Study on Geochemical Prospecting Methods in Forest Swamp Area of Northeast Daxing’an Mountains: Example from Erdaokan Silver Polymetallic Mine Area in Heilongjiang Province

In the shallow forest-swamp overlying area of Erdaokan, Heilongjiang Province, the experimental study on the technical profile of soil and rock debris measurement and sampling methods was carried out by using the method of comparative analysis of different sample sizes in B and C layers. The samples of −5～+20 mesh, −20～+60 mesh and −60 mesh were selected. The differences in geochemical characteristics, element combination and anomaly delineation of each element in different sample sizes were also compared. The results show that the geochemical anomalies of ore-forming elements delineated by different sized samples have the characteristics of Ag-Pb-Zn-Mn multi-element anomaly combination, and the distribution range of anomalies is consistent with the deep ore body, and the element concentration center is in good agreement with the spatial location of the deep ore body, indicating that the ore-body can be effectively indicated by rock debris and soil survey. It can be used as an effective means to find silver-lead-zinc deposits in this area. Through the study, the measurement results of C−20～+60 mesh rock cuttings collected in the mining area are higher and better, which are manifested in higher element content, stronger anomaly intensity, more obvious indication of element combination, and more accurate ore body positioning, which can strengthen the weak soil anomaly, and is conducive to the discovery and identification of weak mineralization information. Therefore, the sampling method of −20～+60 mesh cuttings is suitable for geochemical survey in the study area, which provides a technical basis for the detailed survey of 1∶10 000 geochemical exploration in forest-swamp overlying region including the Erdaokanzi and Duobaoshan ore concentration areas.