Two-dimensional pH distributions and dynamics in bioturbated marine sediments

The seafloor is the site of intense biogeochemical and mineral dissolution-precipitation reactions which generate strong gradients in pH near the sediment-overlying water interface. These gradients are usually measured in one-dimension vertically with depth. Two-dimensional pH distributions in marine sediments were examined at high resolution (65 × 65 μm pixel) and analytical precision over areas of ∼150 to 225 cm² using a newly developed pH planar fluorosensor. Dramatic three-dimensional gradients, complex heterogeneity, and dynamic changes of pH occur in the surficial zone of deposits inhabited by macrofauna. pH can vary by ±2 units horizontally as well as vertically over millimeter scales. pH minima zones often form in association with redoxclines within a few millimeters of inner burrow walls, and become more pronounced with time if burrows remain stable and irrigated for extended periods. Microenvironmental pH minima also form locally around decaying biomass and relict burrow tracks, and dissipate with time (∼5 d). H⁺ concentrations and fluxes in sandy mud show complex acid-base reaction distributions with net H⁺ fluxes around burrows up to ∼12 nmol cm⁻² d⁻¹ and maximum net reaction rates varying between −90 (consumption) to 120 (production) μM d⁻¹ (∼90 nmol cm⁻¹ d⁻¹ burrow length). Acid producing zones that surround irrigated burrows are largely balanced by acid titration zones along inner burrow walls and outer radial boundaries. The geometry and scaling of pH microenvironments are functions of diagenetic reaction rates and three-dimensional transport patterns determined by sediment properties, such as diffusive tortuosity, and by benthic community characteristics such as the abundance, mobility, and size of infauna. Previously, undocumented biogeochemical phenomena such as low pH regions associated with in-filled relict biogenic structures and burrowing tracks are readily demonstrated by two-dimensional and time-dependent images of pH and sedimentary structure.     

Exploiting the dual functions of polymer depressants in fine particle flotation

Fine hydrophilic particles are known to be entrained with water in flotation of many ores. Flocculation of the hydrophilic particles by polymer depressants could potentially reduce the mechanical entrainment of these particles. This paper reports testwork completed on fine particles of several solids, iron oxide, hydroxyapatite and sphalerite, as well as on a relatively coarse quartz sample (− 75 + 38 μm). Dodecylamine was used as a collector for quartz, and several dispersants and polymer depressants, including sodium silicate, sodium metaphosphate, zinc sulfate, cornstarch, corn dextrin and carboxymethyl celluloses (with molecular weights of both 700,000 and 80,000) were used as flotation modifiers. The major part of the testwork involved flotation tests in a 200 mL flotation column. It was observed that flocculation of the fine hydrophilic particles significantly reduced their mechanical entrainment, while dispersion severely aggravated it. Thus, in the flotation separation of synthetic mixtures of the − 75 + 38 μm quartz and fine (reagent grade) iron oxide or hydroxyapatite, polymer depressants that caused flocculation performed better than those that did not cause flocculation.     

Study of stable isotopes for highly deformed aquifers in the Hsinchu-Miaoli area, Taiwan

This study was based on the analysis of isotopic compositions of hydrogen and oxygen in samples from precipitation, groundwater and stream water. In addition, parts of groundwater samples were dated by carbon-14 and tritium. These data are integrated to provide other views of the hydrologic cycle in the Hsinchu-Miaoli groundwater district. The groundwater district is principally composed of Pleistocene and Holocene aquifers. The Pleistocene aquifers are highly deformed by folding and faults into small sub-districts with areas of only tens of square kilometers. These aquifers are exclusively recharged by local precipitation. The Holocene aquifers cover narrow creek valleys, only tens of meters in thickness. The local meteoric water line (LMWL), constructed from rainfall samples in the Hsinchu Science Park, is described by the equation δD=8.02δ¹⁸O+10.16, which agrees with the global meteoric water line. In addition, the precipitation isotopic compositions can be categorized into two distinct end members: typhoon type and monsoon type. The groundwater isotopic compositions are perfectly located on an LMWL and can be considered a mixture of precipitations. Based on the mass balance of isotopic compositions of oxygen and hydrogen, infiltration is more active in the rainy season with depleted isotopic compositions. The amount of infiltration during May–September is roughly estimated to comprise at least 55% of the whole year’s recharge. The isotopic compositions of stream water are expressed by a regression equation: δD=7.61δ¹⁸O+9.62, which is similar to the LMWL. Although precipitation isotopic compositions are depleted during summer time, the isotopic compositions contrarily show an enriched trend in the upstream area. This is explained by the opposite altitude effect on isotopic compositions for typhoon-related precipitations.     

邢台矿区山字型构造的发现及其地质意义

邢台山字型构造位于河北省邯邢煤田内，其前弧向ES突出，脊柱呈ES-WN走向。分别分析了山字型构造脊柱及其东、西翼反射弧构造形迹特征，对研究区找矿具有重要意义。     

淮北煤田孙庄勘探区煤层气赋存规律及影响因素分析

通过对淮北煤田孙庄勘探区地质构造、沉积特征、煤层煤质及煤层气赋存特征的分析，研究认为有利于本区煤层气赋存的主要因素是较大的埋藏深度、较高的壳质组＋镜质组、较高的变质程度、较大的煤层厚度、低透气性的盖层、较缓的地层倾角和封闭性较好的构造条件，推测煤田深部可能具有一定工业价值的煤层气资源。     

Fission track evidence for the Mesozoic Cenozoic tectonic uplift of Mt. Bogda, Xinjiang, Northwest China

1 IntroductionThe Mesozoic-Cenozoic tectonic evolution and ki-netics mechanism of the intracontinental orogen are thekey subjects of continental dynamics (Ma Zongjin andGao Xianglin, 2004) and the key to understanding theregional geological tectonics (Qia…     

藏南地区金和锑矿床(点)类型及其时空分布特征

本文首次对藏南地区金和锑矿床(点)地质特征、成因类型和空间分布特点进行了总结，对金和锑成矿作用与中新生代构造一岩浆活动的关系进行了论证，对区域地壳演化过程中金和锑成矿动力学机制进行了讨论。该区的金和锑矿床(点)可按容矿围岩划分为：①变质岩为主要容矿围岩矿床(点)，包括金和金一锑矿床(点)；②沉积岩为主要容矿围岩矿床(点)，包括金、锑、金一锑和锑多金属矿床(点)；③火山岩为主要容矿围岩矿床(点)，以金一银矿床为代表。根据金和锑矿床(点)空间分布特点和地质特点，将本区划分为4个矿化集中区：拉昂错一马攸木一帕羊金矿化集中区(A)，然勒金和锑矿化集中区(B)，洛扎一措美锑矿化集中区(C)和邛多江金一锑矿化集中区(D)。各矿化集中区内大多数金和锑矿床(点)与燕山晚期～喜马拉雅早期富碱火成岩具密切时空分布关系，它们是古板块对接碰撞期和碰撞期后大规模构造一岩浆活动的产物。近东西向挤压性和南北向张性断裂交汇部位以及富碱火成岩发育区是寻找金和锑矿床(点)的有利场所。     

煤田勘查超千米深孔快速钻进技术探讨

针对目前国内煤田勘查主要机具及工艺技术方法存在的主要问题,结合煤田勘查地层地质条件和超千米深孔施工要求,研制了液压立轴式HTJ-2000型钻机和新型绳索取心钻具,并就配套设备选型、钻进工艺、钻进参数、泥浆指标及应用效果进行了阐述.该项技术的应用,已明显提高了钻效,使钻孔深度达到1 350m.     

基于DSM阴影仿真和高度场光线跟踪的影像阴影检测

介绍了一个建筑物阴影检测的模型。首先利用摄影测量学原理来计算阴影坐标。即用数字表面模型(digitalsurfacemodel,缩写为DSM)和太阳高度和方位来计算建筑物阴影的空间坐标,并由相机模型计算出每个阴影单元对应的扫描行和相机空间坐标。由高度场光线跟踪判断阴影的可见性,对可见阴影计算出它在投影图像上的坐标。然后在这个结果的基础上再对图像进行阴影的细分割。     

贵州关岭生物群中植物化石的发现及其意义

关岭生物群是近年来在我国贵州关岭地区瓦窑组中发现的一个十分重要的生物群 ,其中的植物化石经研究计有 Equisetites cf.arenaceus(Jaeger) Bronn.、Ctenozamitessarrani Zeiller。依据植物化石 C.sarrani常见于晚三叠世和 E.cf.arenaceus系似木贼属中较古老的类型 ,指出含植物化石的地层时代为晚三叠世卡尼期。瓦窑组系海相沉积 ,其中的植物化石无疑为异地埋藏 ,但从化石通常保存尚好来看 ,估计搬运的距离不会很远 ,它们可能是从距海岸不远的陆地被河流带到较平静的海湾或海槽而沉积下来的。此外 ,从该组植物茎干化石具清楚的年轮分析 ,推测卡尼期时 ,贵州关岭一带为非热带雨林地区 ,一年中气候不是四季如一 ,而是有明显的季节变化