Cycles of hydrothermal activity, precipitation of chemical sediments, with special reference to Algoma-type BIF

In this contribution, we present the more or less consistent banding (mm to several cm) from Fe-rich to silica-rich chemical sediments associated with the venting that leads to the formation of banded sediments in several hydrothermal mineral systems, such as volcanogenic massive sulphides (VMS) and sedimentary exhalative (SEDEX) deposits. However, in this contribution we specifically refer to the banded sediments that are commonly known as Algoma-type iron formation (BIF). Algoma-type BIF does provide a somewhat unusual and poorly investigated case of chemical sediments banding. The banding of these chemical sediments in terms of Fe oxides and silica is related to their alternate dominance in the upwelling fluids in a variety of settings ranging from a sea floor spreading centre to continental rift-related settings. Equally important is the concept that Algoma-type BIF may well be associated with and a distal expression of sulphide-bearing mineral systems.