Albitization of plagioclase

Albitization of plagioclase feldspar, as in reaction (3) below, also increases calcium concentrations, but lowers the concentration of sodium ... 

Boles, J.R., 1979. Active albitization of plagioclase in Gulf Coast Tertiary sandstones. Geol. Soc. Am., Abstr. Progr., p. 391. 

Garbarini, J.M. and Carpenter, A.B., 1978. Albitization of plagioclase by oil-field waters. 

Boles, J.R. Ramseyer, K. (1988) Albitization of plagioclase and vitrinite reflectance as paleothermal indicators, San Joaquin Basin. In Studies of the Geology of the San Joaquin Basin (Ed. Graham, S.A.). Soc. Econ. Paleont. Miner. Pacific Sec. Publ., 60, 129-139. 

Tsuchiyama A. (1985a) Dissolution kinetics of plagioclase in the melt system of diopside-albite-anorthite and origin of dusty plagioclase in andesites. Contrib. Mineral. Petrol. 89, 1-16. 

Plagioclase - feldspar solid solution between CaAl2Si208 (anorthite) and NaAlSi30s (albite). Maskelynite is a diaplectic glass of plagioclase composition. 

Morad S., Bergan M., Knarud R., and Nystuen J. P. (1990) Albitization of detrital plagioclase in Triassic reservoir sandstones from the Snorre Field, Norwegian North Sea. J. Sedim. Petrol. 60, 411-425. 

Figure 2.3. Chemical compositions of plagioclases (glass) of the starting material and of the shocked samples at various conditions in terms of mol. % endmembers albite (Ab NaAlSijOg), anorthite (An CaAliSiiCJg), and orthodase (Or, KAlSijOg).

Predicting the Ca/Na ratio of the resultant brine accurately is difficult, and depends on the availability and reactivity of plagioclase and whether or not the brine remains in contact with halite -1- quartz -I- plagioclase. If a halite-saturated (or near-halite-saturated) brine flowed into a clastic section lacking halite as a phase, Na removed from the brine by albitization would cause undersaturation with respect to halite but Na could not be replaced by continued halite dissolution. 

Average anorthite (An) content of plagioclase. fAverage An content of plagioclase, excluding albite (Ab). 

V. C. Juan (National Taiwan University, Taipei, Taiwan) Zeolites and low-temperature plagioclase can be closely correlated. We have done work with thomsonite dehydrated into anorthite, analcime into albite, and in between with intermediate plagioclase into an association of analcime, garronite, and thomsonite. The divisions between different zeolites are also correlated with the structural division of plagioclase. 

---