Study On The Application Of MOMEO Geochemical Survey In Ⅻ Ore Body Of Jinchang Gold Deposit, Heilongjiang Province

Leaching of Mobile Forms of Metals in Overburden, known as MOMEO,developed for the need of prospecting of concealed deposits. It is one of the technicalmethods of deep penetration geochemistry and increasingly widely used inexploration of deposits and the anomaly verification of geochemical prospecting, andso on, and the effectiveness test is gradually conducted, especially in the coveredareas where the normal geological or geochemical methods of prospecting are noteffective. Through the study and summarizing of the theoretical foundation, thehalation mechanism, the extraction method and the measuring technique of MOMEO,this paper selected No. XII ore body of Jinchang gold deposit in Heilongjiangprovince to conduct the study of application test of MOMEO in prospecting.Jinchang gold deposit is located in Dongning county in the east of Heilongjiangprovince, and in terms of regional geotectonics，it is located in the eastern end ofXingmeng orogenic belt, and in the western margin of Xingkai massif. To the north ofit is Jiamusi massif, and to the southwest of it is North China massif. The regionalstructural unit is the uplifted zone of the margin of Zhangguangcai mountains-Taiping mountains and it is in the joint position of the uplifted zone of Taipingmountains and Laoheishan fault depression. In Mesozoic, affected by the subductiongenerated Au mobilization in ancient geological bodies, constituting the advantageousparts for mineralization of the gold deposit. Through the analysis of the existingmaterials and the geological survey of the ore district, it is considered that Jinchanggold deposit is composite type gold deposit, consisting of cryptoexplosive brecciatype ore bodies, ring-radiating fissure filling vein type ore bodies, magmatic dometype ore bodies and magmatic hydrothermal type ore bodies. Through the analysis ofmetallogenic characteristics of No. Ⅻ ore body of Jinchang gold deposit, it isconsidered that No. Ⅻ ore body is magmatic hydrothermal fissure filling veined goldore body. The fissure fillings are mainly Au-bearing pyrite vein-quartz vein. Through the previous evaluation work of general prospecting of the gold deposit,a number of promising mineralization clues were already discovered in the researchedregion.1:100000stream sediment survey and1:10000soil survey were conducted inthis ore district and the pedogeochemical anomaly was defined. However, thecoverage of the researched region is thick, the terrain slopes gently and the outcrop ofbedrock is rare, therefore, the range of the anomaly is large and it is relatively difficultto reveal and evaluate it by directly applying costeaning. Consequently,4soil profileswere layed out on the top part of the known No. XII ore body and the experiment ofthe MOMEO survey method was conducted for the profiles of line24and line26andthe MOMEO survey method and the soil profile survey method were compared andanalyzed.Through the repeated experiment and analysis of extraction methods of Aumobile phase, the procedure of the extraction of Au mobile phase was partlyimproved and relatively suitable analysis procedure was raised, including4Au mobilephases, such as water-extracted phase, clay-adsorbed phase, organics-combinedphase and iron and manganese oxides phase. The analysis method experiment for theextracted mobile phase samples was conducted with graphite furnace atomicfluorescence spectrometry.The statistics of geochemical parameters for4extracted phases of No. XII orebody was conducted. The data indicates that for organics phase and oxides-combinedphase, the average values and background values of the contents of Au were high andthe standard deviations and variable coefficients are also high. Therefore, they can begeochemical evaluation indicators of this region, having indicating significance forprospecting. The water-extracted phase and clay-adsorbed phase only can be seen assupplement or reference.Through the comparison of the distribution situations of Au mobile phaseanomalies in different landscape areas, it is shown that the anomaly type and charactervaries in different landscape areas. The metal mobile phase anomalies are restrictedby different landscape conditions. It is suggested that while adopting MOMEO toprospect, the effectiveness experiment for the phases should be conducted. In the Zhangguangcai mountain-Taiping mountain landscape area, organics phase andoxides-combined phase are the most suitable phases.Through the comparison of the anomaly graphs and the soil geochemical profilemaps, it is shown that the locations of the anomalies are basically the same and the4abstracted phases of MOMEO all can be applied for defining anomalies. Therefore, itcan provide more information for prospecting and better verify the exsitance of1:10000soil geochemical anomalies, having the indicating meaning for the layout ofprospecting.Based on MOMEO anomalies and the soil profile anomaly characters of the toppart of the known ore body, No. XII-3concealed ore body was discovered. Throughthe study of the geochemical survey method of MOMEO applied in Jinchang golddeposit, it is concluded that MOMEO has unique advantage for prospecting, canclearly indicate the location of the ore body on the surface and has certain indicatingmeaning for concealed ore bodies.