Figure 1 Econ Geol 94

Figure 1 Econ Geol 94 Figure 1. Combination pH-pE (Eh) diagram showing redox donation of black shales based on mineral dissolution (from Quinby-Hunt and Wilde, 1994). Boundaries are based on dissolution of minerals from concentrations observed oxic seawater. Reduction of NO₃ to N₂(indicatedby the line of short dashes) is usually considered the boundary between oxic and anoxic conditions. Reduction of SO₄^2--to H₂S and HS^-(long dashes) roughly marks the boundary between oxic and sulfidic species. Note that the correspondence is not exact --pyrite can appear within the sulfate stability zone.

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