福建梅仙铅锌（银）矿床位于闽中裂谷带，是一大型多金属 VMS 型块状硫化物矿床。在详细野外地质考察基础上，通过对梅仙铅锌（银）矿区花岗斑岩2个样品的 LA ICP MS 锆石 U Pb 年代学研究，确定其为燕山期花岗斑岩（（148．9±1．4）Ma，（152．0±2．1）Ma）。全岩地球化学分析结果表明：所研究花岗斑岩具有高硅、富钾、中等含量的铝和全碱以及弱过铝质等特征。其稀土元素配分曲线普遍向右缓倾，且重稀土元素分配曲线比较平坦，富集大离子亲石元素和高强场元素，不具明显的 Nb、Ta 亏损，是产于碰撞后构造背景之下的高钾钙碱性 I 型花岗岩，其母岩浆形成后发生了角闪石、黑云母和斜长石等矿物高程度的的结晶分异作用。梅仙矿区花岗斑岩在空间上与铅锌硫化物矿体和赋矿层位关系密切，岩浆富含挥发分和大离子亲石元素，分异程度高，表明该燕山中期岩浆活动有利于矿区矽卡岩化成矿作用，并可对早期层控块状硫化物矿体进行强烈的叠加改造。%Located in the Central Fujian Rift,the Meixian Pb Zn deposit is a large volcanogenic massive sulfide Pb Zn ( Ag)deposit.Based on a detailed field study,the authors identify Yanshanian porphyry granite (148.9±1.4 Ma,152.0±2.1 Ma)in the Meixian deposit by LA ICP MS zircon U Pb dating.Geochemical analyses show the porphyry granites have high SiO2 and potassium abundances, moderate Al2 O3 ,alkaline contents,and weak peraluminous.Chondrite-normalized REE distribution pattern display right skewed shapes showing fractionation between LREE and HREE with flat HREE pattern.These granites are enriched in large ion lithophile elements (LILEs)and high field strength elements(HFSEs)without obvious depletion in Nb Ta,indicating that they were high-potassium calc-alkaline I-type granite formed in post-collision environment.Their parental magma were experienced strongly fractional crystallization of amphibole,biotite,plagioclase and some other accessory minerals. These porphyry granites are spatially associated with lead-zinc bodies,their magma are enriched in volatile component,large ion lithophile elements and have underwent high degree differentiation by fractional crystallization,indicating the Later Jurassic magmatism in the study area is very favorable for the skarn mineralization and extensively superimposed and reformed the earlier stage massive sulfur lead zinc ore bodies.
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