Abstract
Low-temperature thermochronological techniques, specifically apatite (U–Th)/He and apatite fission-track dating, were used to reconstruct the thermal history of southeastern Thailand. This area is intersected by vast and complex fault networks related to the Cenozoic Mae Ping and Three Pagodas Faults. These were identified from satellite imagery and confirmed by field observations. New apatite fission-track and apatite (U–Th)/He data were collected from crystalline basement blocks within these fault networks. Ages obtained range from 48 to 24 Ma, with most of the samples clustering between 36 and 24 Ma. Thermal history modelling indicates late Eocene–Oligocene exhumation of the exposed granitic and metamorphic basement rocks in southeastern Thailand. Exhumation was regional and was contemporaneous with sinistral fault activity during the late Eocene–early Oligocene along the Mae Ping Fault and Three Pagodas Fault. Moreover, this exhumation occurred coevally with a synrift phase of intracontinental offshore rift basin and half-graben basin development in the eastern Gulf of Thailand. The phase of exhumation ended in the early Miocene, as a result of the changing plate-tectonic forces along the complex plate boundaries of Sundaland. Supplementary material: AFT data, radial plots and the detailed procedure of thermal history modelling are available at https://doi.org/10.6084/m9.figshare.c.4633064
Highlights
All our obtained apatite fission-track (AFT) ages are Cenozoic and range from 48 to 23 Ma (Table 3, Figure 5), with the majority of central ages concentrated near the Eocene–Oligocene transition around c. 33 Ma
Based on our new low-temperature thermochronological data and thermal history modelling on basement rocks in southeastern Thailand, we can draw the following conclusions
Most apatite fission-track and (U–Th)/He ages concentrate around 36–26.8 Ma (24 Ma), which is in agreement with previous estimates of the timing of exhumation along the major Mae Ping and Three Pagodas Fault zones
Summary
The AFT central age for sample NT-02 of 33.7 ± 1.8 Ma combined with a unimodal, moderate to high mean track length value of 13.4 μm and two single grain AHe (FT-corrected) ages of 25.4 ± 0.5 and 29.7 ± 0.3 Ma indicate rapid cooling and associated final late Eocene–early Oligocene exhumation to shallow crustal levels of the metamorphosed rocks exposed in the Klaeng Fault zone (Khao Chao area).
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