Vorlanite (CaU6+)O4—A new mineral from the Upper Chegem caldera, Kabardino-Balkaria, Northern Caucasus, Russia
Vorlanite (CaU6+)O4—A new mineral from the Upper Chegem caldera, Kabardino-Balkaria, Northern Caucasus, Russia
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Vorlanite (CaU6+)O4——一种来自俄罗斯北高加索地区卡巴尔达-巴尔卡里亚上Chegem破火山口的新矿物
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发表时间：
2011
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通讯作者：
J. Janeczek
中科院分区：
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作者：
E. Galuskin;T. Armbruster;I. Galuskina;B. Lazić;A. Winiarski;V. Gazeev;P. Dzierżanowski;A. E. Zadov;N. Pertsev;R. Wrzalik;A. Gurbanov;J. Janeczek
本文报道了一种新矿物-俄罗斯卡巴尔达-纳拉亚尼亚北方高加索上切海姆火山口熔结凝灰岩中钙质矽卡岩捕虏体中的Vorlan。钒铅矿以黑色片状晶体的集合体出现，最长可达0.3 mm，外部对称性为3 μ m。最强的粉末衍射线为[d（λ）/（hkl）]：3.107/（111），2.691/（200），1.903/（220），1.623/（311），1.235/（331），1.203/（420），1.098/（422），0.910/（531）。单晶X射线研究给出等距对称性，空间群为Fm 3 <$m，a = 5.3813（2）<$m，V = 155.834（10）<$3，Z = 2。X射线光电子能谱分析表明，铀钒矿中的铀均为六价态。矿物与萤石、晶质铀矿（U4+O2）等结构。与合成菱面体CaUO 4和大多数U6+矿物相反，钒铀矿中的U6+阳离子以无序的铀酰离子存在。[8] Ca ~（2+）和U ~（6+）在单一位置上呈无序分布，平均分子量为2.33 μ m。钒铅矿被认为是原来菱面体CaUO 4的假晶替代物。我们假设，这个菱面体相转化的辐射损伤立方CaUO 4（vorlanite）。这种新矿物与钾镁矾、钙镁矾、莱因哈德布朗石、拉卡沸石、硼镁矾和硅铝石有关，这些矿物表明浅部的高温形成（>800 °C）。
Abstract The new mineral vorlanite, (CaU6+)O4, Dcalc = 7.29 g/cm3, H = 4-5, VHN10 = 360 kg/mm2, was found near the top of Mt. Vorlan in a calcareous skarn xenolith in ignimbrite of the Upper Chegem caldera in the Northern Caucasus, Kabardino-Balkaria, Russia. Vorlanite occurs as aggregates of black platy crystals up to 0.3 mm long with external symmetry 3̄m. The strongest powder diffraction lines are [d(Å)/(hkl)]: 3.107/(111), 2.691/(200), 1.903/(220), 1.623/(311), 1.235/(331), 1.203/(420), 1.098/(422), 0.910/(531). Single-crystal X-ray study gives isometric symmetry, space group Fm3̄m, a = 5.3813(2) Å, V = 155.834(10) Å3, and Z = 2. X-ray photoelectron spectroscopy indicate that all U in vorlanite is hexavalent. The mineral is isostructural with fluorite and uraninite (U4+O2). In contrast to synthetic rhombohedral CaUO4, and most U6+ minerals, the U6+ cations in vorlanite are present as disordered uranyl ions. [8]Ca2+ and [8]U6+ are disordered over a single site with average M-O = 2.33 Å. Vorlanite is believed to be a pseudomorphic replacement of originally rhombohedral CaUO4. We assume that this rhombohedral phase transformed by radiation damage to cubic CaUO4 (vorlanite). The new mineral is associated with larnite, chegemite, reinhardbraunsite, lakargiite, rondorfite, and wadalite, which are indicative of high-temperature formation (>800 °C) at shallow depth.