皖北新元古代砂质灰岩地球化学特征

Geochemical characteristics of the Neoproterozoic sandy limestone of northern Anhui province

为了解皖北新元古代沉积环境及大地构造背景,采集皖北新元古代赵圩组、倪园组、张渠组和魏集组砂质灰岩进行了系统的地球化学分析,并对刘老碑页岩的稀土特征进行了反演,结果表明,砂质灰岩主要组分为CaO,SiO2,Al2O3和Fe2O3.受到较强陆源物质的影响,稀土总量很低,平均为45.78×10-6mg/g,轻重稀土分异明显.砂质灰岩中碎屑成分与刘老碑页岩来自同一源区,皖北新元古代砂质灰岩形成于湿热、富氧的正常浅海,该区在新元古代时期应属于与Grenvill造山有关(汇聚型),同时又具有伸展性质的弧后盆地.

For knowing the Neoproterozoic depositional environment and tectonic background in northern Anhui province, earth elemental analysis of the Neoproterozoic sandy limestone collected from the Zhaowei Formation, Niyuan Formation, Zhangqu Formation and Weiji Formation in northern Anhui province had been made, and the rare earth elemental characteristics of the shales in Liulaobei Formation had been inversed. The results imply that the sandy limestone is mainly composed of CaO, SiO2, Al2O3 and Fe203. The total rare earth element （REE） contents are low with only 45.78 ×10^-6mg/g on average, and the light and heavy REE are strictly fractionated. The clast in the sandy limestone and the shales in Liulaohei formation are from the same source area. The Neoproterozoic sandy limestone in the northern Anhui province is formed in normal shallow sea with enriched oxygen and hot and damp climate. The tectonic background of the northern Anhui province in Neoproterozoic belongs to a convergence environment linked to the Grenvill orogen and an extensional back are basin simultaneously.