Abstract:

In Chengdu plain，Tangchang area is a representative area with high mercury anomaly in soil.In order to study the source of mercury anomaly，multisection geogas prospecting was performed in Tangchang area.Five measuring lines with total 121 sampling points were laid in workplace of 4 km2.The interval of sampling points was 30 m.A kind of special sampler was used to collect geogas，and the continuous sampling time is 45 d.More than 10 elements in geogas samples were determined by INAA.Several of them，including As，Au，Fe，La，Sm，exhibit a regular abnormal distribution，which reflects the concrete position of the concealed fault in this area.The fault strike is NE 40°，and the fault width is 90～120m.Determined by ICPMS，trace mercury was found in geogas samples above the concealed fault.The regional distribution tendency of mercury anomaly area in west Chengdu plain is consistent with the concealed fault strike at the same position.The mercury can transfer along with the geogas from deep crust to surface soil.As a route way，the concealed fault provides a good condition for the transfer of geogas and mercury，which has become an important source of mercury anomaly in surface soil.The mercury anomaly in soil of west Chengdu plain is a result of earth selfaction

Key words: geogas/concealed fault/ mercury anomaly/ Chengdu Plain