The Ningshan pegmatite district in the South Qinling Orogen hosts numerous Rb-(Be) mineralized pegmatites. In this study, whole-rock geochemistry, mineral geochemistry, and zircon U–Pb isotopes of the Rb-rich and barren pegmatites were determined. The barren pegmatites consist mainly of muscovite, microcline, albite, quartz, and garnet, whereas the Rb-rich pegmatites are mainly composed of muscovite, albite, quartz, and beryl, with minor chrysoberyl, cassiterite and columbite-group mineral. The muscovite and albite are the main Rb-bearing minerals. The U–Pb zircon dating of the Rb-rich and barren pegmatites yielding an age of 212–203 Ma, which is similar to that of the neighboring two-mica monzogranites distributed in the Ningshan area. Compared with the two-mica monzogranites, geochemical features, such as the Zr/Hf, Rb/Sr and Nb/Ta ratios and trace element contents indicated that the Rb-rich and barren pegmatites derived from fractionation of the two-mica monzogranites. In combination, the current and previous results suggest that the fractionation of the two-mica monzogranites caused the generation of the affinitive residual melts that, finally, crystallized to form the pegmatites. Compared to those from the barren pegmatites, the apatite from the Rb-rich pegmatites have higher MnO (14.51–19.12 wt.%) and Cl (0.12–0.16 wt.%) contents and lower F/Cl rartios (20–29). We conclude that these differences reflect unique geochemical signatures, and the geochemical composition of the apatite can be used as exploration guidance for rare metal-rich pegmatites.

中文翻译：

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南秦岭造山带宁山伟晶岩地区晚三叠世富Rb和贫瘠伟晶岩的地球化学对比：对成岩作用和稀有金属勘探的意义

南秦岭造山带的宁山伟晶岩地区拥有众多的b（Be）矿化伟晶岩。在这项研究中，确定了富含Rb和贫瘠伟晶岩的全岩地球化学，矿物地球化学和锆石U–Pb同位素。贫瘠的伟晶岩主要由白云母，微斜晶，钠长石，石英和石榴石组成，而富含Rb的伟晶岩主要由白云母，钠长石，石英和绿柱石组成，还有少量的金绿石，锡石和co石族矿物。白云母和钠长石是主要的含Rb矿物。富Rb和贫瘠伟晶岩的U–Pb锆石年代产生的年龄为212–203 Ma，这与分布在宁山地区的相邻两云母辉长岩相似。与二云母辉长岩相比，Zr / Hf等地球化学特征 Rb / Sr和Nb / Ta比值和微量元素含量表明，富含Rb和贫瘠的伟晶岩是由两云母辉长岩的分馏而得。总而言之，当前和先前的结果表明，两云母辉长花岗岩的分馏导致亲和残余熔体的产生，最后结晶形成伟晶石。与贫瘠伟晶岩相比，富Rb伟晶岩中的磷灰石具有更高的MnO（14.51–19.12 wt。％）和Cl（0.12-0.16 wt。％）的含量以及更低的F / Cl rartios（20–29）。我们得出的结论是，这些差异反映了独特的地球化学特征，并且磷灰石的地球化学成分可以用作稀有金属富辉晶岩的勘探指导。