豫西宜洛盆地上二叠统—下三叠统泥质岩地球化学特征与物源分析

Geochemical signatures and provenance analysis of the Upper Permian to Lower Triassic argillaceous rocks in the Yiluo Basin,western Henan

宜洛盆地晚二叠世—三叠纪沉积充填演化是秦岭造山带与华北克拉通共同作用的结果,物源分析是揭示盆山耦合的重要手段之一。论文采用沉积地球化学分析的方法对宜洛盆地上二叠统—下三叠统泥质岩地球化学特征与物源进行了研究,结果表明:宜洛盆地泥质岩稀土元素球粒陨石标准化曲线显示轻稀土元素富集,重稀土亏损,为右倾式曲线,元素Eu中度负异常,元素Ce轻微亏损,符合上地壳稀土元素分布特征。泥质岩源区源岩属性判别图解显示,宜洛盆地物源以长英质岩为主,主要来自于上地壳,孙家沟组后期有少量古老基底杂岩混入。构造背景判别图解显示,研究区物源经历了被动大陆边缘为主(孙家沟组下段)—活动大陆边缘为主(孙家沟组上段和刘家沟组)—大陆岛弧为主(和尚沟组)的演化;华北克拉通和秦岭造山带是宜洛盆地重要物源区,华北地台北部内蒙古隆起可能提供了一定量的物源。孙家沟组早期以克拉通内部物源为主,孙家沟组土门段之后秦岭微地块物源供给明显,体现了华北克拉通南缘基底隆升,由被动大陆边缘向秦岭初始"弧-陆"碰撞隆升的构造演化过程。这对深入揭示南华北盆地与周围造山带之间的耦合关系具有重要意义。

The sediment filling and evolution of the Yiluo Basin during the Late Permian to the Triassic resulted from the tectonic movement in the Qinlin orogen and the North China craton,and the provenance analysis is interpreted as one of the important tools for revealing the basin-mountain coupling processes. The geochemical signatures and provenance analysis are treated in the present paper for the Upper Permian to Lower Triassic argillaceous rocks from the Yiluo Basin,western Henan. The argillaceous rocks in the Yiluo Basin are characterized by the LREE enrichment,HREE depletion,moderate Eu anomaly and slight Ce depletion,indicating a dominant upper crust origin,with the mixtures of a small amount of ancient basement complexes in the Sunjiagou Formation.The tectonic settings of the provenances in the study area have gone through the transition from the passive continental margin（ the lower member of the Sunjiagou Formation） through the active continental margin（ the upper member of the Sunjiagou Formation and the Liujiagou Formation） to the continental island arc（ Heshanggou Formation）. The Qinlin orogen and the North China craton are believed to be the key provenances for the Yiluo Basin. The cratonic origin during the deposition of the lower member of the Sunjiagou Formation and Qinling origin after the deposition of the Tumen member of the Sunjiagou Formation in the Yiluo Basin indicate the basement uplift on the southern margin of the North China craton,and the tectonic evolution from the passive continental margin to the ＂arc-continent＂collision and uplift of the Qinling block. The results of research in this study are helpful to the understanding of the coupling processes of the southern North China Basin and its surrounding orogenic zones.