PROGRESSIVE BURIAL METAMORPHISM AND SOME GEOCHEMICAL ASPECTS OF GEOSYNCLINAL SEDIMENTATION

VISITACION V. GERVASIO

 

 

 

ABSTRACT


Mineral transformations in the zones of diagenesis and burial metamorphism are directed towards more compact structures, in response to the increasing role of pressure, more than any other factor, in the physico-chemical environment. These are manifested by mineral changes involving: (1) dehydrationódesilication; (2) desilication, accompanied by change in coordination state of Al from tetrahedral to octahedral; (3) transformation into denser polymorphs; (4) increasing fixation of smaller cations with stronger bonds in lieu of bigger ions with weaker bonds; and (5) devitrification of glass.

The analcite to albite transformation in the burial metamorphic zone is herein considered a dehydration-desilication, rather than a dehydration-silicification reaction. SiO2, once released, tends to form quartz rather than take part in silicification. Quartz, having a relatively compact crystal structure, is stable under the prevailing physico-chemical conditions.

 

 

 

Geological Society of the Philippines

Unit 250, 2nd Floor, Cityland Pioneer, 128 Pioneer Street, Mandaluyong City, Philippines

Tel: +(63-2) 633-9025