华南印支期成钨与成锡(锡钨)花岗岩对比研究

A comparative study of the Indosinian W-and Sn(Sn-W)-bearing granites in South China

为了揭示华南印支期与钨锡成矿相关花岗岩的成因和岩浆特征,本文统计分析了华南印支期成钨与成锡(锡钨)花岗岩的地球化学数据。研究结果表明,华南地区印支期钨锡成矿花岗岩均属于高分异的过铝质高钾亚碱性系列,主要为S型花岗岩,部分I/A型。成矿花岗岩的源区主要为富泥质/黏土的壳源,成钨花岗岩和成锡(锡钨)花岗岩的ε_(Nd)(t)值均高于华南地壳平均值,表明其部分受到幔源物质的影响。成钨花岗岩相比成锡(锡钨)花岗岩具有更低的二阶段模式年龄,表明成钨花岗岩源区为更年轻的地壳或可能受到更多的幔源物质的影响。与成钨花岗岩相比,成锡(锡钨)花岗岩为较还原的钛铁矿系列花岗岩,表明低氧逸度岩浆可能有利于锡的富集成矿。成钨花岗岩的锆饱和温度低于成锡(锡钨)花岗岩,这可能是由于钨锡富集源区熔融温度差异造成,这同时也解释了华南印支期钨锡矿分别以钨多金属矿和锡(锡钨)多金属矿在不同区域出现的现象。

In order to reveal the genesis and magmatic natures of Indosinian granites associated with the W and Sn mineralization in South China,a series of geochemical data of the Indosinian W and Sn(Sn-W)mineralization associated granites in South China were collected and statisticly analyzed in this paper.The results show that those Indosinian granites all belong to the highly differentiated high-K peraluminous subalkaline series and they are mainly S-type granites with minor I/A-type granites.The ore-forming granites were mainly sourced from the crust composed of argillaceous/clayey metamorphite.Theε_(Nd)(t)values of the W-and Sn-bearing granites are higher than that of the South China crust,indicating that their magmatic sources could be influenced partly by the mantle materials.The W-bearing granites have relatively young T_(2DM) ages comparing with the Sn(Sn-W)-bearing granites,indicating that the source of W-bearing granites could be relatively young crust or could be influenced by more mantle materials.Moreover,comparing to the W-bearing granite,the Sn(Sn-W)-bearing granite belongs to the relatively reduced ilmenite series granite,indicating that the magma with relatively low oxygen fugacity could be conducive to the Sn enrichment and mineralization.The W-bearing granites have lower zircon saturation temperatures than the Sn(Sn-W)-bearing granites.This may be caused by the difference between melting temperatures of source materials with respectively enriched Sn and W.This also explains why Indosinian W and Sn deposits in South China occurred as respective W polymetallic deposits and Sn(Sn-W)polymetallic deposits distributed in different districts of South China.