Characteristics And Genesis Of The Geziling Iron Deposit In Laiyuan,Hebei Province

Geziling iron deposit is located in the north edge of the Futuyu ore concentration area, and is one of the typical skarn iron deposits in the north segment of the Taihang Mountain tectonic–magmatic metallogenic belt. Detailed orefield geological, ore deposit geological and geochemical studies have been carried out on this deposit, with emphases on demonstration of its alteration zoning, metallogenic period, element migration and mineralization process.Field investigation results show the major control of the Geziling iron deposit by the Wulonggou sub-level structure, especially compression schistosity belt and contacting belt between magmatic body and wall rock. In the area occurred two periods of fault activities, the early period of which played an important role in mineralization, and the late one did some damage to the formed ore deposit.Based on mineral assemblage and texture and structure, iron ores in the Geziling iron deposit can be divided into early taxitic and late vein types. The taxitic type of ores is characterized by an assemblage of skarn minerals with high temperature magnetite, various metasomatic textures, and a taxitic structure, while the vein type of ores by an assemblage of quartz with middle to low temperature magnetite, various crystal grain textures, and vein and net-veined structures.The wall rock alteration and mineralization in the Geziling iron deposit are significant, from the intrusion to carbonate wall rock, occurring dioritic porphyrite, garnet skarn, magnetite-diopside-tremolite skarn, chlorite-magnetite skarn, and chloritie skarn etc. According to vein penetration relation and mineral assemblage, the formation process of the Geziling iron deposit can be divided into five stages, including garnet-diopside, epidote-tremolite, magnetite, quartz-sulfilde, and carbonate ones. Analyses of major, trace, and rare earth elements show an origin of the deposit by contact metasomatism.The obtained various data indicate that the Geziling iron deposit is a typical contact metasomatic skarn deposit formed by a complex formation process. During transformation period of the Mesozoic tectonic regime in the North China from depression to extension, dioritic magma intruded wall rock strata in the Futuyu area to form a mushroom-shaped intrusion. Contact metasomatism of the diroritic magma with the Ordovician limestone and Gaoyuzhuang Formation dolomite resulted in the formation of the skarn. Infiltration metasomatism of iron-bearing fluid along schistosity belts and limestone bedding belts was responsible for the formation of the zoned and layered iron ore bodies.