浙江渡船头“伊利石”应属绢云母

The Argument that the Duchuantou "Illite" of Zhejiang Province Is Actually Sericite

渡船头云母状矿物长期以来被称为“伊利石”,近期经过X射线衍射(XRD)、红外光谱(IR)、差热分析(DTA)、电子显微镜(EM)观察及化学组成等研究后显示:这种呈薄鳞片状、粒度很细(一般小于5μm)、结晶度高的矿物,其d(002)=9.95?,为2M多型,出现特征的3625cm^(-1)、3450cm^(-1)、1020cm^(-1)、935cm^(-1)、825cm^(-1)、799cm^(-1)、755cm^(-1)、543cm^(-1)、480cm^(-1)红外吸收和40—70℃、106.4—111.2℃两弱吸热谷及630—670℃强吸热谷;矿物MgO小于0.25%,结构中八面体Mg^(2+)量小于0.03,以Al^(3+)和Fe^(3+)为主,八面体电荷为-0.052—+0.048/O_(10)(OH)_2,K_2O一般大于9%。上述这些均表明,渡船头“伊利石”应属绢云母。

Mineralogical studies of the Duchuantou 'illite' in Zhejiang province indi-cate that the mineral formerly called 'illite' is: actually sericite. Its XRD, IR,DTA, SEM and TEM data and, es-pecially, chemical composition exhibit chara-cteristics of the typical sericite mineral. The Duchuantou sericite is characterized by MgO<0.25%, K_2O>9%, Si/Al<1.2, octahedral Mg less than 0.03, and octahedral electric charges -0.052-- + 0.048/O_10(OH)_2 whereas illite is noted for MgO>2.0%, K_2O some 8%, Si/Al>1.5,octahedral Mg 0.2--0.4, and octahedral electric charges -0.17--0.40/O_10(OH)_2.The Duchuantou sericite has high crystallinity, flaky form, grain size smallerthan 5 um, sharp and symmetric 9.95 A (002) peak, and 2 M polytype, whileillite generally has low crystallinity, 1 M polytype and gentle (001) peak. Inaddition, the Duchuantou sericite displays characteristic 3624, 3450, 930, 825 and799 cm-1 infrared absorptions, 45--111.2℃ weak endothermic valley and 600-700℃ strong endothermic valley; in contrast, illite does not Show apparent 825,799 cm-1 infrared absorption, but exhibits 100℃ strong endothermal valley and500℃ and 900℃ endothermal valleys.