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运用透射电镜技术,发现了三方晶系直氟碳钙铈矿(Synchysite)多型和微孪晶的存在,确定其中的多型有两种,即6R和3R多型,在3R多型中发现有微孪晶存在,这种微孪晶属(0001)孪晶面的面律(旋转)孪晶。由于直氟碳钙铈矿是钙铈氟碳酸盐系列矿物的一个端员组分,因此,对其多型和微孪晶的研究,有助于揭示该系列中间组分矿物多型和微孪晶的形成机理。 相似文献
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采用CM12透射电镜,对我国四川昌北M稀土矿床中的氟碳钙矿微结构特征作了电子衍射分析和晶格象观察,揭示出氟碳钙铈矿晶体中混合多型体的堆垛序列,在不同部分观测到不同的多型体,其中以氟碳钙铈矿6R多型为常见普通多型体。本次工作发现42R,48R和16H三种新多型,并进一步证明,氟碳钙铈矿晶体中存在的多型结构相当复杂,但以长周期堆垛形成的多型体出现的几率要比短周期堆垛的多型体少得多。 相似文献
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钙-铈氟碳酸盐矿物系列中新规则混层矿物的晶格象研究 总被引:5,自引:2,他引:5
本文用电子衍射和晶格象技术研究钙-铈氟碳酸盐矿物微结构特征。除确定有氟碳铈矿(B),氟碳钙铈矿(BS)、伦琴矿(BS_2)和B_3S_2规则混层矿物外,还首次发现了9种B_mS_n(m≥++n)型新的规则混层矿物。这些新规则混层矿物,往往以共格的形式共存于一个自然晶粒之中。大量的SAED和晶格象揭示了这类稀土矿物各成员之间的相互结构关系。研究表明:钙-铈氟碳酸盐矿物系列中矿物衍生体的微结构特征及其变化是相当复杂的,它们是由不同组分的氟碳铈矿(B)和直氟碳钙铈矿(S)的结构单元层在c轴方向通过不同比例堆垛方式,形成一系列新规则混层矿物及多型。 相似文献
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氟碳钙铈矿结构中晶体缺陷的高分辨电镜研究 总被引:1,自引:1,他引:1
用高分辨电子显微术(HREM)研究了氟碳钙铈矿(BS)晶体结构中的无序堆垛和体衍交生现象,结果表明该矿物的衍生多晶体是由钙-铈氟碳酸盐矿物中不同组分的氟碳铈矿(B)和直氟碳钙铈矿(S)结构单元层沿c方向无序堆垛而成。高分辨结构象揭示出氟碳钙铈矿衍生多晶体的微结构特征。讨论了氟碳钙铈矿结构中的堆垛层错等晶体缺陷现象。 相似文献
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钙稀土氟碳酸盐矿物中新多型体的HREM研究 总被引:1,自引:0,他引:1
利用高分辨电子显微术(HREM)研究了钙稀土氟碳酸盐矿物系列中氟碳铈矿(B)/直氟碳钙铈矿(S)的混层结构。发现并确定了B_5S_2(IH,3R)、B_5S_4(3R,6R)和B_(18)S_(10)(IH)规则混层矿物中5种新多型的晶体结构类型、晶胞参数以及理论晶体化学式等。HREM研究揭示出,在B_mS_n(m>n)型规则混层矿物新多型体的结晶过程中,成矿地质环境是复杂的。阐明了这些多型体是由该系列矿物中的氟碳铈矿(B)和直氟碳钙铈矿(S)结构单元层以不同比例沿c轴方向的有序堆垛构成。 相似文献
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J. Ingrin 《Physics and Chemistry of Minerals》1993,20(1):56-62
A study of polytypism in synthetic polycrystalline pseudowollastonite has been made using conventional and high resolution transmission electron microscopy (TEM and HRTEM). Three polytypes of 2, 4 and 6-layers coexist in the one sample in the form of lamellae parallel to (001). From the electron microscopy images the lamellae are interpreted as combinations of the stacking fault vectors: 1/3 [010], 1/6 [310] and 1/6 [3 $\bar 1$ 0], which are probably all equivalent at high temperatures. The polytype lamellae are stable even after prolonged annealing at high temperatures greater than 1700K. These observations suggest that the most frequently reported 4-layer polytype is not the only high-temperature stable polytype. No evidence of melt is detected in samples annealed in the regime where premelting behaviour of pseudowollastonite has previously been reported (above 1600 K). 相似文献
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D. Ayres 《Australian Journal of Earth Sciences》2013,60(3):273-278
156 samples of naturally‐occurring molybdenite from 87 localities in Australia have been examined to determine the distribution of the hexagonal (2H1) and rhombohedral (3R) polytypes. 90% of the specimens examined are 2H1 polytypes, the remainder being 3R and mixtures of 2H1 and 3R polytypes. The 3R and mixed polytypes are more abundant in porphyry copper deposits or as disseminations, in veins, and in garnet‐quartz pipes in granite. 2H1 polytypes are the sole modification observed in pegmatites, quart‐pegmatite pipes, simple quartz veins, and skarns. The highest average concentrations of rhenium are in molybdenite from porphyry copper deposits, quartz porphyry pipes, skarn deposits, garnet‐quartz pipes, and pegmatites. Low concentrations occur in molybdenite which is disseminated or in quartz veins in granite and in quartz or pegmatitic pipes. Molybdenites in which the 2H1 polytype is dominant have a lower average rhenium content than those with dominant 3R polytype. 相似文献
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The maximum entropy method (MEM) is used here to get an insight into the electron density [ρ(r)] of phengites 2M
1 and 3T, paying special attention to the M1-formally empty site and charge distribution. Room temperature single crystal X-ray diffraction
data have been used as experimental input for MEM. The results obtained by MEM have been compared with those from conventional
structure refinement which, in turn, has provided the prior-electron density to start the entropy maximization process. MEM
reveals a comparatively non-committal approach, able to produce information related to the M1-site fractional occupancy, and
yields results consistent with those from the difference Fourier synthesis, but free of the uncertainties due to the abrupt
truncation of the series. The charge distribution is investigated by means of the notion of ‘‘site basin’’, i.e., those site-centered
volumes delimited by a surface such as ∇ρ·n = 0. In particular, we observe: (1) the overall partitioning of the basin total charge between cation and anion sites, and
the interlayer site charge seems to depend on sample composition, and (2) the apical-oxygen plane total basin charge and hydroxyl
basin charge are presumably related to the polytype. The MEM-determined electron density does not allow full exploration of
the critical points for very complex structures as micas, insofar as conventional room temperature experimental diffraction
data are used. 相似文献
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副硫锑钴矿是硫锑钴矿(CoSbS)的一个同质多象变体。1970年由卡布里(L. J. Cabri)等人发现于加拿大安大略州,他们对该矿物进行了化学分析及X射线粉晶分析等研究。测得该矿物属斜方晶系,a=5.764,b=5.952,c=11.635,空间群为Pbca,Z=8。 相似文献