豫西杜关锰结核稀土元素地球化学

Rare Earth Element Geochemistry of Manganese Nodules in Duguan Area of West Henan Province

豫西杜关锰结核产于华北地台南缘，中元古界官道口群龙家园组下段。杜关锰结核ＲＥＥ范围为（４０．０９～７４．７５）×１０－６，平均为５２．１４×１０－６，为极贫ＲＥＥ型锰结核。锰结核稀土元素经北美页岩标准化后的分布模式较平直，略左倾；Ｃｅ呈弱正异常、无异常和弱负异常，Ｅｕ均呈较显著的正异常。Ｃｅ异常的离散性反映了结核生长过程中氧化—还原条件的波动。杜关锰结核稀土元素具双重来源———海底深部上升热液源和海水源，前者占绝对的优势。杜关锰结核形成于海底深部热液作用的海水体系，属热水沉积成因。

The manganese nodules of Duguan occur at the bottom of Longjiayuan formation in Guandaokou group at the southern margin of North China platform. The total amounts of REE are lower in Duguan manganese nodules; Here, the range from 40.09×10 -6 to 74.75×10 -6 , the average contentration is 52.14×10 -6 . The shale-normalized distribution patterns are close to level or gently inclining to left. The Ce anomalies that show positive, absent and negative anomalies are scatter, which could be the result of fluctuations in the oxidation-reduction conditions. The Eu amonalies are clearly postitive. Based on the rare earth element features discussed and the geological characteristics, the REE in the manganese nodules come of marine deep hydrothermal soultion and seawater, only the source of the hydrothermal solution is absolute superiority. So the manganese nodules formed in the seawater suffered the marine deep hydrothermalism the thermal water system. Dugan manganese nodules are the thermal water sediments.