Early (3700 Ma) Archaean rocks of the Isua supracrustal belt and adjacent gneisses.

A coherent stratigraphy is recognized in the highly deformed, amphibolite facies early Archaean Isua supracrustal belt consisting of layered rocks (with locally preserved sedimentary structures), ultramafic rocks and units of garbenschiefer. Two sequences are recognized now <200 m thick separated from each other tectonically. Sequence A has a transition upwards from predominantly layered amphibolites with banded iron formation horizons to calc-silicate rocks, carbonates and layered felsic metasediments; Sequence B changes upwards from predominantly layered felsic metasediments to ferromagnesian mica schists. The adjacent early Archaean gneisses consist of early multiphase tonalites first intruded by mafic dioritic dykes and then by granitic sheets. Archaean basic dykes cut the supracrustal belt and adjacent gneisses.-W.S.W.