福建紫金山金铜矿床过渡带地球化学特征及地质意义

Geochemical Characteristics and Geological Significance of the Transitional Zone of Zijinshan Gold-copper Deposit in Fujian province

紫金山矿田是东南沿海武夷成矿带中重要的多金属矿集区,是与中生代构造-岩浆活动有成因联系的多金属矿产地。根据对矿田露采区近矿蚀变围岩和金铜矿石的主量元素、微量元素和稀土元素进行了详细的分析和总结。主量元素特征显示,SiO_2、Fe_2O_3在矿石和蚀变围岩中明显富集,Al_2O_3、MnO、MgO、CaO、Na_2O、K_2O在矿石和蚀变围岩中的含量明显低于复式岩体,矿石和蚀变围岩中的富集组分(SiO_2、Fe_2O_3)不可能来自复式岩体,而应该是来自成矿热液,显示了多期次的蚀变作用与矿化密切相关;稀土元素特征显示,蚀变英安玢岩和矿石稀土元素地球化学特征相似,明显富集轻稀土元素,轻重稀土元素内部分异明显且轻稀土元素内部分异现象更严重,Eu弱负异常,二者的稀土元素配分模式图也十分相似,表明成矿流体来源更可能是与英安玢岩同源的岩浆热液;综合研究表明,成矿作用与幔源岩浆的参与有关,成矿物质可能主要来自幔源岩体,紫金山复式岩体也可能提供了部分成矿物质,说明深部可能存在斑岩型铜钼矿床。

Zijinshan orefield is an important polymetallic mineralization district of Wuyi metallogenic belt with the relationship to mesozoic tectonic-magmatic activity. Many researchers have already made lots of researches on mineral deposit geology, petrology, geochemistry, mineralogy and metallogenic epoch, they have got lots of achievements. In this paper, comprehensive analysis on major elements, trace elements and rare elements in alterated rock and mineral ore has been made. The feature of major elements shows that the contents of SiO2 and Fe2O3 are higher in mineral ore and alterated rock than in granite pluton, the content of Al2O3, MnO, MgO, CaO, Na2O and K2O are lower in mineral ore and alterated rock than in granite pluton. The hign content component(SiO2, Fe2O3) impossibly came from alterated rock, but from mineralizing fluid. It’s possible that multi-stage alteration was closely related to mineralization. The feature of rare earth elements shows that the rare earth elements geochemical characteristics of altered dacite porphyrite and ore are similar, obviously enriched with light rare earth elements,the internal differentiation of light rare earth elements is obvious and more serious, Eu weakly negative anomaly, REE distribution pattern diagram of both is also very similar which indicats that the source of ore-forming fluid is more likely to be the same magma hydrothermal fluid related to dacite porphyrite. The comprehensive study shows that the mineralization is related to the participation of mantle derived magma, and the metallogenic material may come mainly from the mantle derived rock, and Zijinshan complex pluton may also provide partial minerals, there may be porphyry copper molybdenum deposit may exist in the deep part.