Magmatic Oxygen Fugacity Implication Of Mineralization

The Awuliya gold deposit is a quartz-vein-type gold deposit which occurs in Dahalajunshan Formation of Tulasu basin in West Tianshan.The bodies of the deposit are controlled by the north-south fault,and the gold mineralization is closely related to the silicified and limonite tuffs.The metallic minerals mainly consist of pyrite and limonite.Non-metallic minerals are quartz and calcite.The ore textures include subhedral texture and metasomatic pseudomorph texture.Comb-like,vein-like and crystal-like are the main ore structures.The alteration is consists of silicification and chloritization.Minrealization can be divided into to two stages:the early quartz-pyrite stage and the late quartz-calcite stage.The LA-ICP-MS zircon U-Pb dating yielded a weighted average age of 365.1±6.1Ma,which belongs to the Late Devonian.The geochemical analysis of the rocks show that both are calc-alkaline volcanic rock series.The characteristics of rare earths and trace elements indicate that they are homologous and characteristic of arc magmatic rocks.The rocks formed due to the southward subduction of the Junggar the ocean beneath the Yili-Midlle Tianshan Plate.The source area of andesite is the mantle-derived magma interacted with sediment from the subduction zone.The strong depletion of Sr,Zr,Hf,Eu in dacite show that it may be the result of differentiation of Andean magma.The results of oxygen fugacity show that the ratio of Ce⁴⁺/Ce³⁺in Boluokenu belt is slightly lower than that of porphyry copper deposit in Yangze plate.The oxidation state of Husite igneous rocks can be clearly divided into two groups:the one related to mineralization is much more high?82.6¹52.3,MH?,the other one is lower?18.0⁴5.9,FMQ?.The volcanic rock series are highly oxidized,which show high Ce⁴⁺/Ce³⁺?72.0¹23.3,MH?.Instead,Nailenggele granites have a significant low Ce⁴⁺/Ce³⁺?23.7⁵5.4?.It is seemingly that high oxygen fugacity of magma is favorable for mineralization of copper-gold-molybdenum.Combined with previous studies,the characteristics of high oxygen fugacity may be inherited from the source region.The arc magmatic rocks in the subduction environment generally have high oxygen fugacity.In addition,it is possibly that the higher degree of rock differentiation usually shows lower oxygen fugacity.The influence of oxygen fugacity on mineralization is important,but it is not the only factor that determines the ore specificity and cannot be used alone as a criterion for distinguishing mineralization.