The Wutonggou iron deposit is located in the well-known iron metallogenic belt in the eastern Tianshan,NW China,and has been regarded as a sedimentary iron deposit.Although hydrothermal overprinting could play indispensable roles in the formation of high-grade iron ores in sedimentary iron deposits,previous studies mainly focused on sedimentary-related iron mineralization,while the nature and contribution of hydrothermal fluids are poorly constrained.Accordingly,an integrated study of ore geology,H-O-C isotopes and^(40)Ar-^(39)Ar dating,is conducted on the Wutonggou deposit,in order to reveal the features,source,and timing of hydrothermal mineralization.The studied deposit includes two mining sections namely the Jianshan and Wutonggou.Theδ^(18)O values of early magnetite from the Jianshan section range from+3.0‰to+5.8‰that nearly consistent with classic magmatic magnetite,while increase to 6.3‰-8.0‰in the late stage.Quartz from the two sections shows comparable H-O isotopic compositions and identical fractionation trends,and is plotted in or periphery to the primary magmatic water area.Calcites from the two sections are broadly similar in carbon and oxygen isotopic compositions,and siderite from the Wutonggou section is plotted in the same region.Thus,comparable stable isotopic compositions and evolution trends indicate similar magmatic fluids contributed hydrothermal iron mineralization in the two mining sections.Moreover,water-rock interactions of varying degrees generated distinct mineralization styles in the Jianshan and Wutonggou sections,and caused the isotopic fractionation in late stages.Biotite extracted from a hydrothermal siderite ore yielded a^(40)Ar-^(39)Ar plateau age of 299.5±2.0 Ma,indicates the timing of hydrothermal iron mineralization is corresponding to the emplacement of vicinity granitoids.Taken together,the hydrothermal mineralization in the Wutonggou iron deposit was the product of remobilization and upgrading of early sedimentary iron ores,and ore-forming fluids were most probab
诸广—贵东地区作为华南热液型铀矿最为重要的花岗岩型铀矿大型矿集区,区内发育了大量与铀矿化作用密切相关的基性岩脉。为了厘定区内基性岩年代学数据,更好地约束铀成矿时限,以诸广中段鹿井地区辉绿岩脉为研究对象,开展了40Ar-39Ar年代学研究。结果表明:辉绿岩全岩40Ar-39Ar同位素年龄为(171.7±1.6)、(169.1±3.8)Ma,反映鹿井地区在中侏罗世(约170 Ma)发生了一次岩石圈伸展裂解作用。诸广—贵东地区至少存在200、170、140、105和90 Ma 5期基性岩浆活动,195、165、125、90、75和55 Ma 6期铀成矿事件,成矿热液往往紧随每次区域性玄武岩事件之后(5~20 Ma),铀成矿与以辉绿岩墙为代表的区域玄武岩事件有紧密的时间、空间和成因联系。辉绿岩脉与成矿构造上的关联性以及来源于地幔的深部岩浆浅部表现形式的成因特点,决定了其可以为铀成矿提供一定的挥发分(矿化剂)和后期铀沉淀富集场所,提高成矿热液对铀的携带能力,进而促进铀的成矿作用。
Objective“Orogenic gold deposits,”which account for 30%of global gold resources(Frimmel and Hennigh,2015),is one of the most important types of gold deposits in the world.This kind of gold deposit is supposed to have spatial and temporal distribution association with the accretionary orogenic belt.The Ailaoshan Gold Belt,where there are many large orogenic gold deposits including Jinchang,Daping,Laowangzhai,Donggualing,and Changan,contribute substantially to Chinese gold resources.The Himalayan orogen and Ailaoshan Orogen,both have experienced the early accretionary orogenesis and the subsequent collisional orogenesis are one of the biggest orogenic belts on the earth.Gold mineralization can be divided into that the earlier Yarlung Zangbo suture zone(59–44 Ma)and the later Ailaoshan Orogen(35–26 Ma)(Li et al.,2017),based on previous geochronological studies.In order to find out if there are any connections between these two gold events,we present 40Ar/39Ar data of hydrothermal sericite collected from the Xiachahe gold deposit in the northwest of the Ailaoshan Gold Belt.However,our new geochronology data regards this as a continuous gold mineralization event resulting from the India–Eurasia collision.
