Observing the reconnection region in a transequatorial loop system

A vertical current sheet is a crucial element in many flare/coronal mass ejection (CME) models. For the first time, Liu et al. reported a vertical current sheet directly imaged during the flare rising phase with the EUV Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO). As a follow-up study, here we present the comprehensive analysis and detailed physical interpretation of the observation. The current sheet formed due to the gradual rise of a transequatorial loop system. As the l...     

A computational method to help identify and measure metallines in high resolution QSO spectra

A computational code is developed to help identify metal absorption linesin high resolution QSO spectra,especially in the Lyα forest.The input to the codeincludes a list of line central wavelengths,column densities and Doppler widths.Thecode then searches for candidate metal absorption systems and assesses the probability that each system could be real.The framework of the strategy we employ isdescribed in detail and we discuss how to estimate the errors in line profile fitting thatare essential to identifi...     

Rapid variability in S5 0716+714

S5 0716+714 is one of the targets in our long term blazar monitoring program carried out with the 1.56-m telescope at Sheshan Station of Shanghai Astronomical Observatory,China.We report a very rapid variability of ΔI = 0.611 ± 0.102 mag over 3.6 min detected in our monitoring program during the period from December 2000 to March 2007.The rapid variability suggests that the mass for the central black hole is log(M/M) = 7.68 8.38.     

Time constraints for the closing of the Paleo-Asian Ocean in the Northern Alxa Region: Evidence from Wuliji granites

The Wuliji pluton in the Northern Alxa Region, Inner Mongolia, is the principal part of Shalazhashan Mountain. It belongs to the Zongnaishan-Shalazhashan Arc Zone, northwestern North China Plate, whose north is Engger Us Ophiolite Belt and south is Qagan Qulu Ophiolite Belt. The pluton was emplaced into Upper Carboniferous-Lower Permian Amushan Formation. According to the research about the original Carboniferous Amushan Formation, the lower and middle sections of the Carboniferous Amushan Formation consist of volcanic, clastic, and carbonate rocks, interpreted to represent the sedimentary association of a volcanic arc and back-arc basin; the upper section of the Amushan Formation is a molasse composed of silty shale, sandstone, gravel-bearing sandstone, and conglomerate. The Wuliji pluton consists mainly of biotite monzonitic granite, amphibole-bearing biotite monzonitic granite, and monzonitic granite. Geochemical analyses show that the pluton has both metaluminous and peraluminous characteristics, and on average has SiO2>70 wt%, Al2O3 >14 wt%, and high contents of Na2O+K2O (8.5 wt%), which define a calc-alkaline series. In addition, REE patterns show enrichment of LREE and weak negative Eu anomalies (δ Eu=0.3-1). Altogether, the samples are depleted in Nb, Ta, Ti, P, Sr, and Ba, and enriched in Rb, Th, and K. These geochemical traits are interpreted to reflect an arc component. A secondary ion mass spectrometry (SIMS) U-Pb zircon age of the biotite monzonitic Wuliji pluton in the Northern Alxa Region, Inner Mongolia, is 250.8±2.0 Ma (1σ). Samples have ε Nd (t) values between 0.1 and 1.3, which suggests that the granites were derived from mixing between the crust and mantle. Based on the SIMS age and geochemical characteristics, Wuliji granite is interpreted to be a post-collisional granite, the result of mantle-derived melt and assimilated juvenile arc crust. However, according to the newest international stratigraphic classification standard, the upper section of the Amushan Formation is Lower Permian in age, indicating that the back-arc basin had already closed in Early Permian. We conclude that the Paleo-Asian Ocean represented by the Engger Us Ophiolite Belt subducted southward in Late Carboniferous, at the same time that the trench-arc-basin system formed in the Northern Alxa Region. The Paleo-Asian Ocean was closed in Early Permian and the Northern Alxa Region entered a post-collisional period in the Late Permian, as indicated by the Wuliji granites. This suggests that the genesis of the Wuliji granites is consistent with the pluton emplacement at the upper crust, which occurred widely in the northern margin of the North China Plate in Late Carboniferous to Triassic.     

Oil Source and Entrapment Epoch of the Ordovician Oil Reservoir in the Kongxi Burial-Hill Zone, Huanghua Depression, North China

An oil flow obtained from the Middle Ordovician Fengfeng Formation carbonate reservoir in the well KG-3, Kongxi burial-hill zone in 1993 marked a breakthrough in petroleum exploration of the high-mature Lower Palaeozoic strata, North China. Both the Lower member of the Fengfeng Formation and the Second Member of the Upper Majiagou Formation in the Middle Ordovician are supposed to be the main source beds. Oil generation peaks range from 1.0% to 1.6% in Ro, showing a "lag effect" of oil generation in high-mature carbonate source rocks under multicyclic tectonic movement conditions. The Kongxi burial-hill zone adjoins a potential Ordovician source kitchen. The KG-3 Ordovician burial-hill reservoir has undergone two oil filling events, i.e., an early event in the Late Carboniferous-Permian and a more significant late event in the early Eogene.     

大别山的构造变形期次和超高压岩石折返的动力学

从构造关系上看,大别山可分为南部,中部和北部3个构造系统,大别山南部构造系统为一套（原地）构造堆叠系统（相对的）,从上到下依次为：（1）未变质的震旦纪一早三叠世沉积盖层,它被造山后的侏罗－白垩纪砂－砾岩不整合覆盖;（2）弱变质的新元古代板岩;（3）高压变质岩系（宿松群）,这些变质岩系大多退变质为绿片岩相;（4）含柯石英榴辉岩超高压变质单元的异地系统;（5）未经历超高压变质作用的原地（相对的）片麻岩系。北西－南东向的拉伸线理在各个地质单元均有表现。从动力学上看,上盘指向NW的剪切运动被后期的褶皱所改变,大别山中部为（混合岩）热穿窿改造系统,系经历了超高压变质作用的地体叠加了混合岩化作用的产物,它与超高压变质地体的界限为一拆离断层,而正是这个拆离断层使超高压变质地体向地表折返并经历了角闪岩相的退变质作用。大别山北部为构造堆叠系统,早期的面理和南北向的挤压线理被轴面北倾的褶皱所改造,这种褶皱对应于大别山中部同折返期的韧性变形的隆升构造。同时建立了地球运力学模型并讨论了逆冲作用和正断层的作用。     

太阳耀斑对电离层天顶方向电子总量的影响

对2000年7月14日太阳耀斑爆发期间北京、武汉、上海3个观测站的GPS数据进行了精化处理,计算出各个卫星交叉点沿天顶方向上的电子总量,并对是否消除仪器偏差的计算结果进行了比较,从时间域、空间域上分析了这次耀斑爆发时电离层电子总量变化的特点。结果表明：利用精化的GPS数据才能更好地反映出太阳耀斑爆发时电离层电子总量的突变情况和变化规律。分析1998年11月22日和2000年7月14日耀斑爆发期间的GPS资料,还发现在耀斑爆发前一天与耀斑爆发相对应的一个时间段内,如果卫星交叉点的运动轨迹是从高纬到低纬的运动,这些交叉点的VTEC(天顶方向上的电子总量)值在该时间段内有迅速增长的异常现象。这是否是耀斑爆发的“前兆”现象,值得进一步研究。     

铂族元素地球化学研究评述

随着分析技术的发展和数据的积累,人们逐渐认识到PGE在地球化学研究方面具有潜在的应用价值。但地幔中PGE的存在形式目前尚不清楚,在许多方面还有争议。文中通过大量的实例综述了近年来PGE的分异机制和其在上地幔分布不均一性方面取得的进展以及存在的问题,结果表明:除Au外,蚀变作用并不影响PGE的分异;PGE主要以硫化物或合金的形式赋存于地幔岩石中,其分布不均匀,单一地依靠PGE与MgO,Cr,Ni的相关性来探讨部分熔融、分离结晶过程中橄榄石、尖晶石、铬铁矿对PGE分异的影响是不全面的,必须考虑硫化物的作用;地幔岩石具有包裹体和粒间两种不同PGE分配模式的硫化物。地幔源区或板内携带PGE流体交代以粒间硫化物为主的地幔岩石。使其PGE发生分异;不管是核幔分离后外核物质的返回,还是单一硫化物的作用都不能完全否定陨石撞击的地球增生假说。在大的区域,上地幔PGE的分布是均一的,但在一定范围内由于不同的大地构造背景,其PGE的分布显示不均一性。     

藏南聂拉木北部喜马拉雅山主脊带侏罗系重解

通过野外调查和地层系统校正,认为前人在该区划分的侏罗纪地层系统存在偏差。下侏罗统在喜马拉雅山主脊带南北两侧岩相变化较大,普普嘎组可能穿时;中上侏罗统岩相变化较小;侏罗系总厚度不超过1400m。中侏罗统鲕粒铁质岩所对应的岩石地层单元按命名先后原则应为定结组,形成于外陆棚环境,可能与全球侏罗纪海泛时期洋流涌入有关,代表特提斯喜马拉雅地区中侏罗世晚巴通期一次沉积地质事件;晚侏罗世基末利期在特提斯喜马拉雅可能存在与欧洲同期的缺氧事件。     

地块活动与成组地震关系的初步探讨

中国大陆构造的成块性与中国地震活动的成组性构成中国地震构造和地震活动的一个突出现象．本文在前人对中国大陆地震成组划分的结果和地块划分方案的基础上,研究了中国大陆地块与成组地震活动之间的关系,发现大部分强震分布于地块边界断层上,成组地震的孕育和发生与块体活动有关．由成组地震震中分布图表现出来的地块活动方式主要有４种:单缝式活动型、单地块活动型、多地块活动型和地块内部活动型．地块活动频度以单缝式活动型为最高,在成组地震中则以单地块活动型为多．大陆内部各地块的活动性有差别,东部比较活跃的地块有太行山和华北平原地块,西部比较活跃的地块有川滇和昆仑-松潘地块．