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1.
主要采用同步辐射貌相术和红外光谱研究了产于南非和我国辽宁天然金刚石的晶体缺陷特征,分析了这两个产地金刚石的同步辐射形貌像和红外光谱的异同,对同步辐射形貌像中星芒像的形成原因进行了分析,认为星芒像是晶体在生长过程中产生的晶格弯曲畸变造成的,与晶体内部片状氮含量无关,辽宁和南非金刚石最大晶格弯曲畸变角分别为1.75°和0.98°。星芒的出现与晶体是否受到熔蚀有密切的关系。辽宁金刚石的星芒像强,晶体受到的熔蚀较弱;南非金刚石的星芒像弱,晶体受到的熔蚀强。  相似文献   

2.
利用同步辐射对天然金刚石晶体进行了形貌学研究,在的完整晶体内观察到晶体以平行{100}生长为主的正常生长,而不是前人所常见的平行{111}生长。生长带方向平行于(100)、(100)和(010)、(010)。生长带分布在偏离晶体中心的曲面内。由生长带的分布与形态可以观察到晶体不同晶面生长速度具有明显差异。  相似文献   

3.
天然金刚石形成于地球深部,反映丰富的地幔信息及演变历史[1-2]。金刚石中特征的氮原子缺陷是追溯其地幔存留时间和保存温度的重要依据[3-4],氮缺陷近年来也被认为是实现量子计算的优良载体,成为炙手可热的研究热点[5-6]。本世纪初新发现的储量巨大的津巴布韦砂矿型天然金刚石,引起了国内外学者的极大关注[7-10]。我们对已获得的津巴布韦金刚石样品进行预研究,注意到该产地金刚石具有特殊的立方体-八面体同时发育的镶嵌结构(下文简称mixed-habit),其氮和氢含量丰富,且氮和氢分别沿八面体生长区{111}和立方体生长区{100}具有择优取向特点。这种mixed-habit结构,不同于传统天然金刚石以八面体生长为主的结构[11],而与高温高压(HPHT)合成金刚石的结构较为相似[12],因而具有特殊的地质学背景和研究意义。我们将在下一阶段对这类金刚石在不同生长方向氮和氢缺陷存在形式及分布规律进行深入定量研究。重点通过电子顺磁共振光谱(EPR)对于不同氮缺陷如孤氮、双氮等的浓度比、占位形式和晶格畸变程度、自旋状态等进行表征,弥补传统红外光谱对于氮缺陷表征的不足。利用密度泛函理论(DFT)模拟不同氮缺陷的形成能解释实验观测的氮缺陷择优取向分布规律。根据对氮缺陷的聚集状态推算对应地幔存留时间和保存温度,追溯其形成过程和演变历史。  相似文献   

4.
天然金刚石同生位错的同步辐射X射线貌相研究   总被引:2,自引:0,他引:2  
利用同步辐射白光透射貌相术研究了辽南天然金刚石的晶体缺陷。采用作者提出的计算晶体缺陷空间取向的方法计算了金刚石中位错的取向。晶体中所有位错均起源于晶核,并且柏氏矢量都平行于[1^-01]。多数位错并非位于{111}面内。位错所在晶面属于[1^-01]晶带,并且多数与{211}或{110}面近于平行。位错线平直,部分有拐折。所有位错均为混合位错。位错走向与生长面近于垂直,多数与<111>夹角较小。所有位错均为同生位错,形成后未发生滑移。晶核在形成期曾受到较大应力作用造成较大的晶格畸变。晶体内部未出现生长带,反映晶体成长过程中环境未发生大的变化。形成晶体的碳质来源不均一,反映了中元古代华北陆台下地壳岩浆成分的不均一性。  相似文献   

5.
直流弧光放电等离子体CVD金刚石薄膜中的晶体类型与特征   总被引:1,自引:0,他引:1  
采用自主研制的直流弧光放电等离子体CVD设备,以甲烷和氢气为气源,在YG6硬质合金基体上制备出主显晶面为(100)、(111)以及纳米晶粒的金刚石薄膜涂层。SEM观测其晶体类型主要为立方体、八面体、立方八面体,其中以立方八面体为主。随着碳源气体浓度的增加,金刚石晶体的形态会呈现从八面体一立方八面体一立方体顺序转变的趋势;而薄膜的表面形貌呈现从主显(111)晶面-(111)与(100)晶面混杂-主显(100)晶面顺序转变的特征。此外,CVD金刚石薄膜中还存在有许多类似接触孪晶、贯穿孪晶、复合孪晶,以及球形或聚晶晶粒形态的晶体,并且多数孪晶属于类似(111)复合孪晶结构。  相似文献   

6.
俄罗斯地台北缘和东北缘的曲面金刚石(英文)   总被引:8,自引:0,他引:8  
曲面金刚石广泛产于金刚石砂矿和含金刚石的金伯利岩管及钾镁煌斑岩中。曲面金刚石是一种特殊的晶体类型 ,它与平坦面金刚石相比 ,不仅晶习不同 ,曲面金刚石常呈四六面体 ,而平坦面金刚石常呈八面体 ,而且它更坚实 ,更具宝石价值。热力学计算和实验表明 ,八面体金刚石比立方八面体和立方体金刚石的形成温度高 ,意味着曲面金刚石形成深度较浅 ,可能在石墨 -金刚石稳定区的边界上。目前对曲面金刚石是生长形还是由平坦面金刚石熔蚀而成尚有不同见解。文章对俄罗斯地台北缘和东北缘的曲面金刚石进行了综合研究。经切割抛光 ,用 X射线形貌法、阴极发光法和普通光学法进行了结构研究 ,还对金刚石进行了光学荧光、 X射线荧光 ( T=77~ 2 90 K)、ESR电子自旋共振、可见光区的吸收谱等研究。用光学测角仪和扫描电镜查明 ,研究区的金刚石中四六面体单形占 60 %~ 80 %、 { 0 65} +{ 365} +{ 1 1 1 }聚形占 8%~35%、平坦面八面体占 0~ 8%且无菱形十二面体。研究发现金刚石表面覆有成分不同的薄膜 ,厚约 0 .1~ 1 μm,其成分有 2 9种之多。表明天然金刚石是在多种金属和碳的熔体中结晶的 ,乌拉尔 -巴西型金刚石的曲面晶为生长晶而非熔蚀晶。在罗蒙诺索夫金伯利岩管中获取的金刚石表面附有超基性岩的原生矿物组合?  相似文献   

7.
苏北古沂沭河流域,通过近二十多年的工作,已发现100多颗金刚石。这些金刚石的特征及其地质意义引起了地质学家的关注。一、苏北金刚石特征到目前为止,苏北古沂沭河流域已发现了100多颗金刚石。最大者52.714克拉,最小者仅几毫克。笔者通过对其中的83颗金刚石镜下详细观察与统计,发现有如下特征:1.金刚石的结晶习性苏北发现的金刚石中见有八面体,菱形十二面体,八面体与菱形十二面体聚形晶体及上述晶体的双晶,连生体。八面体金刚石:本区规则八面体金刚石少见,一般都以不同程度的歪晶出现,或呈沿三次对称轴压平之八面体尖晶石律双晶(图4),或构成平行连生体和不规则连生体。  相似文献   

8.
津巴布韦金刚石独特的形态及其“指纹”特征的意义   总被引:1,自引:1,他引:0  
陆太进  陈华  张健  宋中华  柯捷 《地质通报》2011,30(10):1638-1645
津巴布韦马朗金刚石矿床为近年来发现的特大型高品位金刚石砂矿。对津巴布韦马朗金刚石产区的金刚石样品进行了矿物学和宝石学研究。结果显示,津巴布韦金刚石的晶体形态、表面微细特征等与世界上主要产地的金刚石有较大差异。其中最新发现的“十字架”形熔蚀图像和红色斑点是该产地金刚石的典型特征。“十字架”是由大量大小不等的正方形熔蚀坑沿晶体[100]重叠排列而成的,红色斑点为铁质氧化物沿熔蚀坑棱线生长而成的。研究结果表明,津巴布韦马朗金刚石的形态特征具有产地“指纹特征”的意义,对中国地勘单位赴境外进行金刚石找矿具有借鉴意义。  相似文献   

9.
1981—1986年,我们对玲珑金矿、夏甸金矿、栖霞金矿和三山岛金矿的黄铁矿晶体形态进行了野外和室内研究。其中,晶形统计2495粒,晶体测角300粒,用扫描电子显微镜对60粒晶体进行了微形貌研究。对四个金矿床的研究表明,黄铁矿晶体单形以立方体{100}最常见,出现频率为92.47%,其次为五角十二面体{hko}(其形号包括{210}、{310}、{410}、{810}、{830}、{910}及{11,1,0})出现频率为57.27%;其次为八面体{111},出现频率为16.88%,较少见的为偏方复十二面体{hkl}(其形号包括{321}、{421}、{10,6,5),{18,24,25)及{34,  相似文献   

10.
钛磁铁矿内部尖晶石出溶体的成分组成和形成机制对估算磁铁矿固溶体的成分以计算铁钛氧化物的氧逸度-温度具有重要意义.为了探究攀枝花钒钛磁铁矿中尖晶石的成因及形成机制,运用岩相观察和各种微区原位观测手段,系统研究了各类尖晶石的矿物学特征.尖晶石的粒度在纳微米之间,有3种类型:第1种为钛磁铁矿晶界处不规则的大颗粒尖晶石,Mg#为60~70;第2种为钛磁铁矿颗粒内部的粒状尖晶石,Mg#为71~77;第3种为沿钛磁铁矿(100)方向定向分布的尖晶石片晶,Mg#为75~77.3类尖晶石分别与磁铁矿主晶具有相同的取向关系:{111}Mag//{111}Spl,{110}Mag//{110}Spl和{100}Mag//{100}Spl.3类尖晶石均是磁铁矿主晶的出溶体,钛磁铁矿晶界处及其内部的粒状尖晶石的形成与某些晶体缺陷关系密切,是在降温过程中较早出溶的产物,尖晶石片晶在两者之后以旋节分解出溶形成.   相似文献   

11.
Deformed rocks of the Itabira Iron Formation (itabirites) in Brazil show microstructural evidence of pressure solution of quartz and iron oxides; it appears that magnetite was dissolved and hematite precipitated. The dissolution of magnetite seems to be related to its transformation to hematite by oxidation of Fe2+ to Fe3+. The transformation of magnetite to hematite occurs along {111} planes, and results in the development of hematite domains along {111} that are parallel to the foliation. The difference in volume created by the transformation of magnetite to hematite and the shear stress acting on the interphase boundaries allow fluids to migrate along these planes. The dissolution of magnetite involves the hydrolyzation of the Fe2+—O bonds at interphase boundaries of high normal stress. The high fugacity of oxygen in the fluid phase promotes the reaction of Fe2+ (in solution) with oxygen. Fe2+ ions oxidize to Fe3+ and precipitate as hematite platelets with their longest axes oriented parallel to the direction of maximum stretching. The transformation of magnetite to hematite during deformation plays an important role in the fabric evolution of the iron formation rocks. The transformation along {111} creates planes of weakness that facilitate fracturing. The fracturing plus the dissolution result in a reduction of magnetite grain size, and the oriented precipitation results in layers of hematite platelets. These processes produce a new fabric characterized by a penetrative foliation and lineation.  相似文献   

12.
This paper is a study of the etch pits on the {210} surfaces of pyrite. There is great similarity between them and the etch pits which appear on the {100} and {111} forms. The presence of six-fold growth spirals, frequent on the {210} form surfaces, result from a cooperation of two three-fold growth spirals generated from screw dislocations with the same sign of their Burgers vectors and different modulus.  相似文献   

13.
The internal structure of variety III diamonds (Orlov 1977) was examined by X-ray section topography. The crystal space was found to be divided into six cubic sectors of a face-form of rhombododecahedroid variety III (Shafranovsky 1961). The defect lines on the topographs are the traces of {110} defect planes. It is concluded that separate 〈111〉 fibres are grouped into {110} layers (lamellae). The internal structure of the crystals is characterized by continuous warping of crystal planes and is directly connected with {110} defect planes which are tilt boundaries. Examples of variants of filling cubic sectors are given and their connection with misorientation shown on topographs demonstrated. The characteristic internal structure of variety III diamonds can account for their morphological features and structure-dependent properties; for examples, the cleavage on {110} and {100}.  相似文献   

14.
The results of chromatographic study of the formation of rhombododecahedral diamonds synthesized in the Fe-Ni-(Ti)-C system at 5.5–6.0 GPa and 1350–1450°C are presented, including crystals with rounded surfaces of the rhombododecahedron with parallel striation, which are morphological analogues of natural diamonds abundant at various kimberlite, lamproite, and placer deposits. Chromatography was performed at 150°C with mechanical breakup of diamonds. The stable release of methane when diamonds of habit {110} are crushed is established. It is concluded that the appearance of the habit rhombododecahedron may be related not only to the effect of temperature and pressure on crystal growth but also to reductive conditions of crystallization. At the same time, the appearance of significant amounts of hydrocarbons in the system probably results in stopping of the growth of faces {110} and {100} and, instead, formation of specific surfaces that are composed of microscopic accessories faced by planes {111}.  相似文献   

15.
金刚石中分子氢的赋存状态研究   总被引:1,自引:0,他引:1  
金刚石中分子氢的定向红外光谱研究表明在垂直于(100),(110)和(111)三个方向上所测得分子氢的浓度是不相同的,且不同样品中的变化趋势也不同,即分子氢在金刚石中的定向性不明显;MNDO法计算结果显示分子氢在金刚石中的稳定程度大小关系依次为沿〈111〉定向的键心与反键心组合(a.b+b.c)〉六角体空隙(H)〉四面体空隙(T1)〉菱形中心(C1=C2)〉四面体空隙(T2).  相似文献   

16.
Magnesiowüstite, (Mg0.08Fe0.88)O, and wüstite, Fe0.94O, were compressed to ~36?GPa at ambient temperature in the diamond anvil cell (DAC) at the Advanced Light Source. X-ray diffraction patterns were taken in situ in radial geometry in order to study the evolution of crystallographic preferred orientation through the cubic-to-rhombohedral phase transition. Under uniaxial stress in the DAC, {100}c planes aligned perpendicular to the compression direction. The {100}c in cubic became { $\left\{ {10\bar 14} \right\}$ }r in rhombohedral and remained aligned perpendicular to the compression direction. However, the {101}c and {111}c planes in the cubic phase split into { ${10{\bar{1}}4}$ }r and { ${11{\bar{2}}0}$ }r, and (0001)r and { ${10{\bar{1}}1}$ }r, respectively, in the rhombohedral phase. The { ${11{\bar{2}}0}$ }r planes preferentially aligned perpendicular to the compression direction while { ${10{\bar{1}}4}$ }r oriented at a low angle to the compression direction. Similarly, { ${10{\bar{1}}1}$ }r showed a slight preference to align more closely perpendicular to the compression direction than (0001)r. This variant selection may occur because the 〈 ${10{\bar{1}}4}$ r and [0001]r directions are the softer of the two sets of directions. The rhombohedral texture distortion may also be due to subsequent deformation. Indeed, polycrystal plasticity simulations indicate that for preferred { ${10{\bar{1}}4}$ }〈 ${1{\bar{2}}10}$ r and { ${11{\bar{2}}0}$ }〈 ${{\bar{1}}101}$ r slip and slightly less active { ${10{\bar{1}}1}$ }〈 ${{\bar{1}}2{\bar{1}}0}$ r slip, the observed texture pattern can be obtained.  相似文献   

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