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| Titel |
Field based geothermal exploration: Structural controls in the Tarutung Basin/North Central Sumatra (Indonesia) |
| VerfasserIn |
M. Nukman, I. Moeck |
| 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 |
250067667
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| Zusammenfassung |
| The Tarutung Basin is one of several basins along the prominent Sumatra Fault System (SFS)
which represents a dextral strike slip fault zone segmented into individual fault strands. The
basins are located at right-stepping transfer. The Tarutung Basin hosts geothermal
manifestations such as hot springs and travertines indicating a geothermal system with some
decent potential in the subsurface. As part of geothermal exploration, field geology is
investigated focusing on how the structural setting controls the thermal manifestation
distribution.
A complex fault pattern is now newly mapped and evidences sinistral faults striking E-W
(Silangkitang), normal faults striking SE-NW at the eastern strand of Tarutung
Basin (Sitompul) and normal faults striking NW-SE at the western strand of the
basin (Sitaka). These structures form an angle greater than 450 with respect to the
current maximum principal stress which is oriented in N-S. Secondary sinistral shear
fractures identified as antithetic Riedel shears can be correlated with hot spring
locations at Silangkitang, forming an angle of 500 with respect to the current maximum
stress. A large angle of normal fault and antithetic Riedel shear trend with respect
to the current maximum stress direction indicates that the structures have been
rotated.
Unidentified dextral strike slip faults might exist at the eastern strand of Tarutung
Basin to accommodate the clockwise rotation between the eastern boundary of the
basin and the NW-SE striking normal fault of Panabungan. Normal faults striking
parallel with the SFS East of the basin are interpreted as dilatational jogs caused
by the clockwise rotated block movement with respect to the NW-SE fault trend
sinistral shear along ENE-WSW faults. Silicified pryroclastics in association with
large discharge at hot springs at these NW-SE striking normal faults support this
hypothesis.
As proposed by Nivinkovich (1976) and Nishimura (1986) Sumatra has rotated 20Ë
clockwise since the last two million years due to the increase in sea-floor spreading rate of the
Indian-Australian plate. The combination of regional clockwise rotation of Sumatra with
local clockwise rotation caused by simple shear along the dextral SFS might generate the
complex fault pattern which controls fluid flow of thermal water and placement of hot
springs.
Acknowledgements :
Deutscher Akademischer Austausch Dienst, DAAD.
German Ministry for Education and Research, BMBF.
Badan Geologi – KESDM Bandung, Indonesia. |
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