陕西华阳川铀多金属矿床黑云母~(40)Ar/~(39)Ar年龄及其地质意义

笔者采用Ar-Ar测年技术,获得华阳川铀多金属矿床碳酸岩中黑云母~(40)Ar/~(39)Ar坪年龄132.58±0.70 Ma,等时线年龄133.01±0.74 Ma,含黑云母闪石硫化物伟晶岩中黑云母的~(40)Ar/~(39)Ar坪年龄93.72±2.38 Ma,等时线年龄91.49±1.97 Ma。镜下特征显示,铌钛铀矿的形成晚于碳酸岩中的黑云母及含黑云母闪石硫化物伟晶岩中的黑云母。因此,铌钛铀矿的形成时间应晚于93.72±2.38 Ma。这表明成矿带内除了已知存在三叠纪碳酸岩型Mo-Pb矿和白垩纪斑岩型Mo矿的成矿过程之外,还存在早白垩世之后的岩浆热液型U-Nb-Ti成矿过程。

40 Ar/39 Ar Geochronology of Biotite in Huayangchuan Uranium-Polymetallic Deposit in Shanxi Province and its Geological Significance

In this study , the forming age of Huayangchuan uranium‐polymetallic deposit was performed on the biotite using Ar Ar dating method.Biotite in carbonatite was dated with a plateau age of 132.58 ± 0.70 Ma ,an isochron age of 133.01 ± 0.74 Ma ,and biotite in biotite‐amphibole‐sulfide‐bearing peg‐matite was dated with a plateau age of 93.72 ± 2.38 Ma , an isochron age of 91.49 ± 1.97 Ma.Microprobe examination found that the biotite was formed prior to the betafite , and therefore the betafite was believed to be formed later than 93.72 ± 2.38 Ma ,which suggested there was a later Early Cretaceous magma hydrothermal U Nb Ti mineralization process in Xiaofuyu‐Huayangchuan‐Huan‐glongpu mineralization belte beside the discoved Triassic carbonatite vein‐type Mo Pb , there occured a Cretaceous porphyry Mo metalization process.