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1 均质体光率体及拆射率光波在均质体中传播时 ,向任何方向振动 ,其传播速度不变 ,折射率都相等。因此 ,均质体的光率体是一个圆球体。 (图 1 )其光率体任何方向的切面都是一个圆切面 ,这类宝石在折射仪上表现为只有一个折射率值。当在折射仪上转动宝石 36 0°时 ,仅有一条不动的阴影边界。这是因为圆切面的半径只有一个 ,这时圆切面的半径即代表了均质体的折射率值。所以 ,从均质体的光率体形状 ,解释了这类宝石在折射仪上进行测试时仅有一个值的现象。如表 1。表 1 常见均质体宝石在折射仪间测试结果常见宝石名称晶系光性折射率萤石等轴… 相似文献
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四川冕西霓石碱性花岗岩中的稀土矿物主要为钙稀土氟碳酸盐矿物系列，通过选区电子衍射（SAED）和高分辨透射电子显微术（HRTEM）研究发现该系列矿物晶体结构中广泛发育复杂多样的微观地质异常现象，其主要类型有：（1）由该系列两个端员矿物氟碳铈矿结构层（B）与直氟碳钙铈矿结构层（S）以不同比例沿C轴方向有序堆垛形成的BmSn型规则混层结构；（2）无序堆垛形成的有序一无序结构晶畴；（3）由堆垛层错形成的无序混层结构，氟碳钙铈矿中不同多型体间的共格连生结构和相转变等；（4）氟碳铈矿结构中的平行于[001]方向的平移畴及一维无公度调制结构，该类调制结构可能是由于矿物中原子占位有序度的变化而形成的无序结构状态。 相似文献
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一、非均质矿物的主折光率方程1.一轴晶正光性矿物一轴晶的光率体为旋转椭球。如为正光性,则其主切面如图1所示的椭圆。其方程为: 相似文献
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阜东斜坡区头屯河组短期旋回不同结构类型内储层非均质性研究 总被引：2，自引：0，他引：2
探讨准噶尔盆地阜东斜坡区头屯河组短期旋回不同结构类型内储层非均质性,为后期储集层精细开发以及采油率的提高提供理论指导。主要利用岩心、测井以及地震资料,对两个重点短期旋回不同结构类型中的非均质性特征进行详细分析,发现SSC4主要发育A2和C1两种结构类型;SSC7发育C1和C2两种结构类型,且SSC7的C1结构类型中储集砂体非均质性程度中等-强,为最有利勘探目标;次要勘探目标为SSC4的A2和C1两种结构类型中较强非均质性的储集砂体,SSC7的C2结构类型中储集砂体非均质性程度中等,但本身物性较差,勘探意义不大。这为研究区头屯河组的勘探提供地质指导和依据。 相似文献
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本文系统叙述了垂直入射光下,非均质吸收性矿物光学性质的理论,推导出了下列光性的计算公式:①非均质旋转角Arβ;②非均质视旋转角Ar;③椭圆率2θ;④正交反射率R_ 。这些公式是解释反光显微镜下所发生的光学现象及定量测定的理论基础。最后以赤铁矿为例,计算了它的各种光性数据,计算结果与实测数据完全符合。非均质透明矿物可看作吸收性矿物的特例,令公式中吸收率k=O,即可得到非均质透明矿物各种光性公式。 相似文献
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非均质介质的空间维度变化对重非水相流体（DNAPL） 的运移具有重要的影响。在充分考虑地质体的空间连续
性、不对称性以及各向异性等特征的基础上,采用基于马尔可夫链的转移概率（transition probability） 模型来构建非均质
随机场。该文通过TMVOC-MP软件来模拟DNAPL在非均质介质中的运移规律,探讨非均质随机场的水平空间连续性、
空间维度变化以及侧向运移过程对DNAPL运移的影响。结果表明,介质的水平空间连续性越好,DNAPL在水平方向的
迁移范围越大,在垂向的迁移范围越小;相比于三维模型,二维模型中DNAPL在水平方向的展布更大、在透镜体上的蓄
积量更多,在实际应用中以二维模型代替三维模型会加大模拟结果与实际污染情况之间的误差;侧向运移过程削弱了单
个平面的非均质性对DNAPL运移的控制,当存在侧向运移时,DNAPL绕过透镜体所运移的距离以及在透镜体上的蓄积
量会相应减小。 相似文献
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北堡油田中区东营组储层非均匀性研究 总被引：2，自引：0，他引：2
储层非均质性包括微观和宏观非均质性。通过对岩心薄片,铸体薄片,电镜、Ｘ－衍射等试验数据以及测井储层评价数据分析,揭示冀东北堡油田中区东营组储层非均质特征为：储层岩石居分复杂,不稳定组分含量高,分选差,含泥沙质结构;压实作用、溶蚀作用及粘土矿物转化现象普遍,成岩变化大;中小孔细喉结构,连通性差,微观非均质性强。宏观非均质性较强,层内纵向上渗透率差异明显,渗透率非均质参数值较大;层间非均质程度与层内的相近 平面非均质性强,砂体连通性差,有效砂层系数较小,非均质参数在平面上变化太。采用压裂措施,降低储层非均质性,改善储层连通性,可提高开发效果。 相似文献
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北堡油田中区东营组储层非均质性研究 总被引：5，自引：0，他引：5
储层非均质性包括微观和宏观非均质性。通过对岩心薄片、铸体薄片、电镜、Ｘ－衍射等试验数据以及测井储层评价数据分析,揭示冀东北堡油田中区东营组储层非均质特征为：储层岩石成分复杂,不稳定组分含量高,分选差,含泥沙质结构;压实作用、溶蚀作用及粘土矿物转化现象普遍,成岩变化大;中小孔细喉结构,连通性差,微观非均质性强。宏观非均质性较强,层内纵向上渗透率差异明显,渗透率非均质参数值较大;层间非均质程度与层内的相近;平面非均质性强,砂体连通性差,有效砂层系数较小,非均质参数在平面上变化大。采用压裂措施,降低储层非均质性,改善储层连通性,可提高开发效果。 相似文献
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E. V. Kaneva D. I. Cherepanov L. F. Suvorova A. N. Sapozhnikov V. I. Levitsky 《Geology of Ore Deposits》2011,53(7):678-682
A lazurite sample taken from the Tultui deposits in the Baikal region has been studied using petrographic examination, X-ray
diffraction, and local X-ray spectroscopy (electron microprobe). It is established that the line of the basic cell in the
X-ray diffraction pattern of the orthorhombic lazurite is widened, so the unit-cell parameters should be recalculated from
the interlayer distances of the superstructural reflections. The chemical compositions and unit-cell parameters of the lazurites
from the Baikal region and the Pamirs are different. Two schemes of the chemical substitutions of atoms in the mineral are
assumed: (1) the hauyne cluster [Na3CaSO4]3+ is replaced with a sodalite cluster [Na4Cl]3+, and (2) two hauyne clusters 2[Na3CaSO4]3+ are substituted by nosean clusters [Na4SO4]+ and [Na4H2O]4+ with retention of the total charge. The increase in the Na and Cl contents in the orthorhombic lazurite is accompanied by
a decrease in the unit-cell dimensions. Orthorhombic lazurites from the southern Baikal region and the southwestern Pamirs
were formed in apocarbonate (apocalciphyre) metasomatic rocks at a lower temperature than pyroxene, afghanite, and cubic lazurite. 相似文献
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V. L. Tauson A. N. Sapozhnikov S. N. Shinkareva E. E. Lustenberg 《Geochemistry International》2009,47(8):815-830
The nature of the stability of an incommensurate 3D modulation (ITM) in the structure of Baikal lazurite was evaluated using
the methods of experimental geochemistry and X-ray photoelectron spectroscopy. It was shown that ITM with a period of 4.6a is preserved in the lazurite structure at 550°C almost without changes within the time interval from t = 100 h to at least 2000 h, although its initial (t = 0) development was not restored. In contrast to higher temperatures (≥ 600°C), the activities of gas species have no significant
influence on the process of modulation release, except for the region of low O2, S2, and SO2 fugacities, where the type of modulation changes, and the monosulfide ion appears in the lazurite composition. At T = 550°C and probably at lower temperatures, SO2 fugacity ceases to be the critical parameter of ITM existence. The ordered state of polysulfide and sulfate clusters corresponding
to the ITM period of Baikal cubic lazurite is stable at T = 550°C and is an example of forced equilibrium. It develops in response to a crystal chemical event occurring at a temperature
of T
x
within 600–550°C and is related to the thermal compression of the structure resulting in the isolation of structural cages
containing clusters with different states of sulfur. Their mutual interaction, which leads to the rapid release of the modulation
at higher temperatures owing to the equalizing of cluster sizes in the cages, ceases. As a result, the proportions of reduced
(S22−, and S
x
2−) and oxidized (SO42−, So32−, and S2O32− sulfur species show negligible variations, and there is only partial reduction of sulfate to sulfite and thiosulfate. Lazurite
samples with disulfide and polysulfide ions behave similarly, which suggests that an important condition for the preservation
of ITM is the presence of sulfur-bearing anions with different sizes rather than particular sulfur species in structural cages.
The degree of ordering in the distribution of clusters attained at T
x
remains unchanged owing to the development of forced equilibrium maintained by the energy balance between framework deformation
and cluster ordering. Natural lazurite with an ITM structure could not form at temperatures higher than T
x
, i.e., above 550–600°C 相似文献
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Synthetic melilites on the join Ca2MgSi2O7 (åkermanite) — Ca2FeSi2O7 (iron åkermanite) with Fe/(Fe+Mg) from 0.0 to 0.7 exhibit, at room temperature, an incommensurate phase with a rectangular modulation of a wavelength of about 19 Å in the [110] direction. Upon increase of temperature, they transform to a commensurate melilite structure at about 80° C for Fe/(Fe+Mg)=0.0 and about 250° C for Fe/(Fe+Mg)=0.6. In addition to the T(2) positions of the melilite structure filled by Si, the incommensurate phase exhibits two distinguishable T(1) sites containing the Mg and Fe2+. These two sites merge into one site during the phase transition from the incommensurate to the commensurate phase. A structural model for the incommensurate phase is based on the misfit between the tetrahedral (Mg, Fe2+)Si2O 7 4? sheets and the Ca2+ ions. 相似文献
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MX-1 tridymite is one of the room-temperature polymorphs of SiO2 tridymite and has an underlying monoclinic structure (Cc) with incommensurate modulations along a * and c * (Hoffmann et al. 1983; Löns and Hoffmann 1987). With increasing temperature up to 500° C, MX-1 is reported to experience at least five structural phase transitions. However, its structures and the relationships to other tridymite polymorphs are unclear. We present here a 29Si MAS NMR study of the room-temperature incommensurate structure of MX-1 and its structural phase transitions up to 540° C. Our results suggest that at room temperature, all the Si sites in MX-1 tridymite are in positions with similiar ∠Si-O-Si of ～150° and are consistent with the presence of two incommensurate modulations proposed by Hoffmann et al. (1983). Simulations of the spectra yield modulation amplitudes of 1.33 and 0.87 ppm, corresponding to 0.009 and 0.006 Å for Si-Si. The maximum atomic displacements along a and b due to the modulations appear to be ～0.01–0.02 Å. The structural phase transitions of MX-1 are significantly different from those of MC tridymite below 220° C. Our high temperature results confirm that MX-1 tridymite transforms to the H5 phase at about 65° C. The most important transition occurs near 110° C, where the H5 phase transforms to a phase yielding a single, narrow NMR peak, indicating the disappearance of the superstructure and possibly the onset of the dynamic averaging. The NMR lineshapes of H5 are consistent with the metrically orthorhombic unit cell and commensurate superstructure of 2a, 2b and 10c proposed by Graetsch and Flörke (1991). The phase present above 110° C is probably similar to the OC phase, but has a mean ∠Si-O-Si of ～152.0° at 113° C, 152.9° at 185° C and 154.1° at 500° C. The transitions at ～160 and 220° C for MX-1 are subtle and probably due to impurity MC. Analysis of the modulations in the OS phase of MC tridymite indicates that their amplitudes are of the order of 0.02 Å, significantly less than the value 0.3 Å proposed by Nukui et al. (1979). 相似文献
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安康矿是一种柱红石类新矿物,共化学组成为Ba0.8（Ti,V,Cr）8O16。通讨X光单晶工作。发现其结构在平行c轴方向上,存在一维的不相称超晶格有序。亚结构同柱红石结构,修正的晶胞参数a=10.118（1）A c=2.956（3）A。不相称超结构属四维的布拉维类,可能的超空间群有。不相称超结构与大孔道中的空位、以及由空位引起大阳离子沿c方向上的位移有关 相似文献
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Beta-eucryptite as grown by the flux method has been investigated by in-situ cold- and hot-stage transmission electron microscopy
(TEM). Using electron diffraction and dark-field TEM imaging, we found no evidence for the merohedral twinning that accompanies
structural collapse at the β-to-α-quartz transition, suggesting a true hexagonal symmetry for the aluminosilicate framework
of β-eucryptite. Selected-area electron diffraction (SAED) patterns exhibited a variety of incommensurate structures along
the three a axes with an average modulation period of about 6.5 a. These modulated structures arise from superperiodic stacking parallel to (100) of two structural units with different Li
configurations. In-situ heating experiments show that the modulated structures undergo a reversible transition to the disordered
modification at elevated temperatures. This transition arises from positional order-disorder of Li ions along the main structural
channels. In addition, it appears that at constant low temperature, electron beam irradiation alone can induce a sequence
of transitions similar to those that are thermally induced from the ordered modification to modulated states.
Received: 12 November 1998 / Revised and accepted: 31 December 1998 相似文献
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G��nther J. Redhammer Anatoliy Senyshyn Martin Meven Georg Roth Sebastian Prinz Astrid Pachler Gerold Tippelt Clemens Pietzonka Werner Treutmann Markus Hoelzel Bj?rn Pedersen Georg Amthauer 《Physics and Chemistry of Minerals》2011,38(2):139-157
The compound NaFeGe2O6 was grown synthetically as polycrystalline powder and as large single crystals suitable for X-ray and neutron-diffraction experiments to clarify the low temperature evolution of secondary structural parameters and to determine the low temperature magnetic spins structure. NaFeGe2O6 is isotypic to the clinopyroxene-type compound aegirine and adopts the typical HT-C2/c clinopyroxene structure down to 2.5?K. The Na-bearing M2 polyhedra were identified to show the largest volume expansion between 2.5?K and room temperature, while the GeO4 tetrahedra behave as stiff units. Magnetic susceptibility measurements show a broad maximum around 33?K, which marks the onset of low-dimensional magnetic ordering. Below 12?K NaFeGe2O6 transforms to an incommensurately modulated magnetic spin state, with k?=?[0.323, 1.0, 0.080] and a helical order of spins within the M1-chains of FeO6 octahedra. This is determined by neutron-diffraction experiments on a single crystal. Comparison of NaFeGe2O6 with NaFeSi2O6 is given and it is shown that the magnetic ordering in the latter compound, aegirine, also is complex and is best described by two different spin states, a commensurate one with C2??/c?? symmetry and an incommensurate one, best being described by a spin density wave, oriented within the (1 0 1) plane. 相似文献
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在含于磁铁矿中的四方对称结构氧化铅中观察到柏格斯矢量为２／１１（３１０）的（１１）层错，这些层错平行排列并相互交截，穿插形成沿（１００）方向的调制结构，调制波的平均波长约为１００ｎｍ同时，由多相关性区域的选区电子衍射图测定了磁铁矿中四方和正交氧化铅及方铁矿的取向关系。 相似文献