贵州贞丰县皂凡山矿凝灰岩分解机理研究

Study on decomposition mechanism of tuff in Zaofanshan Mine,Zhenfeng County,Guizhou Province

遇水快速分解的凝灰岩对矿区勘查钻井等工作带来不利,有必要研究凝灰岩的相关性质及快速分解原因,为涉凝灰岩工程应用提供参考。使用XRF、XRD、SEM、ICP-MS及化学实验等方法,对贵州贞丰县皂凡山凝灰岩的分解机理进行了研究。结果表明:1)凝灰岩的主要矿物成分是石英、白云母、黄铁矿、金云母及高岭石,导致凝灰岩遇水快速分解的物质因素为云母和高岭石。2)凝灰岩内广泛存在微片层结构,这些片层结构具有强亲水性黏土的典型微观结构。凝灰岩内部孔隙、裂隙发育。微片层结构与孔隙裂缝均有利于水分在凝灰岩内部扩散与运移,也是凝灰岩快速分解的重要原因。3)凝灰岩中黄铁矿氧化生成硫酸及硫酸盐,ICP-MS测试表明有大量离子在水中快速溶出,溶出也对凝灰岩分解起促进作用。4)钾盐、铵盐及硅酸盐对皂凡山凝灰岩具有显著的离子交换改性稳定作用,碳酸盐/碳酸氢盐具有显著的促进分解作用。钾离子等阳离子的离子交换稳定作用不及碳酸阴离子的促分解作用。富含具有微片层结构的强亲水硅酸盐矿物及硫酸盐溶解是皂凡山凝灰岩快速分解的主要原因。

The tuff which is rapidly decomposed by water,is unfavorable to the exploration and drilling of the mining area.Therefore,it is necessary to study the related properties and causes of tuff’s rapid decomposition,further to provide reference for the application of tuff engineering.In this paper,the decomposition mechanism of Zaofanshan tuff in Zhenfeng County,Guizhou Province was studied by XRF,XRD,SEM,ICP-MS and chemical experiments.The results indicated that:1)The main mineral components of tuff were quartz,muscovite,pyrite,phlogopite and kaolinite.The material factors that caused the tuff to decompose rapidly with water were mica and kaolinite.2)Micro-lamellar structures widely existed in tuff,which were just the typical microstructures of highly hydrophilic clays.Pores and fissures were well developed in tuff.The micro-lamellar structure and pore cracks were conducive to the diffusion and movement of water in tuff,which was also an important reason for the rapid decomposition of tuff.3)Pyrite in tuff was oxidized to sulfuric acid and sulfate.ICP-MS test indicated that a large number of ions dissolve rapidly in water,and dissolution also promotes the decomposition of tuff.4)Potassium salt,ammonium salt and silicate had remarkable ion exchange modification and stabilization effect on Zaofanshan tuff.Carbonate or bicarbonatepresented a significant decomposition promotion effect.The ion exchange stability of cations such as potassium ions was less than the promoting decomposition of carbonate anion.Rich in highly hydrophilic silicate minerals with micro-lamellar structure and sulfate dissolution were the main reasons for rapid decomposition of Zaofanshan tuff.