河南舞阳赵案庄铁矿床成因:来自磁铁矿和磷灰石的矿物学证据  

The genesis of the Zhaoanzhuang Fe oxide deposit in Wuyang region of Henan Province: Insights from magnetite and apatite

作　　者：兰彩云[1,2] 赵太平[1] 罗正传 王长乐[4] 文启付[5] 刘立新 

机构地区：[1]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广州510640 [2]中国科学院大学,北京100049 [3]河南省有色金属地质矿产局第四地质队,郑州450016 [4]中国科学院地质与地球物理研究所,北京100029 [5]河南安钢集团舞阳矿业有限责任公司,舞钢462500

出　　处：《岩石学报》2015年第6期1653-1670,共18页Acta Petrologica Sinica

基　　金：国家重点基础研究发展计划973项目(2012CB416606);中国地质调查局项目(12120114035101;12120113090400)联合资助

摘　　要：河南舞阳赵案庄铁矿位于华北克拉通南缘,赋存于新早古元古界太华杂岩赵案庄组中,是舞阳铁矿的一部分。赵案庄铁矿在时空上与变质的超基性岩关系密切,矿石中的脉石矿物与其寄主岩石的主矿物一致,指示其成因方面的亲缘性。赵案庄铁矿石具有典型的海绵陨铁结构,其中的磁铁矿具有高V（1458×10-6-2524×10-6）、稍高Mg（2502×10-6-4674×10-6）和低Ti（395×10-6-3186×10-6）、Cr（3.30×10-6-66.1×10-6）、Ni（93.0×10-6-176×10-6）、Mn（259×10-6-937×10-6）的特征。磷灰石以粗粒（0.3-1.5mm）、等粒状分散在磁铁矿的粒间,具有高REE总量（4983×10-6-7038×10-6）、高F（2.69%-3.52%）、高F/Cl比值（21.5-78.8）和低Sr（215×10-6-241×10-6）的特征。磁铁矿和磷灰石的化学组成均指示岩浆成因,并携带热液信息。利用磷灰石的微量元素含量反演成矿岩浆的微量元素组成,表明成矿岩浆受到了地层物质的混染。橄榄石低Cr、Ni高Mg的特征也指示岩浆中富挥发分的特征。此外,矿石中大量的碳酸盐矿物指示岩浆中有来自地层的CO2加入,导致岩浆的氧逸度升高,促进了磁铁矿的结晶,并抑制了钛铁矿结晶,是磁铁矿低Ti的一个原因。此外,源区低Ti也是导致磁铁矿低Ti的原因。因此,本文认为赵案庄铁矿属与超基性岩有关的岩浆矿床但受到富CO2流体的影响。As a part of the Wuyang iron deposit,the Zhaoanzhuang Fe oxide deposit is located at the southern margin of the North China Craton and occurs in ultramafic rocks which intruded into the Zhaoanzhuang Formation of the Early Paleoproterozoic Taihua Group. The deposit is closely related to the ultramafic rocks both spatially and temporally,and they have similar mineral assemblages,suggesting similar origin. The ores have classic sideronitic texture. Magnetites from both the ores and rocks are characterized by high V（ 1458 × 10- 6- 2524 × 10- 6）,Mg（ 2502 × 10- 6- 4674 × 10- 6） and low Ti（ 395 × 10- 6- 3186 × 10- 6）,Cr（ 3. 30 × 10- 6- 66. 1× 10- 6）,Ni（ 93. 0 × 10- 6- 176 × 10- 6）,Mn（ 259 × 10- 6- 937 × 10- 6） contents. Apatites from both the ores and ultramafic rocks are present as equigranular coarse grains,occurring interstitially between magnetite grains. They have high ∑REE（ 4983 × 10- 6-7038 × 10- 6） and F（ 2. 69% - 3. 52%） contents as well as high F/Cl（ 21. 5 - 78. 8） and LREE/HREE ratios（（ La/Yb）N= 28 -45） without Ce depletion. It is indicated that magnetite and apatite crystallized in magma with hydrothermal overprinting. Furthermore,the trace elemental contents of the parental magma calculated using the compositions of apatite indicate that the magma underwent crustal contamination. And the olivine of Zhaoanzhuang ultramafic rock is high Mg and low Cr and Ni,indicating olivine crystallized in volatile-rich melts. In addition,a lot of carbonate minerals in ores also show the addition of CO2 from the wall rock into the magma,which increased oxygen fugacity of the magma and enhanced the crystallization of magnetite instead of ilmenite. Therefore,the formation of low-Ti magnetite could be due to both high oxygen fugacity and low-Ti magma source. And the Zhaoanzhuang Fe oxide deposit,classified into magma ores,are genetically related to the ultramafic rocks. The parental magma was contaminated with CO2-rich fluid.

关 键 词：舞阳铁矿 赵案庄铁矿 磁铁矿 磷灰石 超基性岩 早前寒武纪 华北克拉通 

分 类 号：P618.31[天文地球—矿床学]