共查询到19条相似文献，搜索用时 140 毫秒
1.
佛顶山钙铬榴石分布特征及其找矿意义 总被引：1，自引：0，他引：1
本区钙铬榴石含钙铝榴石分子。两者组成类质同像系列矿物。颜色和透明度随成分变化而变化。目前找到的钙铬榴石成翠绿色十分美丽，但是，透明者少，粒度均小于４ｍｍ，达不到宝石级标准，但埋于被积层中的含钙铬榴石铬透辉石岩的转石风化强烈，钙铬榴石易于脱出，晶体保存完整，采选容易，是寻找宝石的理想地区。 相似文献
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钙铬榴石是石榴石族中的稀有品种,文中对近年新发现的西藏东部钙铬榴石样品进行了矿物学特征分析和呈色机理探讨。采用扫描电镜观察钙铬榴石样品的显微结构并进行能谱分析,结果表明其内部含有颗粒很小的铬铁矿和石英包裹体,以及裂隙中充填的方解石和与钙铬榴石为类质同象连续关系的钙铝榴石,从而为该钙铬榴石的夕卡岩成因和产状提供了佐证。采用紫外-可见光分光光度计对样品进行吸收光谱测试,对其颜色指数进行了定量分析,所得样品颜色的主波长为530～540nm,饱和度为80%左右,进而分析了钙铬榴石的颜色主要由Cr3+引起,其呈色机理归因于Cr3+的d轨道电子跃迁。 相似文献
3.
金伯利岩中的镁铝榴石是寻找金刚石的重要指示矿物。镁铝榴石的Cr2O3、CaO等氧化物含量及其颜色、折光率等物理光学性质可作为这种石榴石的标型特征。 本文将山东、辽宁等地金伯利岩中的石榴石的电子探针分析结果按分子数配分的方法计算了端员分子百分数及其他化学参数。用MPV—1显微光度仪测定了石榴石的透射率色散值,通过计算求得颜色指数。按Dawson等人的分类,本次研究样品以铬镁铝榴石为主,其次是低钙-铬镁铝榴石、钙铬-镁铝榴石和镁铬-钙铬-镁铝榴石;钛镁铝榴石和钙镁铝-铁铝榴石等少量。作者用铬、钙、镁三组份数绘制了石榴石与金刚石关系判别图解,分为五个区(A、B、C、D、E)、落入A区的低钙-铬镁铝榴石、铬镁铝榴石和钙铬-镁铝榴石等与金刚石的形成关系最密切。 相似文献
4.
石榴石族是一种广泛分布的造岩矿物。分子式为:R_3~2+R_2~3+Si_3O_(12),其中R~(2+)=Ca、Fe~(2+)、Mg、Mn……,R~(3+)=Al、Fe~(3+)、Cr等。地质上常见的是两个系列,即:铝榴石系列(镁铝榴石、铁铝榴石、锰铝榴石)与铬钙铁榴石系列(钙铬榴石、钙铝榴石、钙铁榴 相似文献
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石榴石宝石是石榴石(garnet)族矿物的总称,岛状硅酸盐、等轴晶系矿物。根据其化学成分可划分成2个系列。铝质系列镁铝榴石:橙红色、红色铁铝榴石:橙红—红色、紫红—红紫色锰铝榴石:橙色—橙红色钙质系列钙铝榴石: 相似文献
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辽宁瓦房店金刚石矿区金伯利岩中的石榴石一直被当作镁铝榴石。为了确定矿区颜色复杂的石榴石种类,本文对矿区的石榴石进行了系统的采样分析,测定了112件石榴石样品的晶胞参数、50件样品的微区化学成分和40件样品的红外光谱。利用石榴石晶胞参数、红外光谱、化学成分和化学分子式方法对矿区石榴石进行分类,结果显示:晶胞参数分类法误差大,容易得出错误结论;红外图谱分类法准确度不高,只能作为参考方法;化学成分分类法太过笼统,达不到详细划分石榴石种类的目的;化学分子式分类法可把矿区的石榴石详细划分6个矿种:镁钙铁-铝铬铁榴石、镁铁钙-铝铬铁榴石、镁钙铁-铝铬榴石、镁钙-铝铬铁镁榴石、镁铁钙-铝铬榴石、镁铁钙-铝铁铬榴石,每种石榴石都充分反映了A、B离子的种类及占位特征,是4种分类方法中最为科学的方法。研究认为瓦房店金刚石矿区金伯利岩中石榴石A端元成分以Mg2+离子占位为主;B端元成分以Al3+离子占位为主。由于阳离子替代普遍,A、B端元成分复杂,瓦房店金伯利岩中不存在单纯意义上的镁铝榴石。 相似文献
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镁铝榴石,英文名称Pyrope来自希腊语,寓意矿物呈火焰般鲜红色。自古以来,镁铝榴石宝石颇为人民所赏识和珍藏。在宝石学上,镁铝榴石宝石归属主要宝石(Major gem)类,并在世界宝石市场上一直是畅销的中档宝石品种。江苏含铬镁铝榴石宝石最早为江苏第六地质队发现,已进行很多工作。作者在此 相似文献
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镁铝榴石,英文名称Pyrope来自希腊语,寓意矿物呈火焰般鲜红色。自古以来,镁铝榴石宝石颇为人民所赏识和珍藏。在宝石学上,镁铝榴石宝石归属主要宝石(Majorgem)类,并在世界宝石市场上一直是畅销的中档宝石品种。 江苏含铬镁铝榴石宝石最早为江苏第六地质队发现,已进行很多工作。作者在此基础上,拟对其宝石矿物学特征作一报导。 一、地质产状 相似文献
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镁铝榴石是找寻金刚石的一种重要的指示矿物。本文应用了聚类分析方法，以镁铝榴石中的钙组分、铬组分、镁组分和镁组分（铁铝榴石）4种成分参数作变量，将56个样品分为6类，讨论了每一类样品的化学成分特点，确定了它们的标型意义，并应用多元判别分析得出了划分这6类和对未知样品进行判别归类的一组判别函数。 相似文献
11.
Anastasia Chopelas 《Physics and Chemistry of Minerals》2005,32(8-9):525-530
Single-crystal Raman spectra of synthetic end-member uvarovite (Ca3Cr2Si3O12) and of a binary solution (59% uvarovite, 41% andradite) have been measured using single crystal techniques. For each of
these garnets, 22 and 21 of the 25 Raman modes were located, respectively. The spectra for uvarovite garnets closely resemble
those of the other calcic garnets, grossular, and andradite. The modes for uvarovites do not fit into the same trends as established
by the other five anhydrous end-member garnets: the high energy “internal” Si–O modes do not depend on lattice constant in
uvarovite. They exceed frequencies for both andradite and grossular. This is likely due to the large crystal field stabilization
energy of trivalent chromium. The low energy and midrange modes are at similar frequencies to the other calcic garnets. 相似文献
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Shreeram Suman Sahu Sahendra Singh Jyoti Sankar Satapathy 《Journal of the Geological Society of India》2018,92(3):291-297
Emerald, the green gem variety of beryl (Be3Al2Si6O18), is the third most valuable gemstone after diamond and ruby. The green colour appearance of the crystal is due to trace of Cr3+ and V3+, which replaces Al3+ ions in the crystal lattice of beryl. The hue of green colour of emerald depends on the quantity of Cr3+ and V3+ present in the crystal. Be is incorporated along with Cr and/or V during the process of crystallization. Since Be is relatively rare in the upper continental crust, therefore specific geological and geochemical parameters are required for Be to be incorporated in the crystal lattice of emerald.The present work was carried out to understand the lithological and structural control of emerald occurrences in and around Gurabanda area within the Singhbhum shear zone (SSZ) of Singhbhum crustal province, eastern India. The biotite and serpentine schist belong to the Paleoproterozoic Dhanjori Group and constitute the major lithology of the area. Pegmatite and biotite schist contains a variety of gem minerals in abundance in the area and the gem quality emerald occur at the contact zone of quartz vein and mica-schist. Lithology and structure are the main controlling factors of gem-mineralization in the study area. The study indicates that regional metamorphism and deformation processes along the shear zone played a significant role in the formation of emerald deposits. It is inferred that Singhbhum shear zone facilitated a favourable condition, where the Be bearing pegmatites interacted with Cr bearing mica schist or ultramafic rocks to produce emerald crystal. 相似文献
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Synthetic, flux-grown uvarovite, Ca3Cr2 [SiO4]3, was investigated by optical methods, electron microprobe analysis, UV-VIS-IR microspectrometry, and luminescence spectroscopy. The crystal structure was refined using single-crystal X-ray CCD diffraction data. Synthetic uvarovite is optically isotropic and crystallizes in the “usual” cubic garnet space group Ia3¯d [a=11.9973 Å, Z=8; 21524 reflections, R1=2.31% for 454 unique data and 18 variables; Cr–O=1.9942(6), Si–O=1.6447(6), Ca–Oa=2.3504(6), Ca–Ob= 2.4971(6) Å]. The structure of Ca3Cr2[SiO4]3 complies with crystal-chemical expectations for ugrandite group garnets in general as well as with predictions drawn from “cubically averaged” data of non-cubic uvarovite–grossular solid solutions (Wildner and Andrut 2001). The electronic absorption spectra of Cr3+ in trigonally distorted octahedra of synthetic uvarovite were analyzed in terms of the superposition model (SM) of crystal fields. The resulting SM and interelectronic repulsion parameters are =9532 cm?1, =4650 cm?1, power law exponent t 4=6.7, Racah B35=703 cm?1 at 290 K (reference distance R 0=1.995 Å; fixed power law exponent t 2=3 and spin-orbit parameter ζ=135 cm?1). The interelectronic repulsion parameters Racah B 55=714 cm?1 and C=3165 cm?1 were extracted from spin-forbidden transitions. This set of SM parameters was subsequently applied to previously well-characterized natural uvarovite–grossular solid solutions (Andrut and Wildner 2001a; Wildner and Andrut 2001) using their extrapolated Cr–O bond lengths to calculate the energies of the spin-allowed bands. These results are in very good agreement with the experimentally determined band positions and indicate the applicability of the superposition model to natural 3d N prevailing systems in geosciences. Single-crystal IR absorption spectra of synthetic uvarovite in the region of the OH-stretching vibration exhibit one isotropic absorption band at 3508 cm?1 at ambient conditions, which shifts to 3510 cm?1 at 77 K. This band is caused by structurally incorporated hydroxyl groups via the (O4H4)-hydrogarnet substitution. The water content, calculated using an integral extinction coefficient ?=60417 cm?2 l mol?1, is c H2O=33 ppm. 相似文献
14.
A. Abduriyim F. L. Sutherland E. A. Belousova 《Australian Journal of Earth Sciences》2013,60(7):1067-1081
Chemical compositions and geochronological data utilising the laser ablation ICP-MS technique are presented for zircon megacrysts found in alluvial gem corundum deposits associated with Upper Cretaceous–Cenozoic alkali basalts in the Inverell district-New England field, New South Wales, eastern Australia. Three localities, Kings Plains, Swan Brook and Mary Anne Gully, produce gem-quality transparent dark brown and yellow zircon megacrysts, mostly under 10 mm in size. Although brown zircon shows relative enrichment in Hf and REE, there are no differences in relative transition metal concentrations between the colours. Chemical homogeneity within a single crystal indicates stable crystallisation conditions. The 206Pb/238U age of zircon megacrysts from these three localities define older and younger groups of 216–174 Ma and 45–37.7 Ma, respectively. The ?Hf values of zircon megacrysts from Kings Plains show +7.51±0.34 in the older group and +10.72±0.31 in the younger group. Swan Brook zircons give +11.54±0.47 and +8.32±0.58, and Mary Anne Gully zircons are +13.67±0.63 and +8.50±0.48, respectively. These zircons from New England alluvial gem deposits have two main formational events around Upper Triassic–Lower Jurassic and Eocene episodes. Most originated from lithospheric mantle and all were brought-up by later host basaltic magmas. 相似文献
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We summarize here the occurrence of a number of semiprecious stones within a major gemstone belt in the Palghat-Cauvery shear zone system close to the northern margin of the Madurai Granulite Block, southern India. The gem mineralization in this belt includes different varieties of corundum (star ruby, sapphire), cordierite (iolite), feldspar (moonstones and sunstone of various hues), beryl (emerald, aquamarine), chrysoberyl (alexandrite), kornerupine, topaz, spinel, crystal quartz and amethyst, among others. Gem mineralisation has not been directly dated, but is associated with pegmatites that crosscut rocks metamorphosed in late Neoproterozoic/Early Cambrian times. Similar aged gem mineralization occurs south of the Achankovil Shear Zone in southern India, as well as in Sri Lanka and Madagascar and strengthen the view of a broad late Neoproterozoic-early Cambrian gemstone province in central Gondwana. The ruby mineralization within this belt can be correlated with similar occurrences in eastern Madagascar, supporting a correlation between the Malagasy Betsimisaraka suture zone and the Palghat-Cauvery shear zone system in southern India. 相似文献
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<正>Eocene felsic porphyric rocks and the high-Mg potassic volcanic rocks(HMPR) occur along the Jinshajiang-Ailao Shan-Red River shear zone(JARSZ) in eastern Tibet.Compared with the HMPR,which are generally believed to be sourced from an enriched mantle,the felsic porphyric rocks show similar K_2O contents,enrichment in LREE and LILE,particularly radiogenic isotope(e.g.Sr and Nd) features much similar to the former,implying generation of the felsic porphyric rocks most likely related to the HMPR,although they both have clearly different major and trace element compositions. The close relationship in spatial-temporal distribution and similar Sr-Nd characteristics between the felsic porphyric rocks and HMPR in eastern Tibet indicate that both of them were possibly formed by a similar tectonic process(event).Combining the basic dikes in southern and eastern Tibet,we suggest that the break-off of north-dipping Neo-Tethyan slab in southern Tibet during 50-40 Ma,triggered formation of high-Mg potassic magma.This led to developing felsic porphyric magma production by partial melting of underplating HMPR in the lower crust,or fractionation crystallization of the high-Mg potassic magmas.The break-off of slab in the Eocene may also have contributed to the abundant ore-forming material related to earlier subduction events,resulting in formation of the porphyric deposits along JARSZ in eastern Tibet. 相似文献
18.
The electronic absorption spectra of natural uvarovite containing 62 mole% of the Cr3+ end-member were studied at pressures between 10−4 and ca. 13 GPa using DAC techniques combined with microscope spectrometric device. With increasing pressure, a barochromic
effect with change from green to red color of the garnet specimen was observed. This change could be interpreted on the basis
of the spectra and the data points derived in an ICE color card. The evaluation of crystal field data from the spectra showed
that 10Dq of chromium increases on pressure while the Racah parameter B, and thus the nature of the chemical bond of Cr–O does not change significantly. 相似文献
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西藏山南努日矿区层矽卡岩型铜钨钼矿床地质特征及深部找矿预测 总被引：2，自引：0，他引：2
西藏努日矿区属冈底斯成矿带东段克鲁-冲木达矽卡岩亚带,通过多年地质普查工作,初步形成大型层矽卡岩型铜钨钼多金属矿床.本文通过对层矽卡岩型铜钨钼矿体地质特征、矿石质量、矿石类型、矿床成因及找矿标志等研究和分析,显示出热水环流和深部侵入岩浆热液的叠加和富集成矿作用特点,为矿区深部寻找斑岩型铜多金属矿提供依据和预测. 相似文献