摘要:
南岭地区钨锡多金属成矿作用和区内中酸性-酸性花岗岩有着密切的成因联系。利用已发表的和野外收集的地质资料,本文尝试对区内成钨锡花岗岩组合(包括与钨锡矿相关的含钨锡花岗岩和成钨锡花岗岩)进行宏观地质判别。判别过程采用循序渐进的方式,首先将成钨锡花岗岩组合与不成矿花岗岩相区别,然后将含锡花岗岩和含钨花岗岩互相区别开来。相对于不成矿花岗岩,成钨锡花岗岩组合通常具有 W、Sn、F、B 化探组合异常、多期多阶段演化特点、适度的构造叠加(即存在明显的热液活动)等共同特点,且三者缺一不可。不成矿花岗岩一般具有 W、Sn、F、B 化探组合为背景值,岩性单一,少见晚期岩株、岩脉(演化不充分)及蚀变的特征。在野外地质工作中,含锡花岗岩一般为花岗闪长岩-二长花岗岩-二云母花岗岩岩性组合。基性端元以普遍发育暗色微粒包体、常见角闪石、含较多的黑云母为鉴别特征。酸性端元中可以含有少量白云母。而含钨花岗岩以黑云母二长花岗岩-二云母花岗岩-白云母花岗岩岩性组合为主,常见含 B 矿物电气石,基性端元少见或不见角闪石、含较少的黑云母,仅见变质岩、围岩捕掳体和黑云母团块,酸性端元白云母含量较高等组合特征可以与含锡花岗岩相区别。
Abstract:
Most tungsten-tin polymetallic deposits are undoubtedly coexist with intermediate-acid granitoids in Nanling Range, South China. This paper focus on the field identifications of granitoids related to W/Sn mineral-ization. In the discrimination process, granitoids related to W/Sn mineralization are firstly differentiated from those unmineralized, and further divided into W series and Sn series from each other. Compared to those unmineralized granitoids, the majority of mineralized granitoids have positive W, Sn, F, B geochemical anomaly, multiple litholo-gies and appropriate tectonic superposition (or hydrothermal alteration). Granitoids unmineralized can be easily i-dentified by W, Sn, F, B background contents, simple lithology, lackness of late granitic stocks/veins and alter-ations. In field exploration, Sn series are easily indentified by granodiorite-monzogranite-two-mica granite lithologies, widespread MME and hornblend in basic end member with higher biotite content (4-6 wt% or higher), and low muscovite content (<1 wt%) in acid end member. While W series can be differed from Sn series by sev-eral other features such as monzogranite-two mica granite-muscovite granite lithologies, biotite noddle, meta-sedimentary and hostrock enclave commonly seen in basic end member with lower biotite content(2-4 wt%) and little hornblend, and identical disseminated tourmaline and high muscovite content (1-2 wt%) in acid mem-bers.
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