河南舞阳铁山庙式铁矿地质地球化学特征与成矿作用

发布时间：2018-04-11 23:13

本文选题：条带状辉石磁铁石英岩 + 浸染状磁铁辉石岩　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：舞阳地区位于华北克拉通南部。舞阳铁矿包括铁山庙式铁矿和赵案庄式铁矿。铁山庙式铁矿赋存于新太古界太华群铁山庙组变质岩系中。矿体呈似层状、透镜状,层位分布稳定,大理岩常为矿体的顶底板。有2种矿石类型:浸染状磁铁辉石岩和条带状辉石磁铁石英岩,其中,浸染状磁铁辉石岩主要由辉石和磁铁矿组成,基本不含石英,与条带状辉石磁铁石英岩明显不同,它是原基性火山岩变来还是其他成因存在争议。本文对矿石和围岩大理岩进行了详细的地质学和地球化学对比研究,试图为探讨铁山庙式铁矿的形成过程提供更多的信息。浸染状磁铁辉石岩、条带状辉石磁铁石英岩、蚀变大理岩和辉石岩中的单斜辉石相似,Al2O3、Ti O2含量低,与来自片麻岩中的单斜辉石Al2O3、Ti O2含量较高明显不同。浸染状磁体辉石岩与条带状辉石磁铁石英岩具有相似的地球化学特征,均主要由Si O2、TFe2O3、Ca O和Mg O组成,而其他氧化物的含量均很低;二者及其中的磁铁矿单矿物稀土元素总量很低,具有La、Eu、Y正异常和较高的Y/Ho比值,无明显Ce和Gd异常。这些特征暗示其为一种典型的化学沉积岩,成矿物质来源于海底热液和海水,形成于较还原海水环境。大理岩的野外地质特征和地球化学特征显示其与矿石具有成因联系。在灰色大理岩中可见黑色磁铁辉石岩薄层或条带,或磁铁辉石岩与白色不纯大理岩薄层或条带互层,显示二者同时形成;辉石岩为热液蚀变大理岩的结果;辉石在蚀变大理岩中普遍存在;蚀变大理岩、辉石岩和矿石中的辉石具有相似的地球化学特征,低的Al2O3和Ti O2含量,Mg O和Si O2呈正相关关系,TFe O和Si O2、Mg O呈负相关关系;大理岩的稀土元素特征与矿石类似,稀土元素总量低,Eu、Y正异常等;这些特征暗示大理岩与矿石关系密切。表明矿石中的辉石不是来自火山岩,而是碳酸盐和硅质岩组成的化学沉积物经变质作用形成的。总之,浸染状磁铁辉石岩和条带状辉石磁铁石英岩的地质和地球化学特征表明它们具有相似的物质来源和成因机制。因此,我们认为舞阳铁山庙式铁矿由沉积的石英-碳酸盐含铁建造变质形成。
[Abstract]:Wuyang area is located in the south of North China Craton.Wuyang iron ore includes Tieshanmiao iron ore and Zhaoshengzhuang iron ore.Tieshanmiao iron ore deposit occurs in the metamorphic rock series of the Tieshanmiao formation of Taihua Group in the Neo-Archaean.The ore body is layered, lenticular and stable in distribution. Marble is often the top and bottom plate of the orebody.There are two types of ore: impregnated pyroxenite and banded pyroxene magnetite quartzite, in which the impregnated magnetite pyroxenite is mainly composed of pyroxene and magnetite, and basically does not contain quartz, which is obviously different from strip-shaped pyroxene magnetite quartzite.Whether it is the origin of the primary volcanic rocks or some other origin is controversial.In this paper, a detailed geological and geochemical comparison of ore and surrounding rock marble is carried out in order to provide more information for the discussion of the formation process of Tieshanmiao-type iron ore.Dipping pyroxenite, zonal pyroxene magnetite quartzite, altered marble and clinopyroxene similar to clinopyroxene have low content of Al _ 2O _ 3O _ 2, which is obviously different from the high content of clinopyroxene Al _ 2O _ 3O _ 2 from gneiss.The igneous pyroxenite and zonal pyroxene quartzite have similar geochemical characteristics. They are mainly composed of Sio _ 2, TFE _ 2O _ 3, Cao and MgO, but the contents of other oxides are very low.The total amount of rare earth elements in both magnetite and magnetite is very low, with the positive anomaly of La-Eu-Y and the high Y/Ho ratio, and there is no obvious ce and Gd anomalies.These characteristics suggest that it is a typical chemical sedimentary rock with ore-forming materials derived from submarine hydrothermal and seawater and formed in a relatively reduced seawater environment.The field geological and geochemical characteristics of marble show that it is related to ore genesis.In gray marble, black magnet pyroxenite thin layer or strip, or magnetite pyroxenite and white impure marble thin layer or strip interlayer can be seen, which shows that both of them are formed at the same time, pyroxenite is the result of hydrothermal alteration marble;The pyroxene is common in altered marble, and the pyroxene in altered marble, pyroxenite and ore have similar geochemical characteristics, and the low content of Al2O3 and TIO _ 2 are positively correlated with Sio _ 2, and there is a negative correlation between TFeO and Sio _ 2Mg-O, and there is a negative correlation between pyroxene and pyroxene in altered marble.The REE characteristics of marble are similar to those of ore, and the total amount of REE is low and EUY is positive anomaly, which suggests that marble is closely related to ore.It is shown that the pyroxene in the ore is not from volcanic rock, but is formed by metamorphism of the chemical sediments composed of carbonate and siliceous rocks.In a word the geological and geochemical characteristics of impregnated pyroxenite and banded pyroxene quartzite show that they have similar material source and genetic mechanism.Therefore, we think that Tieshanmiao iron ore deposit in Wuyang is formed by metamorphism of sedimentary quartz-carbonate iron bearing formation.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.31

【相似文献】