Abstract
The Eastern Tianshan and East Junggar orogenic belts are major constituents of the southwestern Central Asian Orogenic Belt. This study applies low-temperature thermochronology to constrain the thermo-tectonic history of these two domains. Apatite fission track (AFT) dating of Paleozoic basement samples from the Eastern Tianshan and East Junggar dominantly yield Cretaceous (∼126–70 Ma) AFT ages, except for two granitic samples from the East Junggar with older ages of ∼239 and ∼157 Ma, respectively. Thermal history modeling reveals that the Eastern Tianshan and southern part of the East Junggar experienced moderate to rapid basement cooling throughout the Cretaceous. We interpret it as a far-field effect of accretion and collision along the south Eurasia margin since the Early Cretaceous. Major faults were reactivated and thus may have played an important role in controlling localized fast uplift and cooling. We also dated seven Mesozoic sandstone samples collected from the eastern margin of the Junggar Basin. The detrital AFT age peaks, together with inverse thermal history modeling of the basement, reveal that the East Junggar underwent late Permian to Early Jurassic cooling episodes. These cooling events are thought to be related to post-orogenic transpression along major faults and distal effect of Qiangtang-Eurasia collision. Combined with already published evidence, our new data suggest that the Eastern Tianshan and East Junggar did not undergo significant exhumation during the Cenozoic.
Highlights
The Central Asian Orogenic Belt (CAOB), is the largest intracontinental orogenic system in the world, incorporating the mountainous zone between the Siberian Craton in the north and the North China-Tarim Cratons in the south (Fig. 1a)
The adjacent East Junggar occupies a critical position between the Eastern Tianshan and Chinese Altai range in the southern CAOB, but its exhumation history has not been explored extensively by low-temperature thermochronological methods and is poorly understood
We present new apatite fission track (AFT) ages obtained on 14 Paleozoic basement rocks from the Eastern Tianshan, and 6 Paleozoic basement samples and 7 Mesozoic sandstones from the East Junggar
Summary
The Central Asian Orogenic Belt (CAOB), is the largest intracontinental orogenic system in the world, incorporating the mountainous zone between the Siberian Craton in the north and the North China-Tarim Cratons in the south (Fig. 1a). The CAOB was reactivated several times during the Meso-Cenozoic in response to accretion and collision at the southern Eurasian margin In the Eastern Tianshan, for example, several studies reported Cenozoic rapid cooling phases for the Bogda mountain range based on apatite fission track dating, and a distant effect of the IndiaEurasia collision was proposed (e.g., Zhu et al, 2006a; Li et al, 2008; Wang et al, 2008a). Along the Kangguer-Yamansu Arc, Yin et al (2019) carried out both zircon and apatite fission track analyses and proposed that the Tuwu-Yandong porphyry Cu deposits in the Eastern Tianshan experienced protracted slow cooling since the Late Triassic. The adjacent East Junggar occupies a critical position between the Eastern Tianshan and Chinese Altai range in the southern CAOB, but its exhumation history has not been explored extensively by low-temperature thermochronological methods and is poorly understood
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