Connectivity of molten Fe alloy in peridotite based on in situ electrical conductivity measurements: implications for core formation in terrestrial planets

The connectivity of molten Fe-S in peridotite has been experimentally investigated by means of in situ electrical conductivity measurements at high temperatures and 1 GPa. Starting materials were powdered mixtures of peridotite KLB-1 with various amounts (0, 3, 6, 13, 19, 24 vol.%) of the 1 GPa eutectic composition in the Fe-FeS binary system. At temperatures above the eutectic point in the Fe-FeS system (∼980 °C) and below the solidus of KLB1 (∼1200 °C), molten Fe-S in a solid silicate matrix interconnects when the volume fraction is over ∼5%. Conductivity-temperature paths indicate that in the presence of partial silicate melting the connectivity of molten Fe-S in a peridotite matrix is inhibited. Based on observations of retrieved samples, the percolation threshold of Fe-S melts in the presence of low to moderate degrees of silicate melt is estimated at 13±2 vol.%. These results indicate that if the volume fraction of Fe-alloy in a planetesimal was initially greater than 5%, and if early heating by decay of radionuclides raised the temperature of the interior above the Fe-alloy melting point, initial metal segregation was controlled by permeable flow of molten iron alloy in a solid silicate matrix. These conditions were likely met by many terrestrial objects in the early solar nebula. Efficient removal of residual Fe-alloy (5 vol.%) from silicate requires high-degree melting of silicate so that metal can segregate as droplets. Giant impacts during the final stage of accretion of large planetary objects could supply the energy required for high-degrees of melting. Alternatively, if initial metal segregation were delayed until a planetary object grew to large size (∼1000 km in diameter), release of gravitational potential energy due to metal segregation could contribute enough heat to form a magma ocean.     

基于IP核的RAM VHDL设计

介绍了VHDL(Very High Speed Integrated Circuit Hardware DescHption Language)语言和IP核的特点，通过实例，详细阐述了IP核的使用方法和步骤，最后初步阐述了电路的优化方法。     

球层中的非线性自由热对流变粘度模型

粘度为常数或仅随深度变化是地幔对流模型中常用的假设. 本文在常粘度背景下， 通过假定小扰动粘度在纬向上的变化形式， 将粘度的横向变化引入地幔对流模型中， 并给出了变粘度地幔对流模型的数值解法. 对外边界为刚性、 内边界为应力自由（简记为R-F边界）和内外边界均为刚性（简记为R-R边界）边界的两种模型进行了计算， 对比了不同模型、 深度和瑞利数时的环型场的变化特征. 注意到环型场能量主要集中在球层的中、 上部区域， 其速度仅占总速度的几个百分点， 这个比例几乎不随瑞利数的变化而改变， 但其对流图样受瑞利数的影响较大. 环型场的对流形态和速度的分布特征表现出了明显的纬向差异， 这一结果清晰地反映出地幔粘度的横向变化对对流形态的影响. 目前的工作还只是初步的， 但为我们探讨全球大地构造上的某些现象， 例如南北半球的不对称性和差速旋转问题提供了一种可能的研究思路.      

Hydrothermal convection in carbonaceous chondrite parent bodies

Numerical simulations of the thermal evolution of carbonaceous chondrite parent bodies indicate a period of several million years during which convective motion of water could occur. The present study considers variations of permeability, radiogenic heating, and body radius. The model accounts for the radial variation of gravity within the body, melting of ice, freezing of liquid water, and variable water properties and incorporates a realistic equation of state for water. Some regions of a parent body experience no pore water flow while other regions experience hundreds of pore volumes of liquid water flow. The spatial heterogeneity in pore water flow reflects the convective pattern in the body. Hydrothermal alteration of minerals inside the parent body will accordingly vary greatly with location in the body, and one parent body could be the source of chemically diverse meteorites.     

Climatic significance of δ18O records from an 80.36 m ice core in the East Rongbuk Glacier, Mount Qomolangma (Everest)

The δ18O variations in an 80.36 m ice core retrieved in the accumulation zone of the East Rongbuk Glacier, Mount Qomolangma (Everest), is not consistent with changes of air temperature from both southern and northern slopes of Himalayas, as well as these of the temperature anomalies over the Northern Hemisphere. The negative relationship between the δ18O and the net accumulation records of the ice core suggests the "amount effect" of summer precipitation on the δ18O values in the region. Therefore, the δ18O records of the East Rongbuk ice core should be a proxy of Indian Summer Monsoon intensity, which shows lower δ18O values during strong monsoon phases and higher values during weak phases.     

Upper mantle convection driving by density anomaly and a test model

Introduction Richter and Mckenzie (1978) supposed that there is a small-scale convection system in the mantle. For a long time lots of research provides observational data to infer the possibility of a small-scale convection in the upper mantle. For example, Haxby and Weissel (1986) discussed the relationship between SEASAT map and small-scale convection. Baudry and Kroenke (1991), Maia and Diament (1991) found that the geoid and bathymetry exhibit peaks in the 400~650 km range in the Pa…     

Detection of spheriodal free oscillation excited by Peru 8.2 M_s earthquake with five international superconducting gravimeter data

In this paper, authors obtain the spectral peaks of the earth free oscillation and check all normal modes from 0S0 to 0S48 accurately, with the Fourier analysis and the maximum entropy spectrum method dealing jointly with six groups of the observational residual data from five international superconducting gravimeter stations. By comparing the observational results in this paper with three former groups of observations or models, authors notice an extra discrepancy between two observational 0S2 modes excited separately by Peru earthquake and Alaska earthquake, which probably mirrors the anisotropy of the Earth's inner core. The analysis on the splitting 1S2 mode shows that the asymmetric factor of rotationwise spectral splitting is possible to be different from that of anti-rotationwise spectral splitting.     

Behaviour and dynamics of a hydrothermal plume in Lake Banyoles, Catalonia, NE Spain

A hydrothermal plume forms in Lake Banyoles, NE Spain, as a result of convection above a springwater-fed suspension cloud ponded on the lake floor. The plume propagates upwards reaching a level of neutral buoyancy from where a turbidity current spreads out laterally. Two-dimensional temperature and particle concentration measurements show the fate of the hydrothermal plume and its associated turbidity current and reveal its seasonal development. Silt particles transported by the plume have been used as tracers to determine the maximum and equilibrium heights of the plume. When the lake is stratified, the vertical transport of sediment is confined to the lake hypolimnion, as the thermocline limits the vertical propagation of the plume. In contrast, when the lake water column is mixed, the plume reaches the surface of the lake. The field measurements have been compared with models for thermal convection from finite isolated sources. Measurements of the flow velocity at the source of the hydrothermal plume (i.e. the rim current velocity) indicate that cold hypolimnetic water is entrained by the plume. Sedimentation rates measured from sediment traps at the zone where the turbidity current develops vary between 10 and 25 g m⁻² day⁻¹, and result from continuous silt particle sedimentation from the turbidity current. Sedimentation rates in traps are higher for stations situated close to the source than those further away (<5 g m⁻² day⁻¹). Moreover, the results demonstrate that double diffusive sedimentation from the turbidity current was dominant over grain-by-grain settling, causing a mixed distribution of sediments in the region where the turbidity current spreads. The deposition of silt particles could explain the occurrence of silt layers interbedded with biocalcarenites in the littoral zones of the lake and the stratigraphy identified by seismic profiles and cores taken from the lake floor.