A study on silicified volcanic rocks from the Hunter Mine Group (HMG), Abitibi Greenstone Belt, Canada, could provide new information about how to interpret geochemical information in metamorphosed rocks. The team of scientists studied three distinct groups of rocks from the HMG, documenting how compositions of the rocks changed in the subaqueous caldera associated with the site. The study draws links between the three groups of rocks and the processes by which each was formed.

Importantly, rocks from Group 3 contain rare-earth element signatures similar to marine chemical precipitates. The team believes that silification in a hydrothermal depositional setting could produce rocks that appear similar marine chemical precipitates, such as banded iron formations (BIFs). They posit that this process could have been widespread on the early Earth during the Archean. The results could affect how scientists interpret geochemical information preserved in rocks of this type.

The study, “Development of a mixed seawater-hydrothermal fluid geochemical signature during alteration of volcanic rocks in the Archean (∼2.7 Ga) Abitibi Greenstone Belt, Canada,” was published in the journal Geochimica et Cosmochimica Acta. The work was supported by NASA Astrobiology through the Exobiology Program.