云南磷铝石谱学特征研究

使用电子探针、X射线粉晶衍射仪、傅里叶变换红外光谱仪、激光拉曼光谱仪、紫外可见分光光度计等仪器,对最近在云南发现的一种达到宝石级别的磷铝石进行了化学成分、矿物组成、红外吸收光谱、拉曼光谱、紫外可见吸收光谱等方面的研究。化学成分分析结果表明,该磷铝石的主要化学成分为P和Al,并含有少量的Fe和V;X射线粉晶衍射结果显示,该磷铝石的矿物成分主要为磷铝石,杂质较少;红外光谱与拉曼光谱分析均检出磷酸根基团的特征峰,红外光谱分析还显示有结晶水与结构水的存在;紫外可见吸收光谱在300和420 nm附近的吸收归属于Fe3+,630 nm附近较宽缓的吸收带由Fe3+和V3+共同产生。并将磷铝石与绿松石进行了谱学方面的对比分析,以便更好地区分两者。     

冀东迁滦地区沉积变质型铁矿床变质作用程度：来自石榴子石的制约

石榴子石是冀东地区沉积变质铁矿中常见的变质矿物之一。本文采集迁安-滦县地区代表性铁矿中含有石榴子石的岩石样品,对其石榴子石进行电子探针和X-射线粉晶衍射分析,得出司马地区为角闪岩相,杏山-黄柏峪一带为角闪岩-麻粒岩相,水厂-大石河地区为麻粒岩相,这与前人对迁滦地区用主要矿物共生组合等来研究变质相的结论相一致;同时迁滦地区沉积变质铁矿中石榴子石的端元组分和晶胞参数a0随变质程度的增加呈规律性变化: 司马地区的铁铝榴石+钙铝榴石→杏山-黄柏峪一带的铁铝榴石→水厂-大石河一带铁铝榴石+镁铝榴石,其晶胞参数a0值逐渐减小。因此在沉积变质型铁矿床中,变质矿物石榴子石的化学成分及晶胞参数特征对不同地区的变质程度具有示踪意义。     

浙江青田石几个新品种的矿物学特征初步研究

青田蓝花钉、蓝花星、紫罗兰、山炮绿属于浙江青田石的新品种。通过X荧光、电子探针、红外吸收光谱、差热、X射线粉晶衍射、扫描电镜等方法分析测试表明，封门青品种主要由较纯叶蜡石组成，化学成分以富碱、富铝、贫硅为特征；蓝花钉品种蓝色团块由微晶刚玉组成；蓝花星品种的粒状矿物主要为富铁蓝线石；紫罗兰品种紫色花星成分为贫铁蓝线石，其中浅粉红色或灰白色斑点矿物主要为红柱石；山炮绿主要矿物为含铬绢云母，次要矿物为石英，且含少量黄铁矿、红柱石、伊利石等，因其色艳质细而成为青田雕刻石的又一新品种。     

苏州高岭土中的变磷铝石及其成因探讨

变磷铝石(Al[PO_4].2H_2O)为含水的铝磷酸盐矿物,其化学成分和磷铝石(Al[Po_4].2H_2O)相同,但晶体结构截然不同,两者为同质二相体,前者属单斜晶系,后者属斜方晶系。变磷铝石结构中的Al可被Fe~(3+)置换,和红磷铁矿(Fe[PO_4].2H_2O)共同组成类质同象系列。变磷铝石在自然界中的产状国内很少报导。经笔者研究在苏州高岭土矿体的底部发现富集有一种球状变磷铝石,其产状特征对研究苏州高岭土成矿后期的淋滤改造很有意义。本文报导该矿物的矿物学特征并对其成因进行了探讨。     

南平花岗伟晶岩中的羟磷铝锂石矿物学研究

羟磷铝锂石是南平稀有金属花岗伟晶岩中的重要标型矿物，可分为原生和次生两大类，最主要的是前者，一般呈块体状，共生矿物主要有销长石，钾长石，锂辉石，铌钽矿物。本文详细讨论了南平羟磷铝锂石的化学成分、Ｘ射线粉晶衍射资料、红外光谱和差热分析结果。南平原生羟磷铝锂石的交代蚀变作用十分发育，按其先后顺序，交代蚀变矿物组合有：石英—叶钠长石、次生羟磷铝锂石、细晶销长石—石英—次生磷灰石、次生复杂磷酸盐矿物和绢云母。     

内蒙古阿拉善地区绿色戈壁玛瑙的宝石学特征与致色成因研究

内蒙古阿拉善地区经历数亿年的地质活动,产出颜色丰富且结构致密的戈壁玛瑙。通过常规宝石学测试、偏光显微镜及扫描电镜观察、X射线粉晶衍射、电子探针、红外光谱及紫外-可见光-近红外分光光度计等测试分析方法对绿色戈壁玛瑙的宝石矿物学特征及致色成因进行了深入研究。肉眼观察,阿拉善绿色玛瑙呈深绿色至褐绿色,微透明至不透明,相对密度、折射率、摩氏硬度等均符合石英质玉石的特点。偏光显微镜观察,绿鳞石富集于表层,并向内部呈放射状生长;方解石与石英均为隐晶质结构。扫描电镜观察,绿鳞石呈颗粒状分布于石英及方解石之间。X射线衍射分析结果表明,绿色戈壁玛瑙的物相组成主要为石英、方解石和绿鳞石。电子探针分析结果表明绿鳞石的主要化学组成为SiO₂、FeO、Al₂O₃、K₂O和MgO。红外光谱分析也显示存在绿鳞石对应基团的特征峰。表层绿鳞石在紫外-可见光-近红外分光光度计下显示出Fe²⁺与Fe³⁺的特征光谱,Fe²⁺与Fe³⁺之间的电荷转移是其...     

广西邕宁良庆铁陨石

一九七一年在广西邕宁县良庆地区上泥盆统桂宁灰岩层中发现一块重约50kg陨铁。陨铁的相对密度为5.2(实测)。矿物成分是铁纹石、镍纹石、陨硫铁,赤铁矿、磁铁矿、磷铁镍矿、硫铁镍钴矿(?)、方硫铁镍矿。对各矿物均做了电子探针化学成分分析,X-射线粉晶及衍射分析。     

新疆库鲁克塔格兴地塔格群中石榴石的矿物学特征研究

通过电子探针测试和X射线粉晶衍射分析,对新疆库鲁克塔格兴地塔格群中红色石榴石样品的矿物学特征进行了研究。电子探针测试结果显示,不同变质期次形成的石榴石,铁铝榴石端员组分均由核部到边部逐渐增加,锰铝榴石均由核部向边缘逐渐减少,镁铝榴石由核部到边部逐渐增加,钙质系列石榴石总含量很低且变化稳定。研究表明,兴地塔格群石榴石由核部至边缘生长温度整体上升,形成压力基本稳定,石榴石形成环境的变质程度逐渐提高。根据X射线粉晶衍射数据计算出石榴石的晶胞参数较理论值大,是由Ca2+、Mn2+两种大半径离子对Fe2+的置换数目多于小半径Mg2+对Fe2+的置换引起的。     

安徽殿庵山绿松石的宝石学特征研究

安徽省殿庵山地区绿松石属于新近发现的小规模开采的玉石资源。采用电子探针、扫描电子显微镜、傅里叶变换红外光谱仪、紫外一可见光谱仪等测试方法,重点就该地区绿松石的化学成分、矿物组成、微结构、红外吸收光谱、紫外一可见吸收光谱等特征进行综合对比研究。结果表明,该地区绿松石的化学成分以贫Si、相对富Fe为特征,随着FeOT／CuO比值的递增,绿松石色调由蓝逐渐变绿。该类绿松石以结核状、细脉状产出,主要为微晶和鳞片状结构,部分为放射纤维状结构、团粒状结构及皮壳状结构。该类绿松石孔洞内微晶普遍发育,主要以毛发状、微针状、短柱状及板片状相互交织结晶生长,殿庵山绿松石整体显示风化淋滤型矿床所特有的特征。笔者对绿松石的颜色成因及矿床成因进行初步探讨。     

桂林某些岩溶洞穴矿物

洞穴矿物是在洞穴环境下由冷的地下水活动所产生的表生化学沉积作用产物。桂林地区(包括兴安—桂林—阳朔一带)岩溶洞穴中的次生矿物已发现有方解石、文石、石膏、氢氧磷灰石、磷铝石、磷铝钾石、磷钙铝石和半蛋白石等。文章中列举了这些矿物的偏光显微镜、化学分析、x光粉晶衍射、差热分析和扫描电镜等鉴定结果,并概要地探讨了其成因。      

Iron in hibonite: a spectroscopic study

A combined polarized optical absorption and ⁵⁷Fe Mössbauer spectroscopy study of inhomogeneous, Fe and Ti-bearing terrestrial hibonite (Madagascar) has been carried out. Mössbauer data were also obtained on synthetic material prepared under different fo₂ inconditions. A strong band at 5400 cm^-1 in the near-infrared spectra is attributed to spin-allowed d-d transitions of Fe²⁺ occupying tetrahedral sites within the spinel blocks of the hibonite crystal structure. There is agreement with the Mössbauer results, showing that ferrous iron orders onto a single, low-coordinated crystallographic site. Ferric iron is distributed over several positions, but shows strongest preference for the large bipyramidal site located outside the spinel blocks. The colour and pleochroism of hibonite in thin section is related to a prominent UV absorption edge, and several broad absorption bands in the visible spectrum ascribed to charge-transfer transitions involving Fe²⁺, Fe³⁺ and Ti⁴⁺.     

Water in the structure of minerals from mantle peridotites as controlled bythermal and redox conditions in the upper mantle

Hydrous species and the amount of water (OH^? ions and crystal hydrate H₂O) in structures of nominally anhydrous rock-forming minerals (olivine, ortho- and clinopyroxenes) were studied with Fourier spectroscopy in peridotite nodules (19 samples) from Cenozoic alkali basalts of the Baikal-Mongolia region (Dariganga Plateau, Taryat Depression, and Vitim Plateau). Single-crystal samples oriented relative to the crystallographic axes of minerals were examined with an FTIR spectrometer equipped with an IR microscope at the points of platelets free from fluid inclusions. FTIR spectra were measured in regions of stretching vibrations of OH^? and H₂O (3800–3000 cm^?1) and deformation vibrations of H₂O (1850–1450 cm^?1). The water content in mineral structures was determined from integral intensities. To estimate the conditions of entrapment and loss of structural water in minerals, their chemical composition, including Fe²⁺ and Fe³⁺ contents, was determined with an electron microprobe analysis and Mössbauer spectroscopy. The bulk chemical composition of some nodules was determined with XRF and ICP MS. The total water content (OH^? + H₂O) varies from 150 to 1140 ppm in olivines, from 45 to 870 ppm in clinopyroxenes, and from 40 to 1100 ppm in orthopyroxenes. Both water species in the mineral structures are retained down to a depth of 150–160 km in wide temperature and pressure ranges (1100–1500 °C, 32–47 kbar) at the oxygen fugacity of ?1.4 to ?0.1 log units relative to that of the quartz-fayalite-magnetite buffer.     

Variation of infrared absorption spectra in the system Bi2Al4−x Fe x O9 (x = 0–4), structurally related to mullite

The crystal structure of Bi₂Al_4−x Fe _x O₉ compounds (x = 0–4) has striking similarities with the crystal structure of mullite. A complete substitution of Al by Fe³⁺ in both octahedral and tetrahedral sites is a particular structural feature. The infrared (IR) spectra of the Bi₂M₄O₉ compounds (M = Al, Fe³⁺) are characterised by three band groups with band maxima in the 900–800, 800–600 and 600–400 cm⁻¹ region. Based on the spectroscopic results obtained from mullite-type phases, the present study focuses on the composition-dependent analysis of the 900–800 cm⁻¹ band group, which is assigned to Al(Fe³⁺)–O stretching vibrations of the corner-sharing MO₄ tetrahedra. The Bi₂Al₄O₉ and Bi₂Fe₄O₉ endmembers display single bands with maxima centred at 922 and 812 cm⁻¹, respectively. Intermediate Bi₂Al_4−x Fe _x O₉ compounds exhibit a distinct splitting into three relatively sharp bands, which is interpreted in terms of ordering effects within the tetrahedral pairs. Thereby the high-energy component band of the band triplet relates to Al–O–Al conjunctions and the low-energy component band to Fe–O–Fe conjunctions. The intermediate band is assigned to stretching vibrations of Al–O–Fe or Fe–O–Al configurations of the corner-sharing tetrahedral pairs. Bands in the 800–600 cm⁻¹ range are assigned to low-energy stretching vibrations of the MO₄ tetrahedra and to M–O–M bending vibrations of the tetrahedral pairs. Absorptions in the 600–400 cm⁻¹ range are essentially determined by M–O stretching modes of the M cations in octahedral coordination.     

利用吸收和发光光谱技术分析高温高压天然富氢钻石的鉴定特征

对不同类型褐色钻石进行高温高压处理和结构特性研究是钻石研究中的难点和重点之一。前人对富氢钻石的研究主要集中于其特殊的生长结构以及其形成环境的探讨,而对富氢钻石经高温高压处理后的变化特征鲜有涉及。本文对经高温高压处理前后的富氢钻石的红外光谱、紫外可见吸收光谱以及光致发光光谱等谱学特征进行了对比,研究其鉴定特征。结果表明:高温高压处理前后的富氢钻石的光谱特征具有明显差异,特别是红外光谱,经处理后的钻石中与氮氢有关的吸收峰如3310 cm~(-1)、3232 cm~(-1)、3189 cm~(-1)等明显减弱甚至消失,并出现与孤氮有关的新的2688 cm~(-1)吸收峰;紫外可见光吸收光谱中,经处理的褐色钻石中的无选择性吸收(钻石呈褐色的原因)变为孤氮的典型吸收,即550 nm至短波的吸收以及N_3中心(415 nm)的吸收均明显增强,因此钻石也由原来的褐色变为黄色。钻石经处理前后的光致发光光谱中,与氮原子有关的缺陷类型、峰的强度以及缺陷组合也有变化。本文获得的光谱变化特征,为准确鉴定高温高压处理的黄色富氢钻石提供了依据,也为解释与氢和氮相关的晶格缺陷在高温条件下的变化机理提供了理论基础。     

Spectroscopic standard for tetrahedrally coordinated ferric iron: γ LiAlO2:Fe3+

γ LiAlO₂ doped with Fe³⁺ in the tetrahedral site has been examined by extended X-ray absorption fine structure (EXAFS) analysis, and Mössbauer and optical spectroscopy. The isomer shift (IS) is ?0.026 mm/s (Fe-Pd); the quadrupole splitting (QS) is 0.62 mm/s. Anisotropic optical absorption is prominent at ～391, 452, and 463 nm. The K-edge absorption spectrum shows a prominent absorption near 7,113 ev typical of tetrahedrally coordinated Fe³⁺.     

Mie scattering and charge transfer phenomena as causes of the UV edge in the absorption spectra of natural and synthetic almandine garnets

 The UV edge in the electronic absorption spectra of minerals, in many cases influencing their colour, is generally interpreted as the low-energy wing of very strong UV bands caused by ligand–metal charge transfer (CT) transitions (e.g. Burns 1993). However, Mie scattering theory shows that the presence of randomly distributed submicroscopic inclusions with narrow size distribution and a refractive index n _i in a matrix with different refractive index n _m may give rise to a λ-dependent, band-like scattering (e.g. Kortüm 1969). Such scattering bands have so far not been considered as contributing to the UV edge. Single-crystal electronic absorption spectra of eight natural almandine-rich garnets (Alm₆₀–Alm₈₈), two synthetic almandine samples (Alm₁₀₀), all of different colours, and synthetic spessartine were studied by means of a Zeiss microscope-spectrometer in the range 40 000–20 000 cm⁻¹. Special techniques of spectral measurements with crossed analyzer and polarizer, which enable the registration of the scattering effect directly, were used as well. Four of the above garnets were also investigated using transmission electron microscopy. Different types of inclusions, from 10 to several 100 nm in size, were observed in the garnet matrices. They are abundant in cores of synthetic garnets, but very rare in most natural almandines studied. Electronic absorption spectra of the natural almandine garnets show largely varying UV edge position and, hence, intensity at a given wavenumber which correlates with the intensities of spin-forbidden dd bands of Fe³⁺ ions at 27 000 and 28 000 cm⁻¹, superimposed on the long energy slope of the UV absorption. There are also positive correlations between Ti⁴⁺ and Fe³⁺ content, the latter recalculated on the basis of garnet stoichiometry, and UV edge intensity. Thus, the presence of Ti⁴⁺ and Fe³⁺ ions in octahedra, even in very low concentrations (0.0n at. pfu), leads to CT phenomena, that probably involve Fe²⁺ ions in edge-shared dodecahedral position and intensifies ligand- to-metal CT. The different colours of natural almandine garnets with similar Fe²⁺ contents studied here are caused by this effect. Consistent with the absence of inclusions in most natural garnets studied, λ-dependent scattering plays no role in their UV absorption. In contrast, in synthetic almandine and spessartine crystals, a different intensity of UV absorption was observed in inclusion-free rims and inclusion-enriched cores. Some of the latter demonstrate typical scattering patterns when measured at crossed polarizers. Received: 10 April 2001 / Accepted: 27 September 2001     

Optical spectroscopy study of natural Fe, Ti-bearing calcic amphiboles

Over thirty samples of natural Ti-bearing amphiboles with Ti- and Fe-contents ranging from 0.111 to 0.729 atom per formula unit (a.p.f.u.) and from 0.479 to 2.045 a.p.f.u., respectively, were studied by means of optical absorption spectroscopy and microprobe analysis. Thirteen samples were also studied by Mössbauer spectroscopy. A strong pleochroic absorption edge, causing the dark brown colours of Ti-bearing amphiboles, is attributed to ligand-metal and metal-metal charge transfer transitions involving both iron and titanium ions (O^2?→ Fe³⁺, Fe²⁺, O^2?→ Ti⁴⁺ and Fe²⁺ + Ti⁴⁺→ Fe³⁺ + Ti³⁺). A broad intense Y-polarized band ～22?000?cm^?1 (ν_1/2?≈?3700?cm^?1) in spectra of two low iron amphiboles with a relatively low Fe³⁺/Fe_total ratio, both from eclogite-like rocks in kimberlite xenoliths, was attributed to electronic Fe²⁺(M3) + Ti⁴⁺(M2)→Fe³⁺(M3)+Ti³⁺(M2) IVCT transitions. The IVCT bands of other possible ion pairs, involving Ti⁴⁺ and Fe²⁺ in M2 and M1, M4 sites, respectively, are presumed to be at higher energies, being obscured by the absorption edge.     

Spectroscopic active IVFe3+–VIFe3+ clusters in spinel–magnesioferrite solid solution crystals: a potential monitor for ordering in oxide spinels

Optical absorption spectra (OAS) of synthetic single crystals of the solid solution spinel sensu stricto (s.s.)–magnesioferrite, Mg(Fe³⁺Al_1???y)₂O₄ (0?y?≤ 0.3), have been measured between 12 500 and 28 500?cm^?1. Chemical composition and Fe³⁺ site distribution have been measured by electron microprobe and Mössbauer spectroscopy, respectively. Ferric iron is ordered to the tetrahedral site for samples with small magnesioferrite component, and this ordering is shown to increase with magnesioferrite component. The optical absorption spectra show a strong increase in band intensities with Fe³⁺→Al substitution. Prominent and relatively sharp absorption bands are observed at 25 300 and 21 300?cm^?1, while less intense bands occur at 22 350, 18 900, 17 900 and 15 100?cm^?1. On the basis of band energies, band intensities and the compositional effect on band intensity, as well as structural considerations, we assign the observed bands to electronic transitions in ^IVFe³⁺–^VIFe³⁺clusters. A linear relationship (R ²= 0.99) between the α_net value of the absorption band at 21 300?cm^?1 and [^IVFe³⁺]?·?[^VIFe³⁺] concentration product has been defined: α_net=2.2?+?15.8 [^IVFe³⁺]?·?[^VIFe³⁺]. Some of the samples have been heat-treated between 700 and 1000?°C to investigate the relation between Fe³⁺ ordering and absorption spectra. Increase of cation disorder with temperature is observed, which corresponds to a 4% reduction in the number of active clusters. Due to the high spatial resolution (??～?10?μm), the OAS technique may be used as a microprobe for determination of Fe³⁺ concentration or site partitioning. Potential applications of the technique include analysis of small crystals and of samples showing zonation with respect to total Fe³⁺ and/or ordering.     

Polarized electronic absorption spectra of synthetic (Mg,Fe)-orthopyroxenes,ferrosilite and Fe3+-bearing ferrosilite

The assignment of spin-allowed Fe²⁺-bands in orthopyroxene electronic absorption spectra is revised by studying synthetic bronzite (Mg_0.8 Fe_0.2)₂Si₂O₆, hypersthene (Mg_0.5 Fe_0.5)₂Si₂O₆ and ferrosilite (Fe₂Si₂O₆). Reheating of bronzite and hypersthene single crystals causes a redistribution of the Fe²⁺-ions over the M1 and M2 octahedra, which was determined by Mössbauer spectroscopy and correlated to the intensity change of the spin-allowed Fe²⁺ d-d bands in the polarized absorption spectra. The 11000 cm^-1 band is caused by Fe²⁺ in M1 (⁵B_2g→⁵A_1g) and Fe²⁺ in M2 (⁵A₁→⁵A₁), the 8500 cm^-1 band by Fe²⁺ in M1 (⁵B_2g→⁵B_1g) and the 5000 cm^-1 band by Fe²⁺ in M2 octahedra (⁵A₁→⁵B₁). The Fe²⁺-Fe³⁺ charge transfer band is identified at 12500cm^-1 in the spectra of synthetic Fe³⁺ -Al bearing ferrosilite. This band shows a strong γ-polarization and therefore is caused by Fe²⁺ -Fe³⁺-ions in edge-sharing octahedra.