湘南王仙岭地区中生代含钨与含锡花岗岩的岩石成因及其成矿差异机制

Petrogenesis of W-and Sn-bearing granites and the mechanism of their metallogenic diversity in the Wangxianling area, southern Hunan Province

南岭地区以发育多旋回、多成因的花岗岩及其有关的有色和稀有金属矿床著称。王仙岭地区位于南岭中部。晚三叠世的王仙岭含钨花岗岩具有相对较高的P2O5（0．22％）和Al2O3（14.37％）含量，低的Zr＋Nb＋Ce＋Y含量（118μg／g）和稀土总量（65．6μg／g）。花岗岩的初始87Sr／86Sr比值、εNd（t）和εHf（t）值分别为O．7172-0．7305、-7．1～-9．5和-10．2--11．5，对应的Nd和Hf的两阶段模式年龄为1．83～1．95Ga和1．5-2．0Ga。晚侏罗世荷花坪含锡黑云母花岗岩以及花岗斑岩脉具有较低的P2O5（0．04％）和Al2O3（12．91％和12．25％）含量，高的Zr＋Nb＋Ce＋Y含量（334μg／g和385μg／g）和稀土总量（287μg/g和303μg／g）。与王仙岭花岗岩相比，荷花坪花岗岩和花岗斑岩脉具有相对较低的初始87Sr/86Sr比值（〈0．7200），高的εNd（t）和εHf（t）值（-8）以及年轻的Nd和Hf两阶段模式年龄（约1．5Ga）。王仙岭花岗岩具有s型花岗岩的特征，由古元古代变质基底的部分熔融形成；而荷花坪花岗岩花岗斑岩脉具有和A2型花岗岩特征，是由麻粒岩化的中元古代变质基底部分熔融形成。王仙岭岩体富硼，与钨成矿作用密切相关，而荷花坪岩体与花岗斑岩脉富氟，与锡矿化有关。两期花岗岩均为还原性的高分异花岗岩，两者成矿差异可能是由部分熔融形成两类花岗岩的基底钨锡含量差异导致。

The Nanling Range in South China is characterized by well-developed non-ferrous and rare metal deposits as well as related polycyclic and polygenetic granitic rocks. The Wangxianling area is located in the middle part of the Nanling Range. The Late Triassic W-bearing Wangxianling granite has relatively high P2O5 （0.22%） and Al2O3 （14.37%） and low Zr ＋ Nb ＋ Ce ＋ Y （118 μg/g） and REE （65.6 μg/g） contents. Its initial 87Sr/86Sr ratios, εNd（t） and εNf（t） values range from 0.7172 to 0.7305, -7.1 to -9.5, and -10.2 to -11.5, respectively, corresponding to two-staged Nd model ages of 1.83~1.95 Ga and Hf model ages of 1.5~2.0 Ga. The Late Jurassic Hehuaping Sn-bearing biotite granite and granite porphyry have low P2O5 （0.04%） and Al2O3 （12.91% and 12.25%） and high Zr ＋ Nb ＋ Ce ＋ Y （334μg/g and 385 μg/g） and REE （287 μg/g and 303 μg/g） contents. They have lower initial 87Sr/86Sr ratios （〈 0.7200）, higher εNd（t） and εnf（t） values （〉-8） and younger Nd-Hf model ages （-1.5 Ga） than the Wangxianlinggranite. The Wangxianling granite has affinities of the S-type granites, which was derived from partial melting of a Paleoproterozoic metamorphic basement. The Hehuaping granite and granite porphyry dykes have affinities of A-type granites, which were formed by partial melting of a granulitized Mesoproterozoic metamorphic basement. The Wangxianling granite is enriched in boron and related to tungsten mineralization, whereas the Hehuaping granite and granite porphyry dykes are enriched in fluorine and related to tin mineralization. Both the Wangxianling and Hehuaping granites belong to reduced and highly fractionated granitic rocks. Their mineralization diversities are likely caused by the variable tungsten and tin contents in the source basement rocks which were partially melted to form the granites.