平阳矾山明矾石矿床形成的一些热力学条件的研究  

A STUDY ON SOME THERMODYNAMIC CONDITION OF FORMATION OF THE ALUNITE DEPOSIT IN PINGYANG FANSHAN, ZHEJIANG

作　　者：梁祥济[1] 廖志杰[1] 兰翔[2] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]浙江大学地球科学系,杭州310027

出　　处：《浙江国土资源》1998年第1期35-49,共15页Zhejiang Land & Resources

基　　金：中国地质科学院资助

摘　　要：作者在平阳矿山明矾石矿床地质、矿物共生组合、成矿实验等方面工作的基础上，对该矿床形成的一些热力学条件进行了系统研究。研究结果表明该矿床是在50℃～450℃的温度和3×105Pa～780×105Pa的压力下的氧化环境（Eh=－0．40V～＋0．32V，主要是-0.08V～0．24V）中，由含碱性长石的火山碎屑岩、凝灰岩等岩石与含硫、钾、钠等成分的晚期酸性（pH=1．0～4．0）火山气热液在fs2（1．32×10-34×105Pa～3．39×10-3×105Pa）fo2（1．92×00－63×105Pa～1．58×10－19×105Pa）的条件下相互交代作用而形成。The alunite deposit in Pingyang Fanshan, Zhejiang, is the largest in China so far that it is called the Capital of Alunite, and it is alos one of the specially large alunite deposits in the world. The ore bodies of the deposit lie in the medium-acidic pyroclastic rocks and volcanic tuffs of Chao chuan Group in lower Cretaceous Series. The metasomatism is very characteristics in the ore beds. On the basis of the studies for the geologies, rocks and main paragenetic minerals of the deposit and the ore-forming experiments, the authors studied and probed into some thermodynamic conditions in ore-forming process, with the theory of facies equilibrium in the physico-chemistry of petrology and some computer technologies.The results of the studies show that the temperature range of the ore-forming system is from 50℃ to 450℃, and the best temperatures for deposit formation are 250±100℃; the pressure range of the system is from 3 × 105 Pa to 790× 105Pa, the best pressured for deposit formationn are from 20×105Pa to 200× 105Pa ;the range of pH values of the system is from 1.0 to 4/0, but most reactions comcentrate on 2.0±0. 5; the range of Eh values is from -0. 40V to +0. 32V, but most of Eh values are between -0. 12V and +0. 17V, which belong to oxidation enviromment; the oxygen fugacities (fo2) of the system are from 1. 75× 10-64×105Pa to 1. 58 ×10 -19 ×105Pa, and the range of sulfur fugacity (fs2) is from 1. 32 ×10 -34× 105Pa to 1. 26 × 10- 3 × 105Pa; fs2 fo2. These achievements in scientific research basically tally with the field deposlt geologies and the results of the ore-forming experiments.Finally, the authors reached a new conclusion of the deposit formation: the metasomatism of the later volcanlc acid gas and liquid of S, K and Na-bearing compositions with the pyroclastic rocks and valcanic tuffs formed the alunite deposit of Pingyang Fanshan in the oxidation environment at temperatures of 50℃ - 450℃ and pressures from 3 ×105Pa to 790×105Pa.

关 键 词：热力学条件 成矿体系 明矾石矿床 平阳矾山 

分 类 号：P611[天文地球—矿床学]