【摘要】 报道了延怀盆地422个测点的土壤气测量结果,讨论了各气体组分的区域地球化学特征及其控制因素,并探讨了气体地球化学背景场与区域地震地质的关系.2007年9—10月在首都圈西北部延怀盆地进行了野外土壤气体测量,获得该地区土壤气中Rn,Hg,CO2,H2,He和CH4的地球化学背景值分别为8105.8(±5937.4)Bq/m3,9.7(±5.8)ng/m3,395.9(±35.3)×10-6,4.0(±2.3)×10-6,15.9(±10.4)×10-6和12.7(±8.1)×10-6.延怀盆地土壤Rn,Hg,He和CO2气体地球化学背景场在空间上呈现东部高、西部低(以延矾盆地北缘断裂为界)的特征.控制土壤气体地球化学背景场的主要因素是气体组分的来源、地壳结构、断裂构造、地层和微生物作用.延怀盆地内东部上地壳内存在的低速体,构造活动性较强,深部来源的Hg和He,以及来源于花岗岩的Rn等对土壤气的贡献较大,是盆地东部土壤地球化学背景值较高的原因.这与延怀盆地东部地震活动性较强相对应.研究结果为研究区地震地球化学流动测量和异常判识奠定了基础.更多还原

【Abstract】 Geochemical background and origin of soil gases in the Yanhuai basin are discussed based on the regional seismogeological data and concentration of Rn,Hg,CO2,H2,He and CH4 in soil gas measured at 422 investigating sites in field during September to October 2007.The geochemical background values of Rn,Hg,CO2,H2,He and CH4 are 8105.8(±5937.4)Bq/m3,9.7(±5.8)ng/m3,395.9(±35.3)×10-6,4.0(±2.3)×10-6,15.9(±10.4)×10-6 and 12.7(±8.1)×10-6,respectively.The geochemical backgrounds of the soil gases are higher in the eastern part of the Yanhuai basin.The main factors affecting the gasgeochemical background are gaseous origin structure of the crust,faults,stratum and microbe activity.The higher values of gasgeochemical background in the eastern part are attributed to the existence of low-velocity zones in the upper crust,stronger activity of tectonics and more contributions of Hg and He derived from the deep-earth and Rn originated from granite,corresponding to stronger earthquake activity.The result can be applied to identify seismic precursor from monitoring data of gases in the studied area.更多还原