川西列古六组底部凝灰质杂砾岩锆石U-Pb年龄及其意义

发布时间：2018-01-24 13:51

  本文关键词： 扬子西缘 新元古代冰川 列古六组 LA-ICP-MS 锆石U-Pb年龄　出处：《矿物岩石》2017年01期 　论文类型：期刊论文

【摘要】：长期以来,川西地区列古六组一直被认为与新元古代冰川晚冰期(Marinoan)地层南沱组相当,从而认为扬子西缘缺失早冰期(Sturtian)沉积,但缺少可靠的年代学证据。针对川西列古六组底部凝灰质杂砾岩锆石LA-ICP-MS U-Pb定年结果表明,~(206)Pb/~(238)U年龄范围为722 Ma~902 Ma,在~725 Ma,~780 Ma,~820 Ma和~850 Ma具有明显的峰值。其中,最年轻一组~(206)Pb/~(238)U年龄加权平均值为724 Ma±12 Ma,代表列古六组底部杂砾岩的最大沉积时间。列古六组沉积序列特征以及华南Sturtian冰期启动年龄分布范围综合分析可知,川西列古六组下段为早冰期沉积,可与长安组对比,而上段则为间冰期沉积,可与富禄组和大塘坡组对比。因此,扬子西缘存在早冰期(Sturtian)和间冰期沉积,不存在晚冰期(Marinoan)沉积。
[Abstract]:For a long time, the Liegu 6 formation in western Sichuan area has been considered to be equivalent to the Neoproterozoic late glacial Marinoanian formation of the Nantuo formation. It is concluded that the western margin of Yangtze lacks early glacial Sturtian) deposits. However, reliable geochronological evidence is lacking. The zircon LA-ICP-MS U-Pb dating results of the six groups of Liegu conglomerate in western Sichuan show that the zircon from the tuffaceous complex is of great significance. The age range is 722 Ma~902 / 238U and 725 Ma~902 / 780Ma. There are obvious peaks at 820 Ma and 850 Ma, among which the youngest group is 724 卤12 Ma, the weighted average of the age is 724 Ma 卤12 Ma. It represents the maximum sedimentary time of the six groups of Liegu complex, the characteristics of the sedimentary sequence of the six groups and the range of the onset age distribution of the Sturtian glacial age in South China. The lower member of the six member of Liegu formation in western Sichuan is an early glacial deposit, which can be compared with Changan formation, while the upper member is an interglacial deposit, which can be compared with that of Fulu formation and Datangpo formation. There are early glacial Sturtian) and interglacial deposits in the western margin of Yangtze, but no late glacial Marinoan) deposits.
【作者单位】： 中国地质调查局成都地质调查中心;国土资源部沉积盆地与油气资源重点实验室;成都理工大学沉积地质研究院;中国地质科学院研究生院;
【基金】：国家自然科学基金项目(41502114,41672112) 中国地质调查局项目(12120114067901,1212011121105,121201010000150016)
【分类号】：P597.3;P588.212.5
【正文快照】： 1.中国地质调查局成都地质调查中心,四川成都610081;2.国土资源部沉积盆地与油气资源重点实验室,四川成都610081;3.成都理工大学沉积地质研究院,四川成都610059;4.中国地质科学院研究生院,北京p膒苝蘰，

本文编号：1460199