Geochemistry of Granite from the Luowei Tungsten Polymetallic Deposit in Xidamingshan, Guangxi and Its Relationship with Mineralization

The Luowei tungsten polymetallic deposit is a large scale skarn type deposit, which has been newly found in the west part of Xidamingshan by the No.4 Geological Party of Guangxi.The ore bodies are divided into skarn type and quartz vein type, and the former serves as the main mineralization type.In this paper, two kinds of granites are occurred in the Luowei tungsten polymetallic deposit.They are porphyritic biotite granite and fine-grained granite.The petrographic analyses and the testing of major elements and REE about these two kinds of granites have been carried out in this paper.The results show that these granites have similar geochemical characteristics.These granites have high silicon (SiO₂=70.30%~74.78%)and aluminum(12.77%~14.12%)contents, but have poor calcium and magnesium (CaO=1.11%~2.04%, MgO=0.37%~0.71%).Their ΣREE values range from 102.70×10^-6 to 139.69×10^-6, and their LREE/HREE and (La/Yb)_N ratios are 7.70~15.92 and 11.15~31.38, respectively.These granites have low LREE/HREE ratios, with enriched LREE and Eu depletion (δEu=0.37~0.62). These rocks have clearly enrichment of Ta,U,Nd, mild enrichment of K,Th,La,Ce and depletion of P and Nb.The geochemical diagrams show that porphyritic biotite granite and fine-grained granite belong to S-type granite, and they were formed by the partial melting and crystallization of crust-derived materials.The concealed rock mass might be control the formation of the Luowei tungsten poly metallic deposit.The fine-grained granite in late stage shows more strong mineralization specificity for W,Mo,Zn,Cu deposit.