摘要
南盘江–右江成矿带是我国重要成矿带,本文通过研究坤洪磁铁矿床中含矿矽卡岩的岩相学和矿石中磁铁矿的矿物化学特征,探讨磁铁矿床的成因。坤洪磁铁矿床中磁铁矿的形成过程可分为两个阶段:1) 早期进变质矽卡岩阶段形成的较自形磁铁矿(第一世代磁铁矿)含量较少,该阶段的成矿作用相对较弱,是磁铁矿的次要成矿阶段;2) 晚期退变质矽卡岩阶段形成的不规则状磁铁矿(第二世代磁铁矿)含量较多,表明该阶段是磁铁矿的主成矿阶段。两个阶段(两个世代)磁铁矿均具有较典型的矽卡岩型磁铁矿的成分特征,其成矿作用与热液活动密切相关,说明其应属于(岩浆)热液–矽卡岩成因类型,但两个世代的磁铁矿在矿物化学特征上表现出不同的变化趋势,表明二者的成矿流体和成矿物质来源可能存在差异。
The Nanpanjiang-Youjiang metallogenic belt is an important metallogenic belt in China. In this paper, the genesis of magnetite deposits is discussed by studying the petrology of skarnite bearing in the Kunhong magnetite deposit and the mineralochemical characteristics of magnetite in the ore. The formation process of magnetite in the Kunhong magnetite deposit can be divided into two stages: 1) the content of self-shaped magnetite (first-generation magnetite) formed in the early metamorphic skarn stage is less, and the mineralization of this stage is relatively weak, which is the secondary metallogenic stage of magnetite;2) The content of irregular magnetite (second- generation magnetite) formed in the late degenerative skarn stage was large, indicated that this stage was the main metallogenic stage of magnetite. The two stages (two generations) magnetite have the composition characteristics of typical skarn-type magnetite, and their mineralization is closely related to hydrothermal activity, indicated that it should belong to the (magma) hydrothermal-skarn genesis type, but the two generations of magnetite show different trends in mineral chemical characteristics, indicated that the mineralize fluid and mineral-forming source of the two generations may be different.
