| 阿拉善地块前中生代构造归属的新认识 |
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| 关键词:Alxa Block Pre-Mesozoic paleomagnetism zircon U-Pb age Hf isotope |
| 基金项目:国家专项“深部探测技术与实验研究”(编号: SinoProbe08-01; 201011074) |
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| Tectonic Affinity Reconnaissance of the Alxa Block in the Pre-Mesozoic |
| Tectonic affinity of the Alxa Block has long been a topic of much controversy. In this study, samples of Middle–Late Devonian sedimentary rocks were systematically collected from the Niushou Mountain in southeastern Alxa Block. The detrital zircon U-Pb ages define five age populations: 0.4–0.7 Ga, 1.0–1.3 Ga, 1.5–1.8 Ga, 2.4–2.7 Ga and ＞3.0 Ga. Zircons with U-Pb age spectra of 2.4–2.7 Ga, ＞3.0 Ga and their corresponding εHf(t) values are significantly different from data obtained from the North China Block, which implies that the Alxa Block was not part of North China until the Middle–Late Devonian. In addition, paleomagnetic study of the Late Devonian to Middle Triassic strata in the Niushou Mountain and the eastern part of the Alxa Block was carried out and, as a result, the apparent polar wander paths (APWP) were established. These results indicate that the Alxa Block had a close affinity with the Qaidam–Tarim Block, but was separated from the North China Block prior to the Pre-Mesozoic. The Alxa Block suffered from a counterclockwise rotation of 32° with respect to the North China Block during the Indosinian orogeny and finally amalgamated with the North China Block into a unified block before the Early Cretaceous. |
| YANG Zhen-yu,YUAN Wei,TONG Ya-bo,LIU Jing,WANG Yan.2014.Tectonic Affinity Reconnaissance of the Alxa Block in the Pre-Mesozoic[J].Acta Geoscientica Sinica,35(6):673-681. |
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