科洛荡子山硅钡钛石的发现、晶体结构及成因机制  

Discovery,crystal structure and formation mechanism of Keluo-dangzishan batisite

作　　者：张文兰[1] 谷湘平[2] 汤志敏 王小林[1] 邵济安[3] Wenlan Zhang;Xiangping Gu;Zhimin Tang;Xiaolin Wang;Ji’an Shao(State Key Laboratory for Mineral Deposits Research,School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,China;School of Geoscience and Infophysics,Central South University,Changsha 410083,China;School of Earth and Space Sciences,Peking University,Beijing 100871,China)

机构地区：[1]南京大学地球科学与工程学院,内生金属矿床成矿机制研究国家重点实验室,南京210023 [2]中南大学地球科学与信息物理学院,长沙410083 [3]北京大学地球与空间科学学院,北京100871

出　　处：《科学通报》2023年第33期4585-4596,共12页Chinese Science Bulletin

基　　金：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)资助。

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,SiO_(2)=39.47wt%,TiO_(2)=20.02wt%,BaO=16.43wt%,Na2O=7.76wt%,K_(2)O=5.91wt%,Fe_(2)O_(3)=3.96wt%,Nb_(2)O_(5)=1.69wt%,ZrO_(2)=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:(Na_(1.53)K_(0.47))_(∑2)(Ba_(0.65)K_(0.30)Sr_(0.07)Ca_(0.04))_(∑1.05)(Ti_(1.53)Fe^(3+)_(0.30)Nb_(0.08)Zr_(0.07))_(∑1.98)(O_(1.66)F_(0.34))_(∑2)(Si_(4.01)Al_(0.02))_(∑4.03)O_(12).与其他地区的batisite相比较,BaO含量明显偏低,K_(2)O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)A,b=10.47061(19)A,c=13.8854(2)A,V=1171.83(4)A^(3),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.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,platelike,elongate columnar,or needle-like aggregates,with crystal widths of 2-20μm and lengths of 50-200μm.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:SiO_(2)=39.47wt%,TiO_(2)=20.02wt%,BaO=16.43wt%,Na_(2)O=7.76wt%,K_(2)O=5.91wt%,Fe_(2)O_(3)=3.96wt%,Nb_(2)O_(5)=1.69wt%,ZrO_(2)=1.47wt%,Al_(2)O_(3)=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(Na_(1.53)K_(0.47))_(Σ2)(Ba_(0.65)K_(0.30)Sr_(0.07)Ca_(0.04))_(Σ1.05)(Ti_(1.53)Fe^(3+)_(0.30)Nb_(0.08)Zr_(0.07))_(Σ1.98)-(O_(1.66)F_(0.34))_(Σ2)(Si_(4.01)Al_(0.02))_(Σ4.03)O_(12).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)A,b=10.47061(19)A,and c=13.8854(2)A.The cell volume(V)is 1171.83(4)A^(3)(Z=4).The space group type is Imma(i.e.,a body-centered lattice)and the calculated density is 3.351 g/cm^(3)

关 键 词：科洛荡子山 钡钛硅石 化学成分 晶体结构 拉曼光谱 类置同像置换 

分 类 号：P581[天文地球—岩石学]