内生碳酸岩型稀土矿床中磷酸盐作用研究综述

碳酸岩型稀土矿床是全球稀土最主要的来源。磷酸盐是该成矿体系中常见的组分,但对其在碳酸岩稀土成矿过程中的具体作用仍缺少系统的认识。本文综述了磷酸盐在碳酸岩岩浆形成、演化和稀土富集成矿过程中作用,并提出现存问题和研究展望。磷在碳酸盐熔体中具有很高的溶解度。磷的存在有利于稀土在地幔极低程度部分熔融过程和碳酸盐—硅酸盐液态不混溶过程中优先进入碳酸盐熔体,形成初始碳酸岩熔体中稀土的预富集。碳酸岩岩浆演化过程中,稀土将优先进入到不混溶的磷酸盐熔体或独居石和磷灰石等磷酸盐矿物中,这些熔体和矿物的行为很可能是控制体系中稀土行为和成矿潜力的关键因素。岩浆作用过程中形成的富稀土磷酸盐矿物还可为热液阶段稀土矿化提供成矿物质来源。磷酸盐还是热液过程中稀土的有效沉淀剂,有利于轻重稀土矿物在流体晚期阶段成矿。未来工作应更多关注磷酸盐在碳酸岩岩浆演化过程中的作用及其中重稀土的富集机理研究,针对具体成岩成矿过程开展实验岩石学和熔体包裹体研究。     

Influences of the NAO on the North Atlantic CO_2 Fluxes in Winter and Summer on the Interannual Scale

The differences in the influences of the North Atlantic Oscillation (NAO) on the air–sea CO_2 fluxes (f CO_2) in the North Atlantic (NA) between different seasons and between different regions are rarely fully investigated. We used observation-based data of f CO_2, surface-ocean CO_2partial pressure (p CO_(2sea)), wind speed and sea surface temperature(SST) to analyze the relationship between the NAO and f CO_2 of the subtropical and subpolar NA in winter and summer on the interannual time scale. Based on power spectrum estimation, there are significant interannual signs with a 2–6 year cycle in the NAO indexes and area-averaged f CO_2 anomalies in winter and summer from 1980 to 2015. Regression analysis with the 2–6 year filtered data shows that on the interannual scale the response of the f CO_2 anomalies to the NAO has an obvious meridional wave-train-like pattern in winter, but a zonal distribution in summer. This seasonal difference is because in winter the f CO_2anomalies are mainly controlled by the NAO-driven wind speed anomalies, which have a meridional distribution pattern, while in summer they are dominated by the NAO-driven SST anomalies, which show distinct zonal difference in the subtropical NA. In addition, in the same season, there are different factors controlling the variation of p CO_(2sea)in different regions. In summer, SST is important to the interannual variation of p CO_(2sea)in the subtropical NA, while some biogeochemical variables probably control the p CO_(2sea) variation in the subpolar NA.     

珠江口磨刀门水道盐度变化对水文气象要素的频率响应特征

以2010年11月-2011年3月磨刀门水道挂定角、联石湾、竹排沙、平岗和竹银5个测站的盐度、马口水文站流量、三灶站潮位和竹银站的主流向风速为基本数据,应用偏相干谱估计方法分析了各测站盐度变化对潮汐、流量和风的频率响应。经验诊断分析结果表明:1)马口站入海径流存在准1日、半日、1/4日和1/3日等显著的潮致振荡周期;2)各测站盐度变化与潮汐主要振荡周期并不一致,沿磨刀门水道向上游,潮汐对盐度变化的影响递减,竹银站盐度可作为潮汐直接作用下咸潮上溯的平均上限位置;3)消除潮汐和径流的影响后风对盐度变化的作用明显加强;4)各测站盐度变化对潮汐、流量与风的响应过程存在时间超前或滞后但无特定规律,说明磨刀门水道盐度变化过程十分复杂。     

内蒙古赤峰四家子盆地张家口组火山岩稀土元素特征及成因

根据最近几年开展的1∶5万区域地质调查获得的新资料,确认了内蒙古自治区赤峰地区四家子盆地张家口组的存在。四家子盆地晚侏罗世张家口组火山岩广泛分布。张家口旋回火山岩属高钾钙碱性岩石系列,火山岩岩性为流纹岩类、粗面岩类和粗安岩类。张家口火山旋回可分为三个亚旋回。张家口旋回火山岩稀土总量较高,稀土分布模式呈右倾型,轻稀土分馏作用高于重稀土的分馏作用,为轻稀土富集型,总体显示弱负铕异常、弱的负铈异常。稀土元素具有陆内火山岩的基本特征。结合同位素年代学研究成果和其他岩石地球化学资料,综合研究及分析表明,张家口组火山岩成岩物质主要来源于地壳,火山岩的成因以部分熔融为主。     

南海岩石圈厚度变化特征及其构造意义

地震层析资料表明,南海地区,自红河口向南经南海、苏录海到苏拉威西海,岩石圈速度低,底部横波速度仅4.4km/s,岩石圈厚度在60～80km,为薄岩石圈地区;而软流层的速度也较低,在4.2～4.4km/s,但厚度较大,大于200km。从红河—莺歌海断裂带经南海到苏录海,存在一条北西向宽约200km的上地幔北西向低速带,速度在4.05～4.25km/s(面波速度)。它反映了新生代南海地区上地幔的动力学过程。南海岩石圈厚度变化存在明显差异,南海陆缘,岩石圈厚度在70～80km,而在南海洋盆之下,岩石圈厚度超过100km,岩石圈底部存在高速岩石层,并且洋盆下的岩石圈之厚度比大陆边缘厚,在海盆岩石圈下部的60～80km深度上存在一高速层,纵波速度为8.2～8.3km/s。特别是中央海盆及西北海盆与西南海盆,其下部岩石圈中均存在一高速岩石层,这是非常具有构造意义的。由此笔者提出大陆岩石圈裂离、上地幔因减压而部分熔融所产生的基性岩浆形成南海新生代洋壳的猜想。     

A three‐point time discretization technique for parabolic partial differential equations

The Crank–Nicolson scheme has second‐order accuracy, but often leads to oscillations affecting numerical stability. On the other hand, the implicit scheme is free from oscillation, but it has only first‐order accuracy. In this work, a three‐point discretization scheme with variable time step is presented for the time marching of parabolic partial differential equations. The method proposed has second‐order accuracy, is unconditionally stable and dampens spurious oscillations of the numerical results. The application and effectiveness of the new method are demonstrated through several numerical examples. It is shown that, unlike the Crank–Nicolson method, the approach proposed produces no oscillatory response irrespective of the time step adopted. Copyright © 2010 John Wiley & Sons, Ltd.     

DMO方法综述

DMO（倾角时差校正）是一种将非零偏移距地震道转换为零偏移距地震道的数据处理方法，主要针对地层倾角不为零的情况。通过应用DMO，共中心点道集变成以自激自收（垂直入射）定义的共深度点道集。DMO是地震资料处理中一个非常重要的流程，对DMO的发展状况和一些主要算法进行总结，各向异性DMO将有望成为今后的发展方向。     

Transformation of two-pyroxene hornblende granulite to garnet granulite involving simultaneous melting and fracturing of the lower crust, Fiordland, New Zealand

Granulite facies gabbroic and dioritic gneisses in the Pembroke Valley, Milford Sound, New Zealand, are cut by vertical and planar garnet reaction zones in rectilinear patterns. In gabbroic gneiss, narrow dykes of anorthositic leucosome are surrounded by fine‐grained garnet granulite that replaced the host two‐pyroxene hornblende granulite at conditions of 750 °C and 14 kbar. Major and trace element whole‐rock geochemical data indicate that recrystallization was mostly isochemical. The anorthositic veins cut contacts between gabbroic gneiss and dioritic gneiss, but change in morphology at the contacts, from the anorthositic vein surrounded by a garnet granulite reaction zone in the gabbroic gneiss, to zones with a septum of coarse‐grained garnet surrounded by anorthositic leucosome in the dioritic gneiss. The dioritic gneiss also contains isolated garnet grains enclosed by leucosome, and short planar trains of garnet grains linked by leucosome. Partial melting of the dioritic gneiss, mostly controlled by hornblende breakdown at water‐undersaturated conditions, is inferred to have generated the leucosomes. The form of the leucosomes is consistent with melt segregation and transport aided by fracture propagation; limited retrogression suggests considerable melt escape. Dyking and melt escape from the dioritic gneiss are inferred to have propagated fractures into the gabbroic gneiss. The migrating melt scavenged water from the surrounding gabbroic gneiss and induced the limited replacement by garnet granulite.     

热液流体中的离子扩散作用:Ⅰ.示踪扩散系数的理论计算

本文在对已有示踪扩散系数和极限当量电导实验测定数据进行分析的基础上，运用热力学理论建立了离子示踪扩散系数（D0i，T）与标准偏摩尔摘（SOi,25）和温度的函数关系式：应用该方程可计算溶液中离子在任意温度下的示踪扩散系数。文中给出了各类离子的a'j、b'j、cj、dj和ai,j的值，并计算了70种组分在温度25～400℃范围内的示踪扩散系数。与实验数据的比较和分析表明，计算结果的均方差为3％以内。