Relationships between textural and photoluminescence spectral features of carbonado (natural polycrystalline diamond) and implications for its origin
Relationships between textural and photoluminescence spectral features of carbonado (natural polycrystalline diamond) and implications for its origin
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黑金刚石（天然多晶金刚石）的结构和光致发光光谱特征之间的关系及其对其起源的影响
DOI：
10.1134/s0016702916100050
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发表时间：
2016
期刊：
影响因子：
0.8
通讯作者：
H.
中科院分区：
文献类型：
--
作者：
Ishibashi;H.;Kagi;H.;Odake;S.;Ohfuji;H. and Kitawaki;H.
采用场发射扫描电子显微镜（FESEM）对中非共和国（CAR）天然多晶金刚石carbonado的两个纹理对比样品进行了纹理观察、晶体尺寸分布（CSD）分析、紫外激发发光成像和488 nm激光激发光致发光（PL）显微光谱分析。所研究的烘豆样品A和B显示出极其不同的纹理：样品A由多面晶体组成，伴随着丰富的小矩形孔，而样品B具有颗粒状纹理，具有较粗的晶体和稀少的大孔。小于2-3 µm的金刚石晶体在样品A中富集，但在样品B中贫化。这些织构特征表明，样品B金刚石在化学稳定的P-T条件下退火。孔隙特征表明样品A的流体渗透率高于样品B。光致发光（PL）光谱表明，样品A和B分别对应于Kagi等人（1994）分类中的A组和B组碳酸盐，因此样品A显示来自H3中心的发射，而没有任何N-V 0衍生的575 nm发射，而样品B显示来自3 H中心和N-V 0缺陷的发射。此外，样品B的UV激发的发光图像和光致发光光谱表明，在孔的几微米内的金刚石晶体的边缘显示出与AB族碳酸氢根的发光特征类似的发光特征（Kagi等人，1994），表明这种AB族材料是由B族材料通过在低温下从孔填充的、具有放射性元素的材料辐射形成的。认为低温辐照的程度取决于流体渗透性，A组材料由于其渗透性质地而受到强烈辐照，而B组材料由于其渗透性较低的颗粒状质地而未受到显著辐照。这些结果表明，B组碳酸盐岩保留了其原始的PL光谱特征下产生的高压和高温在地幔深处。
Field Emission SEM (FESEM) textural observations, crystal size distribution (CSD) analyses, UV-excited luminescence imaging, and photoluminescence (PL) microspectroscopy excited by 488 nm laser were conducted on two texturally contrasting samples of carbonado, a kind of natural polycrystalline diamond from the Central African Republic (CAR). The investigated carbonado samples A and B show extremely different textures: sample A is made up of faceted crystals accompanied by abundant, small rectangular pores, whereas sample B has a granular texture with coarser crystals and scarce, large pores. Diamond crystals smaller than 2–3 µm are enriched in sample A but depleted in sample B. These textural features indicate that sample B diamonds were annealed under thermodynamically stableP–Tconditions. The pore characteristics indicate that fluid permeability was higher for sample A than sample B. Photoluminescence (PL) spectra indicate that samples A and B correspond to Group A and B carbonados in the classification of Kagi et al. (1994), respectively, so that sample A reveals emissions from the H3 center without any N–V0derived emission at 575 nm, whereas sample B shows emissions from the 3H center and the N–V0defect. In addition, UV-excited luminescence images and photoluminescence spectra for sample B indicate that the rims of diamond crystals within several microns of a pore show luminescence features similar to those of Group AB carbonados (Kagi et al., 1994), indicating that this Group AB material was formed from Group B by irradiation from pore-filling, radioactive-element-bearing materials at a low temperature. The extent of the low-temperature irradiation is considered to depend on fluid permeability, and the Group A material was strongly irradiated due to its permeable texture whereas the Group B material was not significantly irradiated due to its less permeable granular texture. These results indicate that Group B carbonados have retained their original PL spectral features produced under high pressures and temperatures at mantle depths.