EARLY ARCHEAN KOMATIITES OF THE OLEKMA GRANITE-GREENSTONE REGION AND THEIR SM-ND AGE

Abstract

The oldest supracrustal rocks of the Olekma granite-greenstone region constitute a large 0.8 × 9.5-km erosion remnant among infracrustal formations of the Olekma granite-gneiss complex. They are components of the so-called 'oldest mafic-ultramafic rock association' (OMA). Komatiite accounts for 10 to 20 percent by volume of the section of the OMA. It forms flows that range in thickness from 0.3 to over 7 m, some of which are structurally asymmetrical. We dated the rocks studied and determined their REE content by the isotopic dilution method. The Sm-Nd isochron date reflects the time when the volcanic protoliths of the OMA were erupted.