THE CHARACTERISTICS OF KAIPOHAN MANIFESTATION IN NORTHERN RAJABASA GEOTHERMAL FIELD, SOUTH LAMPUNG, INDONESIA
The Rajabasa Geothermal Field is located at Lampung Province, Indonesia. An observation conducted in 2022 showed the appearance of new manifestation in a shape of kaipohan on the northern flank of Mount Rajabasa. Kaipohan is a manifestation with intense gas discharge and the occurrence of argi...
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| Format: | Final Project |
| Language: | Indonesia |
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| Online Access: | https://digilib.itb.ac.id/gdl/view/78881 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | The Rajabasa Geothermal Field is located at Lampung Province, Indonesia. An
observation conducted in 2022 showed the appearance of new manifestation in a
shape of kaipohan on the northern flank of Mount Rajabasa. Kaipohan is a
manifestation with intense gas discharge and the occurrence of argillic-type
alteration, but with surface temperature quite similar to the ambient temperature.
The appearance of this non-thermal manifestation indicates the magmatic gas
activities and possibility of the subsurface fluid behaviour.
This study aims to characterize the kaipohan manifestation, including the
distribution of hydrothermal alteration minerals and both CO2 and H2S gas
discharges. The methods carried out consist of literature study, remote sensing
analysis, detailed field mapping, i.e. soil sampling, soil temperature and pH
measurements, CO2 and H2S gas concentration measurements, and laboratory
analysis, i.e. petrographic, X-Ray Fluorescence (XRF) and both X-Ray Diffraction
(XRD) of bulk and clay treatment analyses.
The results of remote sensing analysis shows that kaipohan is located in a circular
feature at the northern slope of Mount Rajabasa with significant vegetation stress.
Geological analysis shows the lithology of pyroxene andesite lava in kaipohan and
it’s controlled by a normal right slip fault with a trend of NW-SE. The alteration
minerals identified through laboratory analyses consist of cristobalite, tridymite,
kaolinite, pyrophyllite, illite, chlorite, smectite, alunite, and anhydrite. The area of
kaipohan has temperatures of 22–26?C (measured at ~30 cm depth) and soil pH
ranging between 0.16 and 7.00. The direct field measurement of gas using a gas
pump in the kaipohan area yielded concentrations higher than 4000 ppm of CO2
gas and H2S ranging between 5 to over 60 ppm. |
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