Ultrahigh pressure macro diamonds from Copeton (New South Wales, Australia), based on Raman spectroscopy of inclusions

Mining of Cenozoic alluvial deposits at Copeton and Bingara (Eastern Australia) has produced two million macrodiamonds (0.25 ct median size). Raman spectroscopy is used to identify included minerals within uncut Copeton diamonds, with sealed chamber remnant pressures of 31.7 to 35.6 kbar for coesite, 13.6 and 22.7 kbar for clinopyroxene, and 7.6 kbar for grossular garnet. Assuming elastic behaviour, these values generate inclusion entrapment PT loci which intersect, restricting diamond formation conditions: from 250 °C, 43 kbar to 800 °C, 52 kbar. Larger than error (± 100 °C and ± 4 kbar), this range shows a systematic variation in inclusion composition with diamond zoning and N properties. Published research shows 1) Copeton and Bingara diamonds are unique, and 2) modern alluvium in the Bingara district carries mantle-formed garnet, captured by post-tectonic alkali basalt from an extensive diamondiferous ultrahigh pressure (UHP) terrane that stalled at depth because it is dominated by mafic eclogite. The combined Raman and geological results indicate two sets of subduction UHP diamond formation conditions/protolith are required, firstly cooler oceanic slab and secondly including higher temperature continental crust. The Copeton and Bingara stones are UHP macrodiamonds, and Carboniferous ⁴⁰Ar/³⁹Ar age dates on clinopyroxene inclusions should be interpreted as ages of crystallisation, representing the termination of subduction. The characteristic features of ruptured inclusions and etched percussion marks on Copeton and Bingara diamond indicate volcanic delivery to the earth's surface. Alluvial deposits elsewhere in Eastern Australia may carry similar diamond along with diamond of different origin.     

津巴布韦金刚石中石墨包裹体及金刚石异常双折射特征分析

津巴布韦马朗(Marange)金刚石矿以产出混合习性(八面体与近立方体)金刚石为特征,其石墨包裹体仅存在于近立方体区.石墨包裹体的形态、分布及金刚石的异常双折射与应变特征,能反映其从开始结晶到被搬运至地表过程中经历的地质作用.因此,对津巴布韦混合习性金刚石及石墨包裹体的研究不仅能提供与其他产地金刚石有对比意义的数据,且...     

应力诱导各向异性介质中地震波的传播

主要讨论了应力变化如何影响各向异性介质中波速度的问题。推导了一般各向异性介质在初始应力下的Christoffel方程,得到介质中3种波的相速度和初始应力的关系表达式;通过实验数据验证了单轴应力能够诱导各向异性,当施加单轴应力时,速度在沿应力的方向增加最大,在垂直应力的方向增加最小,实验结果与理论推导一致;用Christoffel方程的数值解模拟在3种对称情况下的弹性各向异性介质中初始应力对波速度的影响。数值结果表明:初始应力对各向异性介质中波传播速度的影响,随着各向异性强度的增加而增大,而且速度越慢,影响越大。     

煤体中直立裂隙的多波地震响应及预测

裂隙探测是煤层气勘探开发与煤矿安全生产的重要研究内容。规则发育的直立裂隙在理论上可等效为具有水平对称轴的横向各向同性（HTI）介质,本文通过正演记录研究了HTI介质的多波地震响应,分析了裂隙发育方位对横波偏振特性的影响规律,在此基础上分析了利用横波记录的方位角道集获取地下裂隙参数的可行性与基本原理,为便于工业应用,文中研究了一种基于两个水平分量叠加剖面的角度扫描法求取地下目标煤层的裂隙发育方位。实际资料处理证明了该方法的准确性与可靠性。     

KAGRA引力波探测器中蓝宝石测试镜光学性质研究

低温制冷技术是下一代激光干涉仪引力波探测器的核心技术之一. 日本引力波探测器KAGRA (Kamioka Gravitational Wave Detector)作为该技术的前沿开拓者, 将运行在20K的超低温环境中, 并使用在低温下热噪声较低的单晶蓝宝石晶体作为测试镜. 然而, 高质量大尺寸低吸收率的蓝宝石晶体极难制备. 此外, 由于蓝宝石晶体存在晶格结构不均匀, 很容易导致不必要的双折射效应, 从而影响探测器的目标灵敏度. 基于上述问题, 开发了两套大尺寸光学测量系统, 首次系统研究了KAGRA低温蓝宝石测试镜的光学特性. 首先, 根据探测器对测试镜热噪声的要求, 开发了一套基于光热共光路干涉技术的光学测量系统, 该系统可对测试镜以及测试镜表面涂层的光学吸收进行有效的表征. 其次, 基于光学吸收测量系统, 开发了一套双折射效应测量系统, 该系统可以有效表征测试镜中双折射的均匀性. 目前两套测量系统的搭建与调试已完成, 对蓝宝石测试镜光学吸收的测量灵敏度达到了1.5ppm/cm, 双折射测量系统的空间分辨率小于0.3mm times 0.3mm. 该工作对降低大尺寸低温测试镜双折射效应及提高探测器灵敏度具有重要意义.     

The geotechnical properties and behaviour of a pro-glacial lake clay, and its cementitious stabilization

The Tees Laminated Clay forms a continuous deposit around the Tees estuary in north east England and was deposited in a proglacial lake which occupied the Teesside area during late Devensian times, disappearing about 13 000 years ago. It overlies till, with which it has a sharp contact and reaches a maximum thickness in parts of central Middlesbrough of just over 9 m. The laminations consist of alternating thin layers of clay and silt, and represent seasonal increments of sediment. Kaolinite and illite, with lesser amounts of chlorite, dominate the mineral composition. Quartz tends to account for less than 35%. The notable carbonate content may be diagenetic in origin. The birefringence ratio of the clay minerals indicates a medium degree of particle orientation which suggests a partially flocculated fabric.This laminated clay has a high plasticity. However, the liquid and plastic limits of the silty layers differ significantly from those of the clay layers or the bulk samples. The clay fraction has a greater influence on these limits than the silty fraction. In addition, the linear shrinkage, liquidity indices and consistency indices of the silty layers differ appreciably from those of the clay layers and the bulk samples. The laminated clay is inactive. The orientation of the laminations in relation to the direction of maximum principal stress influences the shear strength, the lowest strengths being developed when these orientations are between 30° and 60°. The stress paths, anisotropic ratios and values of Af indicate that the Tees Laminated Clay is normally consolidated or lightly overconsolidated. The McLamore–Gray concept possibly can be applied to the anisotropic strength behaviour.Tees Laminated Clay can give rise to problems during construction operations since it can lose strength significantly on remoulding. Accordingly, these soils were treated with cementitious materials to determine the extent to which their engineering behaviour was enhanced by the addition of such materials. © Rapid Science Ltd. 1998     

The parent material of Sydney laterites

The petrography of laterites in the Sydney district shows that source rocks range from shales—in which quartz grains are not common and average about 0.03 mm in diameter—to sandstones, with generally abundant quartz grains which may average up to 0.5 mm in diameter. Ferricretes or iron‐cemented duricrusts occur in rocks with coarser quartz grains, such as the Tertiary river gravels of the Maroota area. The porosity and permeability of these rocks have considerably influenced the nature and profiles of the laterites. Two possible sources of sesquioxides in the laterites appear to be the Wianamatta Shale and, perhaps more importantly, basic igneous rocks.     

夕卡岩中石榴石的双折射性之研究

本文研究了河北省涉县符山铁矿夕卡岩中石榴石的双折射性。该石榴石属钙铝-钙铁榴石系列,有较强的双折射性,重折率最大值约为0.009。加热可使双折射性减弱甚至消失。依形成温度,可将石榴石分为两群,重折射率相差一、两个数量级,形成温度较低者其双折射性强。在每一群中,重折率与分子式中八面体位置 Al 含量成上弯曲线关系,最强双折射大致在 And₆₅ Gro₃₅成分处。X 光单晶衍射照相出现异常,衍射点变成由数个点组成的拉长的线,这些点沿一定方向排列,强度和数目有变化,可能是因为结构中八面体位置上 Fe³⁺/Al 有序引起的。有序引起石榴石对称性降低,变为二轴晶,可以较好地解释石榴石双折射性的成因及其变化规律。本文还讨论了环带与双折射性的关系。     

Identification of Mineral Grains in a Petrographic Thin Section Using Phi- and Max-Images

A new approach to identifying grains in a petrographic thin section is presented in this paper. The mineral grain boundaries are detected using two synthetic images, created by mapping the maximum birefringence color intensity (max-image) and the corresponding angular rotation at which it occurs (phi-image), instead of original images obtained by rotating the section between crossed polarizers. Edge detection and image segmentation operations are first applied on the phi- and max-images separately. The two segmented images resulting from edge detection are then combined to generate a new segmented image, which preserves edges with higher reliabilities and eliminates those with lower reliabilities in the two former segmented images. The identification rate is thereby greatly improved. The method has been implemented in C++ in the Linux environment. Two sets of images are used to test the method. Each set has 200 images corresponding to 200 rotation angles between 0 and 180°.     

非偏振保持光纤中随机双折射对自俘获现象的影响

本文用数值计算的方法解非线性耦合薛定谔方程 ,研究了在非偏振保持光纤中随机双折射变化对孤子自俘获传输现象的影响。研究结果表明 :相对于具有保偏特性的强双折射光纤 ,非偏振保持光纤中随机双折射所致的 2个模式间频繁的能量交换 ,减缓了 2脉冲的走离 ,有利于束缚态的形成 ;入射偏振角 θ对孤子的自俘获传输影响非常小 ,这就使光孤子耦合进光纤时不须鉴别光纤的快、慢轴。