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Accueil > Publications > Recherche par années > Années 2000 > 2003

Westall, F ; Folk, RL

Exogenous carbonaceous microstructures in Early Archaean cherts and BIFs from the Isua Greenstone Belt : implications for the search for life in ancient rocks

Precambrian Research 126 (3-4) 313-330

par Administrateur - publié le

Abstract :

The microstructure of HF-etched samples of Early Archaean banded iron formations (BIFs) and cherts from the >3.7 b.y.-old Isua Greenstone Belt (southwestern Greenland) was investigated using high resolution scanning electron microscopy equipped with an electron diffraction system, capable of analysing light elements. The rocks contain both endogenous (of internal origin) and exogenous (of external origin) carbonaceous microstructures. The former consist of inclusions of graphite and, possibly, small, amorphous carbonaceous particles, both embedded in metacherts (however, further in situ TEM studies are needed to verify the endogeneity of the amorphous particles). Moreover, these rocks also contain endolithic microorganisms (i.e. inhabiting cracks in rocks), as well as undifferentiated carbonaceous matter, that occur in fractures and cracks between grains.