邻近算法在微地震震源位置和一维速度模型同时反演中的应用

微地震事件的空间分布可以用来监测水力压裂过程中裂缝的发育情况.因此,震源定位是微震监测中重要的环节.震源定位依赖准确的速度模型,而震源位置和速度模型的耦合易导致线性迭代的同时反演方法陷入局部极小值.邻近算法作为一种非线性全局优化算法,能够最大程度地避免陷入局部最优解.本文将邻近算法应用于单井监测的微震定位和一维速度模型...     

太行山东麓滹沱河出山处新生代沉积相与地貌结构

研究区在大地构造上处于山西台背斜上的五台隆起与辽冀台向斜内的博野拗陷之间的过渡地区,在地貌上位于太行山地与华北大平原之间的过渡带、滹沱河及其主要(右岸)支流冶河出山口地区,是一片点缀有残山的宽广的山前夷平面与冲洪积扇。     

云南羊拉铜矿矽卡岩形成时代与矿床成因：来自石榴子石和磁铁矿组分的约束

羊拉铜矿是金沙江缝合带中部已发现的规模最大的印支期铜矿床,矿体以层状—似层状产出于花岗闪长岩外围、变质砂岩与碳酸盐岩地层的层间破碎带中。该矿床在成因类型上存在喷流-沉积成因、复合成因、矽卡岩成因等多种观点。本文以矽卡岩矿石中石榴子石、磁铁矿为研究对象,利用LA-ICP-MS原位微区分析技术开展了石榴子石U-Pb年代学和石榴子石、磁铁矿成分测试分析,以进一步限定该矿床成矿时代和成因类型。分析结果显示,石榴子石中U、Th、Pb的含量分别为1.18×10^-6～6.69×10^-6、0.04×10^-6～1.43×10^-6、0.11×10^-6～1.16×10^-6,获得Tera-Wasserburg下交点年龄为231.0±5.3 Ma(2σ,n=32,MSWD=2.1),与矿区花岗闪长岩形成时代高度一致。结合磁铁矿微量元素组成与全球矽卡岩型矿床可类比等特征,明确羊拉铜矿床属于典型矽卡岩型铜矿床。石榴子石以钙铁榴石组分为主,具轻稀土富集、重稀土亏损的配分模式,这可能受晶体...     

新疆喀拉通克铜镍矿贵金属矿物定量研究

喀拉通克铜镍矿床产于漏斗状基性岩体中下部的橄榄苏长辉长岩相中,矿石类型分特富铜镍矿石(Ⅰ)、富铜贫镍矿石(Ⅱ)、贫铜贫镍矿石(Ⅲ)及富镍富铜矿石(Ⅳ).由于矿床物质成分复杂特别是金银铂钯矿物颗粒细、品位低、种类多,故首先在进行矿物定性研究的基础上,确定目的矿物的特殊富集流程.然后在人工重砂大样中富集目的矿物,并制成砂光薄片,有代表性的排定视域,引入电子探针-图象分析-计算机联机定量并辅以显微镜定量的综合方法对贵金属元素和矿物进行定量.联机方法是用电子探针以扫描方式提供颗粒电子象和元素X射线面分布象信号给出元素或共存元素的化学信息,对矿物颗粒进行分类,统计出个数及面积百分比.这种方法对微细杂矿物的定量工作颇有成效.     

再力花/菖蒲生物湿地床去除河水中氮磷的试验

采用再力花和菖蒲构建湿地床,以考察其对污染河水的净化效果。6个月的连续试验表明:在水力负荷为0.24 m3/(m2.d)、植物种植密度大于158株/m2的条件下,2种植物存活率均大于93%,说明植物能适应低污染负荷、高种植密度的无土培养环境;再力花和菖蒲湿地床月均去除率分别为:总氮(TN),48.22%～78.53%和43.23%～72.42%;总磷(TP),77.62%～85.67%和58.07%～80.77%。再力花湿地床对TN、TP的净化效果好于菖蒲湿地床;2种植物吸收N、P含量分别占去除总量的比例:N为44.14%、37.75%,P为73.43%、62.05%。湿地床技术可有效去除来水中的TN、TP,通过植物吸收作用累积N、P含量较高,不同种类的植物构建湿地床对污染河水中N、P去除效果存在显著差异,且硝化反硝化和植物吸收是去除N的主要途径,而植物吸收是去除P的有效手段。     

Machine learning reveals the influences of grain morphology on grain crushing strength

Acta Geotechnica - Grain morphology has significant impacts on the mechanical behaviors of granular materials. However, its influences on grain breakage are still poorly understood due to the...     

青海某地第三系红色碎屑岩层中金异常特征及成因探讨

对青海某地第三系红色碎屑岩层中的金异常特征进行了综述,指出金异常主要存在于第三系中段岩层中,异常在水系沉积物中强度最大,并认为金异常由次生富集作用形成.     

Dust supply from river floodplains: the case of the lower Huang He (Yellow River) recorded in a loess–palaeosol sequence from the Mangshan Plateau

The Mangshan Plateau is located on the south bank of the Huang He (Yellow River) just west of the city of Zhengzhou, well outside the Loess Plateau in central China. Mixing models of the grain‐size data indicate that the loess deposits are mixtures of three loess components. Comparison of the mixing model with existing models established for a series of loess–palaeosol sequences from the Loess Plateau indicates that the Mangshan loess has been supplied from a proximal dust source, the Huang He floodplain, during major dust outbreaks. The high accumulation rates, the composition of the loess components, and especially the high proportions of a sandy loess component support this. Owing to the exceptionally high accumulation rates, the Mangshan grain size, magnetic susceptibility and carbonate records provide a high‐resolution archive of environmental and climate change. Copyright © 2008 John Wiley & Sons, Ltd.     

Environmental magnetic studies of sediment cores from Gonghai Lake: implications for monsoon evolution in North China during the late glacial and Holocene

Environmental magnetic studies were conducted on a 9.42-m-long sediment core from Gonghai Lake, North China. Radiocarbon dating indicates that the record spans the last 15,000 cal year BP. The principal magnetic mineral in the sediments is pseudo-single domain magnetite of detrital origin with minimal post-depositional alteration. Although the variations in the concentration of detrital magnetic minerals and their grain size throughout the core reflect inputs from both soil erosion and eolian dust, it is shown that their climatic and environmental significance changes with time. In the lowermost part of the core, ~15,000–11,500 cal year BP, the magnetic minerals were supplied mainly by bedrock erosion, soil erosion and dust input when climate ameliorated after the cold and dusty last glacial maximum. The increasing magnetic susceptibility (χ) in this interval may indicate a combination of changes in the lake environment together with catchment-surface stabilization and a decreasing proportion of dust input. In the central part of the core, ~11,500–1,000 cal year BP, the detrital magnetic minerals mainly originated from dust inputs from outside the catchment when the lake catchment was covered by forest, and catchment-derived sediment supply (and thus the lake sediment accumulation rate) were minimal. The generally low concentration of magnetic minerals in this part of the core reflects the highest degree of soil stability and the strongest summer monsoon during the Holocene. In the uppermost part of the core, the last ~1,000 years, detrital magnetic minerals mainly originated from erosion of catchment soils when the vegetation cover was sparse and the sediment accumulation rates were high. Within this part of the core the high magnetic susceptibility reflects strong pedogenesis in the lake catchment, and thus a strong summer monsoon. This scenario is similar to that recorded in loess profiles. Overall, the results document three main stages of summer monsoon history with abrupt shifts from one stage to another: an increasing and variable summer monsoon during the last deglacial, a generally strong summer monsoon in the early and middle Holocene and a weak summer monsoon in the late Holocene. The results also suggest that different interpretational models may need to be applied to lake sediment magnetic mineral assemblages corresponding to different stages of environmental evolution.     

塔里木盆地塔中北坡奥陶系微生物碳酸盐岩储层形成机制与评价

微生物岩储层是当前的研究热点之一.通过对塔中北坡微生物岩样品的岩芯以及铸体薄片的观察,发现研究区域的微生物岩储层以裂缝-孔隙型储层为主.对其进行全直径孔渗性检测发现,微生物岩储层具有较好的天然气储集物性.通过对微生物岩的形成机制及特点的分析,结合应力敏感实验和成像测井资料,总结出微生物岩储集空间发育的优势因素.原生白云石的生成可以促进方解石的溶解,而塔中北坡微生物岩发生早成岩岩溶作用,部分地区叠加晚期深成热液改造,提高了储集物性;有机质含量较丰富不仅可以在埋藏成岩阶段生成有机酸造成溶蚀,还能够降低微生物岩的极限强度从而容易在构造作用下发生断裂形成裂缝,因此塔中北坡微生物岩储集空间主要以次生作用为主.通过岩石压缩系数的测定,得出微生物岩的抗压实能力一般,但藻屑骨架对藻孔的保护有利,抗压实能力最强的是受到热液作用而硅化的微生物岩,其次是白云石化微生物岩.