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Fig. 22 | Geothermal Energy

Fig. 22

From: Geologic framework of the Fang Hot Springs area with emphasis on structure, hydrology, and geothermal development, Chiang Mai Province, northern Thailand

Fig. 22

Cross-sectional (vertical slices) from the 3D-magnetotelluric survey (final inverted model) of Amatyakul et al. (2016). Stations discussed in text refer to length in meters from the northwest end of profiles. Label “R” is interpreted as crystalline rock. Label “M” is interpreted as Cenozoic basin fill sediments. Profile a is 1 km west of the hot springs. The shallow (< 200 m) low resistivity anomaly “C1” was interpreted earlier in Amatyakul et al. (2016) as a manifestation of the hot springs. Because it lies west of the geothermal area, it is now believed to be the shaly Paleozoic sediment and perhaps the cataclastic clayey rock at the base of the Doi Kia fault. Southeast of the Mae Chan fault, the “C2” anomaly is in the shaly Cenozoic sediment. The C2 low resistivity anomaly may be caused by clay and not by hot pore water. The white line, below 400 m depth, corresponds to the N–NE trending deep structure indicated in Fig. 21b, and shows an apparent dip of 50°SE. Profile b is through the hot springs area and shows the flat lying, shallow (< 80 m deep) low resistivity anomaly at the geothermal area, labeled “C1.” Because Profile b crosses only crystalline rocks from stations 1 to 1600, we believe “C1” on Profile (b) is caused by shallow hydrothermal alteration zones along fractures in the crystalline rocks. To the southeast, Profile b crosses through the stepover zone between segments of the Mae Chan fault from stations 1650–2400. The apparent 36°SE dip between those stations also occurs on profile a and may be a tilted structure within the stepover zone

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