伊犁地块石炭纪铁矿床不同矿化类型成因联系与时空分布

Genetic Relationship and Time-Space Distribution of Varying Metallogenic Typesamong Carboniferous Iron Deposits inthe Yili Terrane

以伊犁地块阿吾拉勒铁矿带为重点研究对象,分析本地区标志性矿化类型与火山-沉积建造间的关系,探讨不同矿化类型成因联系与时空分布规律。研究认为,西天山大中型富铁矿床主要赋存于伊犁地块石炭纪弧后盆地,铁成矿应与早石炭世海相火山活动诱发的熔流体喷溢与火山热液交代作用密切相关。同时,盆地建造类型对矿化样式和不同类型铁矿床的定位具明显的制约。赋存于大哈拉军山组熔岩-火山碎屑岩建造中的铁矿床主要位于火山机构断裂系中,多与容矿火山岩系呈不和谐接触关系,其宏观产状取决于在火山机构-火山穹窿中的具体位置,成矿物质主要来源于火山晚期高温熔流体和火山热液。赋存于伊什基里克组铁矿床的定位和规模,基本受控于水下沉积洼地的古地貌特征,主要属化学沉积铁矿范畴,与上下盘地层一般呈整合接触关系。因此,伊犁盆地石炭纪海相火山岩建造与海相火山-沉积建造间的差异性,很可能是控制不同类型矿床形成与定位的第一要素。

Thenewlydiscoveredmedium-tolarge-sizedirondepositsinwesternTianshan,aremainlydistributedwithin the Yili Carboniferous back-arc basin.The formation of most major iron deposits were intimately linked with Early Carboniferous marine volcanic rocks（hosted by the Dahalajunshan formation）,but some other deposits were genetically related to chemical deposition of iron and silica from seawater in Late Carboniferous time（hosted by the Yishijilike formation）.The iron deposits hosted within volcanic-volcaniclastic rocks of the Dahalajunshan Fm. were chiefly localized in the ring and radiate faults of crater structures and formed by ore-magma and/or high-temperature volcanic hydrothermal fluids,thus they are not concert with the surrounding volcanic strata in their orientations.The deposits hosted within the sedimentary rocks of the Yishijilike Fm. are chemically precipitated along with other sediments from the surrounding seawater, therefore they are conformable with the hosting stratigraphy and controlled by paleo- topography of the basin.However, overprinting by Sedex-type mineralization on these sedimentary iron deposit can not be totally precluded. It is suggested that the differences between the marine volcanic rock package and sedimentary rock package might be the principal and crucial factor in controlling the generation and localization of the iron mineralization in the region.