Geochemical Characteristics Of Dongjianian Silver Ore Deposit,Lingbao City,Henan Province

Dongjianian large sliver ore deposit located in southern fringe of North China block.And the south of Xiaoqinling gold-silver metallogenic belt in western Henan.The regional strata are dominated by mid-deep metamorphic rocks of the Taihua Group in the New Archean.The structure is dominated by Laoyacha anticline and faults of different orders.The magmatic activity is strong and the metallogenic geological conditions are superior.The ore body exists in the secondary structure of Xiaohe fault.The surrounding rocks of the upper and footwall of the fault are respectively the shallow sea-continental sedimentary rocks of the Guandaokou Group and the Xiaohe granite.The research work shall be funded by the Bureau of Geology and Mineral Exploration and Development of Henan Province.This study uses modern metallogenic and geochemical theories.On the basis of previous studies,field geological survey,sample collection and testing were carried out.Mainly achieved the following results:(1)The main element characteristics of the Longjiayuan Formation of the Guandaokou Group of the surrounding rock in the upper wall of the ore body indicate that the shale of the Longjiayuan Formation is deposited in the continental marginal environment.(2)The characteristics of the surrounding rocks and ores rare earth elements show:The total amount of rare earth elements in the metamorphic rocks of the Taihua Group?granite?diabase?silver ore increase in sequence.The metallogenic hydrothermal fluid may come from magmatic pluton and the superposition remelting of metamorphic rocks.The ore has inherited the high content of rare earth elements in magmatic hydrothermal fluid,and has certain similarity with the rare earth elements distribution patterns of other geological bodies.The Y/Ho ratio of each rocks and ores are close to the ratio of chondrites,indicating that the intrusive rocks have a lot of deep-source components.It is speculated that the surrounding rocks and the material components formed in the early stage are added during the mineralization process.(3)The crystallization time of Xiaohe pluton is determined:The Xiaohe pluton was formed in the late period of the Zhongtiao orogeny in the late Paleoproterozoic,with an absolute age 1795±70Ma.(4)The average temperature of the quartz fluid inclusions in the ores is 187?,an average salinity of 8.22%Na Cleqv,an average fluid density of 0.889g/cm~3,and an average ore-forming depth of 5.57km.The deposit is formed in a low-temperature,low-salinity,low-pressure and mid-deep formation environment.The ore-forming fluid is dominated by atmospheric precipitation,and the source of minerals is dominated by surrounding rocks.There may be minerals provided by deep hidden rocks(Indosinian and Yanshanian).It is speculated that the Dongjianian sliver ore deposit was formed in the late Mesozoic.The type of deposit is a mid-deep and low temperature hydrothermal tectonic altered rock type silver deposit.