Abstract
Ijen geothermal area is high-temperature geothermal system located in Bondowoso regency, East Java. It is categorized as caldera-hosted geothermal system which is covered by quaternary andesitic volcanic rocks with steep topography at the surrounding. Several surface thermal manifestations are found, such as altered rocks near Mt. Kukusan and a group of Blawan hotsprings in the northern part of the caldera. Geomagnetic survey was conducted at 72 stations which is distributed inside the caldera to delineate the existence of hydrothermal activity. Magnetic anomaly was obtained by reducing total magnetic measured on the field by IGRF and diurnal variation. Reduction to pole (RTP) method was applied with geomagnetic inclination of about -32°. In general, the result shows that high magnetic anomaly is distributed at the boundary of study area, while low magnetic anomaly is observed in the centre. The low anomaly indicates demagnetized rock that probably caused by hydrothermal activity. It has a good correlation with surface alteration observed close to Mt. Kukusan as well as high temperature reservoir drilled in the centre of caldera. Accordingly, the low magnetic anomaly also presents the possibility of geothermal reservoir in Ijen geothermal area.
Highlights
Ijen Volcanic Complex is located in the Bondowoso, West Java, Indonesia
This paper presents the results of magnetic anomaly, reduce to pole (RTP) anomaly and the upwardcontinuation anomaly which were interpreted to get
The presence of surface manifestation is very rarely, only Blawan hotspring found in the northern part of study area and extremely acid fluid on the top of Mt
Summary
Ijen Volcanic Complex is located in the Bondowoso, West Java, Indonesia. Expectation of geothermal system appearance in the volcanic complex is indicated by the occurrence of Blawan hotspring in the northern part of caldera rim and steam heated extremely acid sulphate water on Ijen crater as the only surface manifestation in this area. The studies of magnetic anomalies are often useful for investigating high temperature geothermal systems hosted by Quaternary volcanic rocks [1]. These anomalies represent the demagnetization of reservoir rocks caused by hydrothermal processes due to thermal fluid and rock interactions. RTP transformation delineates the hydrothermally demagnetised rock which is shown as negative anomalies [2]. This paper presents the results of magnetic anomaly, RTP anomaly and the upwardcontinuation anomaly which were interpreted to get
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