SHRIMP ZIRCON U-Pb AGES OF RHYOLITE FROM THE NAIJ TAL GROUP IN THE EAST KULUN OROGENIC BELT
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摘要: 纳赤台群是东昆仑早古生代造山带中岩石组成复杂的重要岩石地层单位，长期以来对其形成时代存在较大分歧。采用SHRIMP锆石U-Pb定年方法，对格尔木南水泥厂地区出露的纳赤台群石灰厂组流纹岩进行了高精度年代测定，结果表明，流纹岩中13个岩浆岩锆石206Pb/238U年龄平均值为450.4 ± 4.3 Ma，它被解释为火山作用年龄，由此限定纳赤台群石灰厂组火山岩段形成时代为晚奥陶世。Abstract: The Naij Tal Group is a major lithostratigraphic unit with a complex composition in the East Kunlu Paleozoic orogenic belt, and there has long been debate on its formation time. The An average SHRIMP zircon 206Pb/238U age of 450.4 ± 4.3 Ma has been obtained for 15 rhyolite samples collected from the Shihuichang Formation of the Naij Tal Group south of Gelmud. It was interpreted as the age of a volcanic activity, so the Shihuichang Formation of the Naij Tal Group can be considered to form in the Late Ordovician.
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Key words:
- Naij Tal Group /
- zircon U-Pb age /
- Late Ordovician /
- eastern Kunlun orogenic belt
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图 1 格尔木南地质构造简图及采样点位置
1-中三叠统闹仓坚沟组; 2-下三叠统洪水川组; 3-上石炭统浩特洛洼组; 4-志留—泥盆系牦牛山组; 5-奥陶—志留系纳赤台群哈拉巴依沟组; 6-奥陶—志留系纳赤台群石灰厂组碳酸盐岩段; 7-奥陶—志留系纳赤台群石灰厂组火山岩段; 8-纳赤台群水泥厂组; 9-中元古界万宝沟群碳酸盐岩组; 10-志留纪流纹英安斑岩; 11-逆断层; 12-采样点位置
Figure 1. Geological map of south to Golmud and sample sites
图 2 纳赤台群石灰厂组流纹岩地质特征和采样点位置
Figure 2. Characteristics of the rhyolite from Shihuichang Formation of Naij Tal Group and sample sites
图 3 纳赤台群石灰厂组流纹岩显微结构(正交偏光)
Figure 3. Microtexture of the rhyolite from Shihuichang Formation of Naij Tal Group
图 5 锆石U-Pb一致曲线图
Figure 5. The zircon U-Pb concordia diagrams of rhyolite from Naij Tal Group
表 1 纳赤台地区岩石地层单位
Table 1. Lithostratigraphic units in Naij Tal area
表 2 纳赤台群流纹岩DG33-1锆石SHRIMP分析数据
Table 2. SHRIMP U-Pb data for zircons from rhyolite in Naij Tal Group
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