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Relationship between 207Pb NMR chemical shift and the morphology and crystal structure for the apatites Pb5(AO4)3Cl, vanadinite (A = V), pyromorphite (A = P), and mimetite (A = As)
American Mineralogist ( IF 2.7 ) Pub Date : 2021-04-01 , DOI: 10.2138/am-2021-7368
Otto E.O. Zeman 1 , Rupert Hochleitner 2 , Wolfgang W. Schmahl 2, 3 , Konstantin Karaghiosoff 1 , Thomas Bräuniger 1
Affiliation  

In this paper, we discuss information on crystal structure and morphology available from nuclear magnetic resonance (NMR) spectroscopy of 207Pb for the mineral family [Pb(4f)]2[Pb(6h)]3(AO4)3Cl with A = V (vanadinite), P (pyromorphite), and As (mimetite). The isotropic chemical shift of the 207Pb atoms at Wyckoff positions 4f and 6h was (re-)determined from either static single-crystal or magic angle spinning NMR experiments. This isotropic shift can be linearly correlated to the unit-cell volume within the mineral family, and in the wider context of lead-bearing minerals, to the shortest Pb-O distance for position 4f, in which 207Pb is solely coordinated by oxygen. By evaluating the number of resonances and their respective line widths in the 207Pb-NMR spectra of these three naturally grown minerals, it could be established that vanadinite forms single-domain macroscopic crystals with very small mosaicity, whereas pyromorphite crystals show NMR characteristics, which can be interpreted as being caused by significant mosaicity. In some instances, this mosaic spread could be quantitatively approximated by a Gaussian distribution with a standard deviation angle of σ = 5°. In contrast, our mimetite specimen was composed of multiple sub-crystals with a very high variability of orientations, going beyond mere mosaicity effects. By extending the NMR methodology presented here to other minerals, it may be possible to gain new insights about structure-property relationships and the morphology of natural grown minerals.

中文翻译:

207Pb NMR化学位移与磷灰石Pb5(AO4)3Cl,钒铁矿(A = V),焦晶铁矿(A = P)和蒙脱石(A = As)的形态和晶体结构之间的关系

在本文中,我们讨论了有关矿物族[Pb(4f)] 2 [Pb(6h​​)] 3(AO4)3Cl的207Pb的核磁共振(NMR)光谱学信息,其中A = V(钒铁矿),磷(亚焦黄铁矿)和砷(亚铁矾土)。Wyckoff位置4f和6h处207Pb原子的各向同性化学位移由静态单晶或魔角旋转NMR实验确定(重新确定)。该各向同性位移可以与矿物族内的晶胞体积线性相关,在含铅矿物的更广泛上下文中,可以与位置4f的最短Pb-O距离线性相关,其中207Pb仅由氧协调。通过评估这三种天然矿物的207Pb-NMR光谱中的共振数及其各自的线宽,可以确定的是,钒铁矿形成的单畴宏观晶体具有很小的镶嵌性,而亚铁锰矿晶体具有NMR特征,这可以解释为是由明显的镶嵌性引起的。在某些情况下,可以通过具有标准偏差角σ= 5°的高斯分布来定量估计此镶嵌分布。相比之下,我们的mi石样品由多个亚晶体组成,这些亚晶体具有非常高的取向可变性,而不仅仅是镶嵌效应。通过将此处介绍的NMR方法扩展到其他矿物,可能会获得有关结构性质关系和自然生长矿物形态的新见解。可以解释为是由大量镶嵌引起的。在某些情况下,可以通过具有标准偏差角σ= 5°的高斯分布来定量估计此镶嵌分布。相比之下,我们的mi石样品由多个亚晶体组成,这些亚晶体具有非常高的取向可变性,而不仅仅是镶嵌效应。通过将此处介绍的NMR方法扩展到其他矿物,可能会获得有关结构性质关系和自然生长矿物形态的新见解。可以解释为是由大量镶嵌引起的。在某些情况下,可以通过具有标准偏差角σ= 5°的高斯分布来定量估计此镶嵌分布。相比之下,我们的mi石样品由多个亚晶体组成,这些亚晶体具有非常高的取向可变性,而不仅仅是镶嵌效应。通过将此处介绍的NMR方法扩展到其他矿物,可能会获得有关结构性质关系和自然生长矿物形态的新见解。我们的mi石样品由多个亚晶体组成,这些亚晶体具有非常高的取向可变性,而不仅仅是镶嵌效应。通过将此处介绍的NMR方法扩展到其他矿物,可能会获得有关结构性质关系和自然生长矿物形态的新见解。我们的mi石样品由多个亚晶体组成,这些亚晶体具有非常高的取向可变性,而不仅仅是镶嵌效应。通过将此处介绍的NMR方法扩展到其他矿物,可能会获得有关结构性质关系和自然生长矿物形态的新见解。
更新日期:2021-04-01
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