Chemistry of Epidotes and Chlorites in the Tongonan Geothermal Field, Leyte (Philippines)

Abstract

Chlorites and epidotes in altered andesites 4 wells in the Tongonan Geothermal Field were analyzed to any correlations of compositionalvariation with well With increasing well temperature, most of the chlorites show increasing and the show and but increasing tetrahedral Al. This is consistent observed compositional changes in other geothermal and metamorphic areas and is therefore taken to indicate that chlorites and epidotes are in equilibrium with the present-day fluids. However, chlorites from two of the wells studied show trends opposite to those prevailing elsewhere suggestingthatm these cases the minerals formed by a fluid which could have been hotter than the presentday fluid. changes in the compositionof chlorite and epidoteobserved m other (and metamorphic)areas is taken to indicatethe existenceof relictminerals in the alterationassemblage.