摘要
利用微分干涉显微镜、扫描电镜、透射电镜等对小秦岭金矿含金石英脉中黄铁矿晶体的表面微形貌进行了研究。黄铁矿晶体的{210}面上发育自由生长层,表明{210}面是F面,其生长机理受二维成核层生长所制约。除简单的五角十二面体外,其他形态黄铁矿晶体的{210}面上也发育有自由生长层。{210}面上的正条纹有些是由{100}面上生长层的边缘台阶在{210}面上叠堆形成,另一些正条纹则是{210}面上生长层边缘台阶堆叠的产物。透射电镜和电子衍射花样研究表明,负条纹黄铁矿晶体是由30~50nm大小的核团经自动定向附生作用形成,每个核团不是单晶体,而是由许多早先在溶液中形成的小微晶聚合而成。这些特征表明负条纹黄铁矿晶体是在溶液过饱和度极高和温度梯度小的理想环境中形成,它的形成与杂质无关。PBC理论和唐纳哈克定律能较好地解释自然界中黄铁矿晶体{100}面上普遍发育自由生长层、而{210}面上自由生长层极为罕见的原因。除日本释迦内矿区黑矿之上的浮岩凝灰岩中产生出负条纹黄铁矿晶体外,在石英脉型金矿床中也有负条纹黄铁矿晶体产出。
The negative striations and micromorphology of pyrite crystals on a{210}face in the auriferous quartz vein were studied by means of differential interference microscope,SEM and TEM.The{210}faces of pyrite crystals are F-faces,which have developed free growth layers.The mechanism of their crystal growth is controlled by two-dimensional nucleation and layer-by-layer growth.Both simple pentagonal dodecahedron habit and other morphology of pyrite crystals develop free growth layers on the{210}faces.Some positive striations on the{210}faces are formed by piling up of steps of growth layers on the{100}faces,and other positive striations on the{210}faces are formed by piling up of steps of growth layers on the{210}faces.Transmission electron observation reveals that crystals with negative striation are formed through auto-epitaxial settlement of block nuclei 30~50 nm in diameter on growing crystals.Electronic diffraction pattern shows that the single block nuclei consist of many minute crystallites already formed in the solution.This suggests that these crystals have been grown in a reasonable environment characterized by very high super-saturation and low gradient of temperature.Their growth is not related to impurity.Based on an analysis of PBC theory and Donnay-Hark law,we can rea-sonably interpret the phenomenon why free growth layers are commonly seen on the{100}faces but are rarely developed on the{210}faces of pyrite crystals in nature.Besides occurring in the Shakanai mine of Japan,the pyrite crystals with negative striations are also developed in gold deposits of quartz-sulfide veins.
作者
张良钜
ZHANG Liang—ju(Department of Resource and Environment Engineering,Guilin Institute of Technnlogy,Guilin 541004,China)
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2004年第2期167-172,共6页
Acta Petrologica et Mineralogica
基金
广西自然科学基金资助项目(桂科自0229054)
关键词
含金石英脉
黄铁矿晶体
{210}面上的微形貌与负条纹
环境条件
小秦岭金矿
auriferous quartz vein
pyrite crystal
micromorphology and negative striations on a{210}face
environment condition
Xiaoqinling gold deposit
