Rock Geochemistry of the Tongonan Geothermal Field, Leyte, Philippines

Abstract

Major and trace element analyses of 52 whole rock core samples from 30 wells in the Tongonan geothermal field reveal broad geochemical trends that have been integrated into a hydrogeochemical model of the field. The early of the entire field was thought to comprise periods of potassium then hydrogen lite-bearing veins and breccias cut and illite-bearing rocks which have been uplifted by at least 1 and are at or appear within a few hundred of the surface. The mineralisation of the current system below about 3 is conridered to consist of biotite, pyrophyllite, and other porphyry copper mineral The present, shallow than 3 central part of the appears to be undergoing sodium, and to a lesser extent magnesium and iron, these elements being derived from volcanic and tuffs located mainly on the field Heat and chemical transfer alro occurr from the pluton over a wide area to Malitbog, but fluid flow and permeability in the pluton is conridered to be greater in the Upper area where the highest temperatures and greatert amount of mineralisation occurs. Massive withdrawal of fluid for approximately may caure in the Upper Mahiao wells and pipelines.