应用激光拉曼光谱鉴别桂中铝土矿TiO_(2)同质异象矿物  

Identification of TiO_(2) Polymorphs of the Bauxite Deposit in Central Guangxi by Laser Raman Spectroscopy

作　　者：张永清 周红英[1] 耿建珍[1] 肖志斌 涂家润 张然 叶丽娟 ZHANG Yongqing;ZHOU Hongying;GENG Jianzhen;XIAO Zhibin;TU Jiarun;ZHANG Ran;YE Lijuan(Tianjin Center,China Geological Survey,Tianjin 300170,China)

机构地区：[1]中国地质调查局天津地质调查中心,天津300170

出　　处：《岩矿测试》2022年第6期978-986,共9页Rock and Mineral Analysis

基　　金：国家自然科学基金青年基金项目(41803047)。

摘　　要：金红石、锐钛矿和板钛矿为TiO_(2)的三种同质异象矿物。在进行金红石微区原位U-Pb定年时,通常主要依据电子探针数据、辅以阴极发光图像确定研究矿物为金红石,而电子探针数据和阴极发光图像有时并不能有效地区分金红石、锐钛矿和板钛矿,若用于进行定年的矿物中同时存在三种或其中两种TiO_(2)矿物,获得的年龄可能是混合年龄,无显著地质意义。因此,对TiO_(2)同质异象矿物的快速准确鉴别具有重要意义。本文以桂中铝土矿中TiO_(2)矿物为研究对象,将激光拉曼光谱应用于TiO_(2)同质异象矿物的鉴别,准确识别出桂中铝土矿TiO_(2)矿物中存在四组不同特征的激光拉曼光谱谱线。前三组分别具有锐钛矿、金红石和板钛矿的激光拉曼光谱特征峰;第四组具有两种激光拉曼光谱特征谱线,第一种同时具有锐钛矿的特征峰144、198、397、513、636cm^(-1)和金红石的特征峰442、607cm^(-1),第二种同时具有锐钛矿的特征峰144cm^(-1)和板钛矿特征峰153、247、325、636cm^(-1)。结果表明:桂中铝土矿TiO_(2)矿物中除金红石、锐钛矿和板钛矿外,还存在同时具有两种矿物结构特征的中间矿物。分析认为研究区可能经历了后期的区域变质作用,导致TiO_(2)同质异象矿物发生相变,这类中间矿物则记录了相变的过程。本文应用激光拉曼光谱快速准确地鉴别出桂中铝土矿TiO_(2)同质异象矿物,为金红石微区原位U-Pb定年研究中矿物的鉴别提供了新思路。BACKGROUND: Rutile, anatase and brookite are TiO_(2)polymorphs. In the rutile in-situ U-Pb dating, rutile was determined primarily on electron microprobe data and cathodoluminescence images, while these methods sometimes could not effectively distinguish rutile, anatase and brookite. If there are a small number of the TiO_(2)polymorphs in the sample, the obtained age may be a mixed age with no significant geological significance. Therefore, the identification of TiO_(2)polymorphs is very important.OBJECTIVES: To identify TiO_(2)polymorphs from the bauxite deposit in central Guangxi.METHODS: TiO_(2)minerals in bauxite from central Guangxi were used as the research object, and laser Raman spectroscopy was applied to the identification of TiO_(2)isomorphic minerals.RESULTS: Four groups of laser Raman spectral lines with different characteristics were identified. The first three groups have laser Raman spectral peaks of anatase, rutile and brookite, respectively. The fourth group has two kinds of laser Raman spectral characteristic lines, one has both anatase characteristic peaks of 144, 198, 397, 513, 636 cm^(-1)and rutile characteristic peaks of 442, 607 cm^(-1), the other has both anatase characteristic peak of 144 cm^(-1)and brookite characteristic peak of 153, 247, 325, 636 cm^(-1).CONCLUSIONS: The TiO_(2)polymorphs of the bauxite deposit includs rutile, anatase, brookite and intermediate minerals that undergo phase transformation. The study indicates that the bauxite deposit in central Guangxi may have undergone a later regional metamorphism, leading to the transformation of TiO_(2)polymorphs. The laser Raman spectroscopy provides a new method for the identification of TiO_(2)polymorphs andrutile for in-situ U-Pb dating.

关 键 词：TiO_(2)同质异象矿物 激光拉曼光谱 金红石 锐钛矿 板钛矿 

分 类 号：P575.1[天文地球—矿物学]