2004, pp 303-311

Silicates in Carbonate Speleothems, Guadalupe Mountains, New Mexico, U.S.A.

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Abstract

Silicates such as amorphous silica, quartz, trioctahedral smectite (stevensite), and possibly kerolite have formed with carbonate minerals in carbonate speleothems from caves of the Guadalupe Mountains, New Mexico, U.S.A. The likely sources of Si were the disseminated silicate minerals in situ in the Permian dolostone units in which the caves have developed. Ca- and Mg-carbonate mineral precipitation from thin water-films on speleothems due to evaporation and CO2 loss progressively increased the Si/(Ca+Mg) ratio, and concentrated the initially low percent of aqueous silica seeping into these caves. Amorphous silica precipitated with calcite and aragonite in stalagmites because the formation of these materials was rapid and the stalagmites are too young for the crystallization of quartz. The presence of organic material in the stalagmites hints that the amorphous silica may have an organic-related origin. Quartz and trioctahedral smectite formed with the Mg-carbonate minerals such as dolomite, huntite, and hydromagnesite. The authigenesis of quartz at the low temperature (15-25°C) of these caves, like that of well-ordered dolomite, required extensive periods of time (i.e., ≫1 ka) in a stable environment conducive for silicate precipitation. Kerolite-like silicates, in aragonite crusts, seemed to be intermediate precipitates between amorphous silicates and trioctahedral smectite.