【摘要】 云南晋宁地区柳坝塘组凝灰岩SHRIMP锆石U-Pb年龄(890±9Ma、834±34Ma)和Hf同位素分析结果,有利于云南晋宁地区青白口系的年代定位,为中国南、北方青白口纪地层对比提供了可靠的同位素年龄数据。通过同位素年代学研究探讨昆阳群与八街群的关系,对比华南块体青白口系区域地层和构造演化序列,特别是对晋宁运动底界年龄进行限定。对柳坝塘组凝灰岩样品LBT26-3和LBT26-4进行Hf同位素分析。结果显示,柳坝塘组凝灰岩主要来自于中元古代的岩浆物质,几乎不含地壳组分。样品LBT26-3的εHf(t)值较高,二阶段Hf模式年龄较小,说明其组分为更年轻的岩浆物质,显示在柳坝塘组形成时期可能发生了持续的陆壳增生事件,此区域可能更多为洋壳组成。上述年龄为云南青白口纪地层的对比增添了可靠的年代学依据。更多还原

【Abstract】 This paper reports SHRIMP zircon U-Pb(890±9Ma, 834±34Ma) and Hf isotopic analyses of tuff from Liubatang Formation of Qingbaikou System in Jinning County, Yunnan Province. The authors investigated the tectonic background and regional stratigraphic correlation in Yunnan and provided qualified data for the stratigraphic correlation between South China and North China in Qingbaikouan period. Hf isotopic analysis of samples of LBT26-3 and LBT24-4 was conducted. The characteristics of Hf isotopic diagram show that the tuff of the Liubatang Formation came from the Mesoproterozoic magma with the addition of very insignificant crustal composition. The SHRIMP U-Pb dating mentioned above provides new evidence for the metamorphosed strata correlation in Yunnan Province.更多还原