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| Titel |
Preliminary assessment of the geothermal system of the Tiris volcanic area, East Java, Indonesia. |
| VerfasserIn |
F. Deon, I. Moeck, T. Sheytt, M. S. Jaya |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250067055
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| Zusammenfassung |
| Indonesia, with 15 % of the world´s active volcanoes, hosts a total estimated geothermal
potential of 27000 MW of which 1197 MWe in 2011 have been installed. Exploration of
magmatic remote areas is therefore important. Our investigation area is located at the volcano
Lamongan, Tiris East Java, Indonesia, which is part of the modern Sunda Arc Region,
characterized by extensional regime. The average ground water temperature in the area
ranges between 27 and 29 Ë C and the warm springs between 35 – 45 Ë C, evidencing a
geothermal potential of the area. Numerous maars and cindered cones have been located and
studied here, some of them with a NW – SE lineament similar to the Tiris fault (only
observed in satellite images).
In this first exploration stage we characterized the geochemistry of the springs and
investigated the petrology of the rocks. They were analyzed in terms of mineral composition
(optical microscopy and electron microprobe) and major element composition (X-ray
fluorescence). The samples have a typical basaltic – basaltic andesite composition,
with abundant plagioclase with An65 up to An90, as well as olivine and pyroxene.
The plagioclase crystals are several mm large, twinned and show no hydrothermal
alteration.
The fluid chemistry was determined in term of cation and anion concentration with
Inductively Coupled Plasma Mass Spectrometry. The chemistry of geothermal waters
provides specific information about the deep of the fluids in geothermal system and the
discharge location.
The concentrations of Na+, Ca2+, Li+, B3+ and Cl- suggest that the water of the
Lamongan area derive from sea water intrusions. The high permeable pyroclastites, overlain
by lower permeable basalt – andesitic basalt, observed in the field, may have channeled the
sea water from the coast to the Tiris area. A structural lineament, NW – SE, may control the
water intrusion, as the lineament of the springs confirms. The high HCO3-concentration in
the fluid samples, as no carbonate rocks are known in the area, must derive from another
source (magma chamber?). The occurrence of pyroclastites overlain by andesite suggests
the presence of a concealed layer. This could be responsible for capturing SO42-
accounting to the HCO3- excess of the springs, located in the outflow zone of the
system.
Acknowledgements
We thank the German Federal Ministry for Education and Research (BMBF) for funding
this German project under the grant 03G0753A. We would also like to thank Iris Pieper for
the ICP water analyses at the TU Berlin, and DINAS ESDM, Surabaya, Indonesia for their
support in the field campaigns. |
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