南秦岭山阳-柞水矿集区大西沟-银硐子铁-银-铅锌-铜矿床磁铁矿地球化学特征：对矿床成因的约束  

GEOCHEMICAL CHARACTERISTICS OF MAGNETITE FROM DAXIGOU-YINDONGZI DEPOSIT IN SHANYANG-ZHASHUI ORE CONCENTRATION AREA,SOUTH QINLING:CONSTRAINTS ON DEPOSIT GENESIS

作　　者：陈雷[1] 闫臻[2] 王宗起[1] 王瑞廷 任涛 CHEN Lei YAN Zhen WANG Zong-qi WANG Rui-ting REN Tao(MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources,Chinese Academy of Geological Sciences ,Beijing 100037, China Institute of Geology ,Chinese Academy of Geological Sciences ,Beijing 100037,China Geological Exploration Institution of Northwest Mining and Geological Exploration Bureau for Nonferrous Metals,Xi＇an 710054,China No. 713 Team of Northwest GeoExploration Bureau for Nonferrous Metals, Shangluo 726000, China)

机构地区：[1]中国地质科学院矿产资源研究所,国土资源部成矿作用与资源评价重点实验室,北京100037 [2]中国地质科学院地质研究所,北京100037 [3]西北有色地质勘查局地质勘查院,陕西西安710054 [4]西北有色地质勘查局713总队,陕西商洛726000

出　　处：《矿物岩石》2016年第4期38-49,共12页Mineralogy and Petrology

基　　金：国家科技支撑计划课题(2011BAB04B05)

摘　　要：大西沟-银硐子铁-银-铅锌-铜矿床位于中秦岭晚古生代弧前盆地的山阳-柞水矿集区内,矿床产于中泥盆统大西沟组中,主要发育有与地层产状相同的磁铁矿矿石、含重晶石-菱铁矿的纹层状磁铁矿矿石、磁铁矿-硫化物(黄铁矿、黄铜矿)-石英脉型及块状磁铁矿矿石。通过对4种不同矿化类型矿石的磁铁矿进行电子探针及微量、稀土元素的分析,结果显示不同类型的磁铁矿FeOt含量与Al_2O_3,CoO,MgO,SiO_2质量分数整体上均呈负相关关系;从顺层产出的矿石到块状、脉状及纹层状矿石,磁铁矿的FeOt质量分数(分别为49.65%~84.18%,91.5%8~93.39%,92.69%~93.6%,92.25%~93.39%)在逐渐增加,说明有后期含铁物质的富集。在w(TiO_2)-w(Al_2O_3)-w(MgO+MnO)和w(MgO)-w(TiO_2)-w(Al_2O_3)图解中,大西沟-银硐子矿床的磁铁矿表现出既有热水沉积成因,也有热液成因的特征。同时不同产出状态的磁铁矿均富集Mg,Mn元素,并具有相对较低的Ti(6.82×10^(-6)~451×10^(-6),平均324×10^(-6)),V(11.5×10^(-6)~625×10^(-6),平均378×10^(-6)),Sc(0.78×10^(-6)~1.49×10^(-6),平均1.03×10^(-6))质量分数及Co/Ni,Zn/V和Sn/Ga比值,显示具有热液成因特征,而且从层状矿石到块状、脉状及纹层状矿石,热液作用具有逐渐增强的趋势。不同矿化类型的磁铁矿均表现出明显的负Eu异常,但从层状矿石(δEu为0.32)到块状(δEu为0.72)、脉状(δEu为0.48~0.79)及纹层状矿石(δEu为0.57~0.58),负Eu异常逐渐减弱,说明整个成矿环境的氧化性在逐渐增强,但总体仍处于还原环境。因此,研究表明大西沟-银硐子矿床在成矿作用过程中受到后期热液活动影响,成矿作用发生于氧化性增强,还原性减弱的成矿环境。Daxigou-Yindongzi Fe-Ag-PbZn-Cu deposit in the late Paleozoic forearc basin in Mid- Qinling orogenic belt occurred in the Middle Devonian Daxigou Formation. There are four types ore bodies in the deposit, bedded ore, laminated ore contained barite and siderite, magnetite-sulfide （pyrite,chalcopyrite）-quartz vein and massive magnetite ore. The FeOt with Al2O3, CoO, MgO and SiO2 of different types＇ magnetite have negatively correlation. FeOt contents （49.65%-84.18%,91.58%~93.39%,92.69%~93. 6%,92.25%~93.39%） of magnetite gradually increased from the bedded ore to laminated ore,vein and massive magnetite ore,and the enrichment of iron material occurred in the late stage. In the diagram of w（TiO2）-w（Al2O3）-w（MgO＋MnO） and w（MgO）-w（TiO2）-w（Al2O3 ）,the magnetite shows characteristics of both sedimentary meta- morphism and hydrothermal origin. Magnetite from different types of ores are enrich in Mg, Mn, and have lower Ti （6.82 ×10^-6 ~451×10^-6 ,average 324 ×10^-6）,V （11.5 ×10^-6 ~625×10^-6, average 378 ×10^-6 ）, Sc （0.78 ×10^-6 ~ 1.49 ×10^-6 , average 1.03 ×10^-6 ） contents and lower Co/ Ni,Zn/V,Sn/Ga values. It shows that the magnetite has the characteristics of hydrothermal origin with gradually increased hydrothermal process. The negative Eu anomaly of magnetite indicates that the magnetite is formed in reducing environment. However, the negative Eu anomaly gradually weakened from bedded ore （δEu is 0.32） to laminated ore （δEu is 0.57~0.58）,vein （δEu is 0.48~0. 79） and massive magnetite ore （δEu is 0. 72）, indicating that the oxidation is gradually enhanced. It reveals that the Daxigou-Yindongzi deposit is affected by the late hydrothermal activity in the mineralization process, with metallogenic environment of enhanced oxidation and weakened reduction.

关 键 词：磁铁矿 地球化学 热水沉积-改造 大西沟-银硐子矿床 南秦岭 

分 类 号：P588.122[天文地球—岩石学] P597.3[天文地球—地质学]