云开地块西南缘飞鹅岭矽卡岩型铅锌矿床中石英和方解石的矿物学特征研究

Study on Mineralogical Characteristics of Quartz and Calcite from Feieling Skarn-Type Pb-Zn Deposit in Southwest Margin of Yunkai Massif

云开地块西南缘飞鹅岭矽卡岩型铅锌多金属矿床近矿围岩、隐伏岩体、内矽卡岩、外矽卡岩和矿体中石英、方解石的拉曼光谱及红外光谱分析结果表明,与隐伏岩体中新生石英相比,近矿围岩、内矽卡岩和外矽卡岩中的α-石英有不同程度向对称性较低的石英转变的趋势;从近矿围岩→隐伏岩体→内矽卡岩,石英的结晶度和有序度在逐渐升高,外矽卡岩中石英的结晶度和有序度存在明显差异。石英这种微观结构的变化与矽卡岩成矿过程的多阶段演化密切相关,近矿围岩、内矽卡岩和外矽卡岩的石英受热液流体和温度的影响易产生重结晶、结构调整作用。在同一样品中,结晶较早呈半自形-自形晶的方解石具有较高的结晶度和有序度,相反,结晶较晚呈半自形或它形的方解石具有较低的结晶度和有序度。外矽卡岩中方解石晶体包含有二氧化硅杂质,而内矽卡岩和矿体中方解石较为纯净。其原因应与矽卡岩形成阶段相关,早-晚期矽卡岩阶段处于较高温环境下,活跃的含二氧化硅流体容易进入方解石晶体内,相反,晚期硫化物阶段处于较低温环境下,最晚结晶的方解石较为纯净。因此,石英和方解石的谱学特征反映了矽卡岩型矿床成矿的多阶段演化过程。

The Feieling Pb-Zn deposit of skarn-type is located the in Southwest margin of Yunkai massif,China.This ore deposit can be divided into wall rock near ore,concealed rock mass,endoskarn,exoskarn and orebody.The Raman and FTIR spectrum are conducted to study the mineralogical characteristics of quartz and calcite from five types of rocks from Feieling skarn-type de-posit.The analysis shows that the quartz included in the near ore wall rock,endoskarn and exoskarn,comparing with recrystal-lized quartz of concealed rock mass,has a tend to change into low symmetry quartz in varying degrees.The crystalinity and order degree of quartz from near ore wall rock to concealed rock mass and to endoskarn are becoming higher,but that of quartz from different exoskarn samples display no regular.The origin or the quartz microstructure changes may be related to the multi-stage evolution of skarn mineralization process.The quartz,included in near ore wall rock,endoskarn and exoskarn,become easier to recrystallize and adjust microstructure under the influence of the multi-stage hydrothermal and temperature effect.In anyone sample,the earlier crystalline calcite,showing subhedral-euhedral crystal,display higher crystalinity and order degree.On the contrary,the later crystalline calcite,showing xenomorphic crystal,display lower crystalinity and order degree.Calcite crystal of exoskarn rock contains some silica impurity,while endoskarn and orebody rock is pure.The purity of calcite crystal may re-late to Multi-stage evolution of skarn mineralization process.At the early and late skarn stage,active silica-containing fluid is easier to join into calcite,which is under higher temperature environments.On the contrary,at the late quartz-surfide stage,the later crystalized calcite displays higher purity,which is under lower temperature environments.Therefore,spectral characteris-tics of quartz and calcite reflect multi-stage evolution of skarn mineralization process.