摘要
产在科洛荡子山的硅钡钛石(batisite),其寄主岩为荡子山火山岩体中岩浆型暗色包体——白榴霓霞岩.白榴霓霞岩包体为暗灰色,粗粒结构,块状构造,长柱状的辉石类矿物清晰可见,气孔发育.Batisite呈亮白色板状、细长柱状或针状集合体,晶体宽度为2～20μm、长度为50～200μm,多以集合体形式穿插出现在霓石-霓辉石颗粒之间,与之共生、伴生的矿物为霓石-霓辉石、富钛铁透辉石、富Ba钾长石、富Sr磷灰石、霞石、白榴石以及交沸石等.Batisite的化学成分为富Ba、Ti、K、Na的硅酸盐矿物,SiO2=39.47wt％,TiO2=20.02wt％,BaO=16.43wt％,Na2O=7.76wt％,K2O=5.91wt％,Fe2O3=3.96wt％,Nb2O5=1.69wt％,ZrO2=1.47wt％,Al2O3=0.19wt％,CaO=0.40wt％,SrO=1.13wt％,F=1.07wt％.根据O+F=14计算获得的每个分子式单位中每个元素原子数(apfu),其经验化学式为:(Na1.53K0.47)∑2(Ba0.65K0.30Sr0.07Ca0.04)∑1.05(Ti 1.53Fe 0.30Nb0.08Zr0.07)∑1.98(O1.66F0.34)∑2(Si4.01Al0.02)∑4.03O12.与其他地区的bati-site 相比 较,BaO含量明显偏低,K2O含量偏高,因此科洛荡子山的batisite在分子量上(605.03 g/mol)明显低于其他地区的batisite(624.94 g/mol,苏联).Batisite的晶胞参数:a=8.05999(17)Å,b=10.47061(19)Å,c=13.8854(2)Å,V=1 171.83(4)Å3,Z=4.空间群为Imma(体心格子).Batisite的拉曼光谱出现了 142、350、550、760、965 cm-1 等位置的峰,其中965 cm-1附近的峰为Si-O伸缩振动引起,760cm-1附近的峰为Si-O弯曲振动引起,Ti-O、Na-O、K-O、Ba-O键其振动范围在142～550 cm-1之间.科洛荡子山batisite是流体活动、热液蚀变的产物.其物质来源与本地区大量的富K、Na火山喷出岩中含K、Ba、Fe和Na的矿物蚀变有关,强烈的流体活动导致早期形成的矿物发生蚀变,在此过程中所释放的元素及残余流体中的元素为batisite形成提供了丰富的物质来源.而类置同像置换则是batisite的形成机理.
Abstract
We investigated the mineral batisite,which has been discovered in the Dangzishan,Keluo volcanic field,northeast China.We examined its petrography,mineralogy,chemistry,crystal structure,Raman spectroscopic features,and formation mechanisms.The batisite is hosted by dark xenoliths of igneous origin(i.e.,leucitite-ijolite)that occur in the Keluo volcanic field.The leucitite-ijolite is dark gray in color and has a coarse-grained and massive texture.It contains elongate columnar crystals of pyroxene and well-developed vesicles.The batisite is bright white in color,and occurs as radial,plate-like,elongate columnar,or needle-like aggregates,with crystal widths of 2-20 μm and lengths of 50-200 μm.It is located mostly between augite or aegirine grains in the form of aggregates,and associated with minerals such as aegirine-augite,Ti-Fe-rich diopside,Ba-rich K-feldspar,Sr-rich apatite,nepheline,leucite,and harmotome.The batisite is a silicate mineral that is rich in Ba,Ti,K,and Na.Its chemical composition is as follows:SiO2=39.47wt％,TiO2=20.02wt％,BaO=16.43wt％,Na2O=7.76wt％,K2O=5.91wt％,Fe2O3=3.96wt％,Nb2O5=1.69wt％,ZrO2=1.47wt％,Al2O3=0.19wt％,CaO=0.40wt％,SrO=1.13wt％,F=1.07wt％.The calculated atoms per formula unit(apfu)based on O+F=14 atoms lead to an empirical chemical formula of(Na1.53K0.47)∑2(Ba0.65K0.30Sr0.07Ca0.04)∑1.05(Ti1.53Fe3+0.30Nb0.08Zr0.07)∑1.98-(O1.66F0.34)∑2(Si4.01 Al0.02)∑4.03O1 2.Compared with batisite from other regions,the batisite from the Keluo volcanic field has lower BaO and higher K2O contents.Consequently,the molecular weight of batisite from the Keluo-dangzishan volcanic field(605.03 g/mol)is lower than that of batisite from other regions(e.g.,624.94 g/mol in Russia).The batisite is orthorhombic with cell parameters of a=8.05999(17)Å,b=1 0.47061(19)Å,and c=13.8854(2)Å.The cell volume(V)is 1171.83(4)Å3(Z=4).The space group type is Imma(i.e.,a body-centered lattice)and the calculated density is 3.351 g/cm3.The Keluo-dangzishan volcanic field batisite has the same space group type as batisite from the Inagli Massif in Aldan,Russia.The Raman spectra of the studied batisite exhibited peaks at 142,350,550,760,and 965 cm-1,with the peaks near 965 cm-1 caused by Si-O stretching vibration,the peaks near 760 cm-1 caused by Si-O bending vibration,and the Ti-O,Na-O,K-O,and Ba-O bonds having vibrations in the range of 142-550 cm-1.The studied batisite occurs in the Xiaogulihe-Keluo-Wudalianchi-Erkeshan volcanic belt in Heilongjiang Province,which is a NNW-SSE-trending Cenozoic continental rift zone.This region has experienced intense volcanism and upwelling of mantle-derived fluids,with the fluids being rich in volatile components,such as H2O,F,Cl,and P.The fluid activity altered the primary minerals,and the elements released and the residual fluid provided the materials for batisite formation.The formation mechanism of batisite is based on analogous substitution.
基金项目
国家自然科学基金(40672039)
中央高校基本科研业务费专项资金(020614380173)
NETL
NSTL
维普
万方数据