白干湖钨锡矿床发育大量与成矿关系密切的花岗岩.LA-ICPMS锆石U-Pb年代学研究表明含矿更长花岗岩形成于(429.5±3.2) Ma,二长花岗岩形成于(430.5±1.2) Ma.锆石Hf同位素组成表明,二长花岗岩的εHf(t)为-2.31～5.57,T2DM主体为1188～1390Ma;含矿更长花岗岩εHf(t)为-2.17～1.19,T2DM主体为1338～1552Ma,两者具有相同的岩浆来源.在地球化学特征上,二长花岗岩稀土总量高,重稀土相对轻稀土明显亏损,具中等—强烈Eu负异常,富集Y、Zr、Hf、Th、U,亏损Rb、Nb、Ta,属于弱准铝质或弱过铝质A型花岗岩;更长花岗岩受结晶分异以及后期岩浆热液影响,地球化学特征表现出一定的差异.两者均为早志留世造山后局部拉张环境下地幔底侵重熔古老长英质地壳所形成.综合研究认为,矿区钨锡成矿作用主要有两个阶段:第一阶段,早志留世,地幔底侵重熔古老长英质地壳形成的含钨花岗质岩浆侵入过程中,形成了岩体顶边部以及接触带中夕卡岩型、云英岩型钨矿体;第二阶段,岩浆期后热液淋滤围岩钨锡等金属,沿裂隙充填形成了石英脉型钨矿体.%The granites in Baiganhu deposit are closely related to W-Sn mineralization. The results of LA-ICPMS U-Pb isotope dating show that oligoclase granite containing tungsten and tin ores was formed at (429.5±3.2) Ma, and the monzonite granite was formed at (430.5±1.2) Ma. The εhf(t) values of monzonite granite vary from -2.31 to 5.57, and the T2dm varies mainly from 1188 to 1390 Ma. The εhf(t) values of oligoclase granite vary from -2.17 to 1.19, and T2dm varies mainly from 1338 to 1552 Ma. The similar Hf isotopic compositions indicate similar origins of their parental magmas. Major and trace element data of monzonite granite show that it is a weakly metaluminous or peralumious A-type granite, characterized by high ∑REE, LREE enrichment, medium to strong negative Eu anomalies, rich Y, Zr, Hf, Th and U, depleted Rb, Nb and Ta. The oligoclase granite show geochemical characteristics different from those of the monzonite granite, probably because of crystal fractionation and fluid activity during the late stages of magma evolution. Both of the granites were derived from the melting of ancient felsic crust because of mantle underplating during the extension environment. There are two ore-forming stages in the Baiganhu W-Sn deposit. In the first stage, during the intruding process of magmas containing tungsten and tin into wall rocks in Early Silurian period, the skarn-type and greisen-type tungsten ore bodies were formed in the top and contact belt of the granites. In the second stage, metals from wall rocks, such as W and Sn, were leached out by magmatic fluids of the late stage magma evolution, the quartz-veined tungsten ore bodies were formed along the fractures.
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