Geoscientific Survey Results from the Jailolo Geothermal Field, Northern Halmahera, Indonesia

Abstract

The Jailolo geothermal field is located in a peninsula made up of the southernmost young volcanic piles of the volcanic arc that crosses the northwest arm of Halmahera Island. Early volcanism produced a large caldera forming Jailolo Bay. Later volcanism produced a maar at Bobo Payo. Dacitic pyroclastics have been erupted from the later Idamdehe volcanic centre, another maar, with the andesites of the prominent conical peak of G. Jailolo erupted later still. Surface thermal manifestations include steaming ground at the northern margins of the Idamdehe and Bobo Payo maars with the only hot springs lying on the coast; they are contaminated by seawater. Based on geochemical interpretations a water dominated system with reservoir temperatures of at least 2120 C is found. MT survey results show shallow bases of the conductor at both Bobo Payo and Idamdehe and possibly Jailolo volcano. In addition, at Idamdehe there is a coincident gravity high possibly associated with a heat source at depth. Overall, the conceptual model supports a drilling programme at Idamdehe, possibly for a binary power plant development. However since the reservoir temperature is a minimum, higher temperatures at depth that may support a flash plant can not be excluded prior to drilling.