Petrogeneza marmurów z południowo-wschodniej części metamorfiku Śnieżnika (SudetyPetrogenesis of marbles from the south-eastern part of Śnieżnik Metamorphic Massif (Sudetes)
Abstract
Petrogenesis of marbles from the south-eastern part of Śnieżnik Metamorphic Massif (Sudetes)
Abstract
In the Śnieżnik Metamorphic Massif (West Sudetes, Poland) carbonate rocks appear in the Stronie Formation. The results of field researches show that within the Stronie Formation they occur usually in some kilometres long arrays of lenses. Such individual lenses are a few to tens of meters thick and a few to hundreds of meters long. They are of sedimentary genesis and belong mainly to the metavolcanic association. Based on chemical and petrographical studies the following types of rocks with carbonates were distinguished: marbles, marbles with silicates and carbonate-silicate rocks. Further subdivision allows to discern several lithotypes of carbonate rocks: C - calcareous marbles: white, coarse and medium blastic, with homogeneous and flake microstructures; D - dolomite marbles: creamy, fine blastic, with lensoidal or laminated microstructures; CD - calcareous dolomite marbles: white creamy, heteroblastic, laminated; SC, SCD, SD - calcareous marbles, calcareous dolomite marble and dolomite marbles with silicates: white green or white brown, heteroblastic, with lensoidal or laminated heterolitic microstructures; G - graphite marbles and graphite marbles with silicates: light to dark gray, coarse to fine blastic, with lensoidal or laminated heterolitic microstructures; CS - carbonate-silicate rocks: petrographically differentiated. The lithotypes CS, SC and G occur within and at the contact with volcanogenic rocks; the lithotypes C, CD and D are present at the top of carbonate rocks profile. A few badly preserved calcitic bioclasts point to Paleozoic age and biogenic origin of a part of carbonate rocks from the Stronie Formation. The occurrence of carbonate rocks in metavolcanic association, the petrographic features of lithotypes and the relicts of sedimentary structures such as layering, lamination, and sedimentary flows (?) suggest, that the carbonate sediments have been deposited in a shallow water environment, far away from the continental margins, in the area of distinct volcanic activity. The position of dolomite lithotypes in the profile of carbonate rocks and petrographic features of dolomite point to diagenetic dolomitization. Mineral parageneses, decrepitometric data and the results of the carbonate geothermometer indicate amphibolite facies metamorphism at temperature of ca 500°C and pressure of 5 kbar.