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534954 
Journal Article 
The Akilia Controversy: field, structural and geochronological evidence questions interpretations of > 3.8 Ga life in SW Greenland 
Whitehouse, MJ; Myers, JS; Fedo, CM 
2009 
Yes 
Journal of the Geological Society
ISSN: 0016-7649 
GEOLOGICAL SOC PUBL HOUSE 
BATH 
166 
335-348 
English 
WOS:000264218300014 
Field relations, structure and geochronology demonstrate that controversial rocks oil Akilia, SW Greenland, cannot host evidence of Earth's oldest life. Mafic-ultramafic gneiss that contains a layer of quartz-amphibole-pyroxene gneiss, a few metres thick, with purported biogenic graphite is not cross-cut by the protoliths of >3.82 3.65 Ga tonalitic gneiss. The contact between these gneisses is tectonic so their relative ages are unknown, Multiple episodes of intrusion and deformation in the tonalitic gneiss preceded the earliest deformation fabrics and structures seen in the mafic ultramafic gneiss. Although previously interpreted as it volcano-sedimentary stratigraphy, file mafic-ultramafic gneiss displays no evidence of such an origin, and could be partly or wholly derived from igneous intrusions. Existing geochronology indicates that the mafic ultramafic and qtz am px gneisses have ages <3.67 Ga. Metamorphic zircon in the qtz am px gneiss grew at v. 2.68 Ga during late Archaean high-grade events that complicate any protolith interpretation. U Pb dating of apatite from a variety of rocks on Akilia shows that this mineral crystallized, or possibly recrystallized, at c. 1.75 Ga and it thus provides no indication of an early Archaean age for any associated graphite, regardless of whether or not the latter is biogenic. 
southern west greenland; banded iron-formation; isua greenstone-belt; earths earliest life; early archean rocks; supracrustal rocks; southwest greenland; crustal evolution; godthaab district; amitsoq; gneisses