Albite authigenic

Desborough G. A. (1975). Authigenic albite and potassium feldspar in the Green River formation, Colorado and Wyoming. Amer. Mineral, 60 235-239. 

Even detrital or authigenic minerals in bulk equilibrium under some specific diagenetic condition (e.g., detrital albite in contact with albite-saturated water) may still be at disequilibrium with respect to their trace element and isotopic composition, as weU as their structural state. Such disequilibrium favors dissolution, even if fluids are near equilibrium with respect to the bulk mineral. 

Figure 5 Highly microporous aggregate of authigenic albite replacing a K-feldspar (evidenced by the adularia overgrowth, K). Frio Formation, Oligocene, South Texas. SEM image (source Milliken, 1989) (reproduced by permission of SEPM (Society for Sedimentary Geology) fromi. Sedim. Petrol, 1989, 59, 364).

Figure 7 Replacement driven by force-of-crystal-Uzation is characterized by authigenic phases that develop euhedral faces that are not plausibly constmed as crystal growth within pore spaces (a) sphalerite replaces albitized detrital feldspar and adjacent portions of clay-rich matrix, Frio Formation, Oligocene, South Texas and (b) siderite crystal (s) attacks a detrital K-feldspar (K) in sandstone, Breathitt Formation, Pennsylvanian, eastern Kentucky.

Gold P. B. (1987) Textures and geochemistry of authigenic albite from Miocene sediments, Louisiana Gulf Coast. J. Sedim. Petrol. 57, 353—362. 

Fig. 12. Paragenesis and relative mass of authigenic minerals in hydrolysis of coexisting K-feldspar and albite (after Helgeson et al., 1969b).

Authigenic albite occurs as discrete euhedral crystals (10 pm), overgrowths on detrital feldspars, and most commonly as replacement of detrital K-feldspar and plagioclase in the proximal and middle domain. K-feldspar grains in these areas commonly show partial albitization, whereas the detrital plagioclase is totally replaced by albite. Albitized feldspar grains display the typical optical, textural and chemical characteristics outlined by... 

It is also worth noting that sodium-feldspar is a common authigenic mineral, forming contemporaneously with sedimentation, and that authigenic albite generally shows greater purity than albite from other sources. 

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