THE GEOCHEMISTRY STUDY OF ERENTAOLEGAI SILVER DEPOSIT IN INNER MONGOLIA

The Erentaolegai silver deposit is located in Xinbaerhuyo County,Inner Mongolia. The local area was edeg-subjected to the movement in later Yanshan.The faults which had been exited were revived,bringing about intense activity of granite magma.Miscellaneous geologic investigations on the invariable primary elements,trace elements,rare earth elements and the isotopes of oxygen and stronitum show that the magma was the product of the crust-mantle mixture.The magma underwent crystallization differentiation,froming granite and quartz porphyry. From west(rock body)to east,there are four ore belts named Ⅰ,Ⅱ,Ⅲ and Ⅳ arranged successively.The belts had a horizontal zoning in many ways such as the scale of the ore belts,the composition of the ore in the ore veins,ore texture and structure,mineral composition,and the composition of the fluid inclusions.And more,they show the same vertical zoning of ore types,i.e., oxidized ore in the surface,quartz-silicated-typed ore in deeper and sulfide altered rock ore zone in the deepest.The compositions of inclusions in all kinds of ores are identical, i.e., H₂O-CO₂-Ca²⁺Na⁺-K⁺-SO₃^2--Cl^-, showing that they come from the same source.Oxygen isotopes show that meteorological water on earth's surface played an important role in forming the magma and deposit:(1) probably occured OH^- replacing Cl^- made the ore solution be crystallization differentiation,and enriched silver in the quartz porphyry magma;(2) contributing to form a great of quantites ore solution.Many evidences show that granite and quartz porphyry are go with to the ore in the materials such as the characteristics of rare earth elements,trace elements and oxygen,hydrogen,sulfur and lead isotopies.Because quartz porphyry is the latest stage of magma,silver was enriched in the later diagenetic and post-diagenectic ore solution.Quartz porphyry is the parent rock of the deposit.