Observational Evidence of High Ice Concentration in a Shallow Convective Cloud Embedded in Stratiform Cloud over North China

In this study we observed the microphysical properties, including the vertical and horizontal distributions of ice particles,liquid water content and ice habit, in different regions of a slightly supercooled stratiform cloud. Using aircraft instrument and radar data, the cloud top temperature was recorded as higher than -15℃, behind a cold front, on 9 September 2015 in North China. During the flight sampling, the high ice number concentration area was located in the supercooled part of a shallow convective cloud embedded in a stratiform cloud, where the ambient temperature was around -3℃. In this area,the maximum number concentrations of particles with diameter greater than 100 μm and 500 μm(N_(100) and N_(500)) exceeded 300 L~(-1) and 30 L~(-1), respectively, and were related to large supercooled water droplets with diameter greater than 24 μm derived from cloud–aerosol spectrometer probe measurements. The ice particles types in this region were predominantly columnar, needle, graupel, and some freezing drops, suggesting that the occurrence of high ice number concentrations was likely related to the Hallett–Mossop mechanism, although many other ice multiplication processes cannot be totally ruled out.The maximum ice number concentration obtained during the first penetration was around two to three orders of magnitude larger than that predicted by the Demott and Fletcher schemes when assuming the cloud top temperature was around-15℃.During the second penetration conducted within the stratiform cloud, N_(100) and N_(500) decreased by a factor of five to ten, and the presence of columnar and needle-like crystals became very rare.     

南北地震带强震迁移特征及其预测意义

在分析南北构造带构造体系的基础上，研究了该带强震的时空动态图象演化，结果表明，南北带的地震活动有如下特征：（１）经向迁移，其空间演化有步进型和步进折返型两种形态；（２）远程的快速响应；（３）诱发地震的链锁分布，该特征反映了强震间的相互耦合，对未来强震具有示踪意义，（４）时空可公度性，该结果对分析判定本带的地震趋势从而实现正确的预测具有实际意义。     

和(县)含(山)硬石膏矿成因类型、沉积环境及赋矿规律

通过和(县)含(山)硬石膏矿勘查资料,分析研究了该区含矿地层周冲村组(东马鞍山组)岩矿成因类型和代表性剖面岩相划分,认为周冲村组是在早中三叠世缓慢海退和干旱蒸发作用下形成的一套由浅滩—局限海夹潮坪—咸化潟湖—潮上萨布哈的蒸发岩建造,其中的硬石膏矿体主要沉积于咸化潟湖环境;认为早中三叠世的海退和海水咸化过程是循序渐进式发展的,其间发生了许多次小规模海侵或风暴潮,使得咸化潟湖海水的补给和蒸发保持了相对平衡,形成了巨厚硬石膏矿体沉积所需的持续稳定的海水盐度和环境条件;认为早中三叠世的海退有自西向东的退出趋势。同时指出,由于环境差异,本区东部的硬石膏矿品质好于西部。     

超高排土场的粒径分级及其边坡稳定性分析研究

明显的粒径分级是超高排土场区别于土质边坡的最重要特征。针对西源岭413台阶排土场,结合开发的HHC-CA模型和现场散体粒径分布情况的调查,建立了考虑超高排土场粒径分级特征的边坡模型。在此模型的基础上,借助FLAC3D软件分析了现状边坡和各种堆排模式下的边坡稳定性。结果表明:西源岭413台阶排土场现状边坡上部位移矢量表现为下沉,其下沉方向与坡面保持同向,中部位移矢量表现为剪切,下部位移矢量略有反抬升的趋势。其边坡破坏模式为顶部平台拉裂,中部以圆弧形剪出;此排土场的现状边坡处于暂时性稳定阶段。而采用全覆盖式多台阶排土的边坡上部位移矢量表现为下沉,在排土场底部过渡到水平方向;破坏模式为顶部平台拉裂,下部以圆弧形剪出。仅考虑堆积散体的材料强度对排土场稳定性影响时,超高排土场的粒径分级有利于排土场边坡的稳定。     

The Oligocene Lund Tuff, Great Basin, USA: a very large volume monotonous intermediate

Unusual monotonous intermediate ignimbrites consist of phenocryst-rich dacite that occurs as very large volume (>1000 km³) deposits that lack systematic compositional zonation, comagmatic rhyolite precursors, and underlying plinian beds. They are distinct from countless, usually smaller volume, zoned rhyolite–dacite–andesite deposits that are conventionally believed to have erupted from magma chambers in which thermal and compositional gradients were established because of sidewall crystallization and associated convective fractionation. Despite their great volume, or because of it, monotonous intermediates have received little attention. Documentation of the stratigraphy, composition, and geologic setting of the Lund Tuff – one of four monotonous intermediate tuffs in the middle-Tertiary Great Basin ignimbrite province – provides insight into its unusual origin and, by implication, the origin of other similar monotonous intermediates.The Lund Tuff is a single cooling unit with normal magnetic polarity whose volume likely exceeded 3000 km³. It was emplaced 29.02±0.04 Ma in and around the coeval White Rock caldera which has an unextended north–south diameter of about 50 km. The tuff is monotonous in that its phenocryst assemblage is virtually uniform throughout the deposit: plagioclase>quartz≈hornblende>biotite>Fe–Ti oxides≈sanidine>titanite, zircon, and apatite. However, ratios of phenocrysts vary by as much as an order of magnitude in a manner consistent with progressive crystallization in the pre-eruption chamber. A significant range in whole-rock chemical composition (e.g., 63–71 wt% SiO₂) is poorly correlated with phenocryst abundance.These compositional attributes cannot have been caused wholly by winnowing of glass from phenocrysts during eruption, as has been suggested for the monotonous intermediate Fish Canyon Tuff. Pumice fragments are also crystal-rich, and chemically and mineralogically indistinguishable from bulk tuff. We postulate that convective mixing in a sill-like magma chamber precluded development of a zoned chamber with a rhyolitic top or of a zoned pyroclastic deposit. Chemical variations in the Lund Tuff are consistent with equilibrium crystallization of a parental dacitic magma followed by eruptive mixing of compositionally diverse crystals and high-silica rhyolite vitroclasts during evacuation and emplacement. This model contrasts with the more systematic withdrawal from a bottle-shaped chamber in which sidewall crystallization creates a marked vertical compositional gradient and a substantial volume of capping-evolved rhyolite magma. Eruption at exceptionally high discharge rates precluded development of an underlying plinian deposit.The generation of the monotonous intermediate Lund magma and others like it in the middle Tertiary of the western USA reflects an unusually high flux of mantle-derived mafic magma into unusually thick and warm crust above a subducting slab of oceanic lithosphere.     

白龙江中上游地区金矿控矿因素及成矿模式探讨

白龙江中上游地区微细浸染型金矿,是受地层和构造双重控制的金矿床。在阐述矿床空间分布规律、控矿因素、区域矿化和地球化学特征等基础上,初步建立了地质地球化学成矿模式。     

虎头崖铅锌多金属矿床矿体三维空间变化结构及分布规律

文章利用Vulcan和Datamine三维可视化软件建立了虎头崖铅锌多金属矿床矿体的三维实体模型、块体模型及地层三维实体模型;运用地质统计学方法分析了虎头崖矿区67线以东和117线以西矿体的Pb,Zn品位空间变化结构,得出搜索椭球体,实现了虎头崖铅锌多金属矿床矿体、地层形态和铅锌品位变化形态的空间分布展示;结合三维建模结果和铅锌矿体空间变化结构,总结出矿体空间分布规律,并用三维可视化软件对矿体分布规律进行显示,指导隐伏矿体的预测,寻找有利的找矿部位。     

甘肃阳山金矿区黄铁矿的赋存状态与分布特征

甘肃阳山金矿是迄今为止中国发现的最大金矿。已发现的6个矿段均赋存于泥盆系中,矿石中金属矿物主要为黄铁矿和毒砂。黄铁矿有3种类型:微细粒浸染状、半自形颗粒集合体、自形单晶大颗粒;主要分布在千枚岩、花岗闪长岩、石英脉里,具有多期次多类型的特点。根据黄铁矿的特征,金矿化与石英脉体中细粒浸染状的一期黄铁矿有关。黄铁矿为重要的载金矿物之一,自然金(Au)主要以微细粒的形式赋存于黄铁矿晶体的裂隙内以及晶体与晶体的空隙间。黄铁矿赋存状态和分布特征的研究,对矿区进一步找矿具有指导意义。     

丝绸之路经济带沿线国家旅游资源与 入境旅游发展空间格局特征与差异

利用旅游资源丰度指数、旅游流质指数、空间一致性系数和二维矩阵等方法,定量比较分析了丝绸之路经济带沿线18个主要国家旅游资源丰度,入境旅游发展质量,以及旅游资源分布与入境旅游发展质量的空间格局特征与差异。研究表明：丝绸之路经济带沿线国家旅游资源数量与质量差异显著,正形成两极分化突出的格局,中西欧国家最优,中亚国家最弱,入境旅游发展质量也呈现出相似的特征。旅游资源资源分布与入境旅游发展质量,呈现较明显的弱协调性,旅游资源集聚具有较明显的国际旅游导向性,两者发生错位的国家超过三分之二。空间一致性表现为显著的区域差异特征,亚洲相对较好,中西欧次之,东欧最弱。为推进沿线国际旅游合作,提出如下建议：坚定“互联互通、平等包容和合作共赢”发展理念,成立国际旅游合作联盟,督促与落实相关战略部署与重点项目;在求同存异基础上,建立共享机制,提高国家间旅游合作一体化水平和协同发展程度;共同打造丝绸之路经济带世界级旅游线路与旅游资源品牌,着力提升国际旅游发展影响力。