投稿时间：2022-12-13
修订日期：2023-02-20
网络发布日期：2023-09-06
中文摘要:铁建造(IFs)主要形成于前寒武纪,其不仅记录了丰富的岩石圈、大气圈、水圈和生物圈状态及演化的信息,而且也是世界上最重要的铁矿资源类型。最新研究发现,中国新疆阿尔泰地区产出有早古生代IFs,文章以天德Ⅱ号铁矿为典型矿床开展了深入的矿物学研究。天德Ⅱ号铁矿呈层状、似层状赋存于变质火山-沉积岩系中,IFs主要组成矿物为磁铁矿和石英,角闪石和石榴子石次之。此外,可见少量斜长石、黑云母、钛铁矿以及金红石等矿物。片岩中矿物组合与IF类似,但磁铁矿含量较低,而硅酸盐矿物含量较高。IFs和片岩中磁铁矿均较为纯净;角闪石属于镁角闪石-镁钙闪石,斜长石主要为中长石;黑云母为镁黑云母;ⅠFs中石榴子石主要属于铁铝榴石-锰铝榴石系列,与前寒武纪IFs矿物组合一致,这些矿物均为变质成因。据此,笔者推测天德Ⅱ号铁矿原始沉积物为无定形二氧化硅、碎屑物质、碳酸盐以及Fe(Ⅲ)-氢氧化物,其经历了角闪岩相变质作用,根据Grt-Bt地质温度计计算其变质温度为592~617℃,依据Hbl-Pl-Qtz地质压力计获得压力为3.06~3.23 kbar。结合前人研究,笔者认为天德Ⅱ号铁矿可能与前寒武纪阿尔戈马型IFs类似,早古生代IFs的出现为该时期出现缺氧、富铁的海洋环境提供了直接证据。
Abstract:The iron formation (IFs) was mainly formed in the Precambrian, which not only records abundant information about the state and evolution of the lithosphere, atmosphere, hydrosphere and biosphere, but also is the most important type of iron ore resources in the world. The latest research argueded that some Early Paleozoic IFs were present in the Altay area. In this study, a detailed mineralogical study was carried out on the Tiande No.Ⅱ iron deposit as a typical deposit. Tiande No.Ⅱ Iron deposit is stratiform and stratoid, which was hosted in the meta-volcano-sedimentary rocks. The minerals in IFs are dominated by magnetite and quartz, secondly amphibole and garnet. In addition, few plagioclase, biotite, ilmenite and rutile also can be observed. The mineral assemblage of the schist is similar to that of IFs, but magnetite content is lower and silicate mineral contents are higher in the former. The EPMA analysis show that magnetite in both IFs and schist are relatively pure; amphibole belongs to magnesiohornblende -tschermakite; plagioclase is mainly andesine; biotite is magnesia biotite; garnet in IFs mainly is almandine-spessartine. This mineral assemblage is similar to that of Precambrian IFs, and all of the minerals are of metamorphic origin. Accordingly, we proposed that the original precipitates of the Tiande No.Ⅱ iron deposit were composed of amorphous silica, clastic materials, carbonate minerals and Fe(Ⅲ)-oxyhydroxide, and then they underwent amphibolite facies metamorphism. The metamorphic temperature calculated by the Grt-Bt geothermometer ranging from 592℃ to 617℃, and the pressure calculated by the Hbl-Pl-Qtz geobarometer is 3.06~3.23 kbar. Combining with our previous studies, we argue that the Tiande No. Ⅱ iron deposit may be similar to Precambrian Algoma-type IFs, and the appearance of Early Paleozoic IFs provides direct evidence for the occurrence of anoxic and iron-rich marine environments during the Early Paleozoic period.
文章编号：
中图分类号：
文献标志码：
基金项目:本文得到国家自然科学基金(编号:41972075)、中央高校基本科研业务费专项资金(编号:300102272203)和陕西省自然科学基础研究计划(编号:2020JQ-439)联合资助
引用文本：
杨国威,杨秀清,吴佳林,张旭升,韩敏强,王志华.2023.新疆阿尔泰天德Ⅱ号铁矿床矿物学特征及其指示意义[J].矿床地质,42(4):759~772YANG GuoWei,YANG XiuQing,WU JiaLin,ZHANG XuSheng,HAN MinQiang,WANG ZhiHua.2023.Mineralogical characteristics of Tiande No.Ⅱ iron deposit, Altay, Xinjiang and its implications to ore genesis[J].Mineral Deposits42(4):759~772
图/表
