中国大连地区发现含稀土和贵金属矿物组合的新元古界变泥岩

论述一种非常窂见的轻微变质的新元界变泥岩,其中含有碎屑的和自生—成岩的独居石和磷钇矿颗粒以及自然金、锇—铱、铱、锌金属等;还有锆石、金红石,磷灰石、钛铁矿、赤铁矿等重矿物,并伴生少量黄铜矿、斑铜矿、方铅矿等硫化矿物。该变泥岩产于大连金石滩,属于新元古界震旦系十三里台组,是由红色叠层石灰岩和绿色变泥岩互层组成。按照岩石的结构、构造和沉积相标志分析,其沉积环境属于碳酸盐近岸礁滩平原地带的局限盆地,其封闭区域内还原和氧化的化学环境交替出现,细小的碎屑独居石、磷钇矿颗粒以及自然金、锇—铱、铱、锌金属等伴生出现,创造了有利于稀土元素矿物分解和再沉积,在同生沉积和成岩阶段中形成了自生独居石("人形的"、"鸟形的")和磷钇矿("猫形的")。然而贵金属矿物都是碎屑成因的,至于黄铜矿、斑铜矿方铅矿以及锌金属微细脉有可能与后期的流体矿化活动有关。本文认为华北地台的元古宙地层含有较丰富的稀土元素和贵金属,是新元古界变泥岩中所含稀土元素矿物和贵金属的原始来源地。此外,还讨论了独居石和磷钇矿的SHRIMP测年问题。

钾长-夕线石变泥岩中与非均—变形作用有关的纤维状夕线石的生长和富集

在叶理状钾长-夕线石变泥岩中,纤维状夕线石常富集于由粗粒集合体构成的扁豆体之间的叶理中。这些集合体富含石英、长石、黑云母,有或无石榴石,堇青石和残留红柱石。大多数叶理看来象细微褶皱翼。夕线石的聚集可能主要是由于纤维状夕线石集合体能够经受强烈的非同轴变形所造成的。这种变形表现为颗粒边界滑动(纤维滑动),并没有明显的位错聚集。而其他矿物在这些带中不稳定,所以富集于低应变的间叶理带。夕线石的产生,特别是叶理中夕线石的富集,得力于流体流动和局部碱性阳离子的淋滤,因此,强非同轴应变带中不稳定的矿物发生溶解并从这些带中移出。

歧口凹陷中浅层泥岩蚀变校正方法

歧口凹陷滨海海域的钻井液大部分采用水基泥浆。由于中浅层地层受钻井液浸泡的影响,泥岩发生蚀变,导致声波时差测井不能反映原状地层的速度信息,从而影响合成记录标定和井约束反演的效果。统计结果表明,随着水基泥浆对地层浸泡的时间增大,泥岩声波时差变大,速度降低。为此必需对泥岩蚀变进行校正,其校正思路是:在划分出砂泥岩剖面后,以受钻井泥浆浸泡时间较短的井作为标准井,按均值方差法将发生泥岩蚀变的井校正到标准井的分布范围内。泥岩蚀变校正结果表明,利用校正后的声波曲线所做合成记录与井旁实际地震记录对应关系更好,而且薄砂层的反演效果也得到了改善。

基于曲线重构的泥岩蚀变校正技术研究

当用水基泥浆钻井时,地层中的粘土矿物吸水膨胀,产生蚀变现象。在本文中我们启发于曲线重构技术,基于FAUST公式对目标油区不同岩性地层电阻率与密度测井之间的关系进行了统计分析,拟合出电阻率与密度测井之间的关系;基于GARDNER公式对目标油区不同岩性地层声波与密度测井之间的关系进行了统计分析,拟合出水基泥浆影响严重的泥岩类地层中声波与密度测井之间具有良好的统计关系。经过对密度和声波测井曲线的校正,加强储集层与围岩的速度差异,进而提高测井约束地震反演的精度。

泥岩蚀变对声波测井影响的试验研究

通过泥岩岩样浸泡程度与声波时差响应的试验研究,揭示了2000m深度以下泥岩蚀变对声波时差测量的影响规律。结果表明,泥岩含水时的纵、横波速度均大于干岩样的速度,随着浸泡时间的增加,纵、横波速度逐渐增大,当达到一定数值时,纵、横波速度会随着泥岩浸泡时间的增加出现小幅下降,之后就趋于稳定,横波尤为明显。试验结果颠覆了泥岩被水浸泡后声速变小时差变大的一般性认识。试验结果对声波测井资料地震反演以及声波测井资料地质解释具有指导意义。

D区块泥岩段钻井液体系研究

在钻井施工的过程中,井底复杂情况是制约着优快钻井的首要难题。D区块井底存在大段的泥岩层段,由于泥岩的水化作用严重,钻井过程中容易导致井口缩径、井壁垮塌、钻头泥包、卡钻等情况发生。本文首先优选出了适合该区块的抑制剂聚胺HYZ,然后对该钻井液体系流变性及滚动回收率的评价试验最终优选出适合该区块的钻井液体系。

小兴安岭西北部卧都河地区落马湖岩群年代学及构造背景

出露于小兴安岭西北部的“落马湖岩群”是多宝山矿集区重要的地质建造之一,由于缺少化石及顶底不全,其形成时代一直存在争议,制约了对区域构造演化及成矿背景的认识.为了探讨其形成时代及古构造背景,采用锆石U-Pb(LA-ICP-MS)方法对卧都河乡附近的“落马湖岩群”变粉砂质泥岩的碎屑锆石进行了年代学研究,85个测点中68个有效测点年龄介于216~2636 Ma,分为8个年龄组:216~347 Ma(n=8)、430~443 Ma(n=2)、463~502 Ma(加权平均485±5 Ma,n=21)、513~572 Ma(加权平均528±7Ma,n=16)、596~613 Ma(加权平均606±12 Ma,n=7)、718~739 Ma(加权平均730±12 Ma,n=3)、830~882 Ma(加权平均850±26 Ma,n=5)、1769~2636 Ma(n=6),以第Ⅲ—第Ⅶ年龄组构成明显的峰值.综合分析锆石晶态、CL图像、U含量特征及地质体宏观岩相学特点,认为第Ⅲ年龄组代表样品层位沉积下限.结合区域研究成果,认为“落马湖岩群”形成于奥陶纪至志留纪罗德洛世;其碎屑锆石主要来源于“额尔古纳-兴安联合地块”及奥陶纪弧火山岩区,形成于弧后盆地构造背景;其与多宝山弧岩浆岩带共同构成早古生代弧-盆系.

Catastrophe theory-based risk evaluation model for water and mud inrush and its application in karst tunnels

This paper presents a risk evaluation model of water and mud inrush for tunnel excavation in karst areas.The factors affecting the probabilities of water and mud inrush in karst tunnels are investigated to define the dangerousness of this geological disaster.The losses that are caused by water and mud inrush are taken into consideration to account for its harmfulness.Then a risk evaluation model based on the dangerousness-harmfulness evaluation indicator system is constructed,which is more convincing in comparison with the traditional methods.The catastrophe theory is used to evaluate the risk level of water and mud inrush and it has great advantage in handling problems involving discontinuous catastrophe processes.To validate the proposed approach,the Qiyueshan tunnel of Yichang-Wanzhou Railway is taken as an example in which four target segments are evaluated using the risk evaluation model.Finally,the evaluation results are compared with the excavation data,which shows that the risk levels predicted by the proposed approach are in good agreements with that observed in engineering.In conclusion,the catastrophe theory-based risk evaluation model is an efficient and effective approach for water and mud inrush in karst tunnels.

Effects of axial cyclic loading at constant confining pressures on deformational characteristics of anisotropic argillite

Triaxial cyclic loading tests have been performed to assess the influence of plastic deformation on inelastic deformational properties of anisotropic argillite with bedding planes which is regarded as a kind of transversely isotropic media.Considering argillite's anisotropy and inelastic deformational properties,theoretical formulae for calculating oriented elastic parameters were deduced by the unloading curves,which can be better fitted for the description of its elasticity than loading curves.Test results indicate that with the growth of accumulated plastic,strain,the apparent elastic modulus of argillite decreases in a form of exponential decay function,whereas the apparent Poisson ratio increase in a form of power equation.A ratio of unloading recoverable strain to the total strain increment occurred during a loading cycle is defined to illustrate the characteristic relations between anisotropic coupled elasto-plastic deformation and plastic strain.It is significant to observe that high stress level and plastic history have an inhibiting effect on argillite anisotropy.

Creep properties and a creep equation of delay outburst coal and its adjacent mudstone

The study of the creep properties of coal and its adjacent mudstone is very important for understanding the mechanism of delay outburst coal. The samples of delay outburst coal and its adjacent mudstone collected from Yongshanqiao mine were used to carry out triaxial creep tests. The influence of confining pressure and axial compression on the creep test was analyzed. An accelerated creep model was constructed in parallel with a nonlinear viscous component and plastic component. It is connected with the traditional Burges creep model in series. A creep model which can describe the nonlinear viscoelastic-plastic creep model of rock was established and the corresponding creep equation was derived.According to the results of the creep test, the related parameters of the equation were fitted. The results show that, under the same confining pressure, instantaneous creep strain, creep strain of deceleration phase and constant rate creep of the coal and its adjacent mudstone are increased with an increase in the deviatoric stress. But at the same axial pressure, all of the above decrease with an increase of confining pressure. The duration time of the deceleration creep phase increases with the increase in the deviatoric stress. The theoretical values of the creep equation are in good agreement with the experimental results. It indicates that the creep properties of the delayed outburst coal and its adjacent mudstone can be well described by the creep model established in this paper.

Nonlinear creep damage model for soft rock under uniaxial compression

A nonlinear creep-damage model for soft rock under uniaxial compression waspresented,which takes into account both nonlinear creep and damage growth with time.The model is based on the hardening theory,The model is validated through comparisonwith experimental results.

Rheology of Cement Mortars with Crushed Fine Aggregates of Different Lithological Types

Crushed fine aggregates are widely used for full or partial replacement of natural sands in concretes. The crushed sands present different characteristics from the natural sand, especially if taking into account the content of microfine particle, the distribution of particle sizes, the shape features, besides the different lithological origin. From the rheological point of view, the crushed sands frequently provide mixtures with high yield stress, high viscosity, high cohesion and internal friction, which hinders its use in concrete. This study is focused on the evaluation of the rheological behavior of concrete mortar phase when using different lithological types of crushed sand in total replacement of natural sand. The lithological types surveyed were granite, calcitic limestone, dolomite limestone and mica schist. Each of these sand types was studied in two ways： in natura and with adjusted grading curve. The results show the best performance of calcitic limestone providing lower viscosities and lower yield stress in mortars.