| Abstrakt: |
Abstract An extensively exsolved cummingtonite from central Massachusetts, studied by transmission electron microscopy (TEM), contains nm-scale discs of hornblende which represent the youngest exsolution event. Because of the small size of these lamellae, it is only possible to obtain qualitative energy dispersive X-ray (EDX) analyses on a standard analytical TEM. An alternative new method to verify the presence of nm-scale exsolutions, called electron spectroscopic imaging (ESI), is described in this paper. By using electrons which have lost energy to Ca atoms (Ca1,2,1,3), ESI clearly distinguishes between the matrix and the disc-shaped lamellae. In contrast to EDX spectroscopy, ESI has the advantage that light elements can also be analysed, and that the electron beam does not have to be focused to reach a spatial resolution of < 2 nm, thus minimizing beam damage to the sample. The potential for quantification using ESI is discussed; for most of the mineralogically important elements (Z < 30) quantitative analyses can be obtained with the same accuracy as with EDX spectroscopy. |
