南岭芙蓉锡矿田锡石原位LA-ICP-MSU-Pb年代学及地球化学研究：对成矿流体来源和演化的意义  

In situ LA-ICP-MS U-Pb age and geochemical data of cassiterite of the Furong tin deposit, the Nanling Range: Implications for the origin and evolution of the ore-forming fluid

作　　者：王志强[1] 陈斌[1] 马星华[1] 

机构地区：[1]北京大学地球与空间科学学院,造山带与地壳演化教育部重点实验室,北京100871

出　　处：《科学通报》2014年第25期2505-2519,1-11,共15页Chinese Science Bulletin

基　　金：国家自然科学基金(41272067);中国地质调查局项目(1212010011309)资助

摘　　要：芙蓉锡矿是位于南岭骑田岭岩体南部的大型锡矿田．本文通过对赋存在相关岩体和围岩中矿床的锡石进行原位LA—ICP-MS定年和地球化学的研究，对芙蓉锡矿田的成矿时限及成矿流体的来源和演化进行了讨论．岩体中锡石LA-ICP-MSU．Pb等时线年龄为156，5＋4。1 Ma，锡石具有明显的环带结构，从核部到边部Fe的含量明显降低；锡石含有较高含量的高场元素（如Nb，Ta，Ti和sc等）和较低的（La／Lu）N比值（0．006—0．038）．而围岩中锡石LA-ICP-MSu-Pb等时线年龄为153．6±1．4Ma，锡石从核部到边Fe含量也明显降低，但整体含量低于岩体中锡石；锡石的高场强元素含量非常低，具有相对较高的（La门Lu）N比值（0．011-0．084）．分析数据表明，锡石成分环带与锡石中Fe的含量有关．锡石中主要存在Fe和sn的类质同象替代，同时也伴随着Nb，Ta，Sc，Ti和REE等与sn的替代反应（尤其是岩体中的锡石）．高F岩浆经过高程度的演化，高分异熔体在深部与具有高w，Sn，HFSE含量的寒武纪地层发生强烈相互作用，大量富F，HFSE，HREE，Fe和sn的流体大量出溶，首先在岩体内部形成锡矿（156—159Ma）．随着成矿热液运移到碳酸盐岩地层，并与碳酸盐岩围岩发生相互作用，使得在围岩中形成的锡矿（153．6Ma）具有明显的碳酸盐岩地层流体的特征．The Furong deposit, located in the southern Qitianling pluton, is a giant tin deposit. In this paper, we studied the geochronology using the in situ LA-ICP-MS U-Pb method and geochemistry of cassiterite occurred in the pluton and country rocks. The cassiterites from the pluton yielded an isochron age of 156.5＋_4.1 Ma. Fe contents of the cassiterites with typical zonal textures decrease from core to rim. These cassiterites have high contents of HFSE （e.g. Nb, Ta, Ti, Sc） and low values of （La/LU）N. The cassiterites from the country rocks yielded an isochron age of 153.6＋_1.4 Ma. Fe contents of these cassitedtes are lower than those of the cassiterite from the pluton, which also show a decrease trend from core to rim. The cassiterites occurred in the country rocks show very low contents of HFSE and relative higher values of （La/LU）N （0.011-0.084） than those from the pluton. Our data indicate that zonal texture of cassiterites is related with the Fe content. Isomorphous substitutions of the cassiterites occurred mainly between Fe and Sn, which is accompanied by substitution of Nb, Ta, Sc, Ti and REE by Sn （especially in the cassiterites from the pluton）. Highly-evolved magma with high-F contents interacted intensively with the Cambrian sedimentary rocks with high W, Sn and HFSE contents. Ore-forming fluid enriched in F, HFSE, HREE, Fe and Sn exsolved and precipitated within the pluton in early stage （156-159 Ma）. And then, the ore-forming fluid transported to, and interacted with, the Devonian-Carboniferous carbonate strata, resulting in the formation of the cassiterites in the country rocks.

关 键 词：南岭 芙蓉锡矿 锡石U-Pb定年 LA—ICP—MS 微量和稀土元素 成矿流体 

分 类 号：P618.44[天文地球—矿床学]