桂东地区鹰扬关构造混杂岩40Ar/39Ar年龄及其构造意义

40Ar/39 Ar Dating of Yingyangguan Tectonic Melange in the Eastern Guangxi, China and Its Tectonic Implications

鹰扬关构造混杂岩出露于湘粤桂三省(区)交界处,构造上位于扬子陆块与华夏地块结合带西南段。对鹰扬关构造混杂岩变质沉积岩和变质火山碎屑岩中绢云母及白云母开展了40Ar/39Ar年代学研究,获得了(377.8±2.6)、(320.4±2.1)、(287.6±2.1)、(227.4±1.5)、(223.5±1.5)Ma的坪年龄和(209±10)、(172±48)Ma的等时线年龄,分别记录了泥盆纪晚期、石炭纪晚期、二叠纪早期、三叠纪晚期和侏罗纪中期的构造热事件改造。这一系列定年结果表明鹰扬关构造混杂岩从晚古生代到早中生代经历了复杂的构造演化过程,佐证了对鹰扬关构造混杂岩构造变形序列的认识,为区域构造过程的探讨和对比提供了更精准的约束。

Yingyangguan tectonic melange is distributed in the junction of Hunan,Guangdong and Guangxi,China,which is tectonically located in the southwestern segment of Yangtze block and Cathaysia block joint belt.Sericite and muscovite samples collected from meta-sedimentary and meta-volcanic clastic rocks of Yingyangguan tectonic melange yielded 40Ar/39Ar plateau ages of(377.8±2.6),(320.4±2.1),(287.6±2.1),(227.4±1.5),(223.5±1.5)Ma,and isochrone ages of(209±10),(172±48)Ma,respectively.40Ar/39Ar chronology indicates Yingyangguan tectonic melange suffers complicated tectonic evolution from Late Paleozoic to Early Mesozoic,including tectonothermal events of Late Devonian,Late Carboniferous,Early Permian,Late Triassic and Middle Jurassic.It enhances the understanding about tectonic deformation sequence of Yingyangguan tectonic melange,and provides precise timing constraints for discussion and comparison of regional tectonic processes.