内蒙赤峰鱼眼石矿物学特征及其水的赋存状态研究

MINERALOGICAL CHARACTERISTICS AND WATER OCCURRENCE OF APOPHYLLITE FROM CHIFENG,INNER MONGOLIA

采用显微镜和XRD,EMPA,FTIR,RAMAN,TGA等现代测试方法对内蒙赤峰鱼眼石的晶体形态、矿物组合、化学成分、谱学特征、热力学性质等进行了测试分析,初步探讨了鱼眼石晶体形态的成因以及水的赋存状态。赤峰鱼眼石晶体呈粒状—假立方状,由四方柱{100}、四方双锥{111}和平行双面{001}聚合而成,无色-浅粉红色,玻璃光泽,透明到半透明,与钙铁辉石、雪硅钙石和毒砂等矿物共生。赤峰鱼眼石的主要化学成分为w(SiO_2)50.22%~52.73%,w(CaO)24.16%~25.28%,w(K_2O)3.57%~5.80%和w(F)2.62%~3.48%,含有少量的Na_2O,Al_2O_3和Cr_2O_3,平均成分的晶体化学式为:(K_(0.964)Na_(0.109))_(1.073)Ca_(4.036)[(Si_(7.727)Al_(0.091)Cr_(0.073))_(7.891)O_(20)](F_(0.828)OH_(0.172))_(1.000)·7.775H_2O。硅的含量不足导致硅氧四面体层活性氧与层间阳离子的键强增大,促使鱼眼石晶体沿c轴方向的生长,形成粒状—假立方状晶体形态。红外光谱中3 556 cm^(-1)和1 691 cm^(-1)吸收峰以及96.7℃,255.9℃,418.9℃,437.7℃的主要失水温度均表明赤峰鱼眼石中的水属于结晶水,而600℃以后仍有少量的失重,以及红外光谱中3 418 cm^(-1)和3 242 cm^(-1)吸收峰的出现,又反映出赤峰鱼眼石中部分水具有结构水的特点。

The crystal morphology,mineral assemblage,chemical composition,spectral characteristics and thermodynamic properties of apophyllite from Chifeng,Inner Mongolia are tested and analyzed by modern methods including microscopy,XRD,EMPA,FTIR,Raman,TGA etc.,and two issues as the genesis of apophyllite crystal morphology and the occurrence state of water are discussed.It shows that the crystal of Chifeng apophyllite is granular to pseudocubic,and formed by tetragonal prism{100},tetragonal bipyramid{111}and pinacoid{001}.The crystal is colorless to light pink,with features of vitreous and transparent to translucent,and is symbiosis with minerals such as hedenbergite,tobermorite and arsenopyrite,etc.Chemical analysis reveals that the main chemical components of Chifeng apophyllite are w(SiO2)50.22%-52.73%,w(CaO)24.16%-25.28%,w(K2O)3.57%-5.80%and w(F)2.62%-3.48%,and contain a small amount of Na2O,Al2O3 and Cr2O3.The crystal chemical formula for the average component is(K0.964Na0.109)1.073 Ca4.036[(Si7.727Al0.091Cr0.073)7.891O20](F0.828OH0.172)1.000·7.775 H2O.It is considered that the insufficient content of silicon leads to the increase of the bond strength between reactive oxygen species and cations in the tetrahedral layer of silicon oxygen,which promotes the growth of apophyllite crystals along the c-axis direction and forms the granular-pseudocubic crystal morphology.The absorption peaks of 3556 cm^(-1) and 1691 cm^(-1) in infrared spectra and the main water loss temperatures of 96.7℃,255.9℃,418.9℃and 437.7℃all indicate that the water in Chifeng apophyllite belongs to crystalline water,but there is still a small amount of weight loss after 600℃.The presence of absorption peaks of 3418 cm^(-1) and 3242 cm^(-1) in infrared spectrum also reflects that part of the water in Chifeng apophyllite has the characteristics of structural water.