LOW LIMIT OF MN2-ACTIVATED CATHODOLUMINESCENCE OF CALCITE - STATE-OF-THE-ART()

In the literature, the lower limit for Mn2+-activated cathodoluminesce nce (CL) of calcite is variously reputed to over a very wide range of values above 10 ppm Mn. Our spectroscopic investigations of the CL res ponse in natural calcite reveal that below 10 ppm manganese content Mn 2+-activation is also present. Using the Quantitative High Resolution Spectral analysis of CL (QHRS-CL) an activation by Mn2+ in the range o f 700 ppb is proved, which cannot be determined visually. So, if not q uenched, the minimum Mn2+ content for Mn2+-activation is one atom in t he irradiated calcite crystal lattice volume. As the intrinsic (backgr ound blue) luminescence is used to determine non-altered biogenic calc ite, the limit of Mn2+-activation plays an important role in the inter pretation of diagenetic processes. Our results of spectroscopic analys es require a revision of current opinions about the diagenesis of calc ite as revealed by CL investigation. (C) 1998 Elsevier Science B.V. Al l rights reserved.