Characteristics of emission centers in alkali feldspar: A new approach by using cathodoluminescence spectral deconvolution
Characteristics of emission centers in alkali feldspar: A new approach by using cathodoluminescence spectral deconvolution
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DOI：
10.2138/am.2010.3427
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发表时间：
2010-11
影响因子：
3.1
通讯作者：
M. Kayama;S. Nakano;H. Nishido
中科院分区：
文献类型：
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作者：
M. Kayama;S. Nakano;H. Nishido
智利巴塔哥尼亚安第斯山脉Cerro Balmaceda岩体正长岩中的碱长石显示出岩浆至高温和低温热液阶段形成的多种岩石显微结构，阴极发光（CL）显示出广泛的蓝色、紫色和粉红色至红色，亮度变化。它们的CL光谱呈现出两个发射波段：一个在蓝色区域的405-420 nm，另一个在红红外（IR）区域的700-760 nm。能量单位的非对称形状的光谱峰表明每个单独的发射重叠，这对应于不同的发光中心。蓝色发射带被分离成两个以3.055 ~ 3.076和2.815 ~ 2.845 eV为中心的高斯曲线拟合的光谱峰。3.055 ~ 3.076 eV的发射强度与TiO2含量呈正相关，表明Ti4+杂质作为发射中心被激活。在光学显微镜下，在2.815-2.845 eV处，可以看到清澈无特征的长石（CF），其强度明显高于在低温水热反应中形成的斑块状微透石（PMP）的强度，与Fe3+杂质中心引起的红红外发射强度成正比。在2.815 ~ 2.845 eV处的峰值可归因于与Al-O-Al和Al-O-Ti桥相关的氧缺陷。大部分区域在700 ~ 760 nm处有CL发射，其强度随杂质Fe2O3含量的增加而增加。Fe3+离子作为红红外发射的激活剂。富ab相和富or相的发射分量分别为1.644 eV （754 nm）和1.727 eV （717 nm）。CF的红红外发射由1.677 eV （739 nm）和1.557 eV （796 nm）的发射成分组成，分别由富or相和富ab相的Fe3+杂质中心组成。这两种组分的中心波长都比PMP富ab和富or相的发射带长，表明低温热液交代反应使Fe3+离子周围的构型状态发生了从T2到T1的变化。因此，Fe3+离子进入T1位的有序状态、多相次氯酸盐的存在以及化学成分控制了红红外发射峰的位置。
Abstract Alkali feldspars in syenite from the Cerro Balmaceda pluton in the Patagonian Andes, Chile, show various petrographic microtextures formed during the magmatic to high- and low-temperature hydrothermal stages in which cathodoluminescence (CL) shows a wide range of blue, violet, and pink to red colors with variable brightness. Their CL spectra exhibit two emission bands: one at 405-420 nm in the blue region and the other at 700-760 nm in the red-infrared (IR) region. Asymmetrically shaped spectral peaks in energy units suggest overlapping of each individual emission, which corresponds to various luminescence centers. Blue emission bands were separated into two spectral peaks fitted by Gaussian curves centered at 3.055-3.076 and 2.815-2.845 eV. A positive correlation is found between emission intensities at 3.055-3.076 eV and TiO2 contents, suggesting the activation of a Ti4+ impurity as an emission center. The intensities at 2.815-2.845 eV, where clear and featureless feldspar (CF; not affected by hydrothermal metasomatism) is shown under optical microscopy, which have intensities appreciably higher than those showing patched microperthite (PMP), formed during low-temperature hydrothermal reactions, correlate reciprocally with the intensities of red-IR emission caused by a Fe3+ impurity center. The peak at 2.815-2.845 eV can be attributed to oxygen defects associated with Al-O-Al and Al-O-Ti bridges. Most of the areas show CL emissions at 700-760 nm in the red-IR region, in which intensities increase with an increase in Fe2O3 contents as impurities. The Fe3+ ion acts as an activator for the red-IR emission. The Ab-rich and Or-rich phases of PMP have emission components at 1.644 eV (754 nm) and 1.727 eV (717 nm), respectively. The red-IR emission from CF consists of emission components at 1.677 eV (739 nm) and 1.557 eV (796 nm), according to an Fe3+ impurity center in the Or-rich phase and in the Ab-rich phase as cryptoperthite, respectively. Both components are centered at a wavelength longer than the emission band of Ab-rich and Or-rich phases of PMP, suggesting a change in configurational state around the Fe3+ ion from the T2 to the T1 site by low-temperature hydrothermal metasomatic reactions. Accordingly, the peak positions of the red-IR emission are controlled by the ordering state of Fe3+ ion into the T1 site, the existence of multiphase perthite and chemical composition.