安徽宿州寒武纪猴家山组灰岩微量元素地球化学特征

GEOCHEMICAL CHARACTERISTICS OF TRACE ELEMENTS IN LIMESTONE OF HOUJIASHAN FORMATION FROM SUZHOU,ANHUI PROVINCE

为研究寒武纪猴家山组石灰岩地球化学特征及地质背景,对宿州地区寒武纪猴家山组石灰岩进行系统的岩石学和微量元素地球化学测试,分析灰岩中微量元素的来源及其特征,探讨古海水及古气候条件,反演灰岩形成的海水稀土配分模式。研究结果表明:猴家山组石灰岩元素U,Pb,Sr富集,Nb,Pr,Zr,Hf明显亏损;稀土总量偏低(2.19×10-6～9.95×10-6),轻稀土略亏损,NdSN/YbSN值在0.35～1.28变化,轻重稀土分异微弱,石灰岩样品均具有程度不同的La正异常、Ce负异常和Y正异常;Mo,V等元素指示了氧化程度较高的水体环境,Sr/Ba,Sr/Cu反映了盐度较大的海洋环境和干旱的气候条件;猴家山组灰岩反演海水稀土特征与新元古代海水略有差异,与正常海水稀土组成特征一致。

Petrological and trace elemental analysis were carried out for understanding the geo- chemical characteristics of limestone from Cambrian （Houjiashan Formation） and its geological background in Suzhou area. The origin of trace element and its characteristics in limestone were studied, the ancient seawater and paleoclimate analyzed, and the rare earth elemental distribution patterns of seawater discussed respectively. It was showed that the limestone was rich in U,Pb, Sr,poor in Nb,Pr,Zr, Hf. REE in limestone were characterized by lower total REE （1.63×10^-6- 7.79×10^-6 ）, light LREE depletion （NdSN/YbSN = 0. 35 - 1.28）, slight fractionation between LREE and HREE,and various degree in negative Ce anomaly,positive La and Y anomaly. It also revealed that the ancient seawater was well oxygenated with high salinity, and the paleoclimate was drought evidenced by analytical data of Mo, V, Sr/Ba and Sr/Cu, respectively. The inversion of seawater from Houjfashan limestone conformed that it had a slight difference to seawater of Neoproterozoic,and in accordance to the rare earth element characters of normal sea water.