|
Journal: |
Journal of Asia Earth Science 2018 No.156
clicks:246 |
|
Title:
|
|
|
Author:
|
YuQin QiaoFeng GangChenaYanChencKaizhenZoucQianLiudQianqianJiaoeDingwuZhoubLihuiPanaJindongGaoa |
|
Adress: |
Shandong Provincial Key Laboratory of Depositional Mineralization & Sedimentary Minerals, Shandong University of Science and Technology, Qingdao 266590, China |
|
Abstract:
|
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 |
|
Comment: |
|
|
|
|
