Strontium-bearing minerals

In an extensive review of the geochemistry of volatile-bearing minerals in mantle xenoliths, Ionov et al (1997) have pointed out that although minerals such as mica, amphibole, and apatite are often referred to as hydrous, in many cases they have very low H2O contents (Boettcher and O Neill, 1980). In such cases, these minerals may have significant amounts of fluorine, chlorine and CO2. Mica, amphibole, and apatite, together with the oxide phases, are important hosts for titanium, potassium, rubidium, strontium, barium, and niobium (Table 9). 

In summary, the Sr/ Sr ratios of calcite in carbonate rocks of Triassic, Permian, and Devonian age indicate that this mineral did not precipitate from seawater. Instead, the calcite probably precipitated from pore water percolating through the sediment after deposition. The strontium in solution in the pore water originated by incongruent dissolution of detrital grains of K-feldspar, biotite, and other Rb-bearing minerals in the sediment. We conclude that even marine sandstones (e.g., the Alexandra Formation) may contain diagenetic carbonate lenses and concretions that formed after deposition and therefore did not form in a marine environment. 

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