Devonian post-orogenic extension-related volcano-sedimentary rocks in the northern margin of the Tibetan Plateau, NW China: Implications for the Paleozoic tectonic transition in the North Qaidam Orogen
| Autor: | Jindong Gao, Gang Chen, Qiao Feng, Qian Liu, Dingwu Zhou, Yan Chen, Yu Qin, Qianqian Jiao, Lihui Pan, Kaizhen Zou |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
geography
geography.geographical_feature_category Paleozoic 020209 energy Geochemistry Geology 02 engineering and technology 010502 geochemistry & geophysics 01 natural sciences Unconformity Devonian Craton Mountain formation Carboniferous 0202 electrical engineering electronic engineering information engineering Rodinia Late Devonian extinction 0105 earth and related environmental sciences Earth-Surface Processes |
| Zdroj: | Journal of Asian Earth Sciences. 156:145-166 |
| ISSN: | 1367-9120 |
| DOI: | 10.1016/j.jseaes.2018.01.009 |
| Popis: | The Maoniushan Formation in the northern part of the North Qaidam Orogen (NQO), NW China, contains key information on a Paleozoic change in tectonic setting of the NQO from compression to extension. Here, new zircon U–Pb, petrological, and sedimentological data for the lower molasse sequence of the Maoniushan Formation are used to constrain the timing of this tectonic transition. Detrital zircons yield U–Pb ages of 3.3–0.4 Ga with major populations at 0.53–0.4, 1.0–0.56, 2.5–1.0, and 3.3–2.5 Ga. The maximum depositional age of the Maoniushan Formation is well constrained by a youngest detrital zircon age of ∼409 Ma. Comparing these dates with geochronological data for the region indicates that Proterozoic–Paleozoic zircons were derived mainly from the NQO as well as the Oulongbuluk and Qaidam blocks, whereas Archean zircons were probably derived from the Oulongbuluk Block and the Tarim Craton. The ∼924, ∼463, and ∼439 Ma tectonothermal events recorded in this region indicate that the NQO was involved in the early Neoproterozoic assembly of Rodinia and early Paleozoic microcontinental convergence. A regional angular unconformity between Devonian and pre-Devonian strata within the NQO suggests a period of strong mountain building between the Oulongbuluk and Qaidam blocks during the Silurian, whereas an Early Devonian post-orogenic molasse, evidence of extensional collapse, and Middle to Late Devonian bimodal volcanic rocks and Carboniferous marine carbonate rocks clearly reflect long-lived tectonic extension. Based on these results and the regional geology, we suggest that the Devonian volcano-sedimentary rocks within the NQO were formed in a post-orogenic extensional setting similar to that of the East Kunlun Orogen, indicating that a major tectonic transition from compression to extension in these two orogens probably commenced in the Early Devonian. |
| Databáze: | OpenAIRE |
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