新疆阿尔泰克兰盆地金属矿床地质特征及成矿作用

Metallic ore deposits in the Kelan Basin,Altay,Xinjiang:Geological characteristics and metallogenesis

在前人工作基础上,文章综述了新疆阿尔泰克兰盆地金属矿成矿背景和地质特征。其赋矿地层主要为上志留统—下泥盆统康布铁堡组变质火山沉积岩系,少数为中-上泥盆统阿勒泰组变质火山沉积岩系。成因类型划分为海相火山岩型、矽卡岩型、Sedex型、造山型和伟晶岩型5种类型,其中海相火山岩型为主要类型,进一步划分出VMS型、火山热液型、火山沉积型和矿浆-火山热液型4个亚类型。根据同位素测年结果,矿床成矿时代分为3期:早泥盆世(410~389 Ma),是主要成矿期,与海相火山作用有关,主要形成海相火山岩型,少数矽卡岩型矿床;晚石炭世—二叠纪(320~258 Ma),主要形成与岩浆期后热液、伟晶岩或构造热液活动有关的矽卡岩型、伟晶岩型稀有金属矿和造山型金矿;早-中三叠世(248~232 Ma),形成少量伟晶岩型稀有金属矿。硫同位素表明矽卡岩型铁矿的硫来自与成矿有关的花岗岩;火山沉积岩型和矿浆-火山热液型铁矿的硫除来自火山岩外,还有细菌还原海水硫和闪长岩;VMS型矿床的硫主要是海水硫酸盐细菌还原硫和来自岩浆(来自火山喷气或火山作用)。

This paper deals with the geological characteristics and metallogenic-tectonic background of metallic ore deposits in the Kelan Basin,Altay,Xinjiang.The main host rocks for metallic ore deposits in this region is metavolcanic-metasedimentary rocks of the Upper Silurian-Lower Devonian Kangbutiebao Formation,with minor Middle-Upper Devonian Altay Formation.These metallic ore deposits can be divided into several types such as submarine volcanogenic,skarn,Sedex,orogenic and pegmatite types,with the submarine volcanogenic type being predominant.The submarine volcanic rock type can be further divided into VMS,volcano-hydrothermal,volcano-sedimentary and ore magma-volcano-hydrothermal subtypes.Based on the isotopic age data,the authors hold that the metallic ore deposits in the Kelan Basin were essentially formed in three periods：（1） Early Devonian（410~389 Ma）,which was the main metallogenic period and was related to the marine volcanism,when submarine volcanogenic type was mainly formed,with minor skarn type deposits;（2） Late Carboniferous-Permian（320~258 Ma）,during which magmatic hydrothermal-related skarn-type deposits,pegmatite-type,and tectonic hydrothermal activity-related orogenic-type Au deposits were formed;（3） Early-Middle Triassic（248~232 Ma）,during which a few pegmatite-type rare-metal deposits were formed.Stable isotopic data indicate that sulfur in skarn-type Fe deposits within the Kelan Basin was derived from granites related to Fe mineralization;sulfur of volcano-sedimentary and ore magma-volcanic-hydrothermal type deposits was derived from volcanic rocks,bacterial reduction of sulfate from seawater,and diorites;sulfur of VMS-type deposits was derived from the bacterial reduction of sulfate from seawater and magma（volcanic exhalation or volcanism）.