Beziehungen zwischen Calciumgehalt und Bildungsbedingungen der Dolomite

Petrography and Geochemistry of Red Sea Dolomite

“…Goldsmith and Graf (1958) have postulated that higher salinities favor the precipitation of well-ordered dolomites. Füchtbauer and Goldschmidt (1965) reported that dolomites formed at higher salinities contain less excess CaC03 in the lattice, based upon field studies of carbonates from the Lower Tertiary of Libya and Upper Permian and Upper Jurassic of northern Germany. Similarly, Marschner (1968), studying the Triassic Keuper Formation of northwest Germany, concludes that the Mg/Ca ratio of dolomite is dependent upon degree of hypersalinity at the time of formation and that stoichiometric dolomite is formed only under conditions of hypersalinity.…”

Sedimentary History of the Red Sea

“…The dolomites just above and within the evaporites, generally of finer crystal size, have a stoichiometric composition of [(Caso Mg5o) CO3] and show better ordering (Goldsmith and Graf, 1958). Both types of dolomite are interpreted as early diagenetic with the Ca/Mg ratio being indicative of paleosalinity conditions, analogous to the dolomites of the Zechstein (Füchtbauer, 1964;Füchtbauer and Goldschmidt, 1965) and the Triassic Keuper Formation (Marschner, 1968).…”

Data Report: Geochemistry of Pliocene and Miocene carbonates from the Eratosthenes Seamount (Site 965)

“…The relative amounts of calcite and dolomite were estimated from variation in the heights of the d(104) peaks in the X-ray patterns (Tennant and Berger, 1957). Degree of order in the dolomite lattice was estimated from the ratio of the peaks near 2Θ ≈ 35.3° and 37.3° (Füchtbauer and Goldschmidt, 1955).…”

“…FTIR spectroscopy indicates that only LMC or calcium-rich dolomite are present. Although, the XRD pattern of dolomite generally shows the ordering reflex near 2Θ ≈ 35.2°, the excess calcium in the dolomite and the estimated degree of ordering in the dolomite lattice of dolomite-rich samples (>40% dolomite) indicate low temperatures during dolomite formation (Füchtbauer & Goldschmidt, 1955). …”

“…The relative amounts of calcite and dolomite were estimated from variation in the heights of the d(104) peaks in the X-ray patterns (Tennant and Berger, 1957). Degree of order in the dolomite lattice was estimated from the ratio of the peaks near 2Θ ≈ 35.3° and 37.3° (Füchtbauer and Goldschmidt, 1955).Stable carbon and oxygen isotope ratios of the calcite and dolomite fractions were measured on CO 2 liberated from the carbonates by the reaction with anhydrous phosphoric acid using the sealed vessel method (Böttcher, 1996). The procedure to separate CO 2 from the calcite and dolomite fraction is based on the different reaction rates of calcite and dolomite with phosphoric acid (Walters et al, 1972;Al-Aasm et al, 1990).…”