Mountain building mechanism is one of fascinating research topics since the theory of plate tectonics has being proposed. The difference between frontal offscraping and basal underplating can be differentiated based on the relative timing between deformation and maximum metamorphic temperature. Taiwan is a classical arc-continent collision orogen due to Cenozoic oblique convergence between the Eurasian and Philippine Sea Plates. Its basement, the Tananao Metamorphic Complex (TMC), is expected to be experienced various orogenic events. Only the Tertiary sedimentary cover was influenced by one tectonic event. Although the basal underplating is the likely possible mechanism for the Hsuehshan Range based on previous studies, the mountain building mechanism of the southern Hsuehshan Range is not fully investigated yet. To explore the mountain building mechanism of the southern Hsuehshan Range, this study will conduct the following task: (1) gathering the distribution of maximum metamorphic temperature along the Southern Cross-Island Highway, the Taipei-Ilan Highway and Xindian-Wulai Highway based on published data of vitrinite reflectance and also filling out the missing data; (2) collecting geological maps and cross-sections, integrating the geological cross-sections and paleotemperature profiles, and investigating the possible mountain building mechanism; (3) conducting field mapping and collecting geothermometric sample at where the geological and geothermometric data is mssing; (4) analyzing the quartz vein information to estimate the stress state and pore pressure at different stages; (5) reconstructing paleostress state for different stages. Based on works and information completed by this study, the effect of stratigraphic thickness did not be able to cause the difference of maximum metamorphic temperature. The maximum metamorphic temperature distribution did not mimic with large-scale folded formation. There might be fault active to cause the temperature jump in the northern part of Hsuehshan Range. In summary, mountain building mechanism in northern part of Hsuehshan Range tended to be the basal accretion, as the results of other previous works. As for the southern part of Hsuehshan Range, the prediction of basal accretion is better than that of frontal accretion inferred from the available data. It is interesting to find out the late tectonic activity of faulting event in the northern Hsuehshan Range after maximum metamorphic temperature overprint. It intrigues future works, such as (1) what the relationship between those faults? And (2) whether these faults are still active?
|Effective start/end date||2018/08/01 → 2019/10/31|
- mountain building mechanism
- frontal offscraping
- basal underplating
- vitrinite reflectance
- geological cross-section
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