小秦岭（陕西段）变质杂岩核构造与金矿

华北古地台南缘的小秦岭地区呈现为一典型的变质杂岩核构造。其主要构造要素：变质杂岩核（古台隆区），平缓韧性滑脱带（古台隆与古台坳过渡带）和多型拆离构造（古台隆区）较为完整可辨。其发展演化可能经历了地槽期、地台期和地洼期，在地洼期成型。该构造体系控制了区内糜棱岩型、石英脉型和破碎蚀变岩型（糜棱岩亚型和石英岩亚型）金矿的时空分布。提供了一类在没有深层矿源直接导入的条件下金矿形成作用的典型区域成矿实例。     

小秦岭地质构造新认识

本文初步厘定了小秦岭区域构造格局及其动力学背景，将小秦岭划分为两个次级构造单元，北部基底岩系上隆区（太华台拱）及南部盖层沉积区（金堆－卢氏台凹）。北侧紧邻渭河断凹。两者之间为一套古老糜棱岩代表的韧性剪切带所分隔，自中，新生代以来，该区处于伸展构造环境，中南部（金堆－卢氏台凹）、北部（渭河断凹）为多期拆离构造，中部（太华台拱）抬升，形成了“拆离－变质杂岩核”构造，该构造控制着本区的金矿。     

南极洲乔治王岛柯林斯冰帽冰芯层位和密度变化的一般特征

柯林斯冰帽两支冰芯层位记录证实了该冰帽主冰穹顶部（海拔约７００ｍ）属暖渗浸带，小冰穹顶部（海拔约２５０ｍ）属渗浸带。雪、冰的层位分布和密度变化包含了一定的测年信息。主冰穹顶冰芯密度－深度曲线在表层呈现韵律性变化，与层位记录中的融化冻结现象相对应，据此粗略划分年层，断定当地年积累雪层厚度为３－３．５ｍ，折合水当量１６５０－１９２５ｋｇ／ｍ２ａ，年平均积累速率约为２．０ｍ／ａ（冰当量）。主冰穹顶成冰深度为３８－３９ｍ，此深度以上密度自上而下缓慢增加，但以下由于含水层的出现，密度迅速升高，在５－６ｍ区间达到９００ｋｇ／ｍ３。小冰穹冰芯除表层外，密度基本在８００－９００ｋｇ／ｍ３之间，冰芯中雪冰互层，存在污化面，４０ｍ以下发现很厚的火山灰沉积物。小冰穹平均年积累率约为０．７ｍ／ａ（冰当量），成冰深度７－８ｍ，成冰年限为１０年左右     

Sorted stripes orientated by wind action: Some observations from sub-antarctic marion island

Sorted stripes found on the volcanic scoria and glacial deposits of sub-Antarctic Marion Island indicate a distinct preferred orientation. Despite uniformity of slope and material, the stripes are predominantly aligned parallel to the wind. It is suggested that melting of needle ice by the early morning sun is of only limited importance in the sub-Antarctic owing to the almost continual overcast conditions. The effect of the wind is so great that in exposed situations stripes are formed on horizontal surfaces.     

Ice accumulation rate in Changme-Khangpu glacier,Sikkim

Vertical profiles of¹³⁷Cs and²¹⁰Pb have been determined in a 9 m column of ice from accumulation zone of Changme-Khangpu glacier in north Sikkim valley.¹³⁷Cs activity varies from 4 to 22 dpm/ L. In many samples²¹⁰Pb occurs at a level of 20 to 65 dpm/ L which is much higher than the expected fallout value.¹³⁷Cs and²¹⁰Pb activities correlate well with each other but not with the dust content. Possibility of²¹⁰Pb production in the nuclear explosions is discussed. Several peaks appear in the depth profile of¹³⁷Cs and²¹⁰Pb which can be matched with Chinese atmospheric nuclear explosions with some phase difference if a uniform ice accumulation rate of 0.7 m per year is assumed since 1969.     

中国南海珊瑚岛礁泻湖砂层钻探取心技术

中国南海珊瑚岛礁拥有巨大的资源潜力和科研价值。科学钻探是珊瑚岛礁研究工作中获取地层资料的重要技术手段。南海珊瑚岛礁地下普遍存在多层厚层泻湖砂层，主要结构为无胶结或轻微胶结的细粒珊瑚砂，这种层位钻探取心极端困难，是影响钻探成果的主要难题之一。南海两个岛礁所实施的3口千米以上深井施工过程中，为解决泻湖砂层钻探取心难题，在分析泻湖砂层性状的基础上，综合研究钻具合理选用、钻进参数控制、钻井液性能控制等钻探工程核心内容，形成了较完整的适用于泻湖砂层钻探取心的“多要素组合钻探取心技术”。使用该技术能确保珊瑚岛礁泻湖砂层岩心采取率达到95%以上，并基本保持岩心原状性。该研究成果对于珊瑚岛礁钻探具有重要的借鉴作用。     

Late Mesozoic extensional tectonics in the North China Craton and its adjacent regions: a review and synthesis

ABSTRACT

The late Mesozoic tectonics of the North China Craton (NCC) and its adjacent regions were characterized by a general lithospheric extension and remarked by extensional dome structures, such as the metamorphic core complexes, syn-tectonic plutons, rolling-hinge structures, and widespreadgraben/half graben basins. According to our own field observations, laboratory work, and previous results of other groups, from north to south, five extensional domains have been delineated, namely Transbaikalia–Mongol–Okhotsk, western part of NCC, eastern part of NCC and Korea, Qinling–Dabie and its neighbouring, and the interior of South China Block, respectively. As the largest crustal scale extensional tectonic realm in the world, these domains are featured by a NW–SE extensional direction with strong extensional exhumation of middle to lower crust rocks to the surface along detachment faults. Geochronological work on these ductile detachment faults constrain a narrow activity period around 130 Ma except several extensive structures along the Tan–Lu fault, which documents a relative longer extensional period. The foundering of the lower part of the lithosphere could be a possible mechanism of this continent-scale extensional tectonics. This geodynamic model could help us to enhance the knowledge of the time, scale, and mechanism of the NCC destruction from the view of structural analysis.     

宝钢地区钢管桩土芯闭塞性状研究

开口钢管桩在沉桩过程中,桩端土一部分将进入管内形成"土塞"或"土芯",一部分则被挤进土的四周.土芯进入管内的高度,将直接影响桩的设计.土芯闭塞的研究具有代表性的有山原法、田岛法等.对土芯高度能否做到事先预估,就宝钢地区的钢管桩土芯闭塞的实测资料经过整理分析拟合得到D-η曲线,并与实测值及山原法作比较,得到较合理的预估值.重点讨论了在宝钢地区开口钢管桩的桩径D对η的影响,可推断其它桩径在这一地区的沉桩的土芯高度,土芯承担的荷载,钢管桩的应力场,位移场.亦为相似工程提供可能的参考.     

Analyse isotopique de l'air piégé dans la glace pour quantifier les variations de température

Isotopic measurements in polar ice core have shown a succession of rapid warming periods during the last glacial period over Greenland. However, this method underestimates the surface temperature variations. A new method based on gas thermal diffusion in the firn manages to quantify surface temperature variations through associated isotopic fractionations. We developed a method to extract air from the ice and to perform isotopic measurements to reduce analytical uncertainties to 0.006 and 0.020$\text{‰}$ for δ¹⁵N and δ⁴⁰Ar. It led to a 16±1.5 °C surface temperature variation during a rapid warming ($\text{?70}\text{000}$ yr). To cite this article: A. Landais et al., C. R. Geoscience 336 (2004).     

Martian hillside gullies and icelandic analogs

We report observations of Icelandic hillside gully systems that are near duplicates of gullies observed on high-latitude martian hillsides. The best Icelandic analogs involve basaltic talus slopes at the angle of repose, with gully formation by debris flows initiated by ground water saturation, and/or by drainage of water from upslope cliffs. We report not only the existence of Mars analog gullies, but also an erosional sequence of morphologic forms, found both on Mars and in Iceland. The observations support hypotheses calling for creation of martian gullies by aqueous processes. Issues remain whether the water in each case comes only from surficial sources, such as melting of ground ice or snow, or from underground sources such as aquifers that gain surface access in hillsides. Iceland has many examples of the former, but the latter mechanism is not ruled out. Our observations are consistent with the martian debris flow mechanism of F. Costard et al. (2001c, Science295, 110-113), except that classic debris flows begin at midslope more frequently than on Mars. From morphologic observations, we suggest that some martian hillside gully systems not only involve significant evolution by extended erosive activity, but gully formation may occur in episodes, and the time interval since the last episode is considerably less than the time interval needed to erase the gully through normal martian obliteration processes.