摘要
安徽繁昌地区作为长江中下游Fe、Cu、Au成矿带中的重要矿集区,发育一系列以桃冲铁矿为代表的磁铁矿型铁矿床。对桃冲矿区分布的岩浆岩、围岩与赋矿矽卡岩的稀土元素地球化学特征对比,表明三者稀土含量及其配分模式存在差异,桃冲铁矿夕卡岩稀土总量较低,轻稀土富集重稀土亏损,呈右倾过渡型配分模式,具明显Eu正异常。通过对桃冲铁矿床内包裹体的岩相学、显微测温、激光拉曼光谱探针分析,桃冲铁矿体中发育有熔融包裹体、气液相包裹体、含子晶多相包裹体、纯液相包裹体4种类型。成矿流体具中高温、高盐度、富水特征,富含Na+、Ca2+、Mg2+、K+、Cl-、SO24-离子。结合透岩浆流体成矿理论探讨成矿流体及演化,认为形成铁矿床的物质来源为深部富铁夕卡岩矿浆,侵位过程中受构造环境影响,因温压条件的迅速改变含矿流体与夕卡岩浆发生解耦作用,于构造薄弱部位贯入形成矿体。
The Fanchang District as an important metallogenic cluster district in the Fe-Cu-Au polymetallic metallogenetic belt along the Middle-Lower Yangtze Reaches,develops a series of magnetite deposits represented by Taochong iron deposit.Comparing the REE geochemical characteristics of the magmatic rock,wall rock and ore-bearing skarn in Taochong ore zone,the content and the distribution patterns of REE are significantly different.The skarn has a pattern of LREE enrichment and HREE depletion transitional right-dipping pattern with a positive Eu anomaly.Four types of fluid inclusion: melt inclusion,liquid-gas two-phase inclusion,daughter-minerals bearing polyphase inclusion and liquid phase inclusion,have been found in minerals from Taochong iron deposit on the basis of the petrography,microthermometry and Raman spectrum analyses.Ore-forming fluids are medium-high temperature,high salinity,water-rich,and rich in Na+,Ca2+,Mg2+,K+,Cl,SO2-4.Ore-forming fluid features and developments are discussed combining with the theory of transmagmatic fluids.It is considered that the origin of iron deposit is Fe-rich skarn ore-magma from the depth.The decoupling of ore-forming fluid and skarn took place in the process of emplacement.The deposit was formed by injection in the weak tectonic belt caused by structural processes.
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2012年第4期82-95,共14页
Earth Science Frontiers
基金
中国科学院创新重要方向性项目(KZCX1-YW-15-04)
安徽省公益性地质工作项目(2007-3)
关键词
夕卡岩
矿床成因
透岩浆作用
桃冲铁矿
长江中下游成矿带
skarn
metallogeny
transmagmatic fluid
Taochong iron deposits
Middle-Lower Yangtze polymetallic metallogenic belt