The Isua Greenstone Belt is an Archean greenstone belt in southwestern Greenland, aged between 3.7 and 3.8 billion years. The belt contains variably metamorphosed mafic volcanic and sedimentary rocks, and is the largest exposure of Eoarchaean supracrustal rocks on Earth. Due to its age and low metamorphic grade relative to many Eoarchaean rocks, the Isua Greenstone Belt has become a focus for investigations on the emergence of life and the style of tectonics that operated on the early Earth. Overview The Isua Greenstone Belt, also known as the Isua supracrustal belt since it is composed primarily of supracrustal rocks, is located in southwestern Greenland, in the Isukasia terrane, near the Nuuk capital region. It forms the largest supracrustal enclave in the Itsaq Gneiss Complex, which predominantly comprises 3850 - 3600 million year old (Ma) felsic orthogneisses. The greenstone belt comprises two major sequences of metamorphosed mafic volcanic and sedimentary rocks, which were divided on the basis of zircon uranium-lead dating. These sequences are the 'southern terrane', which has an age of approximately 3800 Ma, and the 'northern terrane', which has an age of approximately 3700 Ma. The younger southern terrane is further subdivided into two subterranes: one predominantly comprising boninite-like metavolcanic rocks, and the other comprising tholeiitic and picritic metavolcanics. The Isua Greenstone Belt is bounded to the West by the Ivinnguit Fault, which divides the Eoarachaean Itsaq Gneiss Complex from younger (Mesoarchaean) rocks of the Akia Terrane. Elsewhere, it is bounded by felsic orthogneisses of the Itsaq Gneiss Complex. These show a similar age division to the supracrustal rocks of the Isua Greenstone Belt itself, with 3800 Ma gneisses to the south of the belt, and 3700 Ma gneisses to the north of the belt. Scientific methods A large number of geological and geochemical methods have been applied to the rocks of the Isua Greenstone Belt. These include subdivision of the various lithologies and units within the belt using a combination of geological mapping and U-Pb zircon dating, typically using sensitive high-resolution ion microprobe (SHRIMP), analyses; major and trace element chemistry; structural analyses; geothermobarometry and metamorphic modelling using phase diagrams to determine metamorphic conditions; and a wide range of stable, radiogenic, and short-lived isotope systems. Lithologies The Isua Greenstone Belt comprises many different lithologies. The most abundant rock types are mafic metavolcanic rocks with a range of compositions from boninite-like to tholeiites and picrites. Though boninitic amphibolites at Isua