辽西中生代沉积岩稀土、微量元素地球化学特征及其构造背景

Geochemical Characteristics of REE and Trace Elements of Mesozoic Sedimentary Rocks and Its Tectonic Setting In Western Liaoning

辽西地区在中生代时期经历了三次火山—沉积旋回,形成的沉积岩中蕴含大量的地壳演化信息。采用电感耦合等离子体质谱(ICP-MS)测定了该区中生代沉积岩的稀土、微量元素含量,应用微量元素La—Sc—Th、Th—Co—Zr/10沉积构造背景判别图解对区域构造背景进行了探讨。结果表明:1中生代沉积岩稀土元素含量较高,具有后太古宙沉积岩特征;2三叠纪不同时期沉积岩具有相同的微量元素曲线分布型式,侏罗纪、早白垩世期间沉积岩的稀土元素曲线相对分散,分别具有两种、三种微量元素分布曲线型式,反映沉积物源的变化和活化的沉积构造背景;3中生代时期,构造环境复杂,大陆岛弧型为主,三叠纪—侏罗纪期间处于转型期,兼有稳定的被动大陆边缘型特征,早白垩世兼有活动大陆边缘型特征,构造环境更为活化。

There had been three-whole-gyre volcanic—edimentary rocks during Mesozoic in Western Liaoning province. And lot of information on the crustal evolution can get from sedimentary rocks. We had determined the contents of REE and trace elements using the inductively coupled plasma mass spectroscopy （ICP-MS）, and also utilized the discriminant diagrams of La-Sc-Th, Th-Sc-Zr for sedimentary tectonic setting. The results are. （1） the contents of REE were high in the Mesozoic sedimentary rocks, and the patterns were approximately consistent with post-Archean sedimentary rocks. （2） Trias sedimentary formations had the same normalized patters, however, the REE patterns of different sedimentary strata of Jurassic and early Cretaceous were dispersive, two and three types respectively, which reflected the change of provenance and the active tectonic setting. （3） the sedimentary tectonic setting during Mesozoic was mainly the continental island arc, and in Trias-Jurassic sometimes was the stable-passive continental margin. And in the period of early Cretaceous the setting was more active, sometimes with the characteristic of the active continental margin.