Formation of framboidal iron sulfide in the water of a permanently anoxic fjord - Framvaren, South Norway

Framvaren, a super-anoxic fjord in South Norway, has been the subject of research for six years. As part of the scientific program, the chemistry of iron in the water and the sediments has been investigated. Several particulate iron phases have been observed in the anoxic water, including silicate-bound iron from the source rock of the area, finely dispersed amorphous iron sulfide (which bleeds through 0.4 μm Nuclepore filters) and framboidal iron sulfide in the size range 3–10 μm. Although conclusive mineralogical evidence of framboidal pyrite formation in the water is lacking, several observations support the formation of pyrite at the oxic-anoxic interface where metabolizable organic matter, elemental sulfur and reactive iron are abundant.