| The Luotuofeng copper polymetallic deposit is located in the middle reaches of the Nalinguole river in Golmud City,Qinghai Province,It belongs to the Qimantag-doulan Variscan iron,cobalt,copper,lead,zinc,tin,wollastonite?antimony and bismuth?metallogenic belt of the east kunlun metallogenic belt.During the Late Variscan-Indosinian orogenic tectonic cycle,due to the northward subduction of the Paleo-Tethys Ocean,the lithosphere was dismantled and the mantle-derived magma intruded,resulting in the strong Cu,Mo,Pb,Zn polymetallic mineralization in the Luotuofeng area.Based on field investigation,this paper discusses the petrogenesis of the Luotuofeng copper polymetallic deposit which is relatively weak by studying the metallogenic background,the geological characteristics of the deposits and geophysical and geochemical characteristics of the deposits.and provided heoretical basis for prospecting work of porphyry copper-molybdenum polymetallic deposit in the study area.According to the study of the geological characteristics of the deposit show that:?1?The Luotuofeng copper polymetallic deposit is mainly located in the late Indosinian period granodiorite porphyry and granodiorite and K-feldspar granite,and is controlled by the NE trending fault zone.?2?The mineral combination is mainly composed of chalcopyrite,pyrite,molybdenite,galena,sphalerite,etc.,showing the characteristics of medium-to-high temperature assemblages.?3?The surface alteration characteristics of the study area are obvious.The ore bodies are mainly produced in the silicified zone and the sericitization zone,and no potassium zone is observed.?4?Based on the study and analysis of the occurrence characteristics and structural structure of the ore bodies,the Luotuofeng porphyry copper-molybdenum deposit can be divided into three metallogenic stages: gas metallogenic stage,hydrothermal metallogenic stage and supergene metallogenic stage.The metallogenesis of copper and molybdenum in the gas metallogenic period is very weak,and the hot fluid is mainly magmatic water;the high temperature hydrothermal metallogenic stage has experienced several molybdenum mineralization,which is the most important metallogenic period of the ore area,forming molybdenum-copper orebody;the middle-low temperature hydrothermal metallogenic stage is mainly carbonation stage,molybdenum mineralization is weak,and the whole hydrothermal activity is over.The sulfur isotope study shows that the composition is consistent with that of 34 S,and is near the value of 0,indicating the source of magma,and the metallogenic material mainly comes from the upper mantle or deep crust.O-H isotopic studies show that the ore-forming fluids are mainly from magmas,and the ore-forming fluids belong to the category of magmatic water with deep source characteristics.By fluid inclusion testing research think copper polymetallic deposit mineralization metallogenic Luotuofeng pressure are mainly concentrated in about 15 50 mpa,metallogenic average depth of 1.75 Km,bed ore-forming temperature range is 280 340 ?,ore-forming fluid is a rich CO2 and CH4,N2,reducing hydrothermal fluid.The fluid inclusions are dominated by gas-liquid two phases and are rich in CO2,consistent with the fluid characteristics of typical porphyry deposits.The LA-ICP-MS U-Pb dating of zircon shows that the metallogenic age of the Luotuofeng copper polymetallic deposit is in the late Indosinian period?232.5-214.1 Ma,T2-T3?,which is consistent with the metallogenic time of the same type deposits in the region.In summary,the characteristics of surface alteration of the Luotuofeng copper polymetallic deposit are relatively complete,and the existence of deep-reduced hydrothermal fluids and ore-forming rock masses indicate that the genetic type of the deposit is a porphyry deposit.It provides a theoretical basis for prospecting and exploration of porphyry copper-molybdenum polymetallic deposits of study area in the future. |
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