Fractal Nature of the Band-Thickness in the Archean Banded Iron Formation in the Yellowknife Greenstone Belt, Northwest Territories, Canada

Banded iron formations (BIFs) are chemically precipitated deposits on the Precambrian sea floor and are characterised by alternations of repeat Fe-rich and Si-rich layers [1]. Temporal varia‐ tions in the volumes of BIFs are considered to be related to early evolution of the atmosphere, oceans, life and the Earth’s interior [2, 3]. In general, BIFs contain various scales of banding. Bands with a thickness of several tens of meters to meters, a thickness of centimetres and a thickness of submillimetre to millimetres are named macrobands, mesobands and microbands, respective‐ ly [4]. Some depositions are related to periodic phenomena, such as annual cycles [4], tidal and solar cycles [5–7], and Milankovitch cycles [8, 9] in the Precambrian. On the other hand, quanti‐ tative analysis of the banding is limited to Paleoproterozoic Hamersley (Superior-type) BIFs, although BIFs occur within an age range from 3.8 Ga to about 0.7 Ga [10]. Therefore, it is necessa‐ ry to investigate different BIFs, in terms of both their age and type, clarified by size and litholog‐ ical facies (i.e., Superiorand Algoma-types) to understand the nature of their banded structures.