Silica Heat Flow and Thermal Structure of Southern Taiwan

This paper uses silica geothermometry to measure silica heat flows which are estimated from 72 hot and 2 cold springs and published heat flow data to outline the variation trends of regional heat flow and distribution pattern, as well as the tectonic thermal structure in the southern Taiwan. The regional heat flow values show wide varieties in different geological terranes, i.e. 80.3~154 mW/m2 in the Coastal Range, 63.7~256 W/m2 in the Central Range, 53.8~134 mW/m2 in the Hengchun Peninsula, 59.6~61.9 mW/m2 in the Western Foothills, respectively. The highest heat flow estimates of over 220 W/m2 are obtained in the Chinfeng, Chihben and Lulu hot springs where are located in the line of the easternmost Central Range of Taiwan. Meanwhile, it shows that the distribution pattern increase from the Coastal Range to the highest in the east Central Range, then decrease to the west. Combining the exhumation model of Taiwan and regional silica heat flow in this study, a Finite Element Method is employed to model the thermal and tectonic structure of the southern Taiwan. The modeling shows that the hot materials of ­exhumation­" may distribute in the east of the Central Range. The result is the same as the distributions of medium- to high-grade metamorphic rocks as well as the results of previous study. However, the absolute heat flow values are different between the modeling and measurements. The difference may be attributed to not consider (i) the magmatic residual heat in the Coastal Range; (ii) the slow heat loss during the rapid uplift rate in the Central Range; (iii) the frictional heat of faulting in the western foothill.