SEVERAL PROBLEMS ON THE CONDITIONS OF FORMATION AND LAW OF DISTRIBUTION OF ENDOGENIC METALLIC ORE DEPOSITES IN JIANGSU PROVINCE

The magmatic activity and endogenic metallic mineralization in Jiangsu province mainly occurred in Yanshanian time.The formation and distribution of this kind of ore deposit in the province are controlled by multiple structural systems, of which the latitudinal structural belt,the Neocathaysian system and the reflex arc of the eastern wing of the Huaiyang epsilon structure are the most conspicuous.Large ore deposits are commonly developed in the compounding portions of two or more structural systems. The Yanshanian intrusions,whether basic,intermediate or acid,are all closely related to the formation of metallic mineral deposits,which is mainly manifested in the metallogenic specialization of magmatic rocks.This conforms with the metallogenic features of copper and iron deposits in the middle and lower reaches of the Changjiang（Yangtze）River.Besides, the shape, spatial position and attitude of the intrusions are all intimately associated with the migration of ore fluids and concentration of useful elements. The controlling effects of the stratigraphy and country rocks on ore formation are also conspicuous.Of the strata of various ages,carbonate rocks are undoubtedly the most favourable to ore formation,of which magnesian carbonate rocks are commonly more favourable.Of the ore-forming strata the Middle Ordovician,middle Lower Carboniferous,Lower Permian and middle Lower Triassic are relatively favourable to ore formation. The ore-forming materials were derived from multiple sources,but the magma source tends to be dominant and the crust source comes next.In forming an ore deposit,the ore-forming materials are often not derived from a single source.The Mount Qixia lead-zinc-silver deposit is an example.But it should be noted that of these sources there is bound to be a principal source. The availability of the sources of ore-forming materials does not mean that in any circumstances an ore deposit may be formed,and one should also consider that these materials require transport and concentration through a particular medium as well as certain geological settings to form industial orebodies.These problems must be solved,too. Finally,models of ore genesis that relatively conform to objectice reality and are of reference value may be established using a vast amount of firsthand materials available.In the paper only idealized model maps of metallic deposit formation in the Liguo ore field and the Ningzhen district are cited as representives.An attempt is made to study through the model maps the problem on geology and mineral resources that are to be solved.