Simulating Precambrian banded iron formation diagenesis

Preservation of Fe isotope heterogeneities during diagenesis and metamorphism of banded iron formation

We present the iron isotope composition of primary, diagenetic and metamorphic minerals in five samples from the contact metamorphosed Biwabik Iron Formation. These samples attained peak metamorphic temperatures of <200, <340, ~500, <550, and <740 C respectively. dFe of bulk layers ranges from –0.8 to +0.8&; in some samples the layers may differ by >1& on the millimeter scale. Minerals in the l...

Using modern ferruginous habitats to interpret Precambrian banded iron formation deposition

Early Earth processes are typically identified through the study of mineralogical, elemental and isotopic features in the rock record, including Precambrian banded iron formations (BIF). However, postdepositional processes often obscure the primary geochemical signals, making the use of BIF as proxies for paleo-seawater and the paleo-biosphere potentially imprecise. Thus, alternative approaches...

Iron isotopes constrain biologic and abiologic processes in banded iron formation genesis

The voluminous 2.5 Ga banded iron formations (BIFs) from the Hamersley Basin (Australia) and Transvaal Craton (South Africa) record an extensive period of Fe redox cycling. The major Fe-bearing minerals in the Hamersley–Transvaal BIFs, magnetite and siderite, did not form in Fe isotope equilibrium, but instead reflect distinct formation pathways. The near-zero average dFe values for magnetite r...

Fossilized iron bacteria reveal pathway to biological 2 origin of banded iron formation 3

Formation and Diagenesis of Carbonate Sediments

7.03.3 SOURCES AND DIAGENESIS OF SHOAL-WATER CARBONATE-RICH SEDIMENTS 75 7.03.3.1 Sources of Shoal-water Carbonates 75 7.03.3.1.1 General considerations 75 7.03.3.1.2 Sources of carbonate muds 76 7.03.3.1.3 Formation of carbonate sands 76 7.03.3.2 Early Marine Diagenesis of Shoal-water Carbonate-rich Sediments 77 7.03.3.2.1 Pore-water chemistry 77 7.03.3.2.2 Precipitation of early carbonate cem...