Młodszy prekambr i sylur rejonu Myszkowa

Abstract

LATE-PRECAMBRIAN AND SILURIAN IN THE MYSZKÓW AREASummaryThe Silurian rocks, in particular those deriving from the uppermost part of the bore-hole Mrzygłód-9, represent sediments only slightly transformed by magmatic intrusions as well as the least influenced by regional epigenetic processes.Symptoms of the thermal influence are only visible in the lowermost layers in which the clay-siltstones were isochemically transformed into blastopellitic slates. The Silurian sediments from the bore-hole Mrzygłód-6 show a high degree of contact thermal transformation. The mineral association, amphibole (tremolite) – wollastonite – chlorite, indicates temperatures of about 500°–600°C. The chemical composition of these rocks suggests that the primary sediments were greywacke siltstones with clay-carbonate matrix. The late Precambrian sediments of the region under investigation display features characteristic of formations accumulated in a geosynclinal marine basin and composed of material deriving from an alimentation area built of metamorphic rocks accompanied by spilites and keratophyres. The occurrence of a greater quantity of volcanic elements in the finer grained material indicates volcanic activity simultaneous to the sedimentation processes or slightly preceeding them. This could allow one to compare the investigated Precambrian sediments with those of the Barrandien spilite stage, as well as with the basaltic rocks from bore-holes in the area of north-eastern Poland. Evidence of secondary processes in the Precambrian sediments suggests that the components of sedimentary origin were transformed in conditions of raised temperature and pressure characteristic of the early stages of regional metamorphism.