| 羌塘地块南部晚白垩世火山岩离子探针测年及其对红层时代的约束 |
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| 关键词:terrestrial red-beds volcanic rocks Late Cretaceous SHRIMP U-Pb isotopic dating southern Qiangtang Block |
| 基金项目:青藏高原地质矿产调查评价专项“羌塘盆地油气地质构造保存条件研究”(编号: 1212011221111) |
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| SHRIMP U-Pb Isotopic Dating of the Late Cretaceous Volcanic Rocks and Its Chronological Constraint on the Red-beds in Southern Qiangtang Block |
| Although no qualified chronological data are available for the red-beds, stratigraphic systems of redbeds outcropped widely in southern Qiangtang Block have been mostly regarded as belonging to the Miocene Kangtuo Formation according to regional geological survey at a scale 1:250,000. In this study, the red beds intercalated with volcanic rocks were discovered in the field, and magmatic zircons were selected from the volcanic rocks, which were suitable for the SHRIMP U-Pb isotopic dating so as to provide isotopic ages of high resolution for volcanic eruptions and further to give constraint on geological time of the related red-beds. The SHRIMP 206Pb/238U isotopic ages of magmatic zircons are (83.3?1.3) Ma and (75.65?0.82) Ma respectively for the trachyte-andesite intercalations in red beds of northern Belog Co and the andesite overlying red-beds in northern Zagya Zangbu. These high-resolution isotopic ages not only well reveal periods of volcanic eruptions in Late Cretaceous but also provide chronological evidence for the Late Cretaceous basins of red-beds in southern Qiangtang Block. Geological time of the terrestrial red-beds outcropped widely in southern Qiangtang basin should be changed from the Miocene Kangtuo Formation to the Upper Cretaceous Abushan Formation according to the SHRIMP U-Pb isotopic dating of volcanic rocks in northern Belog Co and Zagya Zangbu. Such change is significant for the better understanding of tectonic evolution and geological preservation conditions of oil-gas systems in southern Qiangtang Block. |
| WU Zhen-han,WU Xue-wen,ZHAO Zhen,LU Lu,YE Pei-sheng,ZHANG Yao-ling.2014.SHRIMP U-Pb Isotopic Dating of the Late Cretaceous Volcanic Rocks and Its Chronological Constraint on the Red-beds in Southern Qiangtang Block[J].Acta Geoscientica Sinica,35(5):567-572. |
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