嵩山地区BIF地球化学特征及其地质意义

发布时间：2018-03-23 23:02

本文选题：嵩山　切入点：BIF　出处：《河南理工大学》2015年硕士论文

【摘要】：嵩山地区位于华北克拉通南缘,地层出露齐全,是我国前寒武纪地质研究的经典地区之一,BIF的发现是嵩山近年地质研究重大进展之一。BIF是条带状铁建造(Banded Iron Formation)的英文简称,对于研究前寒武纪地质及铁矿找矿具有重要意义。本次工作主要依托1:5万区域地质调查项目,通过地质剖面测量、地质填图,采集样品开展岩矿鉴定、硅酸盐全分析、微量分析、稀土分析等,研究BIF地质地球化学特征,探讨其形成大地构造环境和原岩性质和来源,取得成果如下:(1)BIF赋存于新太古代登封群金家门组中,主要岩性为磁铁石英岩及角闪磁铁石英岩,斜长角闪岩,黑云变粒岩及二云石英片岩等。磁铁石英岩呈细粒花岗变晶结构,条纹、条带状构造,矿物主要为石英(55%~75%)、磁铁矿(25%~35%)、角闪石(5%±)等。(2)磁铁石英岩主量元素主要由SiO2、Fe2O3和FeO组成,TFe2O3平均为39.39%,微量元素相对富集K、Rb、Ba、Th等大离子亲石元素,亏损Nb、Zr、Hf、Ti等高场强元素;矿石稀土元素含量很低,ΣREE平均为40.95×10-6,经过PAAS标准化后具有轻稀土相对亏损、重稀土相对富集的稀土配分模式;LaN/YbN平均值为0.53;Eu/Eu*平均值为1.31,Eu弱正异常,Ce轻微负异常(Ce/Ce*平均值为0.90)等特征。(3)磁铁石英岩形成于火山活动间歇期的稳定的火山喷气沉积阶段,在缺氧的海水环境下硅和铁先后沉积,形成条纹、条带状构造,硅和铁主要来自于火山活动,硅铁沉积过程中很少有碎屑物质加入。(4)BIF带原岩主要为基性火山岩、砂泥质沉积岩。角闪岩原岩为基性火山岩,具有岛弧拉斑玄武岩和洋中脊玄武岩地球化学特征,指示拉张初期的弧后盆地环境;变粒岩、二云石英片岩原岩主要为砂质、泥质沉积岩,沉积过程中可能有部分中酸性火山岩加入,指示沉积环境可能为远洋盆地靠近大陆边缘区域,沉积过程中受到大洋内火山活动的影响。(5)嵩山地区BIF的地球动力学背景为汇聚板块边缘的俯冲环境。(6)BIF的发现为嵩山地区铁矿找矿指明了方向,今后加强在郭家窑和万安山BIF带的南北延伸方向上的找矿工作,可望发现一定规模的鞍山式铁矿床。
[Abstract]:The Songshan area is located in the southern margin of North China Craton, and the strata are well exposed. It is one of the classical areas of Precambrian geological study in China. The discovery of BIF is one of the important advances in recent years in the geological research of Songshan Mountain. BIF is an abbreviation for banded Iron formation of strip iron. It is of great significance for the study of Precambrian geology and ore prospecting. This work mainly relies on the 1: 50 000 regional geological survey project, through geological profile survey, geological mapping, collection of samples to carry out rock and ore identification, and silicate analysis. Trace analysis, rare earth analysis, etc., to study the geological and geochemical characteristics of BIF, and to discuss its tectonic environment, original rock properties and origin. The results are as follows: 1) BIF occurred in the Jinmen formation of the New Archean Dengfeng Group, The main lithologies are magnetite quartzite and hornblende quartzite, amphibolite, biotite granulite and Eryun quartz schist, etc. The magnetite quartzite is of fine granitic texture, striped and striped structure. The main elements of magnetite quartz quartz are mainly composed of Sio _ 2, Fe _ 2O _ 3 and FeO, the average TFE _ 2O _ 3 is 39.39, and the trace elements are relatively enriched in large ion lithophile elements such as K _ (Rb) Ba _ (Th) and depleted high field strength elements such as NB, Zr, HfT _ (Ti). The content of rare earth elements in ore is very low, 危 REE is 40.95 脳 10 ~ (-6) on average. After PAAS standardization, the ore has the relative depletion of light rare earth elements. The rare earth distribution model with relative enrichment of heavy rare earth elements, LaN- / YbN, has a mean value of 0.53 EU / EU * and the average value of 1.31 EU weak positive anomaly ce is slightly negative anomaly. The average value of ce / ce * is 0.90)) the magnetite quartzite is formed during the stable volcanic exhalation stage during the period of volcanic activity interval. In anoxic seawater environment, silicon and iron have been deposited successively, forming stripes and banded structures, silicon and iron are mainly derived from volcanic activity. During the deposition of ferrosilicon, very few clastic materials are added to the original rocks of the BIF belt, which are mainly basic volcanic rocks. Sandy argillaceous sedimentary rocks. Amphibolites are basic volcanic rocks with geochemical characteristics of island arc tholeiite and mid-oceanic ridge basalt, indicating the back-arc basin environment in the early tensioning stage, metamorphic rocks, eryun quartz schist protolites are mainly sandy, The muddy sedimentary rocks may be joined by some intermediate-acid volcanic rocks during the deposition process, indicating that the sedimentary environment may be near the continental margin of the ocean-going basin. The geodynamic background of BIF in Songshan area is the subduction environment of convergent plate margin. The discovery of BIF indicates the direction of iron ore prospecting in Songshan area. In the future, it is expected to find a certain scale Anshan iron deposit by strengthening the prospecting work in the north-south extension direction of Guojiayao and Wananshan BIF belt.
【学位授予单位】：河南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.31

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