北京城南平原区钻孔中发现太古宙片麻岩

北京市地质调查研究院在进行1：5万庞各庄镇幅和1：25万北京市幅区域地质调查过程中，相继在北京市大兴区安定镇（兴热2井）、榆垡镇（兴热1井）两个地热钻孔中发现了太古宙片麻岩，不但对全面了解太古宙片麻岩在北京地区的分布范围及深度有重要意义，而且对确定地热井的隔水底板下限有重要的现实意义。兴热2井位于北京市大兴区安定镇铁道部培训中心，埋深2050m以下为太古宙片麻岩。兴热1井位于北京市大兴区榆垡镇，埋深1610m以下为太古宙变质岩。从△T磁异常图可见，固安、榆垡、安定、廊坊一带为片麻岩隆起区。

The Discovery of Archaeozoic Gneiss in Drilled Wells of Beijing's Plain Area

During the regional geological surveying of the 1:50000-scale Panggezhuang sheet and l:250000- scale Beijing sheet,the Beijing Geological Survey discovered Archaeozoic gneiss from two geothermal drilled wells in Anding Town(Well Xingre-2)and Yufa Town(Well Xingre-1)of the Daxing District,Beijing.The discovery is not only of key importance for understanding the distribution extent and depth of Archaeozoic gneiss in Beijing,but also of practical significance for determining the impermeable footwalls of the geothermal wells. Well Xingre-2 is located in the Department of Railway Training Centre in Anding Town,where the Archaeozoic gneiss is buried below the depth of 2050 m.On the other hand,Well Xingre-1 lies in Yufa Town,with the Archaeozoic gneiss buried below 1610 m.As can be seen from the A T magnetic anomaly map,the region around Gu'an,Yufa, Anding and Langfang is a gneissic upwelling area.