鄂尔多斯盆地西北部特拉敖包铀矿产地华池-环河组黄铁矿特征及其成因探讨

The Characteristics and Genesis of Pyrite in Telaaobao Uranium Occurrence in the Northwest of Ordos Basin

特拉敖包铀矿产地位于鄂尔多斯盆地西北部,区内白垩系发育大量铀矿化。目前,针对该区的铀成矿作用尚未开展深入研究,但发现华池-环河组黄铁矿与铀富集关系密切。黄铁矿常具有一定的标型特征,因此文章在野外地质调查和岩相学基础上,利用扫描电镜、电子探针与LA-ICPMS原位分析等技术,对特拉敖包铀矿产地黄铁矿矿物学特征、主微量元素和硫同位素开展研究。结果表明:特拉敖包铀矿产地华池-环河组黄铁矿分布形式多样,黄铁矿根据其形态差异主要分为三类:单颗粒自形晶黄铁矿、胶状黄铁矿和莓球状黄铁矿。胶结状黄铁矿含有较高的Co、Ni、Mo与As,单颗粒黄铁矿与莓球状黄铁矿含有生长薄边,薄边的Co与As含量较高。黄铁矿的特征表明特拉敖包铀矿产地华池-环河组砂岩还经历了高温流体与低温流体的双重作用。

The Telaaobao uranium occurrence is located in the northwest of Ordos Basin,where a large amount of uranium anomalies have been discovered in the Cretaceous series,pyrite in Huachi-Huanhe Formation was found closely related to uranium enrichment,but deep research was not conducted.In the typomorphic characteristics of pyrite in Telaaobao uranium occurrence was studied in field geological survey,petrography,main and trace elements and sulfur isotopes in the uranium deposit of Telaaobao by using scanning electron microscopy,electron probe and LA-ICP-MS in situ analysis.The results showed that the pyrite of Huachi-Huanhe Formation in Telaaobao uranium occurrences occurs in various forms,and can be divided according to its morphological feature into three types:single particle idiomorphic pyrite,colloidal pyrite and berry-spherical pyrite.Cemented pyrite contains higher Co,Ni,Mo and As,while single-particle pyrite and berry-globular-pyrite have thin growing edges,and the thin edges have higher Co and As contents.It was believed that the sandstone of Huachi-Huanhe Formation in the Telaaobao uranium occurrence experienced the action of both high and low temperature fluids.