蒙古戈壁阿尔泰巴音陶勒盖地区二长花岗岩LA-ICP-MS锆石U-Pb年龄及其地质意义
LA-ICP-MS zircon U-Pb dating of monzogranite in Bayintolgoi, Gobi-Altay, Mongolia, and its geological implications
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摘要: 蒙古戈壁阿尔泰省巴音陶勒盖地区地处南戈壁-阿尔泰构造带南缘,区内构造活动活跃,中酸性侵入岩比较发育。采用LA-ICP-MS锆石U-Pb测年技术,对区内二长花岗岩中的锆石进行同位素年龄研究。阴极发光图像显示,锆石颗粒多为自形-半自形,且有明显的初始岩浆振荡环带,少见蚀变微区,结合较高的Th/U值(0.65~1.79),断定其为典型的岩浆成因锆石;30颗锆石的206Pb/238U年龄加权平均值为300.2±0.9Ma,显示二长花岗岩成岩时代为晚石炭世,代表了华力西中期的一次构造-岩浆事件,为约束南戈壁-阿尔泰构造带晚石炭世深成岩浆活动时限提供了新证据。Abstract: Bayintolgoi region in Mongolia is located in the southern South-Gobi-Altay tectonic zone. In this region, tectonic move-ment is active and intermediate-acidic intrusive rocks are well developed. Analysis of LA-ICP-MS zircon U-Pb ages was conduct-ed for zircons from monzogranite in Bayintolgoi, Mongolia. As revealed by the cathodoluminescence images, all the zircons from monzogranite are euhedral-subhedral and have oscillatory zoning, with almost all the zircons having high Th/U ratios. These charac-teristics suggest a magmatic genesis of the analyzed zircons. 30 zircons yielded a weighted mean 206Pb/238U age of 300.2±0.9Ma. The results show that the monzogranite was formed in Upper Carboniferous and there existed a tectonic-magmatic event in the Middle Variscan. These data provide new evidence for the Upper Carboniferous orogeny in South-Gobi-Altay tectonic zone.
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Key words:
- monzogranite /
- LA-ICP-MS zircon U-Pb ages /
- South-Gobi-Altay /
- Mongolia
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