PRELIMINARY GEOCHEMICAL RECONNAISSANCE MAPPING OF DEIDEI AND IAMALELE GEOTHERMAL RESOURCES, FERGUSSON ISLAND, ESA’ALA DISTRICT, MILNE BAY PROVINCE, PAPUA NEW GUINEA

Abstract

A geochemical analysis of samples (water, gas and rock) from Deidei and Iamalele thermal areas of the Milne Bay Province of Papua New Guinea (PNG) revealed that the Yaiyaiboalana and Seuseulina hot springs in Deidei thermal area contain high levels of Cl at neutral pH with low bicarbonate. This was obtained following a chemical reconnaissance survey carried out by Mineral Resources Authority (MRA) in April 2013. The samples were analyzed at the New Zealand Geothermal Analytical Laboratory (NZGAL), GNS Science, Warakei, New Zealand.
Samples collected from Munamelala in the Iamalele thermal grounds were analyzed to be steam heated acid sulphate fluids (pH~1.7, SO4 ~2500 mg/L, and very little Cl~1mg/L) which could not be used to infer geothermal reservoir conditions.
Based on silica (TQZ) geothermometry and cation geothermometry, Yaiyaiboalana and Seuseulina hot springs may well be fed from high temperature geothermal reservoir conditions suitable for electrical power generation. The calculated reservoir temperature (TNa/K) inferred for Yaiyaiboalana and Seuseulina springs were 270°C and 280°C respectively.
Possible contamination by seawater is likely as the springs are situated approximately one kilometer inland from the sea at an elevation of 9-23m above sea level. However, there is insufficient data to conclude whether sea water is an end-member component as high temperature water – rock interaction has modified the composition and the water isotopic data is inconclusive.