安徽庐江泥河铁矿矿床地球化学特征及其对成因的制约  

Geochemistry characteristics of Nihe iron deposit in Lujiang,Anhui Province and their constrains to ore genesis

作　　者：张舒[1,2] 吴明安[1,2] 赵文广[1] 张宜勇[1] 李小东[1] 汪晶[1] 

机构地区：[1]安徽省地质调查院,合肥230001 [2]合肥工业大学资源与环境工程学院,合肥230009

出　　处：《岩石学报》2014年第5期1382-1396,共15页Acta Petrologica Sinica

基　　金：国家"973"项目(2012CB416806);中国地质调查局地质调查工作项目(1212011120862);深部探测技术与实验研究专项(Sinoprobe03-04-06);中国地质科学院地质研究所合作研究专题(DD01-16)联合资助

摘　　要：泥河铁矿位于长江中下游成矿带庐枞中生代火山岩盆地中,矿床具有典型玢岩型铁矿的地质特征,是研究玢岩型铁矿成因的良好对象。本次工作在详细的野外观察及室内研究的基础上,对泥河铁矿主成矿期矿石矿物的稀土元素、硫同位素及铅同位素进行了分析测试工作。主成矿期磁铁矿、黄铁矿稀土元素配分模式呈现LREE富集、HREE曲线平直、Eu轻微负异常的特征,与赋矿砖桥组熔岩、闪长玢岩的稀土元素配分模式较为一致,结合矿石矿物与围岩的铅同位素特征,推测成矿金属元素主要来源于赋矿的火山-次火山岩,可能有少量壳源物质的加入。黄铁矿与硬石膏的硫同位素表现出双峰式分布的特征,说明岩浆活动与三叠纪膏盐层均对硫有所贡献。三叠纪膏盐层在泥河铁矿的成矿过程中,不仅仅是重要的矿化剂,同样是铁质沉淀的氧化剂。综合矿床地质与地球化学特征,认为泥河铁矿是由次火山岩体演化产生的含矿高温热液在闪长玢岩穹窿顶部,通过交代充填作用形成的玢岩型铁硫矿床。Nihe iron deposit is located in the Luzong volcanic basin, which is one of the important ore concentrated areas in the Middle-Lower Reaches of Yangtze metallogenetic belt. The strata mainly cropping out in the mining area includes Zhuangqiao Formation and Shuangmiao Formation consisting of Mesozoic volcanic rocks. The mainly intrusive rock is the pyroxene diorite porphyrite. The ore bodies occur as lens at the top of the diorite porphyrite dome and as bedded bodies controlled by Zhuanqiao Formation. The ore structure mainly includes vein-network structure and disseminated structure. The ore mineral association consists of magnetite, anhydrite and diopside, which is similar to the mineral associations of the porphyry-like type iron deposits in Ningwu Basin. The alteration of the deposit can be classified into three zones spatially, bottom-up as follows： dark-colored alteration zone, superimposed alteration zone and upper light-colored alteration zone. Based on the detailed field geological investigation and petrologic study, the analysis of REE, sulfate and lead isotope are carried on the ore minerals. The magnetite and pyrite are characterized by LREE enrichment （ LREE/HREE = 3.55 - 33.67）, slight fractionation of HREE （ （Gd/Yb） N = 0. 91 - 3.01 ）, positive Eu anomaly （δEu = 0. 59 - 1.89）, which is similar to the diorite porphyry and andesitic lava of Zhuanqiao Formation. The characteristics of lead isotope and REE imply that the metal of Nihe deposit is mainly derived from the volcanic and suhvolcanic rocks, mixing with few amount of material of crust. The 634S values of pyrites range from -2‰ - 10‰, whereas the δ34S values of gypsums range from 16‰ -20‰. The bimodal distribution of the δ34S indicates that sulfate of Nihe deposit is derived from the magmatism and Triassic gypsum-salt layer such as Zhouchongchun Formation. According to the geological and geochemical characteristics, Nihe iron deposit can be classified into porphyry-type iron deposit. The fluids evolved from the subvol

关 键 词：稀土元素 硫同位素 铅同位素 玢岩铁矿 矿床成因 泥河铁矿 长江中下游成矿带 

分 类 号：P595[天文地球—地球化学] P618.31[天文地球—地质学]