银根地区Landsat8卫星数据地下水信息反演及其对砂岩型铀矿勘查的指示

Inversion of groundwater information from Landsat 8 satellite data in Yingen region and its indications for the exploration of sandstone type uranium deposits

有针对性地利用遥感技术识别铀成矿环境、条件与控矿要素是开展砂岩型铀矿遥感勘查的重要内容。由于砂岩型铀矿中铀的富集过程是成矿流体在储层中迁移并与周围环境相互作用的结果,而地下水是最常见的含铀流体,因此在砂岩区开展地下水信息的遥感识别对铀矿勘查具有重要指示意义。以内蒙古银根地区为研究对象,选择Landsat8卫星遥感数据为主要数据源,以地下水活动产生的地表热异常、植被异常和湿度异常作为突破口,利用热红外波段结合大气参数反演了地表温度,同时采用多光谱波段结合归一化植被指数(NDVI)和不规则梯形模型(OPTRAM)反演了地表植被和湿度信息。反演结果表明:银根地区地表植被信息与地下水富集程度之间存在良好正相关关系,可作为识别地下水活动的首选依据,相比而言,地表温度和湿度信息则易受不同岩性和岩石蚀变作用影响,仅可作为识别地下水活动的辅助依据。利用地表植被、温度和湿度信息,在银根地区南部圈定了5处北东走向的富水带。通过将富水带与构造解译结果整合,在银根地区南部斜坡带上成功识别出泄水构造与隐伏泄水构造。结合前人钻探资料,发现所识别的泄水构造与铀矿化存在一定关系,可能促进了地下水循环并控制着铀矿的形成,由此认为下一步铀矿找矿工作可围绕泄水构造或隐伏泄水构造开展。

Uranium is of great significance to economy and national defense.Sandstone type uranium deposit is an important type of uranium resource,thus attracts more and more attentions in recent years.Identifying uranium metallogenic environment and condition,and distinguishing the ore-controlling factor are important contents of remote sensing technology in the exploration of sandstone-type uranium deposit.Since uranium mineralization in a sandstone-type uranium deposit is closely related to the interaction between the migrated ore-forming fluid and the ore-bearing wall rock,and groundwater is the most common uranium-bearing fluid,it is of great significance to identify groundwater information using remote sensing technology.Previous studies have shown that Bayingobi basin has good uranium-forming potential,and several areas,such as Tamusu,Benbatu and Yingen,have been proposed as prospects.In this study,the Landsat 8 data covering Yingen area in Inner Mongolia,were collected and used to extract surface temperature,surface vegetation information,and humidity information,respectively by the thermal infrared band combined with atmospheric parameters,the multispectral bands combined with normalized vegetation index(NDVI),and the multispectral bands combined with irregular Trapezoid model(OPTRAM).Because the surface temperature,vegetation growth and surface moisture generally associate with groundwater activity,the inverted results were used to investigate the groundwater information for Yingen area.The results show that the surface vegetation information has a good positive correlation with the groundwater formation in Yingen area,it has been observed that the soil in vegetated areas is generally wet with white salt and alkali,thus the surface vegetation could serve as a primary indicator for identifying groundwater activities.In contrast,surface temperature and humidity information are easily affected by different lithologies,and rock alterations,thus they could only be used as auxiliary indicator for identifying groundwater activities.Based on the surface vegetation,temperature,and humidity information,five NE-trending water-rich belts in south Yingen area were delineated.By integrating the water-rich zones with the results of structural interpretation,the drainage structures and the hidden drainage structures were successfully identified in the southern slope of Yingen area.The drainage structures usually developed close to the water-rich zones that are characterized by high NDVI and humidness but low surface temperature.Combined the identification results with the previous drilling data,the relationship between the drainage structures and the uranium mineralization was recognized.Therefore,it is proposed that the further uranium ore exploration work can be carried out in or around the drainage structures or hidden drainage structures in south Yingen area.