Strontium calcite

Katz, A., Sass, E., Starinsky, A. and Holland, H.D. (1972) Strontium behavior in the aragonite-calcite transformation An experimental study at 40-98°C. Geochim. Cosmochim. Acta, 36, 41-496. 

The Mountain Pass (USA) operation treats a relatively complex ore. The major REO mineral is bastaenesite with minor amounts of synchisite, parasite and monazite. The major gangue minerals are calcite, barite, silicates, and dolomite. The amount of the individual gangue minerals in this ore are variable and change on a yearly basis. There are two major ore types treated at the Mountain Pass concentrator (a) high calcite ore (35-45% CaO) and (b) a high barite-dolomite ore (so-called brown ore). Barite also contains significant quantities of strontium. 

Bodine, M. W., H. D. Holland, and M. Borcsik (1965), "Coprecipitation of Manganese and Strontium with Calcite. Symposium Problems of Postmagmatic Ore Deposition", Prague2, 401-406. 

An experimental study of strontium and lead diffusion in calcite, and... 

Unfortunately, there is generally a large scatter in the values obtained for these partition coefficients. A possible reason for this scatter, as shown by the study of Lorens (1981), is probably the major effect of precipitation rate on the values of the partition coefficients. It is interesting to note that the partition coefficients for the transition and heavy metals in calcite, studied by Lorens (Cd2+, Mn2+, Co2+), have a negative linear log partition coefficient- log precipitation rate relation, whereas Sr2+ has a positive relation. This behavior may be explained by the fact that the transition metal carbonates are isostructural with calcite, whereas strontium carbonate is isostructural with aragonite. Also, as precipitation rates increase, partition coefficients tend towards unity. 

Figure 7.39. Schematic diagram illustrating the effects of climate on meteoric diagenetic pathways for coeval carbonates originally composed of a polymineralic assemblage of calcite with various amounts of magnesium and strontium-rich aragonite. (After James and Choquette, 1984.)...

The depth distribution of the Sr/Ca ratios of the recrystallized calcites in these sediments was calculated from the Sr2+/Ca2+ concentrations in the pore waters and appropriate values of the strontium distribution coefficient as a function of temperature from 5-25°C, where... 

Bodine M.W., Holland H.D. and Borcsik M. (1965) Coprecipitation of manganese and strontium with calcite. Symposium Problems of Postmagmatic Ore Deposition, Prague 2,401-406. 

Jacobson R.L. and Usdowski H.E. (1976) Partitioning of strontium between calcite, dolomite, and liquids. Contrib. Mineral. Petrology 59, 171-185. 

Schifano G. and Censi P. (1986) Oxygen and carbon iosotope composition, magnesium and strontium contents of calcite from a subtidal patella coerulea shell. Chem. Geol. 58, 325-331. 

Using the solubility product constants for calcite and strontianite and assuming a calcium activity of 1.6 mmol/L, a distribution coefficient of 0.8 for strontium and 0.98 for calcite, and a ratio of 50 1 (=0.02) in the solid-solution mineral, the following equation gives the activity of strontium ... 

Sr/ Sr ratios in several samples of glacial runoff in the Himalayas are consistent with carbonate being the main source of calcium and strontium, but Ca/Sr ratios are relatively low. This suggests that these waters may precipitate calcite or aragonite when they warm (Jacobson et al., 2002). 

Several studies have used radiogenic isotopes to study groundwater questions on relatively short (or local) length scales (<2 km). Stuckless et al. (1991) combined the use of strontium and uranium isotope measurements, in studies of groundwaters and secondary calcite deposits in fault zones at Yucca Mountain, Nevada. They tested whether veins formed by upwelling of deep-seated waters... 

At intermediate depths (down to 500 m) groundwaters rapidly increase in concentration primarily by the addition of SO4 and Cl. The concentration of bicarbonate ions decreases because of the precipitation of mineral phases such as calcite. Local variations in chemistry and anions may be due to a variety of rock-water interactions or local processes that result in Na-SO4, Na-HC03, and Mg-S04 type waters. The pH begins to rise in this zone and oxygenconsuming reactions and redox mineral controls tend to lower the Eh. The brackish and saline waters found at these intermediate depths have longer residence times. Deep saline waters and brines occur in most locations below depths of 500 m. These fluids are Ca-Na-Cl or Na-Ca-Cl in composition and can have total dissolved loads up to 350 g L. Minor elements such as bromide and strontium can here be thousands of milligrams per liter. 

As subaerially exposed corals interact with meteoric waters, they are altered to calcite. This alteration results in a lost of strontium from the skeleton, and will obviously have strong effects on Sr/Ca paleothermometry. To avoid this problem, researchers routinely screen for the presence of calcite in fossil corals. A new study (McGregor and Gagan, 2003) demonstrates that local diagenesis can have marked affects on coral Sr/Ca, with a very large positive bias on... 

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