菲律宾海西北部岩芯记录的125 ka以来的地磁场强度及其影响因素

沉积物记录的地磁场强度首先提供了模拟地磁场演化的数据约束,其次提供了沉积物的年龄信息. 本文报道了菲律宾海西北部岩芯记录的地磁场相对强度,并结合岩石磁学和沉积学性质探讨了影响强度的各个因素. 除底部红粘土层的局部磁偏角偏转可能揭示了沉积后改造以外,磁化率各向异性和地磁场方向特征表明沉积物为原状沉积. 岩石磁学性质表明沉积物符合磁性均一性,可以记录可靠的地磁场强度. 由于红粘土层及其下部的磁偏角异常,本文讨论其上部约125 ka的结果. 常规归一方法获得的两个地磁场强度参数NRM/ARM(特征剩磁和非磁滞剩磁比值)和NRM/κ(特征剩磁和磁化率比值)与其它记录对比得到时间-深度对比点,对比点之间的年龄为线性内推或者外推. 地磁场强度时间模型上的岩芯氧同位素与全球氧同位素综合曲线一致证明强度结果的有效性和对比的正确性. 磁化率为归一参数的强度大多低于以非磁滞剩磁为归一参数的强度,频谱和相关分析证明NRM/ARM不与ARM和磁性矿物粒度(ARM/κ)相关,也没有轨道周期性,而NRM/κ却与κ和ARM/κ相关,而且有13~12 ka的周期. 由此我们认为NRM/ARM记录的地磁场强度比NRM/κ更好地消除了气候印记. 进一步探讨了超顺磁含量、碳酸钙含量、磁性矿物组成以及磁性矿物粒度变化与地磁场强度差值的关系,发现末次间冰期较高的超顺磁含量和磁性矿物粒度的较大范围变化造成了地磁场强度差值,后者至少造成了90%差异. 中等含量的碳酸钙和较小的磁性矿物组成变化不是磁场强度差值产生的原因. 如何校正磁性矿物粒度变化的影响将是下一步工作的重点.     

Assessment of Water Quality in the Elbe River at Low Water Conditions Based on Factor Analysis

An assessment of water quality measurements during a long‐lasting low water period in the Elbe River is presented. Weekly samples were taken from May to December 2003 at a sampling site in the middle part of the Elbe River. For multivariate data analysis, 34 parameters of 46 samplings were considered. As a result of this analysis, 78% of the variance of the data set is explained by five factors. They can be assigned to the following latent variables: season (37.5%) > tributaries (12.7%) > re‐suspension (10.4%) > discharge (9.4%) > complexation (8.5%). For the investigated sampling site, two key processes were identified as dominating factors on the water quality during low water conditions. First, seasonal phytoplankton development caused changes in redox conditions with consequences for re‐solution of pollutants from sediments. Second, tributaries have a higher impact on the main stream, due to changes in mixing processes. Therefore, in addition to flood investigations, monitoring strategies, and management plans should be developed in order to survey changes in water quality during low water conditions.     

Low induction number, ground conductivity meters: A correction procedure in the absence of magnetic effects

Ground conductivity meters, comprising a variety of coil–coil configurations, are intended to operate within the limits provided by a low induction number (LIN), electromagnetic condition. They are now routinely used across a wide range of application areas and the measured apparent conductivity data may be spatially assembled and examined/correlated alongside information obtained from many other earth science, environmental, soil and land use assessments. The theoretical behaviour of the common systems is examined in relation to both the prevailing level of subsurface conductivity and the instrument elevation. It is demonstrated that, given the inherent high level of accuracy of modern instruments, the prevailing LIN condition may require operation in environments restricted to very low (< 12 mS/m) conductivities. Beyond this limit, non-linear departures from the apparent conductivity that would be associated with a LIN condition occur and are a function of the coil configuration, the instrument height and the prevailing conductivity. Using both theory and experimental data, it is demonstrated that this has the potential to provide biased and spatially distorted measurements. A simple correction procedure that can be applied to the measured data obtained from any of the LIN instruments is developed. The correction procedure would, in the limit of a uniform subsurface, return the same (correct) conductivity, irrespective of the ground conductivity meter used, the prevailing conductivity or the measurement height.     

Rayleigh波勘探中“之”字形频散曲线“起跳点”频率研究

当层状介质中存在低速层的时候,实际提取到的Rayleigh波频散曲线往往会发生“之”字形回折.已有研究表明,“之”字形回折与各模式的激发能量有关.特别的,“之”字形回折的“起跳点”(发生“之”字形回折的点)与介质参数有一定关系,因此在应用中它反映了介质的一些特征.但是,这一关系是怎样的还没有人进行详细研究.本文计算了三...     

Long-term river discharge and multidecadal climate variability inferred from varved sediments, southwest Alaska

Sedimentological analyses of 289 years (AD 1718-2006) of varved sediment from Shadow Bay, southwest Alaska, were used to investigate hydroclimate variability during and prior to the instrumental period. Varve thicknesses relate most strongly to total annual discharge (r² = 0.75, n = 43, p < 0.0001). Maximum annual grain size depends most strongly on maximum spring daily discharge (r² = 0.63, n = 43, p < 0.0001) and maximum annual daily discharge (r² = 0.61, n = 43, p < 0.0001), while varve thickness is poorly correlated with maximum annual grain size (r² = 0.004, n = 287, p = 0.33). Relations between varve thickness and annual climate variables (temperature, precipitation, North Pacific (NP) and Pacific Decadal Oscillation (PDO) indices) are insignificant. On multidecadal timescales, however, regime shifts in varve thickness and total annual discharge coincide with shifts in NP and PDO indices. Periods with increased varve thickness and total annual discharge were associated with warm PDO phases and a strengthened Aleutian Low. The varve-inferred record of PDO suggests that any periodicity in the PDO varied over time, and that the early 19th century marked a transition to a more frequent or detectable shifts.     

铜陵矿集区深部找矿工作的一些思考

铜陵矿集区深部结构特征为该区大规模成岩成矿作用奠定了良好的基础,浅表已发现的矿床只是矿集区成矿系统的一部分。除此之外,深部还应有多个可以找寻的矿床(矿体)的富集空间。与成矿相关的花岗岩研究表明,铜陵矿集区可能存在与宁芜火山盆地同期的成岩成矿作用,是铜陵矿集区找矿的新方向。铜陵矿集区奥陶系灰岩中铜金矿化作用的初步研究表明,除传统矿床类型外,前泥盆纪地层中的成矿作用应该在今后的找矿工作中得到关注。覆盖区成矿预测初步研究表明,铜陵矿集区向斜核部及褶皱倾伏端等地段具有与已知典型矿床相似的成矿条件。铜陵矿集区的进一步找矿工作应该在上述地段运用矿田构造系统分析、深部地球物理探测和工程验证等方法逐步展开。     

黑龙江省黑河市争光金矿流体包裹体研究及矿床成因

黑龙江省黑河市争光金矿床位于大兴安岭东北缘的多宝山矿集区,矿体呈脉状产于闪长岩体与中奥陶统多宝山组凝灰岩的接触带,受断裂构造控制.流体成矿作用可分为4个阶段:石英-黄铁矿阶段、石英-多金属硫化物阶段、方解石-石英-硫化物阶段、碳酸盐阶段.其中阶段2和3具有复杂的金属硫化物组合并含金,即黄铁矿-闪锌矿-方铅矿-黄铜矿±自然金.石英及方解石中流体包裹体类型单一,主要为气液两相水溶液包裹体,大小集中于3 ～ 15μm,气液相比集中于5％～10％.包裹体均一温度介于119 ～ 305℃,盐度集中于0.3％ ～ 10.4％ NaCleqv,密度介于0.760.99g/cm3.从阶段2至阶段4,流体均一温度从150～ 220℃,经140～190℃,降为130～150℃.综合矿床地质特征和成矿流体研究,认为争光金矿床属低硫型浅成低温热液矿床.     

云南铁矿资源现状及扩大远景途径

全省上表铁矿111处,总储量32.16亿吨,其中有11.27亿吨暂不能使用.而且,富铁矿少,难选矿多,分布边远,难以满足经济发展需求.必须解决菱铁矿、高磷矿选矿问题,以及有远景磁异常补充深部找矿问题,可望取得突破.     

云南兰坪罗善铅锌矿控矿因素及成因

铅锌矿赋存于上三叠统三合洞组下段（T3s1）灰岩容矿岩层中及近南北向、北北东向、北西向断裂破碎带内,少数赋存在近东西向节理裂隙中,成因具多成矿阶段、多成矿物质来源特征,层位＋构造控制的中低温热液型铅锌多金属矿床.     

华南沿海2011年7月15—18日持续暴雨过程中的季风槽与中尺度对流系统相互作用

应用NCEP FNL再分析资料及位涡分离反演等方法,对华南沿海2011年7月15—18日持续暴雨过程中季风槽与中尺度对流系统的相互作用进行了研究,主要针对暴雨发生期间季风槽气旋性涡度向上发展的机理及其对季风槽维持发展和中尺度对流系统活动的影响进行分析。结果发现,季风槽的中尺度对流系统发展于弱斜压性环境中,大多在槽东西两端涡度中心区发展最强。南侧盛行的西南低空急流为对流反复发生提供了对流发展的“可维持性”条件,是对流得以组织发展成为中尺度对流系统的重要原因。涡度收支诊断表明,季风槽气旋性涡度生成主要由中尺度对流系统低层辐合引起。位涡分离反演结果证实,季风槽气旋性环流增强主要由与中尺度对流系统潜热加热相关的扰动位涡造成,并随着中尺度对流系统加热峰值高度升高而向上发展,是大尺度环流对中尺度对流系统潜热加热动力响应的结果。在季风槽东西两端,由于中尺度对流系统发展强烈且持续,具有更高的加热效率,引起的气旋性涡度向上发展最为明显。其结果可引起中尺度对流系统西南一侧向北非地转风发展,并在地转偏向力作用下增强西风,维持低空急流的发展,为对流反复发生提供条件。这些都说明季风槽大尺度环流与中尺度对流系统相互作用在中尺度对流系统和持续暴雨形成过程中有重要作用。