Research On Geochemical Characteristics And Genesis Of Ulandler Cu-Mo Deposit,Estern Mongolia

The Ulandler ore deposit is located in Ulandler Area,Sunitezuo Village,north-central Inner Mongolia.Two parts of ore bodies are developed in the deposit.The upper one,occurred in the quartz diorite and granodiorite,presents multilayered veinlike and stockwork forms,and exhibits the northwest-trending for the controlling of regional tectonic.The lower one is adamellite with the disseminated molybdenite,occurred in the nearby intrusive contact zone.The LA-ICP-MS zircon U-Pb age,measured in sample WL-17(adamellite)and WL-20(quartz diorite)are 135.4±2.1 Ma and 282.5±2.4Ma.The SHRMP zircon U-Pb age measured in granodiorite is 299.3±2.4Ma(Tao Jixiong,2009).The Re-Os molybdenite age is 134.0 ± 4.2 Ma(Tao Jixiong,2009).The data indicate the adamellite is considered as the results of mineralization intrusions.24 granite samples were collected in Ulandler area.In order to identify the ore-forming process,the concentration of major elements,trace elements and rare earth elements of these rock samples were measured.The high K calc-alklline?adamellite in Ulandler is peraluminous A-type granites.It is assumed that the rock sources of adamellite is from shallow-middle crust,and its geological environment is extensional tectonic setting.Generally,the geochemical characteristics shows the enrichment of Large Ion Lithophile Elements,especially fro Rb and U,and the deficit of High Field Strength Elements,especially for Sr?Ba?Ti?P.And the analysis of rare earth elements shows the enrichment of LREE and deficit of LREE,with the moderately abnormal concentration of Eu.The U-Pb age,measured in adamellite is 135.4±2.1 Ma,indicating that the oredeposit is formed in Late Yanshanian.After the collision between Siberian craton and Sino-China craton,Ulandler magma system and ore-forming fluids system invade upward.Parts of the ore-forming fluids traps the magma and then become the disseminated ores.The other fluids migrate subsequently,because of the magmatic thermal pressure and the internal fluid pressure.The latter fluids are controlled by the North-Western treading faults,and move upward due to the tectonic fissures and weak zone.Finally,the accumulation of fluids in the specific site,form the veinlike and stockwork ore bodies.