鄂尔多斯盆地砂岩型铀矿成矿时代及铀富集时空规律

Metallogenic epoch of sandstone type uranium deposits in the Ordos Basin and the temporal and spatial regularity of uranium enrichment

铀成矿年龄是砂岩型铀矿研究中的热点与难点,为了深入认识鄂尔多斯盆地砂岩型铀矿的时空分布规律,本文对全岩U-Pb定年、电子探针法EMPA、LA-ICP-MS、fs-LA-ICP-MS、SIMS等方法的适用性和限制性进行了分析,统计和对比了盆地内20多个砂岩型铀矿床的成矿年龄、含矿层位信息,并以鄂尔多斯盆地东北部典型矿床为例,系统地分析了砂岩型铀矿成矿过程,结果显示,鄂尔多斯盆地砂岩型铀矿含矿层位主要为中侏罗统直罗组,下白垩统洛河组,其次为下白垩统马东山组、罗汉洞组,铀成矿时间大部分集中在中新世,与新生代构造事件有较好耦合。盆地东北部由东向西,东胜-纳岭沟-塔然高勒-大营-巴音青格利矿床中矿体海拔高度大致相当,而矿体在含矿层位中的相对位置则逐渐上升。反映出各矿体的形成均受近同期的成矿事件控制。鄂尔多斯盆地砂岩型铀矿成矿作用时间主要集中在中新生代且与新生代构造事件有较好耦合,东北部典型矿床中铀矿体产出在同一目的层的不同部位,均指示出铀成矿可能与新生代构造活动紧密相关。

Uranium mineralization age is a hot and difficult point in the study of sandstone type uranium deposits.In order to deeply understand the temporal and spatial distribution of sandstone type uranium deposits in Ordos Basin,the applicability and limitation of whole rock U-Pb dating,electron probe method EMPA,LA-ICP-MS,fs-LA-ICP-MS,SIMS and other methods are summarized and compared,and counts and compares the mineralization age and ore bearing horizon information of more than 20 sandstone type uranium deposits in the basin.Taking the typical deposits in the northeast of Ordos Basin as an example,the metallogenic process of sandstone type uranium deposits is systematically analyzed.The results show that the ore bearing horizons of sandstone type uranium deposits in Ordos Basin are mainly Middle Jurassic Zhiluo Formation,Lower Cretaceous Luohe Formation,followed by Lower Cretaceous Madongshan Formation and Luohandong Formation.The uranium mineralization time is mostly concentrated in Miocene,which is well coupled with Cenozoic tectonic events.From east to west in the northeast of the basin,the elevation of the ore bodies in the Dongsheng-Nalinggou-Tarangaole-Daying-Bayinqinggeli deposit is roughly the same,while the relative position of the ore bodies in the ore bearing horizon is gradually rising.It reflects that the formation of each ore body is controlled by the near contemporaneous metallogenic events.The mineralization time of sandstone type uranium deposits in Ordos Basin is mainly concentrated in the Mesozoic Cenozoic era and has a good coupling with the Cenozoic tectonic events.In typical deposits of the northeastern Ordos Basin,the uranium ore bodies are produced in different parts of the same target layer,indicating that uranium mineralization may be closely related to the Cenozoic tectonic activities.