冀北隐伏火山热液型铀矿地表地球化学异常

Surface geochemical anomalies of concealed volcanic hydrothermal uranium deposit in northern Hebei

为研究华北地区火山热液型铀矿地表地球化学异常特征与深部铀矿体的关系,选取冀北覆盖区典型的隐伏火山热液型铀矿——大官厂铀矿床为研究对象,在大官厂矿区布置了土壤调查采样,并在有矿钻孔和矿化钻孔上方采集了土壤样,进行土壤瞬时氡、活动态铀及^(210)Po测试分析,探讨这3种地球化学特征与深部铀矿体的关系。结果显示:高品位钻孔附近的土壤瞬时氡明显高于矿化孔,同时,土壤面积样中瞬时氡的高值与深部铀矿体对应较好;高品位铀矿钻孔中^(210)Po略高,但面积性分布的土壤样中^(210)Po的离散度小,分布较均匀,在矿区和无矿区的数值无差别;高品位孔中的活动态铀无明显异常,在土壤面积样中,活动态铀的最大值位于已知的无矿区。由此获得初步认识,在大比例尺上探测深埋藏铀矿体时,土壤瞬时氡浓度异常可以指示深部隐伏铀矿体的异常,而活动态铀与^(210)Po异常不及瞬时氡灵敏。

The Daguanchang uranium deposit,a typical concealed volcanic hydrothermal uranium deposit,was selected to investigate the relationship between surface geochemical characteristics and deep uranium ore bodies of volcanic hydrothermal uranium deposits in North China.The samples for soil survey were collected in the Daguanchang mining area.They were taken from the soil in the upper part of boreholes revealing deposits and mineralization for the analyses of the instantaneous radon(Rn)concentration,mobile-state uranium,and ^(210)Po of soil.Then,this study explored the relationships between these geochemical characteristics and deep uranium ore bodies.The results are as follows.The soil in the upper part of boreholes revealing high-grade deposits(also referred to as high-grade boreholes)had significantly higher instantaneous Rn concentration than that in the upper part of boreholes revealing mineralization(also referred to as mineralization boreholes).The high instantaneous Rn concentration in the soil samples collected from a large area corresponded well to the deep uranium ore bodies.The high-grade boreholes had slightly high ^(210)Po.However,the ^(210)Po in the surface soil samples showed small dispersion and relatively uniform distribution and did not exhibit differences between the barren and mining areas.Mobile-state uranium in high-grade boreholes did not exhibit significant anomalies.The maximum anomaly value of mobile-state uranium in soil samples collected from a large area occurred in the known barren areas.Therefore,it can be preliminarily concluded that,for the exploration of deeply buried uranium ore bodies on a large scale,the anomalies of instantaneous Rn concentration in the soil can indicate the anomalies of deeply buried uranium ore bodies,while the mobile-state uranium and ^(210)Po in soil are less sensitive than instantaneous Rn.