金在气相中迁移与有机质演化生烃关系的实验研究

AN EXPERIMENTAL STUDY ON THE MIGRATION OF GOLD IN GAS PHASE RELATED TO HYDROCARBON GASES PRODUCED BY THE EVOLUTION OF ORGANIC MATTER

火山喷气沉积物中微米级金的发现、化探地气测量检测出金等现象表明 ,在自然界金可在气相内存在。但是金以何种形式存在及其迁移机理尚待探讨。本项研究选取并制备了有地质意义的含硫有机金属化合物———烷基硫醇衍生纳米金 ,将其添加至含有机物质的自然样品中 ,在专门设计的真空加热装置中用泡塑收集其在不同温度条件下的气相产物 ,分析对比实验中产生的气相带出金的含量和气体成分 ,并与金的氯金酸水溶液作用过的样品进行对比。模拟与有机质密切相关的金在气相中迁移的地质过程。实验结果表明 ,含十二烷基硫醇衍生纳米金样品及其纯物质在升高温度条件下的气相产物带出金高于同样条件下用氯金酸处理过的含金样品。金的迁移与升高温度时产生的烃类气体有关。该实验为与有机质演化生烃有关的金气相迁移成矿过程提供了实验依据 ,由于十二烷基硫醇衍生纳米金中纳米金团簇是稳定存在于烷基硫醇结构内 ,因而实验也说明了金的纳米簇团迁移与有机质之间的密切关联。与有机质及其气相演化产物密切相关的金的气相迁移 ,是金在自然界呈气相迁移的重要形式之一。

Phenomena such as natural precipitation of gold crystals of 5～40μm in diameter in volcanic gas, and the discovery of gold by geochemical geogas measurements indicate that gold could exist in a gaseous phase in nature. Firstly, in this experimental study a sulphur-bearing alkanethiol-derivatized gold nanoparticles has been selected. The alkanethiol-derivatized gold was put in the mud-stone samples bearing terreau. At various elevated temperatures the gaseous products were collected by foam plastics in a special device. The measurements of the contents of gold in foam plastics and the composition of gas phase were carried out and the comparison between various samples has been made. Experimental results indicate that the contents of gold from the samples with alkanethiol-derivatized gold nanoparticles added are higher than those treated with chloroauric acid. The phenomenon is obviously related to the hydrocarbon gases at elevated temperature, but can also be interpreted from the migration of gold nanoparticles. However the gold nanoparticles have to be stabilized in the thiol-structure, the migration of gold is related mainly to the hydrocarbon gases produced by the experiments. The results provide experimental evidence for migration of gold related with organic evolution in the mineralization, and also show the close relation between the migration of gold nanoparticles and the organic matter in geological process.