碳酸盐岩成岩作用的微量元素地球化学特征

作者以巢县地区震旦系到三叠系的碳酸盐岩为例,探讨了在不同成岩环境下,碳酸盐岩中微量元素Sr、Na、Fe、Mn的分布特征。主要经历了大气淡水成岩作用的灰岩(奥陶系、石炭系和州组上部、黄龙组、船山组)有较低的Sr(188×10-6)、Na(132×10-6)、Mn(149×10-6)含量;而以海底成岩作用为主的灰岩(石炭系金陵组、和州组下部、二叠系栖霞组、三叠系南陵湖组),则有较高的Sr(515×10-6)、Na(396×10-6)、Mn(404×10-6)值;与以准同生后成岩白云岩化作用为主的多成因白云岩(震旦-寒武系)相比,准同生的萨布哈白云岩(三叠系东马鞍山组)有稍高的Sr(138×10-6)、Na(806×10-6),而前者的Sr、Na含量分别为103×10-6、604×10-6.Mn的含量在两类白云岩中差异不明显。与灰岩相比,白云岩化作用将有较高的Na和较低的Sr、Mn.此外,Fe的含量与Ca+Mg含量呈负相关趋势明显,这表明了陆源物质对于Fe的干扰不容忽视。 

GEOCHEMICAL CHARACTERISTICS OF CARBONATE ROCK DIAGENESIS

The paper deals with the distribution of trace elements,such as Sr.Na,Fe.Mn in carbonate rocks occurred under various diagenetic environments with a case study of the carbonate rocks(Z-T)in the Chao County.The limestones(O,upper part of C1h.C2h.C2c)origined mainly from meteoric diagenesis are characterized by low concentrations of Sr(188ppm),Na(132ppm),Mn(149ppm),while the limestones(Clj,lower part of C1h.P1q,T1n)mainly derived from submarine diagenesis by high concentrations of Sr(515ppm),Na(396ppm),Mn(404ppm).The penecontemporaneous sabkha dolomites(T2d),in comparison with penecontemporaneous-back poly-origin dolomites(Z-∈)which origin mainly from diagenesis dolomitization,has high concentrations of Sr(138ppm),Na(806ppm),and the later have low concentrations of S(103ppm)and Na(604ppm).It is significant for the difference in Mn content between the dolomites.The dolomite rocks,in comparison with the limestones,have high Na and low Sr,Mn.Moreover,it is obvious that Fe content tends to be negative correlation with Ca+Mg content and it is suggested that Fe content should be influenced by terrigenous cleposits.