Petrogenesis of W-and Sn-bearing granites and the mechanism of their metallogenic diversity in the Wangxianling area, southern Hunan Province
ZHANG Rong-qing;LU Jian-jun;WANG Ru-cheng;YAO Yuan;DING Teng;HU Jia-bin;ZHANG Huai-feng;State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University;Nanjing Institute of Geology and Mineral Resources,CGS;Shandong Zhengyuan Institute of Geological Exploration, China Central Bureau of Metallurgy and Geology;Uranium Resources Company Limited, China Guangdong Nuclear Power Corporation;
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/86 Sr ratios, εNd(t) and εHf(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(334 μg/g and 385 μg/g) and REE(287 μg/g and 303 μg/g) contents. They have lower initial 87Sr/86 Sr ratios( 0.7200), higher εNd(t) and εHf(t) values( –8) and younger Nd-Hf model ages(~1.5 Ga) than the Wangxianling granite. 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.