Ankerite cement mesogenetic

Fig. 8. Composition of eodiagenetic (Cl and Dl) and mesogenetic (C2, D2 and D3) calcite and dolomite/ankerite cements.

The stability relationship between dolomite and ankerite depends on the temperature and activity ratio of Fe /Mg " (Fig. 5c). Formation waters from Norwegian North Sea reservoirs (Egeberg Aagaard, 1989) have log (aFe2+/aMg2+) of -3 to -2 and fall within the stability field of dolomite and ankerite (Fig. 5c). Both of these minerals are widely reported as mesogenetic cements in these sediments (Saigal Bjorlykke, 1987 Morad et al., 1990). 

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