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    辽宁凤城翁泉沟硼铁矿床磁铁矿的成因研究

    Genesis of magnetite of the Wengquangou vonsenite deposit, Fengcheng county, Liaoning Province

    • 摘要: 提要:辽宁凤城翁泉沟硼铁矿床产于古元古代辽吉裂谷带,赋存于下辽河群的含硼岩系里尔峪组中。其矿石矿物主要为硼镁铁矿、磁铁矿和硼镁石等;脉石矿物主要为蛇纹石、白云石、金云母等。翁泉沟硼铁矿床中的磁铁矿分为3种类型:变质形成的粗粒磁铁矿(Ⅰ型)、热液蚀变而成的细粒磁铁矿(Ⅱ型)和网脉状磁铁矿(Ⅲ型),其中,I型显示均质性,Ⅱ、Ⅲ型显示非均质性。均质性磁铁矿的镁、铝元素含量高于非均质性磁铁矿,硅含量低于非均质性磁铁矿,导致前者硬度高于后者。元素含量差异可能是磁铁矿发生非均质化的原因。研究结果表明,翁泉沟矿床的成矿过程包括了沉积变质和后期热液叠加作用。

       

      Abstract: Abstract:The Wengquangou vonsenite deposit, Fengcheng county, Liaoning Province, is located in the Liao-Ji Palaeoproterozoic rift and hosted in the boron-bearing series within the Lieryu Formation, lower Liaohe Group. The main ore-minerals are ludwigite, magnetite and szaibelyite, coexisting with gangue minerals including serpentine, dolomite and phlogopite. The magnetite can be distinguished in terms of occurrence from coarse-grained metamorphic (I), fine-grained hydrothermal (II) and stockworks (III). Type I is optically homogeneous and Types II and III appear to be heterogeneous. As detected using electronic microprobe and energy spectroscopy, the homogeneous magnetite has higher contents of Mg and Al and lower Si content than the heterogeneous, resulting in that Type I is harder than types II and III. It is possible that the discrepancy in element contents caused the transformation from homogeneous to heterogeneous magnetite. Study on magnetite shows that the formation process of the Wengquangou deposit includes sedimentary-metamorphism and hydrothermal overprint.

       

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