One of the major metamorphic terranes of the Bohemian Massif, the
Erzgebirge, is interpreted
to record a subducted part of a Palaeozoic margin of Gondwana. A geochemical
study on non-calcareous
metasediments from the various metamorphic units from lower greenschist
to granulite
facies metamorphism supports a recently established thrust model. Geochemical
discrimination and
correlation from the metasediments of the Erzgebirge suggest repetition
of an early Palaeozoic
metasedimentary sequence in metamorphic thrust units. This new finding
is in line with recent radiometric
dating of intercalated metarhyolitic rocks, which yielded ages of around
480 Ma. It is furthermore
supported by correlation with a low-grade standard section in Thuringia,
which represents the
transition from an orogenic belt to a passive margin setting, with highly
mature sediments. Significant
geochemical signatures have been identified in three different lithotypes,
which reappear in at least
three metamorphic units of the Erzgebirge. Geochemical correlation of these
units was established
using simple comparison of averages and with statistical techniques. The
identification of significant
geochemical signatures from different lithotypes in metamorphic suites
has important implications for
terrane analysis and reconstruction of ancient tectonic settings.
The repetition of lithologies and their distinct chemical compositions
in progressively metamorphosed
units is useful for examining element mobility during Barrovian metamorphism.
Statistical comparison
implies that Li is progressively depleted from the greenschist to amphibolite
facies, whereas Ca
exhibits some enrichment. All the other elements studied are considered
to be immobile.