Sn、Fe、W、Pb和Zn在花岗岩熔体及共存流体相之间的分配实验研究:850℃和400MPa

Experimental study on distribution of Sn, Fe, W, Pb and Zn between granite magma and coexistent fluid at 850 ℃ and 400 MPa

本实验的目的在于了解花岗岩岩浆演化过程中,F/Cl在介质中的不同比值对Sn、Fe、W、Pb和Zn等元素从岩浆熔体进入超临界水热流体相中的影响。采用天然花岗岩为原始样品,实验在大型内加热装置容器(Harwood Engineering Co.Inc.)中进行。实验条件为850℃,400MPa,fO2=2.1×10-13(NNO),恒温约120～128h。固/液比值≈1,固样质量约250mg,Ar为压力介质。实验结果显示,介质中F/Cl比值变化对W的分配系数影响不大。而其他元素均随Cl浓度增高,分配系数增大,并有以下顺序:DV/LZn>DV/LFe>DV/LSn>。通常认为四价Sn较为稳定并与F关系密切,而本实验显示,二价Sn可能较为稳定并与Cl关系密切。在快速淬火过程中,沉淀在金管壁上的玻璃碎屑富集了较多的成矿元素,且观察到玻璃包裹体及盐类包裹体。

The influences of the F/Cl ratio on the entrance of Sn, Fe, W, Pb and Zn into supercritical thermal fluid in the processes of granite magma evolution are experimentally explored. The experiments are carried out with a big heating container （Harwood Engineering Co. Inc. ） and the samples are natural granites. Experimental conditions： temperature is 850 ℃, pressure is 400 MPa, fO2 = 2. 1 ×10^-13 （NNO）, keep constant temperature for 120- 128 h, solid/liquid≈ 1, the solid sample mass is about 250 mg, pressure medium is Ar. The results of the experiments show that the influence of ratio F/Cl on the distribution coefficient of W is slight, but the distribution coefficients of other elements all increase with increasing concentration of Cl and there is a sequence： D^V/L Zn 〉 D^V/L Pb 〉 D^V/L Fe 〉 D^V/L Sn . It is usually considered that the stability of Sn^4＋ is closely dependent on F; however, our experiments show that Sn^2＋ is more stable and its stability is dependent on Cl. Many mineralization elements are enriched in the glass scraps that are deposited on the wall of gold-pipe in process of quick quenching; glass enclosure and salt enclosure are also found.