Genesis of tuff interval and its uranium enrichment in Upper Triassic of Ordos Basin,NW China

Recently measured high gamma ray values in the Yanchang Formation of the Upper Triassic in the Ordos Basin have added an interesting and controversial twist to the study of the formation’s uranium enrichment and genesis. High uranium and thorium contents in the tuffaceous layer cause high gamma ray values in the Yanchang Formation. Petrographic studies, major elements, rare earth elements (REEs), and trace elements have been systematically analyzed to determine the composition, geochemical environment, and diagenetic processes of the layer. The observed color of the tuffaceous layer in the study area varies from yellow to yellowish brown. The tuff consists of matrix supported with sub-rounded to sub-angular lithic fragments. These lithic fragments probably derived from pre-existing rocks and incorporated into the tuffaceous layer during volcanic eruption. Quartz, plagioclase, and biotite were observed in well to poorly sorted form, in addition to framboidal pyrite and organic laminae. Measured ratios of SiO₂/Al₂O₃ ranged from 3.277 to 6.105 with an average of 3.738. The ratio of TiO₂/Al₂O₃ varied from 0.037 to 0.201 with an average of 0.061, indicating that the sediments of the tuffaceous layer originated from an intermediate magma. REE distribution patterns show sharp negative Eu anomalies, indicating a reducing environment, which is suitable for uranium deposition. A reducing environment was confirmed by black shale in the base of the Yanchang Formation. Such black shale has high organic matter content that can take kerogene from mudstone and provide a reducing environment for uranium enrichment in the tuffaceous layer. Moreover, negative Eu anomalies and the REE patterns indicate a subduction-related volcanic arc environment as the magma source of the tuffaceous layers. High values of Rb, Ba, and Sr might be the result of fluid phase activities; low values of Hf and Eu indicate the involvement of crustal material during diagenesis of the tuff. Discrimination diagrams (Th/Yb vs Ta/Yb, Th/Hf vs Ta/Hf) suggest an active continental margin as the tectonic setting of source volcanoes. Plots of Nb versus Y, Rb versus Y + Nb, TiO₂ versus Zr, and Th/Yb versus Nb/Yb of the tuffaceous content point to calc-alkaline continental arc-related magmatism. We concluded that uranium enrichment in the tuffaceous layer was supported by oxidation–reduction.     

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天津市地面沉降分布广,沉降速率大。本文针对当前地面沉降研究和防治过程中所遇到的勘查资料严重缺乏、禁采难以全面实现等难题,提出了土水比指标量。通过概念分析和对多年数据的分析,认为土水比可以检验地下水开采量数据的统计精度,指示地下水资源补给及土层释水条件,并表明沉降的严重程度,反映地下水资源的保障程度。建议在沉降防治工作中,以土水比作为指标,通过相关分析模型来制定压采量。     

泉州市地下水功能区划分

本文针对泉州市地下水资源的分布特点,依据全国地下水功能区划分技术大纲,选取了地下水系统中具有代表性的驱动因子、状态因子和响应因子,综合地下水的资源供给功能、生态环境维持功能和地质环境稳定功能,将地下水功能区划分为开发区、保护区和保留区,并以完整的水文地质单元为基础,以防止泉州地下水污染和海水入侵为控制目标,依据地下水的...     

哈萨克斯坦HK-2井中石炭统沉积环境分析

HK-2井位于哈萨克斯坦西部阿特劳州阿特劳市西北约320 km处。该井钻遇的中石炭统岩石类型包括白云岩、石灰岩、硅岩、砂岩和黏土岩,但以硅岩和黏土岩为主,而且成分混杂,交互频繁,富含有机质和深水相的浮游、游泳类微体生物化石。根据岩石中硅质放射虫化石含量高,硅质海绵骨针个体保存完整,有机质含量高,颜色暗,组分细小,泥质、硅质成分为主及生物组合单一等特征,认为该地区中石炭统为深水沉积环境。目前正在勘探的HK-2井所在的乌拉尔区块也已发现深水类型油气藏存在的苗头,建议对该地区深水相油气藏进行调研,同时对该区块和相邻区块能够获得的地震剖面进行追踪分析研究。     

青藏高原地面有效辐射变化及其对表层土温的影响

利用青藏高原格尔木、狮泉河、昌都日射站及中国科学院冰冻圈观测研究站的观测资料,分析了高原有效辐射的变化,在此基础上结合土壤温度资料讨论了高原北部有效辐射的变化对表层土壤热状况的影响.结果显示：1）青藏高原有效辐射变化因所处的区域不同而异,高原东北部、西部及高原腹地有效辐射总体呈减小的趋势,高原东南部有效辐射呈增大的趋势...     

废弃防空洞及软弱地基的加固处理

针对工程填土地层及废弃防空洞,拟采用锤击沉管挤密碎石桩法进行加固处理。但在处理部分防空洞后,因震动大、噪音高,对周边居民和民居影响严重而停工。通过多次试验,摸索出钻孔夯填法并结合灌浆法回填防空洞,喷浆桩法加固软弱地基等经验,并对废弃防空洞的回填加固机理进行了简要分析。经检测,加固处理效果显著。至今,住宅楼建成4年使用正常。     

北京怀柔长园花岗杂岩体岩石学和构造变形特征及其地质意义

本文描述北京北部燕山地区怀柔长园杂岩体及围岩构造变形迹象 ,并对其成因进行了初步分析。认为中、晚侏罗世时期构造应力场的变化是杂岩体内岩石构造变形的主要因素 ,并以此为根据为该地区燕山期构造 岩浆事件序列的建立提供部分证据。     

EFFECTS OF AGRICULTURE RECLAMATION ON THE HYDROLOGIC CHARACTERISTICS IN THE SANJIANG PLAIN, CHINA

1 THE NATURAL ENVIRONMENTAL CHARACTERISTICS The Sanjiang Plain is located in the northeast of Heilongjiang Province, China. Russia borders this region in the north and east. Its total area is 1.088×107ha. The area of plain occupies 61.21％of the total land area and that of hill and mountain amounts to 38.79％of the total land area. It is not only one of the most important regions with large area of fresh water wetlands and with varieties of rare migratory waterfowls, but a…     

南麂列岛潮间带环境本底调查

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