四川平武板状绿柱石矿物学特征及板状成因

在综合该区绿柱石产出背景的基础上,从围岩蚀变、矿物共生组合、矿物标型形态和绿柱石测温测压等方面确定平武绿柱石矿床是气成高温浅成石英脉型矿床。文中对绿柱石矿物进行了湿法化学分析、X射线粉晶衍射分析、微形貌分析,研究了该区绿柱石的形态、物性、化学成分及类质同象特征,确定该区绿柱石为板状晶形的含铯钠锂绿柱石,碱金属平均质量分数为2.412%(Li2O+Na2O+K2O+ Rb2O+Cs2O)。板状含碱绿柱石一般发育在伟晶岩中,气成高温热液矿床中产出板状含碱绿柱石极为罕见。在以上工作基础上,从绿柱石形成的内因和外因两方面探讨了绿柱石的板状成因。

Mineralogical characteristics of beryl in Pingwu County, Sichuan Province, south-west China

The colorless transparent tabular beryl in Pingwu County, Sichuan Province is a rare and special mineral among beryls. The unique tabular configuration and other characteristics of the beryl have drawn wide attention. The geologic setting, wall-rock alteration, accompanying mineral assemblages, crystal morphology and temperature and pressure of formation of the mineral,suggest that the beryl deposit is a shallow-seated hypothermal quartz vein type. Growth zoning on crystal faces are present. Samples of this beryl were tested by X-ray powder diffractometer and cell parameters were calculated. The chemical composition of the mineral was also analyzed by wet chemistry analysis and the formula derived. The Pingwu County beryl is sodic-lithium rich because it contains abundant Li~+, Na~+, Rb~+ and Cs~+. The average content of alkali(Li_2O+Na_2O+K_2O+Rb_2O+Cs_2O) is up to 2.412%. Tabular alkali-rich beryl can be found in granites, but tabular alkali-rich beryl in hypothermal deposit is very rare. This paper describes the geologic characteristics of deposits, the mineralogical characteristics of beryl, and the physical and chemical condition of mineralization, and explains the genesis of this tabular beryl.