Definition of archaean in English:


(also archaeal)

noun & adjective

    Definition of Archaean in English:


    (US Archean)


    • 1Relating to or denoting the aeon that constitutes the earlier (or middle) part of the Precambrian, in which there was no life on the earth. It precedes the Proterozoic aeon and (in some schemes) is preceded by the Priscoan aeon.

      • ‘The answers to questions about early life on Earth are preserved in the oldest rocks, and Canadian earth scientists include some of the world's best Archean geologists and laboratories equipped to study Archean rocks.’
      • ‘However, most Archean volcanic rocks occur as deformed and fault-fragmented packages termed greenstone belts.’
      • ‘The geological history of Archaean greenstone belts is controversial and, to date, no tectonic model for their evolution has been agreed upon.’
      • ‘Comparison of the ‘bar code’ from the approximately 35 different Archean continental fragments (at least eight of which are in Canada) represents a key tool for proposing reconstructions between these fragments.’
      • ‘The contacts between the complex and the Archaean metamorphic rocks are intrusive.’
      1. 1.1The Archaean aeon or the system of rocks deposited during it.


    Late 19th century: from Greek arkhaios ancient + -an.