【作者】 王春龙；

【导师】 王义天； 董连慧；

【作者基本信息】 中国地质科学院 ， 矿物学、岩石学、矿床学， 2012， 硕士

【摘要】 阿吾拉勒铁铜成矿带为西天山地区重要的晚古生代成矿带,总体表现为东铁西铜的特征。松湖中型铁矿位于成矿带中段,赋存于石炭系大哈拉军山组火山-沉积岩系中,为成矿带中典型的火山岩型铁矿。本论文在充分收集前人资料和野外地质调查的基础上,对松湖铁矿开展了基础地质、矿床地质与构造、元素和同位素地球化学、流体包裹体、地质年代学、成矿机制等方面的研究工作,并与国内外的典型火山岩型铁矿进行对比,获得以下主要认识和研究进展：(1)矿区围岩为一套火山碎屑岩-沉积岩组合,岩性包括安山质-英安质岩屑晶屑凝灰岩、凝灰质砂岩、含角砾岩屑晶屑凝灰岩、晶屑熔结凝灰岩、灰岩、钙质粉砂岩以及砂屑灰岩,根据其原生沉积构造以及火山碎屑物特征,推断该套岩系形成于滨浅海相洋底浊流沉积作用。(2)矿体呈似层状赋存于凝灰质砂岩中,产状陡倾,与围岩基本呈整合接触。主要控矿构造为近东西向等距离分布的高角度压扭性断裂,其次为近东西向、北北西向以及北东向的节理裂隙,构造应力场分析表明其形成于近南北向右行的压剪性应力场中,可能与晚古生代增生造山作用有关。(3)矿石矿物主要为磁铁矿,其次为赤铁矿、黄铁矿及黄铜矿,脉石矿物主要为钾长石、绿泥石、方解石、绿帘石及阳起石等。主要呈块状、条带状、团块状、角砾状构造,其次为脉状和浸染状构造,结构主要为半自形-他形粒状,碎裂及重结晶结构发育。磁铁矿的电子探针分析表明,早阶段形成的磁铁矿具有岩浆型磁铁矿的特征,晚阶段磁铁矿则表现为火山热液成因。(4)围岩蚀变主要类型包括钾长石化、绿泥石化、阳起石化、绿帘石化、方解石化、黄铁矿化及黄铜矿化等,在垂向和水平方向上均发育分带性。(5)根据野外及室内观察的矿物共生组合以及相互穿插关系,将松湖铁矿的成矿作用可分为热液期和表生期,热液期可进一步划分为五个阶段,即钾长石-绿泥石-磁铁矿阶段、阳起石—绿帘石-磁铁矿阶段、硫化物-磁铁矿阶段、石英-方解石-硫化物阶段以及方解石-赤铁矿阶段。(6)矿石中的磁铁矿与围岩的稀土元素特征表明二者同源,硫同位素特征表明矿石中的硫来源于岩浆硫,以上表明成矿物质来源于火山作用。(7)对成矿作用后期流体的碳氧同位素组成以及流体包裹体研究表明,流体主要为水—岩反应的产物,石英-方解石-硫化物阶段属中温、中-低盐度的NaC1-H2O体系,至方解石-赤铁矿阶段演化至中-低温、高-中盐度的NaC1-H2O体系。(8)通过与国内外典型矿床的综合对比,认为松湖铁矿的成因类型为海相火山热液型,矿体形成晚于围岩,成矿作用主要与火山作用及火山期后热液作用有关。构造背景为岛弧靠近弧后盆地一侧,与石炭世南天山洋向伊犁-中天山板块的俯冲作用有关。更多还原

【Abstract】 The iron copper mineralization belt of Awulale is an important Late Plaeozoic metallogenetic belt in western Tianshan, where the characteristic of mineral resources distribution is that iron deposits locate in the east and copper deposits locate in the west. As a typical volcanogenic iron deposit, the medium-sized Songhu iron deposit is located in the center of the metallogenetic belt, which is hosted by lower Carboniferous Dahalajunshan volcanic-sedimengtary Formation. Based on combination of predecessors works and fieldwork of geological survey, we focused on study of basic geology, ore geology and structure, element and isotope geochemistry, fluid inclusion, geochronology, mineralization mechanism, and comparation with typical volcanogenic iron deposits domestic and overseas, and achieved several understandings and progresses as follows.(1) The host rock is a lithological association of volcaniclastic and sedimengtary rock, including andesitic and dacitic debris-crystal fragment tuff, tuffaceous sandstone, debris-crystal fragment tuff with laplli, welded ignimbrite, limestone, calcareous siltstone and calcarenite. According to primary sedimentary structure and features of pyroclastics, the lithological association was sedimented by turbidity in costal or shallow water.(2) Ore bodies which occur as stratoids are hosted in tuffaceous sandstone, with steep occurance and in conformity with wallrock. The deposit is controlled by the structures that consisted mainly of near E-W striking faults and subordinately of near N-S, NNW and NE trending faults and joints, which is generated by regional NS-trending dextral shear regime that related to accretionary orogenetic process in late Paleozoic.(3) Ore minerals are mainly magnetite, with minor hematite, pyrite and chalcopyrite, while gangue minerals are mainly potassium feldspar, chlorite, calcite, epidote and actinolite etc. Ore structure mainly occur as massive, stripped, agglomerated and brecciated, minor are vein and disseminated, whereas ore textures dominantly display as subhedral-anhedral granular, recystallization and cataclastic are developed. Electron microprobe analyses of magnetite imply that mangnetite formed in early stage show features of magmatic genesis, while the ores in latter stage belong to volcanic hydrothermal type.(4) The alteration of wallrock with zonation in vertical and horizontal are mainly of potassic feldspathization, choritization, actinolitization, epidotization, calcitization, pyritization and chalcopyritization etc.(5) Field evidence and petrographic observation indicate two periods of metallogensis, including hydrothermal period and supergene oxidation period. Hydrothermal period can be subdivided into five stages, including potassium-chlorite-manetite, actinolite-epidote-magnetite, sulfide-magnetite, quartz-calcite-sulfide and calcite-hematite stages.(6) The rare earth element feature of wallrock and magnetite suggest the ore-forming and rock-forming materials were derived from the same source, sulfur isotope datas show sulphur in ores is deprived from the magma, based on that we suggest the ore-forming material sourced from volcanism.(7) The fluid in later stage is studied through carbon-oxygen isotope and fluid inclusion, revealed that it is derived from water-rock reaction, which belong to high-middle temperature, middle-low salnity NaCl-H2O system in quartz-calcite-sulfide stage, then evoluted to middle temperature, high-middle salnity NaCl-H2O system in calcite-hematite stage.(8) In comparation with typical volcanogenic iron deposits domestic and overseas, we draw the conclusion that the genetic type of Songhu iron deposit is marine volcanic-hydrothermal type, the mineralization is mainly related to volcanism and hydrothermal process in post-volcanic period. The tectonic setting of mineralization is back-arc basin which is formed by the subduction of the Southern Tianshan Ocean northward beneath the Ili-Central Tianshan plate in Carboniferous.更多还原