Garnet is one of the most significant minerals in metamorphic rocks, that provides key information on prograde, peak-metamorphic and retrograde parts of the pressure-temperature （PT） path. Such results require a det...Garnet is one of the most significant minerals in metamorphic rocks, that provides key information on prograde, peak-metamorphic and retrograde parts of the pressure-temperature （PT） path. Such results require a detailed knowledge of its different growth domains. For iron-poor compositions, the cathodoluminescence （CL） microscopy is an important and often overlooked method and allows to identify the internal structures of all garnet grains in one thin section within only a few seconds. The advantage of the CL-microscope is to deliver low magnification images in true color, not only of garnet but also, for instance, of other rock forming silicates, carbonates, sulfates, etc., of metamorphic, but also of sedimentary and magmatic origin, using polished thin sections. Internal structures of grossular from Mexico and pyrope from the Italian Alps were characterized and visualized by CL-microscopy. The different growth domains were additionally studied using CL-spectra and electron microprobe （EMP） analysis. Grossular shows a patchy zonation in its core while in mantle and rim zones oscillatory zoning is observed. It contains zones of anomalous birefringence, zones of orange and bluish luminescence and zones lacking luminescence. Different but low amounts of the activator elements Mn2＋ and Eu2＋ are responsible for the orange and bluish luminescent domains. Pyrope is also characterized by oscillatory growth zones, shows a dull luminescent core with a change of crystal morphology during growth, and displays an increase of brightness from core towards rim--the outermost rim, however, is lacking luminescence. The different luminescent zones are characterized by different amounts of Dy3＋, Tb3＋, Sm3＋ and Sm2＋ as activator elements. Because of slow diffusion rates of activators such as the REEs Sm, Dy and Tb, it can be still possible to visualize possible prograde and/or peak pressure stage growth domains of garnet, even if later high temperature events may have homogenized the major element profiles. S展开更多
We present here the first observation of cathodoluminescence (CL) images of Met.(Cu, Ag)-TCNQ anion radical salts organic thin films which were prepared in sat urated TCNQ/CH3CN liquid-phase by self-growth. The erperi...We present here the first observation of cathodoluminescence (CL) images of Met.(Cu, Ag)-TCNQ anion radical salts organic thin films which were prepared in sat urated TCNQ/CH3CN liquid-phase by self-growth. The erperiments were carried out by means of Hitachi S-450 type scanning electron microscopy(SEM). Comparsion of CL images with secondary electron(SE) images of the same point on the organic thin film indicates that the shape of Met.(Cu, Ag)-TCNQ in CL images corresponds very well to that in the SE images. The results observed also shows that the CL intensity of CuTCNQ is stronger than that of AgTCNQ under the same experimental conditions. Based on the above results, a brief discussion about the preliminary mechanism of CL from Met.(Cu,Ag)-TCNQ has been given.展开更多
文摘Garnet is one of the most significant minerals in metamorphic rocks, that provides key information on prograde, peak-metamorphic and retrograde parts of the pressure-temperature （PT） path. Such results require a detailed knowledge of its different growth domains. For iron-poor compositions, the cathodoluminescence （CL） microscopy is an important and often overlooked method and allows to identify the internal structures of all garnet grains in one thin section within only a few seconds. The advantage of the CL-microscope is to deliver low magnification images in true color, not only of garnet but also, for instance, of other rock forming silicates, carbonates, sulfates, etc., of metamorphic, but also of sedimentary and magmatic origin, using polished thin sections. Internal structures of grossular from Mexico and pyrope from the Italian Alps were characterized and visualized by CL-microscopy. The different growth domains were additionally studied using CL-spectra and electron microprobe （EMP） analysis. Grossular shows a patchy zonation in its core while in mantle and rim zones oscillatory zoning is observed. It contains zones of anomalous birefringence, zones of orange and bluish luminescence and zones lacking luminescence. Different but low amounts of the activator elements Mn2＋ and Eu2＋ are responsible for the orange and bluish luminescent domains. Pyrope is also characterized by oscillatory growth zones, shows a dull luminescent core with a change of crystal morphology during growth, and displays an increase of brightness from core towards rim--the outermost rim, however, is lacking luminescence. The different luminescent zones are characterized by different amounts of Dy3＋, Tb3＋, Sm3＋ and Sm2＋ as activator elements. Because of slow diffusion rates of activators such as the REEs Sm, Dy and Tb, it can be still possible to visualize possible prograde and/or peak pressure stage growth domains of garnet, even if later high temperature events may have homogenized the major element profiles. S
文摘We present here the first observation of cathodoluminescence (CL) images of Met.(Cu, Ag)-TCNQ anion radical salts organic thin films which were prepared in sat urated TCNQ/CH3CN liquid-phase by self-growth. The erperiments were carried out by means of Hitachi S-450 type scanning electron microscopy(SEM). Comparsion of CL images with secondary electron(SE) images of the same point on the organic thin film indicates that the shape of Met.(Cu, Ag)-TCNQ in CL images corresponds very well to that in the SE images. The results observed also shows that the CL intensity of CuTCNQ is stronger than that of AgTCNQ under the same experimental conditions. Based on the above results, a brief discussion about the preliminary mechanism of CL from Met.(Cu,Ag)-TCNQ has been given.
