钨在花岗岩岩浆体系中的分配特征以及对成矿作用的影响

Distribution characteristics of tungsten in the granite magma system and impact on mineralization

不同岩浆体系过程,钨分配特征不同,迁移沉淀和成矿机制表现也截然不同。热液型钨矿在时空和成因上,与花岗岩岩浆体系有着密切联系。在花岗岩岩浆体系中W主要以钨酸(根)和碱性钨酸盐离子存在并迁移,后因流经理化条件(温度、盐度、pH值)骤变而沉淀成矿。分析4种典型钨矿床实例显示:(1)均与A型花岗岩体系有关,夕卡岩型和斑岩型钨矿与I型也有关;(2)成矿流体来源并无明显壳幔之分,均有大气饱和水参与,夕卡岩型钨矿可能有幔源流体加入,斑岩型和云英岩型钨矿成矿流体较复杂,受变质水影响较大;(3)石英脉型钨矿中以气液两相水溶液包裹体为主,属中—中高温、中低盐度NaCl-H_2O±CO_2体系;夕卡岩型、斑岩型及云英岩型钨矿中除富气液相水溶液包裹体外,还含有钠盐、钾盐子晶包裹体,均属中高—高温、高盐度NaCl-H_2O-KCl±CO_2体系。

In different processes of magma system, the distribution of tungsten differs, as well as migration and precipitation ore -forming mechanism. There is close relationship between hydrothermal tungsten ore and granite magma system in spatial and temporal aspects and genesis. Tungsten tends to be transported as simple tungstate or alkali-tungstate ion, and precipitate to form hydrothermal tungsten deposit when physical and chemical conditions （temperature, pressure and pH） change suddenly. By analyzing four types of tungsten deposits, the results show that ①elated to A type granite magmatic system. The skarn type and porphyry type tungsten deposits are mainly related to I type granite magmatic system; ② no obvious identification of source of ore-forming fluid from crust or mantle, there is atmospheric water mixed; The fluid of skarn type tungsten deposit maybe partly from Mantle source ; The source of ore-forming fluid of porphyry and greisen type tungsten deposits are more complicated and influenced by metamorphic water greatly; ③ The inclu- sion type in quartz vein type tungsten deposit is mainly gas and liquid two-phase aqueous inclusion, with characteristics of high temper- ature and low salinity in NaCl-H2O±CO2. The inclusion in skarn type, porphyry type and greisen type tungsten deposits includes not only rich vapor liquid aqueous inclusion type, but also sodium salt, potassium salt crystal inclusion, which belong to a medium-high and or the high temperature, high salinity of NaCl-H2O-KCl±CO2 system.