Variations of some heavy minerals in recent beach sands

The influence of shape, size, and specific gravity of mineral grains on the variation of the content of these minerals in beach sands has been investigated for fixed conditions of sedimentation on the beaches of the Baltic Sea and Michigan Lake. The coefficient of variation was used as a measure of the variance. Linear models tested by the analysis of variance were applied and revealed that the shape of grains and the combined effect of the size and specific gravity are responsible for the main part of the variation.     

基于相对密度和X射线粉晶衍射技术测定硬玉岩中硬玉的含量

硬玉岩能否命名为宝石级"翡翠",其硬玉的含量是关键参数,目前测量岩石中矿物质量分数的方法多为有损分析,难以应用于珠宝玉石检测中。本文基于硬玉岩矿物组成及其质量分数的变化,建立了一种通过测量硬玉岩相对密度获得硬玉质量分数的无损分析方法。对186件相对密度在3.30~2.88之间的硬玉岩样品采用静水称重法测试,根据相对密度范围进行分组,利用X射线粉晶衍射、人工重砂分析、电子探针、红外光谱、拉曼光谱等技术确定硬玉岩的主要矿物及其质量分数,进而统计分析硬玉质量分数与硬玉岩相对密度的线性关系。研究表明:硬玉岩的主要矿物为硬玉和杂质矿物钠长石、方沸石。随着硬玉的质量分数(wA)下降,钠长石、方沸石质量分数增加,硬玉岩实测相对密度(SG)发生相应变化,两者的线性方程为wA=1.3454×SG-3.4531(相关系数为0.9814),线性关系良好。由于本方法的硬玉岩实测相对密度近似等于理论相对密度,即可通过测量相对密度获得硬玉的质量分数,这种无损测试方法适用于相对密度在3.3~3.0,硬玉含量在95%~60%,硬玉与钠长石的质量分数之和在90%~97%之间的硬玉岩样品。     

应用顺磁性液体测量微小矿物比重和磁化系数的初步研究

一、前言 比重是矿物的一个重要物理常数。迄今为止,测量比重已有多种经典方法。但对于测量微小矿物比重及扩大比重测量范围,已有的方法已不能满足要求。为此,笔者利用六十年代后发展起来的磁流体新技术,利用对于仅在垂直方向上有梯度变化的磁场中,顺磁性液体具有“按比重分层的现象”这     

滹沱河现代沉积物的比重研究

比重是物质的重要物性之一,是物质成分和结构的反映。不同矿物的比重可以相差若干倍,因而用以鉴定矿物的种类。在河流动力学有关基本原理和计算公式中,比重是一种重要的因素,在沉积岩石学中被视为沉积物的沉积三要素(粒度、比重和形状)之一。我们对滹沱河现代沉积物进行沉积构造、粒度、矿物成分和扫描电镜等项分析的同时,对沉积物的比重作了一些分析,探讨了沉积物的比重在河流沉积体系中的变化情况。     

一种斜绿泥石质仿田黄

田黄是一种产于福建寿山、以地开石或珍珠陶石为主要矿物组成的玉石,其具有＂形＂＂皮＂＂格＂＂纹＂特征。由于田黄的价格昂贵,市场上常有田黄仿制品出现。主要介绍一种斜绿泥石质田黄仿制品材料,该斜绿泥石质仿田黄为黄色至褐黄色,玻璃光泽,半透明,具有似＂萝卜丝纹＂与＂红筋＂,外貌上与田黄十分形似,较易混淆,但斜绿泥石质仿田黄的透明度较田黄的好;该斜绿泥石质仿田黄的实测折射率为1.585,相对密度为2.81,二者均较田黄的高;X射线粉末衍射分析,斜绿泥石以14.39,7.14,4.74,3.55处的衍射峰为特征,而田黄则没有14附近的衍射峰;红外光谱的结果显示,虽然斜绿泥石质仿田黄和田黄均在3 700~3 400 cm-1范围内具有羟基吸收,但前者显示宽吸收基础上叠加了3 679,3 671,3 651和3 629 cm-1处4个极弱的肩形峰,而后者却有3 700,3 645,3 625 cm-1处的尖锐的强吸收峰。运用X射线粉末衍射分析或红外光谱、折射率和相对密度等测试方法可将其区别开。     

Correlation of mineralogical and textural characteristics with engineering properties of selected granitic rocks from Turkey

Granitic rocks show a variety of engineering properties that may affect quarrying operations, tunneling, mining, slope stability and the use of rock as a construction material. The physical and mechanical properties are a function of the mineralogical and textural characteristics of the rock. The purpose of this study is to apply correlation analysis to investigate the relationships between petrographical and engineering properties of granitic rocks. A variety of granitic rock samples from different parts of Turkey were subjected to petrographic studies. The same samples were then tested to determine specific gravity, dry and saturated unit weight, water absorption, effective and total porosity, sonic velocity, Schmidt hardness, point load strength index, uniaxial compressive strength, tensile strength and modulus of elasticity. The relationships between these properties and the petrographical characteristics are described by simple regression analyses. The study revealed that the influence of the textural characteristics on the engineering properties appears to be more important than the mineralogy. It also determined that the types of contacts, grain (mineral) shape and size significantly influence the engineering properties of the granitic rocks.     

重液变温分离单矿物在铷锶年代学中的应用

报道了应用重液变温分离法分离白云母、黑云母、透长石和石英等单矿物,进行铷锶等时线年龄测定的研究结果。这些结果表明,同一单矿物具有微小比重差的组分,其Rb、Sr同位素比值具有明显的线性展布,在铷锶年代学研究中具有良好的应用前景和潜力。     

Distribution of heavy minerals in Nizampatnam-Lankavanidibba coastal sands,Andhra Pradesh,East Coast of India

Heavy mineral analysis was carried out for the beach and fore dune sediments along 60 transects of Nizampatnam-Lankavanidibba coastal area. The heavy mineral assemblage in this area with decreasing abundance of opaques (Ilmenite + magnetite, 47.67%), pyriboles (20.35%), garnets (3.66%), epidote (3.23%) and with less than 3.0% concentration of sillimanite, zircon, staurolite, kyanite, apatite, spinel, monazite, biotite, topaz, leucoxene and chlorite. The heavy mineral concentrations are high in the finer fractions i.e., +120 and +230 (ASTM) than the coarse fraction (+60) of sand. In the seven sectors, heavy mineral assemblage is same but their concentrations are different. The sectors nearer to the river mouth contain high concentration of high specific gravity heavy minerals (ilmenite and magnetite) than sectors away from the river mouth. The redistribution of heavy minerals is controlled by creek dynamics, longshore currents, size and specific gravity of the heavy minerals.     

奇台县某金矿矿石特性及可选性试验研究

通过对金矿石化学及矿物组成、自然金形态、嵌布粒度、嵌布方式等深入研究,查明了该矿石性质。利用浮选法和氰化法进行可选性试验研究,浮选试验精矿品位为46.86 g/t,回收率达85.14%,氰化试验最高浸出率96.38%。综合分析认为,采用浮选法选矿较合理。     

颗粒形状对粗粒土孔隙特征和渗透性的影响

粗粒土的颗粒级配、形状和密实度都是影响其孔隙结构,进而影响其渗透特性的重要因素。但长期以来,对颗粒形状影响的关注度较少,其主要原因在于不容易定量描述颗粒形状及其影响的孔隙结构特征。选取已获取长宽比和圆形度的不规则形状碎石、规则形状的球和八面体颗粒分别装填试样,针对颗粒级配和颗粒形状的差异,开展孔隙结构特征和渗透性的对比研究。通过CT扫描试样内部结构图像,重构试样的三维孔隙结构并计算孔隙比表面积。通过渗透试验测得试样的渗透系数。结果表明：试样孔隙比表面积是表达孔隙结构特征的有效参数,在相同级配和孔隙率的条件下,试样孔隙比表面积随颗粒圆形度和趋近球形程度的增加而减小;相同级配和孔隙率的条件下,渗透系数随孔隙比表面积的减小而增大,随颗粒圆形度增大而增大;球形颗粒试样的渗透性最强,试样颗粒越偏离球形,孔隙系统中水流阻力越大,试样渗透性越弱。     

根据重力场研究华南地壳结构

华南与华北重力场相比有明显的差别,前者为很强的负异常,它是由于地壳花岗岩化作用使岩石圈密度减小引起的。在沿海地区布格重力异常与莫霍界面起伏没有相关性,地壳与上地幔密度不均匀对重力场分布起主要作用。华南广泛分布花岗岩类,反映了该区特定的地壳结构。花岗岩出露面积与重力等值线有较密切的对应关系,这对于应用重力定量解释推断花岗岩的地下形状具有有利条件。本文讨论运用重力模型研究华南地壳与上地幔结构和花岗岩的地下形态,并探讨花岗岩的成因及其与矿产的关系。     

One size does not fit all: Refining zircon provenance interpretations via integrated grain shape,geochronology, and Hf isotope analysis

Sediment provenance studies commonly utilize isotopic signatures to resolve detrital mineral sources and routing. However, non-unique ages and geochemical characteristics across geographically distinct crystalline source regions can lead to significant ambiguities in mineral provenance interpretations. Such ambiguity is apparent in southern Australia’s Cenozoic Eucla Basin, which hosts world-class heavy mineral sand resources. Here, new Hf isotope data are provided from four heavy mineral prospects (N = 8, n = 844 [N = samples, n = grains]). Zircon grain shape data are also presented for a suite of detrital Eucla Basin samples (N = 22, n = 35,604) and the basin’s underlying basement, the Coompana Province (N = 13, n = 824). The data are integrated with published detrital and non-detrital primary zircon data to investigate the efficacy of grain shape analysis to better resolve the basin’s mineral provenance. Zircon Hf isotope compositions indicate a primary Mesoproterozoic juvenile source for zircon melts (～1250–1000 Ma, ?2.5 < ?_Hf > ～+5) with additional contributions from a range of juvenile to evolved late Archean to Phanerozoic-aged zircon bearing magmas (?28.0 < ?_Hf > +11). U–Pb geochronology and Hf isotopes are incapable of differentiating Mesoproterozoic-aged source rocks bounding the region for the majority of heavy mineral deposits analyzed as potential sources express overlapping crystallization ages and similarities in Hf-isotope characteristics. However, distinct zircon grain shapes (i.e., perimeter, major axis and circularity) facilitate improved differentiation across these Mesoproterozoic sources. Filtering of U–Pb age, Hf isotope and shape data implicate the underlying Madura and Coompana provinces as dominant sediment sources for Eucla Basin detritus aged ～1400–1000 Ma. The lack of direct sediment pathways between the underlying basement provinces and placer sediments analyzed demonstrates the significance of zircon reworking from intermediate sedimentary basins in the formation of the economically significant Eucla Basin beach placers. Zircon grain shape represents a cheaply acquired and readily incorporated grain characteristic that can enhance provenance investigations.     

Geotechnical and mineralogical characteristics of marl deposits in Jordan

Marls and marly limestone deposits cover most of Northern Jordan, where Amman City and its suburbs are located. These deposits serve as foundations for most buildings and roads as well as fill material for structural back filling, especially road bases and sub-bases. The present study aims at investigating the geotechnical characteristics and mineral composition of the marl units of these deposits through field investigations and laboratory testing. Using X-ray diffraction technique along with chemical analysis, representative samples of marl horizons were tested for mineral composition, and for a set of index and geotechnical properties including: specific gravity, grain size, Atterberg limits, Proctor compaction and shear strength properties. The test results show a positive linear relationship as expected between the clay content and both liquid and plastic limits. The tests results also show an inverse linear relationship between the clay content and the maximum dry density in both standard and modified compaction. This is attributed to the adsorption of water by the clay minerals. The relationship is more prominent in the case of modified compaction test. The results also indicate a similar relationship for the angle of internal friction. No clear correlation between cohesion and clay content was apparent.     

DEM Simulation of Direct Shear: 2. Grain Boundary and Mineral Grain Strength Component Influence on Shear Rupture

The influence of mineral grain and grain boundary strength is investigated using a calibrated intact (non-jointed) brittle rock specimen subjected to direct shear with a particle-based distinct element method and its embedded grain-based method. The adopted numerical approach allows one to independently control the grain boundary and mineral grain strength. The investigation reveals that, in direct shear, the normal stress (σ _n) applied to a rock specimen relative to its uniaxial compressive strength (UCS) determines the resulting rupture mechanism, the ultimate rupture zone geometry, and thus its shear stress versus horizontal displacement response. This allows one to develop a rupture matrix based on this controlling parameter (i.e., σ _n/UCS). Mineral grain strength reductions result in the lowering of the apparent cohesion intercept of the peak linear Coulomb strength envelope, while grain boundary strength reductions change the peak linear Coulomb strength envelope to a bi-linear or curved shape. The impact of grain boundary strength is only relevant at σ _n/UCS ratios <0.17 where tensile and dilatant rupture mechanisms dominate. Once shear rupture begins to be the dominant rupture mechanism in a brittle rock (i.e., at σ _n/UCS ratios >0.17), the influence of weakened grain boundaries is minimized and strength is controlled by that of the mineral grains.     

软弱夹层粘粒含量与抗剪强度参数的关系分析

分析表明,赋存环境相同、粘土矿物成分以伊利石为主的软弱夹层,在相同稠度状态下粘粒含量与抗剪强度参数具有很好的相关性。通过现场和大量的室内试验成果,建立了各种稠度状态下粘粒含量和抗剪强度参数之间的相关关系式,揭示了在研究粘粒含量对抗剪强度参数影响时,还应当考虑软弱夹层所处的天然状态。结合《温凝土重力坝设计规范》中提出的用粒度成分定量指标选取软弱结构面抗剪强度参数,对软弱夹层抗剪强度参数取值问题进行了探讨。     

Emplaced Geotechnical Characteristics of Hydraulic Fills in a Number of Australian Mines

Hydraulic fills used in Australian mines have similar grain size distributions whilst having quite different specific gravity values, typically in the range of 2.7–4.4. When produced and distributed in slurry at 65–75% by solid content, they settle to produce fills with similar geotechnical characteristics. The fills under investigation have been found to settle, in the laboratory, to a dry density of about 0.56 × specific gravity, a saturation water content of about 17–34%, and a porosity of 37–49%. A quick estimate of the optimum water content that gives the minimum porosity may be obtained by locating the intersection of the saturation curve and minimum porosity line, which may simply be done on a water content vs. porosity plot. However, transportability of the slurry requires it to be mixed at water content substantially greater than the optimum water content. As the tailings settle out of suspension, they settle to relative density of 50–80%. This paper shows that the current empirical relationships relating relative density and N-value to friction angle for sands will significantly underestimate the friction angle of the hydraulic fills. Based on limited experimental data, a unique relationship between relative density and friction angle is proposed for hydraulic fills placed in some Australian mines.     

Ontogenetic analysis of individual olivine grains in ultramafic rocks

The morphology and internal structure of individual olivine grains from ultramafic rocks in the Guli and Gal’moenan dunite massifs differing in origin are considered. To restore the ontogeny of mineral aggregates, traces of elastic deformation retained in mineral grains have been used. Comparison of anatomy of olivine grains from these two massifs showed that the mechanism of accommodation of rocks to changing geological settings is expressed as the response of the mineral aggregate structure and variation in the anatomy of individual mineral grains. At the level of individual grains, this is annihilation of older defects and origination of younger dislocations; refinement of the crystal lattice; exsolution; formation and transformation of new mineral phases; and creep and migration of subboundaries within grains. At the aggregate level, this is rotation and migration creep of the internal boundaries of rock; formation of new boundaries of mineral intergrowths; reorientation of boundaries; and variation in their extent, density, and grain dimensions. The prehistory of massifs controls the manifestation and abundance of various elastic deformations and related types of recrystallization of olivine grain boundaries and subboundaries in aggregates. New conditions and accommodation of mineral aggregates to these conditions have instigated specific schemes of recrystallization, which bear information on the history of rocks and their massifs.     

等轴锶钛石在我国的首次发现

笔者于1985—1986年,对华北地区岩浆岩型磷灰石矿床进行研究时,在山西省临县紫金山的钛榴霞石正长斑岩中,发现了与苏联的达乌松矿（Tausonite）相似的矿物,即等轴锶钛石。该矿物在我国的首次发现,对这一地区碱性岩的矿物学和岩石学研究无疑是很有意义的。本区等轴锶钛石一般为淡棕色,呈立方体或不规则柱状,折射率N=1.977±0.002,比重为4.66,均质体,个别具光性异常并呈环带构造,晶胞参数a0=3.905A,空间群Pm3m,晶胞体积v=59.55A。本文重点对该矿物的地质产状、矿物共生组合、物理性质与光学性质、矿物化学成分及X射线分析进行了研究。笔者认为本区等轴锶钛石是富钛富碱贫硅的碱性岩浆中早期结晶的产物。     

Clinopyroxenes in Kimberlites of China

The author studied the grain size, shape, colour, altered coat, mineral species, chemical composition,end- member components and infrared spectra of clinopyroxenes occurring as megacryst, macrocryst andgroundmass minerals, intergrowths with pyrope and ilmenite and minerals in deep-seated xenoliths and inclu-sions in diamonds in kimberlites of China. The clinopyroxenes under study were compared with megacrystclinopyroxenes in basalts and minerals in their deep-seated xenoliths and clinopyroxenes in lamproites andminettes. The coexisting clinopyroxene-pyrope pair was studied. Besides the author also studied the origin ofclinopyroxenes in kimberlites, P-T conditions for their formation and their reflected tectonic environments ofthe kimberlite formation. He suggests that this mineral is an indicator for diamond exploration.