Abstract: Northwest Hebei is an important lead-zinc-silver polymetallic ore-rich area in the province.Based on the previous research and knowledge, the ore bearing strata, five km rockmass buffer area, and 1 km and 3 km composite overlay buffer areas of different level structures and abnormal areas found in geochemical and geophysical exploration that were closely related to ore formation were extracted from GIS platform.Weighted overlay model was used on ArcView platform to carry out the forecast and evaluation of ore formation prospective zone in the areas under study.Through setting up of two different influence ratios for evidence layers, it was found that there was a poor coincidence between geochemically abnormal areas and known deposits, and therefore, in prospective area forecast, geochemical exploration evidence layer should not be assigned with a too high influence ratio.However, gravity abnormality could better reflect the medium acidic rockmass at depth.In light that the known lead-zinc deposit points were mostly distributed around the rockmass, it was concluded that the ratios of the influence of geological ore-controlling factors and gravity abnormality on orebodies could be properly increased.As a result, an ideal forecast effect map was obtained, based on which the areas where further major exploration to be made were proposed.

Key words: Geological information system, Weighted overlay model, Forecast