Steinhardtite, a new body-centered-cubic allotropic form of aluminum from the Khatyrka CV3 carbonaceous chondrite
Steinhardtite, a new body-centered-cubic allotropic form of aluminum from the Khatyrka CV3 carbonaceous chondrite
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DOI：
10.2138/am-2014-5108
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发表时间：
2014-11-01
影响因子：
3.1
通讯作者：
Yudovskaya, Marina
中科院分区：
文献类型：
--
作者：
Bindi, Luca;Yao, Nan;Yudovskaya, Marina
斯坦哈德铁矿是一种新矿物，来自喀特尔卡陨石；它是铝的一种新的同素异形体。它以罕见的晶体形式出现在陨石碎片中，直径约为10 μ m，陨石碎片中含有撞击冲击期间压力和温度不均匀分布的证据，其中陨石的某些部分至少达到5gpa和1200摄氏度。陨石碎片中含有高压相阿伦石、钴石、辉石和一种未命名的尖晶石，其成分为Fe3-xSi3Ox （x近似于0.4）。其他矿物包括透辉石、Ni-Al-Mg-Fe尖晶石、磁铁矿、透辉石、橄榄石、斜长石、霞石、镍长石、含铜三辉石、二十面石、卡辉石、铜长石、带状长石和含铝带状长石。由于施泰因哈德石的晶粒非常小，所以不可能确定这种矿物的大部分物理性质。平均9次电子探针分析（从两个不同的碎片中获得）得出公式Al0.38Ni0.32Fe0.30，以1个原子为基础。透射电镜和x -射线单晶衍射结果表明，施泰因哈德岩为立方体，空间群im(3)大于m， A = 3.0214(8)埃，V = 27.58(2)埃(3),Z = 2。在晶体结构[R-1 = 0.0254]中，三种元素在单晶胞的起源处无序，呈体心立方填充（α - fe结构类型）。5条最强的粉末衍射线[d单位埃（I/I-0） （hkl）]为：2.1355 (100)(110)；1.5100 (15) (200);1.2329 (25) (211);0.9550 (10) (310);0.8071(30)(321)。这种新矿物已被IMA-NMNC委员会批准（2014-036），并以普林斯顿大学物理系教授Paul J. Steinhardt的名字命名，以表彰他对Khatyrka陨石的矿物学研究的非凡和热情，这是一种独特的CV3碳质球粒陨石，含有第一个天然准晶相二十面体陨石。这里描述的含有必要数量的Ni和Fe的Al的多晶态的恢复表明，Al可能是假定的地球铁-镍核异常低密度的一个贡献候选者。
Steinhardtite is,a new mineral from the Khatyrka meteorite; it is a new allotropic form of aluminum. It occurs as rare crystals up to similar to 10 mu m across in meteoritic fragments that contain evidence of a heterogeneous distribution of pressures and temperatures during impact shock, in which some portions of the meteorite reached at least 5 GPa and 1200 degrees C. The meteorite fragments contain the high-pressure phases ahrensite, coesite, stishovite, and an unnamed spinelloid with composition Fe3-xSi3Ox (x approximate to 0.4). Other minerals include trevorite, Ni-Al-Mg-Fe spinels, magnetite, diopside, forsterite, clinoenstatite, nepheline, pentlandite, Cu-bearing troilite, icosahedrite, khatyrkite, cupalite, taenite, and Al-bearing taenite. Given the exceedingly small grain size of steinhardtite, it was not possible to determine most of the physical properties for the mineral.A mean of 9 electron microprobe analyses (obtained from two different fragments) gave the formula Al0.38Ni0.32Fe0.30, on, the basis of 1 atom. A combined TEM and single-crystal X-ray diffraction study revealed steinhardtite to be cubic, space group im (3) over barm, with a = 3.0214(8) angstrom, and V = 27.58(2) angstrom(3), Z = 2. In the crystal structure [R-1 = 0.0254], the three elements are disordered at the origin of the unit cell in a body-centered-cubic packing (alpha-Fe structure type). The five strongest powder-diffraction lines [d in angstrom (I/I-0) (hkl)] are: 2.1355 (100)(110); 1.5100 (15)(200); 1.2329 (25)(211); 0.9550 (10)(310); 0.8071 (30)(321).The new mineral has been approved by the IMA-NMNC Commission (2014-036) and named in honor of Paul J. Steinhardt, Professor at the Department of Physics of Princeton University, for his extraordinary and enthusiastic dedication to the study of the mineralogy of the Khatyrka meteorite, a unique CV3 carbonaceous chondrite containing the first natural quasicrystalline phase icosahedrite.The recovery of the polymorph of Al described here that contains essential amounts of Ni and Fe suggests that Al could be a contributing candidate for the anomalously low density of the Earth's presumed Fe-Ni core.