, respectively. The existence of heavy metals as sulphides is thought to have restricted the metal‐uptake efficiency of E. acicularis at the mine site. The results of this study indicate that E. acicularis shows great potential in the phytoremediation of mine tailing and drainage rich in heavy metals.     

1.5 Ma以来黄土高原风尘堆积的岩石磁学记录与中更新世气候转型

通过对黄土高原中部朝那剖面黄土-古土壤序列系统的岩石磁学分析,建立了1.5Ma以来黄土高原高分辨率岩石磁学指标演化序列。岩石磁学记录表明本区1.5Ma以来以0.93和0.62Ma为界经历了3个不同的气候演化阶段。在1.5～O.93和0.62～0Ma期间各种磁学参数大致呈同步变化趋势,能较好地与深海氧同位素（MIS）曲线相对应,而在0.93～0.62Ma期间（相当于L9底到L6顶,MIS24-MISl6）,尽管磁化率、饱和剩磁强度（Mr）、饱和磁化强度（Ms）与剩磁矫顽力（Bcr）、矫顽力（Bc）曲线的峰谷能与MIS的峰谷相对比,但该阶段的磁学参数变化幅度和形式明显不同于1.5～0.93和0.62Ma以来的两个演化阶段。磁化率、Mr和Ms在0.93Ma突然降低,此后变幅很小,反映夏季风较弱且相对稳定,一直维持到0.62Ma前后。在0.9Ma前后Bc、Bcr突然增大,可能反映了冬季风突然增强,然后宽幅波动下降。这种变化可能是黄土高原风尘堆积对中更新世气候转型事件的响应。黄土高原岩石磁学记录的中更新世气候转型事件发生于0.93Ma,结束于0.62Ma。造成这次气候转型事件的原因除了与全球冰量和太阳辐射变化有关之外,还可能与中更新世青藏高原急剧隆升而激发的亚洲内陆干旱化加剧,从而导致亚洲内陆沙漠的形成与扩张有关。     

Motion of iron sulfide inclusions inside a shock‐melted chondrule

Abstract— We calculated the trajectories of molten spheres of iron sulfide inclusions inside a melted chondrule during the nebular shock wave heating. Our calculations included the effects of high‐velocity internal flow in the melted chondrule and apparent gravitational force caused by the drag force of nebular gas flow. The calculated results show that large iron sulfide inclusions, which have radii 0.23 times larger than those of the parent chondrules, must reach the surface of the melted chondrule within a short period of time (<<1 s). This effect will provide us with very important information about chondrule formation by nebular shock wave heating.     

Source characteristics of the 1992 Nicaragua tsunami earthquake inferred from teleseismic body waves

We analyzed the broadband body waves of the 1992 Nicaragua earthquake to determine the nature of rupture. The rupture propagation was represented by the distribution of point sources with moment-rate functions at 9 grid points with uniform spacing of 20 km along the fault strike. The moment-rate functions were then parameterized, and the parameters were determined with the least squares method with some constraints. The centroid times of the individual moment-rate functions indicate slow and smooth rupture propagation at a velocity of 1.5 km/s toward NW and 1.0 km/s toward SE. Including a small initial break which precedes the main rupture by about 10 s, we obtained a total source duration of 110 s. The total seismic moment isM _o =3.4×10²⁰ Nm, which is consistent with the value determined from long-period surface waves,M _o =3.7×10²⁰ Nm. The average rise time of dislocation is determined to be 10 s. The major moment release occurred along a fault length of 160 km. With the assumption of a fault widthW=50 km, we obtained the dislocationD=1.3 m. From andD the dislocation velocity isD=D/0.1 m/s, significantly smaller than the typical value for ordinary earthquakes. The stress drop =1.1 MPa is also less than the typical value for subduction zone earthquakes by a factor of 2–3. On the other hand, the apparent stress defined by 2E _s /M _o , where andE _s are respectively the rigidity and the seismic wave energy, is 0.037 MPa, more than an order of magnitude smaller than . The Nicaragua tsunami earthquake is characterized by the following three properties: 1) slow rupture propagation; 2) smooth rupture; 3) slow dislocation motion.