| 阜平杂岩中低品位磁铁矿的形成与深熔作用的关系 |
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| 引用本文：.2009.Formation of low-grade magnetite deposit and its relationship with anatexis in Fuping complex [J].Mineral Deposits,28(5):653~662 |
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| 基金项目:国土资源大调查项目“中国与亚洲早前寒武纪构造与地层划分对比”（ 121201061 1802、1212010711815）、国家自然科学基金“南极拉斯曼丘陵深熔过程的研究”（405 72041）和中央级公益性科研院所基本科研业务费资金“东南极普里兹带从罗迪尼亚到冈瓦 纳古陆的演化”( J0704) |
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| 中文摘要:在中-高级变质的阜平杂岩中可以形成低品位磁铁矿。除碎屑岩中继承的磁铁矿外，新生变质磁铁矿多呈斑晶，可出现于多种岩石类型，如变基性岩、中性岩、酸 性岩和变沉积岩中，表明新生磁铁矿的形成不受层位控制。磁铁矿可由物理重结晶 和化学反应2种形式形成，重结晶过程主要为矿物颗粒的加粗，但没有明显的脱水反应。变质化学反应形成的磁铁矿与各单元所经受的后期变质事件改造有关，这类磁铁矿的出现与岩石中TFe的含量没有必然的联系，关键在于变质反应中是否有适量的铁组分的迁移和富集。变 质反应过程中，初期黑云母变质转化形成角闪石，即变质反应不全是脱水或吸水过程，表明阜平杂岩主要的变质过程发生在含水体系中。在进一步的变质改造中，黑云母、角闪石可深熔转 化形成磁铁矿。在片麻岩的含水熔融过程中，Mg、Ca优先迁移，而Fe(Ti, Al)迁移微弱，造成Fe(Ti, Al)与Mg组分的分离，残留的相对富铁组分形成磁铁矿、钛铁矿。磁铁矿 结晶时没有明显的挤压或剪切，张应力可能占主导地位，相应的深熔作用主要发生在构造静应力期或体系略微抬升的过程中。 |
| 中文关键词:地质学 磁铁矿 变质过程 有水深熔作用 组分活动 阜平杂岩 |
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| Formation of low-grade magnetite deposit and its relationship with anatexis in Fuping complex |
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| Abstract:The low-grade magnetite deposit could be formed in the high amphibolite-granulite facies metamorphic complex. Except for the detrital magnetite in the paragneisses, the newly-formed magnetite in the metamorphic process usually occurs as euhedral porphyryblasts. The magnetite ores can be found from the metabasic rock, metaintermediate rock to acid rock and metasedimentary rocks, suggesting that the formation of magnetite was not confined to any special layers but was related to the metamorphic event which prevailed in nearly all the rock units in the Fuping complex. Not necessarily related to the high total iron contents of the bulk chemistry, the formation of metamorphic magnetite was dependent on the adequate migration and enrichment process of the iron component. It can be discerned that the major metamorphic event of the complex was of hydrous and two formation styles of magnetite, recrystallization and chemical reaction. The recrystallization is manifested by the coarsening of magnetite, with no obvious dehydration reactions taking place. As to the metamorphic reaction processes, the initial biotite was transformed into hornblende, suggesting that the reactions were not through dehydration or hydration metamorphism. In the further transformation, both biotite and hornblende could be changed into magnetite in the anatexis process. In the aqueous partial melting of the complex, the Mg, Ca elements preferentially migrated, while Fe(Ti) (Al?) weakly migrated, which was responsible for the differentiation between the components Fe(Ti) (Al?) and Mg, and the residues were relatively rich in iron and magnetite with the formation of minor ilmenite. In this process, extensional stress was predominated with no obvious compression or shearing, and the corresponding partial melting occurred essentially in the static stress or slightly uplifting system. |
| keywords:geology, magnetite, metamorphic process, aqueous partial melting, component migration, Fuping complex |
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