Clay minerals authigenic formation

Von Damm and Edmond (1984) utilized the lakes of the Ethiopian and northern Kenya rift zones to examine reverse weathering (the formation of authigenic clay minerals), because here evaporative concentration had not proceeded to the extent that salt precipitation interfered with a mass balance approach. They found that —60% of an alkalinity deficit could be accounted for by processes other than carbonate precipitation, and concluded that solute magnesium was lost as rapidly to clay as solute calcium was to carbonate. This situation, particularly in volcanic terrain, was also initially recognized at saline Lake Abert, Oregon, by Jones and VanDenburgh (1966). 

Allophane production. Allophane is a non-crystalline, hydrous aluminosilicate of highly variable composition, which forms as a common colloidal constituent of soils it may be an intermediate in the formation of some authigenic clay minerals. 

Formation of clay minerals. It is generally agreed that some of the dissolved silica in soils is utilized in the formation of authigenic clay minerals however, the quantitative significance of this process is unclear (McKeague and Cline, 1963). 

Zeolite deposits that formed by the above mechanism commonly show a vertical zonation of authigenic silicate minerals similar to that in the John Day Formation. Tertiary tuffs at the Nevada Test Site in southern Nevada were altered after burial by subsurface water (59), but the authigenic mineral zonation is more complex than that in the John Day Formation. The upper zone consists of unaltered glass with local concentrations of chabazite or clay minerals. Zeolitic tuff continues downward for as much as 6000 feet. A zone rich in clinoptilolite underlies the zone of unaltered glass and is succeeded downward by zones rich in mordenite and analcime, respectively. 

Ar/ Ar analyses of authigenic muscovite, timing of stylolitization, and implications for pressure solution mechanisms Jurassic Norphlet Formation, Offshore Alabama. Clays and Clay Minerals, 41, 269-279. 

Prentice Hall, Upper Saddle River, NJ Shieh YN, Suter TG (1979) Formation conditions of authigenic kaolinite and caldte in coals by stable isotope determinations. Clays Clay Miner 27 154-156 Siddall M, Kaplan MR (2008) A tale of two ice sheets. NatGeosci 1 570-571... 

Freed RL, Peacor DR (1992) Diagenesis and the formation of authigenic illite-rich I/S crystals in Gtrlf Coast shales TEM study of clay separates. J Sed Petrol 62 220-234 Frey M (1969) A mixed-layer paragorrite/phengite of low-grade metamorphic origin. Contrib Mineral Petrol 14 63-65... 

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