Geothermal Systems of Northern Thailand and Their Association with Faults Active During the Quaternary

Many of northern Thailand hot springs systems are associated with regions of active faulting. An arcuate pattern of wells with high-fluoride water occurs in the Chiang Mai basin. The pattern is parallel to the Mae Tha fault which cuts Paleozoic and Mesozoic rocks 10 km east of the basin. The San Kamphaeng geothermal system is within parallel faults in Paleozoic rocks. The Mae Tha fault is believed to be active in the Quaternary. A conceptual diagram shows deep groundwater circulation driven by ~300 to 800 meters of relief in the hills east of the basin. The Mae Chan geothermal system lies along the active, left-lateral, strike-slip Mae Chan fault in northernmost Thailand. The Mae Chan hot springs emanate from Triassic granitic rocks in the fault zone. Several other hot springs emanate from the along the fault. It appears that late Cenozoic activity along faults creates permeability that allows upward flow of deep (> 2 km) percolating groundwater. These systems are currently being evaluated by geothermometry of water chemistry, geophysical exploration, and detailed geologic mapping. Aim is to establish drilling locations for wells that will provide 2-5 MWe of power generation.