Active albitization of plagioclase, Gulf Coast Tertiary.

Abstract

The conditions controlling on-going albitization in a modern burial setting are documented on the basis of a study of feldspathic sandstones of the Wilcox (Eocene) and Frio (Oligocene?) formations of the Gulf Coast basin of Texas. The diagenetic process takes place in a zone at 2500-2800 m burial depths, at T 110o-120oC, under fluid P of approx 0.2-0.5 kbar and total overburden P of approx 0.58- 0.66 kbar. Surface dissolution kinetics, as controlled by the character of the surfaces and lattice defects of the albitized plagioclase grains and pore-fluid or ion mobility, are important factors in the albitization process, which is considered to involve a solution-precipitation mechanism rather than solid-state diffusion.-M.S.