赣东北朱溪超大型钨矿床是目前世界上最大的夕卡岩型钨矿床,为确定其成矿物质来源及成矿时代,在详细钻孔岩心编录基础上,本文对白钨矿运用LA-ICP-MS法分析了其单矿物的微量元素、稀土元素,并进行Sm-Nd同位素定年研究.结果显示:白钨矿微量元素中Mo、Nb、Ta富集,而Rb/Sr＜0.04,Nb/Ta=1.69～8.46、Zr/Hf=3.06～6.75,显示成矿物质的壳源特征.白钨矿的∑REE变化大(∑REE=3.25×10-6～229.95×10-6),LREE与HREE之间分馏明显 ((La/Yb)N=36～19 984),属于轻稀土富集型.依据δEu值的特征,将白钨矿分为δEu正异常(δEu=1.44～9.06)的轻稀土富集型和δEu负异常(δEu=-0.25～-0.82)的轻稀土富集型;在空间上,由远到近接近花岗岩,白钨矿的∑REE逐渐升高,δEu由正异常逐渐转变为负异常,有与花岗岩稀土配分曲线趋于一致的趋势.白钨矿Sm-Nd等时线年龄为(144±5)Ma,143 Nd/144 Nd初始比值为0.512 020,其εNd (t)为-9.753,二阶段模式年龄为1 745 Ma,其年龄与物质来源与朱溪花岗岩的一致,表明朱溪钨矿床是朱溪矿区隐伏花岗岩进一步演化的产物.%Zhuxi tungsten deposit in northeastern Jiangxi Province is the largest skarn type of tungsten deposit in the world up to now.On the basis of carefully logging on the drilling core,we analyzed the content of REEs and trace elements in the scheelite through method of LA-ICP MS,and dated the deposit age by Sm-Nd isotopic dating.The results show that the scheelite is enriched in trace elements,such as Mo,Nb,and Ta,and has ratios of Rb/Sr＜0.04,Nb/Ta=1.69-8.46,Zr/Hf=3.06-6.75,indicating a crust-origin of the minerals in the deposit.∑REE content of the scheelite varies greatly (∑REE=3.25 × 10-6-229.95× 10-6)with a evident fractionation between LREE and HREE ((La/Yb)N =36-19984),belonging to LREE-enriched type.On the basis of δEu values,the LREE-enriched type of scheelite can be divided into δEu positive anomaly (δEu=l.44-9.06) and δEu negative anomaly (δEu=-0.25--0.82).Spatially,∑REE content of the scheelite increases gradually and δEu changes from positive to negative anomalies when approaching to the granite,showing a similar tendency with the granite REE distribution curve.Sm-Nd isochron age of the scheelite is 144±5 Ma.Initial 143Nd/144Nd ratio is 0.512020,and the eNd(t) is 9.753.Two stage model age is 1745 Ma,which is consistent with the Zhuxi granite in age and mineral sources,indicating that the Zhuxi tungsten deposit is an evolutionary product from the Zhuxi hidden granite.
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