Place, role and significance of the propylites in Bulgaria

Independently of the wide development of the medium and low temperature hydrothermal alterations of the Upper Cretaceous and Tertiary volcanics in the Srednogorie and Rhodope zone, their terminological designation and use are too various. Typical cases in this respect are the propylites. Very often their classical determination given in 1868 by Rithoffen (Русинов, 1972) as hydrothermal alteration of andesites and dacites preceding the gold-silver ore mineralization is neglected. Especially for Bulgaria, a similar destiny have had the results obtained by Lewien (1933). For a long time they were insufficiently rationally used in our geological practice where terms "strong", "medium" and "weakly" altered volcanics are used frequently instead of the proposed by the same author three main types of propylitization - carbonate, chlorite and sulphide (pyritic) type. The evolution of the opinions of Strashimir Dimitrov (Димитров, 1961) about the sense of the term "propylitization" is quite interesting. In 1936 he considered the hydrothermal alterations of the Upper Cretaceous andesites in the Srednogorie zone as a result of a "deep autometamorphosis". He connected to this process also the origin of ore mineralization of native copper, some deposits of copper sulphides and manganese ores. In 1946 S. Dimitrov used the term "propylitization" and considered it as dominantly zeolitic, chloritic and pyritic. In 1955 he mentioned a "greenschist facies" metamorphism that had developed in submarine conditions...