| 四川攀枝花钒钛磁铁矿床Fe同位素特征及其成因指示意义 |
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| 引用本文：王世霞,朱祥坤,宋谢炎,陈列锰.2012.四川攀枝花钒钛磁铁矿床Fe同位素特征及其成因指示意义[J].地球学报,33(6):995-1004. |
| DOI：10.3975/cagsb.2012.06.20 |
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| 基金项目:中国地质大调查项目(编号: 1212011120295);国家“973”项目(编号: 2012CB416806, 2012CB416804);国家自然科学基金(编号: 41103002, 40730420) |
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| 中文摘要:本文系统研究了四川攀枝花含钒钛磁铁矿层状岩体全岩和矿石矿物磁铁矿的Fe同位素组成特征。研究获得全岩δ57Fe的范围为0.02‰～0.25‰, 平均值为0.17‰, 磁铁矿的δ57Fe范围为0.05‰～0.61‰, 平均值为0.36‰。相对于磁铁矿单矿物, 全岩Fe同位素组成变化不大。相对于全岩, 磁铁矿具有相对重的Fe同位素组成, 并且其相对偏重程度与样品中磁铁矿的含量呈反相关关系。磁铁矿Fe同位素组成与形成环境氧逸度之间的负相关关系表明磁铁矿从岩浆中结晶出来之后没有发生重力分异, 赋存于岩体和矿体中的磁铁矿是原位结晶的。磁铁矿的Fe同位素特征表明攀枝花岩体是多次岩浆补充和分离结晶共同作用的结果: 形成下部岩相带过程中, 玄武质岩浆补充频繁, 形成巨厚的块状磁铁矿层, 其中的磁铁矿的δ57Fe值变化较小; 而形成中部岩相带过程中, 玄武质岩浆补充的频率逐渐降低, 形成多个旋回以及交替产生的磁铁辉长岩和辉长岩。同时, 形成攀枝花岩体和矿体的初始岩浆的氧逸度很高, 在高氧逸度环境下富集成矿, 演化过程中岩浆体系氧逸度逐渐降低, 很好地解释了攀枝花V-Ti磁铁矿主矿体赋存在含矿岩体下部的辉长岩中的成矿机制。 |
| 中文关键词:攀枝花钒钛磁铁矿 全岩 磁铁矿 Fe同位素 矿床成因 |
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| Fe Isotopic Characteristics of V-Ti Magnetite Deposit in Panzhihua Area of Sichuan Province and Their Genetic Implications |
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| Abstract:The whole rock and ore mineral magnetite Fe isotope compositions of layered rocks and ores in the Panzhihua vanadium-titanium magnetite deposit of Sichuan Province were analyzed in this paper. The distribution range of δ57Fe in the whole rock is about 0.02‰ to 0.25‰, with the average of 0.17‰, and that in magnetite is about 0.05‰ to 0.61‰, with the average of 0.36‰. Fe isotope composition of magnetite is higher than that of whole rock in every sample, and there exists a negative correlation between the heavy degree and the magnetite content. The negative correlation between Fe isotope composition of magnetite and environmental oxygen fugacity suggests that the magnetite in the whole rock was in-situ crystallized, and no gravitational differentiation of magnetite happened. The characteristics of magnetite Fe isotope composition demonstrats that the process of magma complement and fractional crystallization resulted in the formation of the Panzhihua vanadium-titanium magnetite deposit. During the creation of bottom petrofacies, frequent basaltic magma complement formed bulk magmetite with insignificant variation of δ57Fe. During the creation of middle petrofacies, infrequent magma complement formed many alternations of magnet gabbro and gabbro. The ore-forming oxygen fugacity of the initial magma in Panzhihua was relatively high, and the oxygen fugacity gradually decresed with the magma evolution. The conclusion also reveals the ore-forming mechanism of the Panzhihua vanadium-titanium magnetite deposit in Sichuan. |
| keywords:Panzhihua V-Ti magnetite whole rock magnetite Fe isotope genesis of deposit |
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