川西须家河组火山岩夹层时代及其地质意义

发布时间：2018-09-15 05:14

【摘要】：四川盆地西部的上三叠统须家河组作为反演前陆盆地构造演化的物质基础,因缺少精确的同位素地层年龄阻碍了对盆山演化的进一步理解。作者在四川盆地西部须家河组中发现了一套火山(碎屑)岩夹层,通过LA-ICP-MS U-Pb同位素定量分析,获得1件凝灰岩样品中岩浆锆石的结晶年龄,其加权平均值为(214.7±1.6)Ma,属于晚三叠世诺利期。该年龄结果对四川盆地西部须家河组岩石地层单元的划分与对比可提供重要参考,同时为进一步约束龙门山隆升与川西前陆盆地的演化、古特提斯洋关闭等重大事件时限提供了新证据。基于四川盆地及周缘的区域火山活动对比结果,表明诺利期中期(210~222 Ma B.P.)是中国西部地区一次强烈的区域火山喷发阶段,其范围从羌塘地体延伸到东昆仑地体,所对应的构造事件并非传统的印支运动作用。
[Abstract]:The Upper Triassic Xujiahe formation in the western part of Sichuan Basin is the material basis for inversion of tectonic evolution of Foreland basin. The lack of accurate isotopic stratigraphic age hinders further understanding of basin-mountain evolution. The authors found a set of volcanic (clastic) rock intercalations in the Xujiahe formation in the western part of Sichuan Basin. The crystallization age of magmatic zircon in a tuff sample was obtained by LA-ICP-MS U-Pb isotope quantitative analysis. The weighted average value is (214.7 卤1. 6) Ma, belonging to the late Triassic Norrie period. The results can provide important reference for the division and correlation of lithostratigraphic units of Xujiahe formation in the western Sichuan basin, and further constrain the evolution of Longmenshan uplift and western Sichuan Foreland basin. The time frame for major events, such as the closure of the Gutertes Ocean, provides new evidence. Based on the results of regional volcanic activities in Sichuan Basin and its periphery, the results show that the middle period of the Norley period (210 ~ (22) Ma B.P.) It is a strong regional volcanic eruption stage in western China, which extends from the Qiangtang terrane to the East Kunlun terrane. The corresponding tectonic event is not a traditional Indosinian movement.
【作者单位】： "油气藏地质及开发工程"国家重点实验室(成都理工大学);中国石化西南油气分公司勘探开发研究院;
【基金】：国家自然科学重点基金项目(41230313) 国家自然科学基金青年基金项目(41102064)
【分类号】：P588.14

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