燕山赤城地区中元古界硅质岩地球化学特征

The Geochemical Characteristics of Siliceous Rocks in Mesoproterozoic Erathem in Chicheng Area of Yanshan Belt

燕山赤城地区中元古界（高于庄组和雾迷山组）硅质岩具低Al2O3和TiO2（质量分数平均为0．06％和0．01％），高TFe2O3（质量分数平均为0．68％），高Fe与Ti质量分数比和（Fe＋Mn）与Ti质量分数比（分别平均为131和140）的特征。区内硅质岩中MnO与TiO2质量分数比大于远洋环境硅质岩，且Fe2O3与TiO2质量分数比较高，而Al2O3与（Al2O3＋Fe2O3）质量分数比较低，表明其形成于远离陆源碎屑干扰而受热液作用影响的远岸环境，硅质主要来源于海底热液。

The content of Al2O3 and TiO2 （the mass fraction was 0.06% and 0.01%, respectively） of silicalite was low and the content of TFe2O3 was high （the average mass fraction was 0.68%） in Mesoproterozoic Erathem （Gaoyuzhuang and Wumishan Formations） in Chicheng Area of Yanshan Belt, and it had characteristics of high ratio of Fe/Ti, Fe ＋ Mn/Ti （the average value was 131 and 140, respectively）. The mass fraction ratio of MnO/TiO2 of silicalite in the area was higher than that of siiicalite in the ocean environment, and it was characterized by high ratio of Fe2O3/TiO2, low ratio of Al2O3/CAl2O3＋Fe2O3）. All these characters indicate that silicalite is formed in the far shore environment of which keeps away from the disturbance of terrigenous detrital and is influenced by hydrothermai process. The siliceous matter mainly comes from the seafloor hydrothermal fluid.