Thermal and denudational history of granitoid batholith recorded by apatite fission track in the Dulong River region in northwestern Yunnan, since Late Miocene
滇西北独龙江岩体晚中新世以来的热史和剥蚀历史的磷灰石裂变径迹记录

The nine-apatite fission track ages of the granodiorite samples from a vertical profile in Dulong River region, where the intensively tectonic transition of the plateau occurs from east Tibet to west Yunnan, range from 4 to 6. 8Ma. The fission track analyses show that these samples are under the exhumed partial annealing zone and the apparent ages obtained are cooling ages with part mixed ages. The thermal history reveals there are at least three prominent cooling phases recorded by rock samples since Late Miocene time. The earlier deduced forward is at about 13 - 8Ma; the middle and the later are at about 5.5Ma and 2. 8Ma respectively, which are consistent with the timing of the regional unconformities. The denudation rates obtained from cooling history of these three phases are about 0. 10 - 0. 12mm/a, 0. 26 - 0. 3mm/a and 0. 85 - 1.02mm/a, indicating that the denudation processes are coincident with the sedimentary records in the basins developed around the margin of the southeastern Tibetan-northwestern Yunnan Plateau and adjacent areas. These results can provide quantitative timing reference to probe into the deformation of tectonic uplifting/extension the southern Tibetan-northern Yunnan plateau since Late Miocene time.