Siderite-ankerite-bearing metasandstones and phyllites (SAMP), identified recently in the broader area of Jasenie (Nizke Tatry Mts., Tatric Unit), are described in detail. On the basis of petrological, mineralogical, chemical composition and phase equilibria observations the authors argue that the formation of the SAMP has followed a sedimentary → low degree metamorphic ± mylonitization and not high degree metamorphic → diaphthoritic ± mylonitization pathway, advocated by other petrologists. They also attempt to establish the criteria for distinguishing in this area the low temperature metasediments from the diaphthorized and blastomylonitized augen gneisses and amphibolites.