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《Geoscience》 2018-02
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Zircon U-Pb Ages and Geological Significance of Volcanic Rocks from Maoniushan Formation in the Northern Margin of Qaidam Basin

ZHANG Yaoling;NI Jinyu;SHEN Yanxu;WANG Chaoqun;GAO Wanli;HU Daogong;School of Earth Sciences and Resources,China University of Geosciences;Institute of Geomechanics,Chinese Academy of Geoscience;Minmetals Exploration and Development Co.Ltd.,China Minmetals Corporation;Cores and Samples Center of Land & Resources;  
The molasses of Maoniushan Formation rest unconformably on pre-Devonian strata and record the closure time of the Early Paleozoic ocean in the northern margin of Qaidam Basin. This research determinates zircon U-Pb isotopes from two rhyolite-tuff samples of volcanic rock member of upper Maomiushan Formation of Maoniushan mountain,northern margin of Qaidam Basin. The weighted mean206 Pb/238 U ages of magmatic zircons from two samples are( 396. 5 ± 2. 4) Ma( n = 17,MSWD = 3. 3) and( 395. 8 ± 1. 2) Ma( n = 20,MSWD= 1. 1),interpreted as the formation time of the volcanic rocks. Combining past dating results about Maoniushan Formation of East Kunlun orogenic belt,we concluded that the formation time of the Maoniushan Formation around Qaidam Basin should be Late Silurian to Late Devonian,and the Caledonian movement of East Kunlun and northern margin of Qaidam Basin ended before Early Devonian instead of Late Devonian,as traditional thought.
【Fund】: 中国地质调查局柴达木盆地及周缘油气基础地质调查子项目(121201104000150007)
【CateGory Index】: P588.14
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