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投稿时间：2022-12-13 修订日期：2023-02-20 网络发布日期：2023-09-06
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.
YANG 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