A REPLICATION MECHANISM OF THE TRANSMISSION OF GENETIC INFORMATION DURING PSEUDOMORPHOUS REPLACEMENT OF ALBITE BY SANIDINE

Abstract

The replacement of albite by potassic feldspar in 0.1 m KHCO3 solution at 300°C and a pH of 9 was modelled experimentally with the use of polished plates of albite and smaller polished plates of sanidine tightly aligned against each other. The sharp imprints of sanidine plates on the albite surface observed after the trials indicated that the reaction proceeded more actively within an imprint. The origin of the imprints resulted from the accelerating effect of the sanidine surface upon the K-feldspathization of the albite. This effect extends for a distance of tenths of millimeters, thus ensuring the transmission of genetic information on the loci of defects in the precursor mineral. Two modes of pseudomorphous replacement are recognized: (1) the advance of the smooth sanidine surface into the albite plate as a flat projection, with a depression of the same shape and size formed at the albite surface and (2) the dendritic growth of sanidine in tunnel-like hollows, which resulted from selective albite dissolution. Most likely, the difference in the replacement mode is caused by the nonuniform distribution of structural defects in albite along specific crystallographic directions, with defects serving as sites of the most active albite dissolution. The mechanism of the long-range effect of the sanidine surface, which is apparently related to its charge, should be taken into account in the modern theory of crystal growth.