Precambrian greenstone belts host different ophiolite types

Abstract

We use in this study the new description and classification of ophiolites in order to identify potential ophiolite complexes in four Precambrian greenstone belts, ranging in age from 3.8 Ga to 2.0 Ga, and their tectonic origin. The mafic-ultramafic rock assemblages in the 3.8 Ga Isua (Greenland) and 3.5 Ga Barberton (South Africa) greenstone belts show geochemical signatures that are comparable to those of Phanerozoic suprasubductionzone ophiolites. The 2.7 Ga greenstone belts of the Wawa greenstone belts of the Superior Province (Canada) and the 1.95 Ga Jormua Complex (Finland) display subduction-unrelated geochemical patterns, and represent plume-and continental margin-type ophiolites, respectively. This geochemical and tectonic diversity of the Precambrian greenstone belts is reminiscent of the Phanerozoic ophiolites, and suggests that the modern plate tectonics operated as far back as the early Archean, albeit perhaps in a different mode.