硼酸盐矿物的振动光谱研究：Ⅱ：红外光谱特征

本文通过观测在不同温度下加热过的硼酸盐矿物的红外光谱,并与喇曼光谱结果进行比较,讨论了红外光谱谱带的归属。结果表明,通过观测不同温度下加热过的样品的谱带特征有助于谱带的归属。     

硼酸盐矿物的振动光谱研究：Ⅰ：喇曼光谱特征

本文利用激光喇曼光谱研究了不同类型的硼酸盐矿物,讨论了它们的谱带特征及其归属。研究结果表明,具简单基团的喇曼光谱可以作出比较明确的归属,且与红外光谱结果一致,而同时具三、四配位硼的矿物,其配阴离子虽很复杂,各种谱带相互叠加,但仍可以对主要谱带作出初步的归属。     

蛇纹石族矿物的红外光谱特征及其研究

蛇纹石族矿物的红外吸收光谱,早在50年代末期已有报道,70年代以来,特别是偏振光的红外光谱技术应用后,对蛇纹石族矿物的红外光谱与晶体结构之间的关系,有了进一步的研究,对谱带的归属也作了阐述^[2,3]。     

具磷灰石假象绿松石的岩石矿物学及谱学特征

采用x射线粉晶衍射（XRD）、博里叶变换红外光谱（FTI码以及拉曼光谱等方法对安徽马鞍山具磷灰石假象的绿松石进行了研究。结果表明：其主要矿物组成为绿松石,保留了磷灰石六边形的形态特征。XRD~U试的特征谱线d值为36745～36748（111）、29008～29025（123）、34247～34293（2101、32709～32781（113）、61626～61781（011）3020130～20162（301）,与绿松石的标准衍射谱线基本致。红外光谱测试分析表明：3510～3465cm。间的谱带归属绿松石0（OH）的伸缩振动,3300～3070cm’间的谱带归属为绿松Nu（M-H。O）伸缩振动,1210-1012cm’间的谱带归属为绿松石U3口O。）ira缩振动,在838cm。附近的吸收谱带归属为绿松石6（OH）弯曲振动,655-480cm。间的谱带归属为绿松石u4（P04）弯曲振动。拉曼光谱测试分析表明：3466cm’附近的尖锐拉曼谱峰归属于绿松石（OH）基团的伸缩振动所致,宽缓的拉曼谱峰3281cm’~03078cm’归属于绿松石中水合络离子的伸缩振动,798cm’谱峰则是由于OH的弯曲振动所致。     

锂绿泥石的红外光谱研究

本文给出了产于河南和贵州的锂绿泥石红外光谱,以及光谱中各谱带的频率、吸收强度、主要谱带的归属和灼烧样品的红外光谱。这两个矿物的光谱与以前发表的锂绿泥石的光谱有差别,而和白云母、伊利石的光谱相似;文中给出了它们的鉴定特征。根据红外光谱认为,锂绿泥石的结构可能是复杂的,不含有H_2O形式的水;它更接近二八面体型结构。锂绿泥石灼烧到453℃时,OH根全部脱失,结构向非晶态转化,到800℃后,转变成莫来石、非晶态SiO_2和LiO_2。     

海拉尔盆地煤及其显微组分的红外漫反射光谱特征

利用红外漫反射光谱和谱带分离技术,从海拉尔盆地煤及其显微组分的红外漫反射光谱图中,在３１００－２８００ｃｍ＾－１范围内分辨出１２或１３个峰,并确认了结构归属,同时建立了５个反映有机质化学结构组成特征的参数,讨论了煤与显微镜组分的生烃潜能。     

云南金顶异极矿晶体化学特征与颜色成因探讨

为研究云南金顶铅锌矿床中异极矿谱学特征和颜色成因,利用湿法化学全分析、振动光谱仪、X光粉晶衍射仪和电子探针对5组异极矿样品谱学特征和化学成份进行研究。湿法化学全分析得出了异极矿的化学成份,成份中出现了可能致色的铜、铁和镍元素;X光粉晶衍射和振动光谱分析得出异极矿晶胞参数和特征谱线表明样品蓝色和白色环带均为异极矿,5组样品的平均晶胞参数为：a=0．8372nm,b=1．0702nm,c=0．5116nm;红外光谱测试中获得了未见报道的452cm。以下异极矿晶体结构吸收峰,同时分析了异极矿中的结构水、结晶水吸收谱带;对红外光谱和拉曼光谱中的各吸收谱带和特征峰进行了归属。通过电子探针、红外光谱、拉曼光谱测试和分析认为异极矿的蓝色与Cu^2＋的类质同像替代有关,白色异极矿不含铜元素,白色和蓝色异极矿结构相似,异极矿玻璃光泽和土状光泽与其含有较多的结晶水有关。     

云龙锡矿锡石的振动光谱和电子顺磁共振谱研究

本文用振动光谱和电子顺磁共振谱研究了云龙锡矿锡石的谱学特征。根据红外光谱的谱形、吸收频率和吸收峰强度特征,将云龙锡矿锡石的红外光谱划分成两种类型:A型谱和B型谱。红外光谱特征的研究结合宏观地质特征的研究表明:氧化物阶段锡石的红外光谱为A型谱,硫化物阶段锡石的红外光谱为B型谱。随着锡石成分和结构的变化,锡石的拉曼光谱的谱型、振动频率也发生变化,反映了锡石的成矿条件的差异。云龙锡矿锡石的EPR谱研究表明,云龙锡石中含有呈类质同象进入锡石晶格的V~(4+),根据V~(4+)的稳定场研究,云龙锡石主要形成于相对碱性和偏还原的条件下。     

傅里叶变换红外光谱鉴定粘土矿物复合组分的研究

应用傅里叶变换红外光谱可以达到最大信噪比的特性,有效地获得了粘土矿物复合体中的单体差示红外谱图。避免了X衍射光谱中的矿物间衍射线的覆盖和色散型红外光谱中谱带重叠等不利因素,为粘土矿物复合体的鉴定提供了新的途径。研究表明,对痕量和近似的矿物组分都可以得到谱峰不受任何影响的纯正的红外谱图。差示定量结果也十分满意。     

一种翡翠的仿制品透辉石微晶玻璃的宝石学特征

针对市场上出现的一种外观酷似翡翠的透辉石微晶玻璃,利用常规宝石学检测仪器、X射线粉末衍射和红外光谱等测试方法,对该材料样品的宝石学特征、物相组成及谱学特征进行了初步研究。结果显示,在宝石显微镜下透辉石微晶玻璃显示特征的放射状晶花,具球晶结构;X射线粉末衍射分析表明,其主要物相为透辉石和玻璃质;红外光谱分析显示,该样品的谱学特征与翡翠的红外光谱有较大的差异。     

Multistage Svecofennian metamorphism: Evidence from the composition and U-Pb age of titanite from eclogites of the Belomorian Mobile Belt

The first geochemical study of titanite from eclogites and associated rocks of the Belomorian Mobile Belt (BMB) by secondary ion mass spectrometry made it possible to establish the compositional features of this mineral in the garnet-bearing and garnet-free assemblages. Titanite from garnet-bearing assemblages is characterized by upward convex REE pattern and lowered HREE content relative to LREE, as well as the average Gd_N/Yb_N ratio around 16.5. Titanite from metaultrabasic rock inherits the specific features of the host rock, which should be taken into account when comparing with titanite from metagabbro. Results of U-Pb (TIMS) dating of titanite confirms the identification of the early and late stages of the Svecofennian metamorphism in the studied areas of BMB: early metamorphism with the peak eclogite facies conditions at around 1900 Ma, retrograde amphibolite facies metamorphism at 1870–1880 Ma, and late allochemical metamorphism accompanied by the pegmatite formation with an age of 1840 Ma.     

U-Pb dating and trace element of titanite and garnet as indicators of the age and ore-forming condition of skarn W deposit: A case study of the Xiaoyao W polymetallic deposit in southern Anhui,China.SCIEI北大核心CSCD

逍遥矿床是安徽南部新发现的大型钨多金属矿床,其精细的岩浆-热液时限及成矿作用仍不明确。本文对其开展了石榴子石和榍石的U-Pb年代学和微量元素分析,发现逍遥矿床发育多阶段榍石(岩浆榍石和热液榍石),岩浆榍石与石英、磁铁矿、长石共生,而热液榍石与石英、方解石、辉钼矿、黄铜矿关系密切。逍遥矿床中石榴子石和榍石中均具有一定的U含量,其中石榴子石中U含量较低(平均为15.9×10^(-6)),岩浆榍石和热液榍石的U含量较高(平均值大于100×10^(-6))。石榴子石和榍石U-Pb同位素定年结果显示成岩和W多金属矿化均形成于150Ma左右,指示W多金属矿化与花岗闪长岩密切相关。岩浆榍石、钾长石、石英、磁铁矿矿物组合指示逍遥成矿岩浆具有氧化性强和富水的特征。逍遥钨矿中的石榴子石以钙铁榴石为主且富集W、Sn特征,指示早期流体为氧化性流体。此外,热液榍石中HFSE元素的高度富集表明其成矿流体为富碱、富F的热液系统,为钨、铅、锌、铜、银、钼多金属的富集提供了有利热液条件。综上所述,石榴子石和榍石能够有效指示矽卡岩W矿的成矿时代和成岩成矿条件。     

榍石：U－Pb定年及变质P－T－t轨迹的建立

榍石在各类岩石中普遍存在，其稳定性受全岩成分、氧逸度和水活度以及温度和压力等因素影响。它在岩浆岩中主要存在于高Ca/Al比值的岩石中，在变质岩中常见于绿片岩相、蓝片岩相和角闪岩相岩石，在钙质变质岩中其稳定范围可达榴辉岩相或高压麻粒岩相。一般榍石结构中U含量较高，且具有高达高角闪岩相上限的U Pb同位素体系封闭温度，是理想的U-Pb定年矿物。由于榍石的组成元素均为岩石中的主要元素，很容易与其它矿物、熔体及流体发生反应，所以榍石的U-Pb年龄记录的更可能是结晶年龄，而不是简单的扩散重置年龄；也因为它容易反应，变质榍石复杂的U Pb体系可能记录了岩石的整个变质历史信息。通过与榍石平衡共生的矿物组合或利用榍石Zr温压计可确定岩石的P T条件，结合相关的榍石年龄信息即可建立变质过程的P T t轨迹。利用SHRIMP、LA MC ICP MS以及LA ICP MS方法可对不均一榍石颗粒内部进行原位微区分析得到有意义的U Pb年龄；利用榍石中Zr含量对温度，尤其是对压力比较敏感，可建立榍石Zr含量温压计。     

Geochemical and Sm–Nd isotopic study of titanite from granitoid rocks of the eastern Dharwar craton,southern India

Titanite occurs as an accessory phase in a variety of igneous rocks, and is known to concentrate geologically important elements such as U, Th, rare earth element (REE), Y and Nb. The differences in the abundances of the REEs contained in titanite from granitoid rocks could reflect its response to changes in petrogenetic variables such as temperature of crystallization, pressure, composition, etc. Widespread migmatization in the granodiorite gneisses occurring to the east of Kolar and Ramagiri schist belts of the eastern Dharwar craton resulted in the enrichment of the REEs in titanite relative to their respective host rocks. A compositional influence on the partitioning of REEs between titanite and the host rock/magma is also noticed. The relative enrichment of REEs in titanite from quartz monzodiorite is lower than that found in the granodioritic gneiss. Depletion of REE and HFSE (high field-strength elements) abundances in granitic magmas that have equilibrated with titanite during fractional crystallization or partial melting has been modelled. As little as 1% of titanite present in residual phases during partial melting or in residual melts during fractional crystallization can significantly lower the abundances of trace elements such as Nb, Y, Zr and REE which implies the significance of this accessory mineral as a controlling factor in trace element distribution in granitoid rocks. Sm–Nd isotope studies on titanite, hornblende and whole rock yield isochron ages comparable to the precise U–Pb titanite ages, invoking the usefulness of Sm–Nd isochron ages involving minerals like titanite.     

In situ LA-(MC)-ICP-MS trace element and Nd isotopic compositions and genesis of polygenetic titanite from the Baogutu reduced porphyry Cu deposit,Western Junggar,NW China

Titanite (sphene, CaTiSiO₅) is sensitive to changes in temperature, oxygen and water fugacity, and fluid composition. In order to understand formation processes and the nature of hydrothermal fluids, various types of titanite from Cu ores at the Baogutu reduced porphyry Cu deposit were chosen for detailed study. Magmatic titanite is associated with biotite, plagioclase and K-feldspar, whereas hydrothermal titanite occurs with K-feldspar, chlorite, actinolite and calcite. The formation of hydrothermal titanite was related to hydration of igneous minerals under high fH₂O, whereas the widespread replacement of ilmenite by titanite (without magnetite) indicates a relatively low oxygen fugacity. Magmatic titanite has low Al, high Fe, Y, Sn, Zr, Nb and REE contents, relative to hydrothermal titanite. On the basis of the Zr-in-titanite and Al-in-chlorite geothermometers, formation temperatures for magmatic and hydrothermal titanite are estimated to be 687–739 °C and 250–670 °C, respectively. The gradual decrease in REE, Y and Sn contents from magmatic to late hydrothermal titanite was probably caused by precipitation of REE-bearing minerals. Magmatic and hydrothermal titanites have similar chondrite-normalized REE patterns with negative Eu anomalies and relatively flat HREE. Randomly selected titanites have Nd isotopic compositions similar to the host rocks. Thus, both magmatic and hydrothermal titanite are believed to have been predominantly derived from a mantle source.     

变基性岩部分熔融过程中榍石的微量元素效应:以南迦巴瓦混合岩为例

南迦巴瓦地区广泛出露的中下地壳变基性岩部分熔融形成的层状混合岩和淡色花岗岩,为研究部分熔融过程中榍石的地球化学行为对熔体的微量元素组成的影响提供了良好的机会。相对于源岩或熔融残留体,淡色体亏损Ti、V、REE、Y、Nb、Ta、U等元素,与混合岩中榍石的微量元素特征互补。混合岩、淡色体和榍石微量元素特征表明南迦巴瓦角闪岩部分熔融形成的淡色体的微量元素特征主要受控于榍石的地球化学行为。角闪岩脱水部分熔融过程中,由于长英质熔体的低Ti溶解度,榍石以未熔残留体形式存在于暗色体中,导致熔体亏损Ti、REE、Nb、Ta、V、U等元素和Sr/Y比值相对升高。关键元素在榍石和熔体之间的配分系数受熔体成分影响明显。角闪岩中变质榍石D_Nb/Ta<1,因此变质榍石残留导致熔体Nb/Ta相对于源岩升高;而高Si-Al花岗质熔体中榍石D_Nb/Ta>1,因此与高Si-Al熔体平衡的榍石的分离（转熔或结晶分异）将导致熔体Nb/Ta比值相对源岩降低。榍石在部分熔融过程中的微量元素效应为理解变基性岩部分熔融产生熔体的地球化学特征提供新的认识。     

安徽官山两种坡缕石粘土的成分与红外吸收谱

本文采用多种成分分析手段对官山两种不同颜色坡缕石全粘土进行了研究。全粘土湿化学分析扣除SiO2含量计算得到的坡缕石阳离子数与电子探针获得的阳离子数一致。配位八面体阳离子计算表明，粉红色坡缕石为三八面体矿物，灰白色坡缕石是介于三八面体矿物和二八面体矿物间的中间类型。X射线粉末衍射的K值法对全粘土矿物定量分析有着较高的精度，同时用电子探针波谱可准确测定坡缕石粘土的成分。官山两种不同颜色含坡缕石的全粘土红外吸收谱能反映其中坡缕石的吸收谱特征。对X射线光电子能谱研究表明两种不同颜色的坡缕石中的铁主要是Fe^3 ，这与全岩湿化学分析的结果是一致的，同时也还可以作为电子探针成分分析的补充。     

Titanite dates crystallization: Slow Pb diffusion during super‐solidus re‐equilibration

Titanite can be found in rocks of wide compositional range, is reactive, growing or regrowing during metamorphic and hydrothermal events, and is generally amenable to U–Pb geochronology. Experimental evidence suggest that titanite has a closure temperature for Pb ranging from 550 to 650°C, and thus titanite dates are commonly interpreted as cooling ages. However, this view has been challenged in recent years by evidence from natural titanite which suggests the closure temperature may be significantly higher (up to 800°C). Here, we investigate titanite in an enclave of migmatitic gneiss included within a granite intrusion. The titanite crystals exhibit textural features characteristic of fluid‐mediated mass transfer processes on length scales of <100 µm. These textural features are associated with variation in both Pb concentrations and distinct U–Pb isotopic compositions. Zr‐in‐titanite thermometry indicates that modification of the titanite occurred at temperatures in excess of 840°C, in the presence of a high‐T silicate melt. The Pb concentration gradients preserved in these titanite crystals are used to determine the diffusivity of Pb in titanite under high‐T conditions. We estimate diffusivities ranging from 2 × 10^?22 to 5 × 10^?25 m²/s. These results are significantly lower than experimental data predict yet are consistent with other empirical data on natural titanites, suggesting that Pb diffusivity is similar to that of Sr. Thus our data challenge the wide‐held assumption that U–Pb titanite dates only reflect cooling ages.     

Small-scale transport of trace elements Nb and Cr during growth of titanite: an experimental study at 600?°C, 0.4 GPa

Trace element distribution in titanite overgrowths on rutile has been investigated experimentally at 600?°C, 400?MPa and f_O2 near NiNiO buffer. Compositionally homogenous Cr- or Nb-doped synthetic rutile single crystals or Nb-containing natural rutile crystals were the source of Cr, Nb and Ti to synthesize titanite using the double-capsule technique. All element exchange with the source of Si, Ca and Al occurred via a NaCl–H₂O fluid. Titanite forms quickly and exclusively around the rutile crystals. The titanite overgrowth separates rutile from the bulk fluid, and all elements from rutile dissolution have to pass through the titanite rim. Trace element concentrations in titanite show a considerable scatter in experiments with and without Al, although the average concentrations of Cr or Nb of titanite around compositionally homogeneous synthetic rutile approach the expected values for closed system conditions. Variability of Al with Cr or Nb in the titanite is not correlated. The Al zoning is irregular and patchy, and also the distribution of trace elements does not show systematic trends in the spatial distribution. In experiments using zoned natural rutile, the concentrations of Nb in titanite are related to the Nb zoning in rutile, but the contents also vary unsystematically. Under the controlled conditions of the experiment, the explanation for the strongly irregular spatial distribution is most likely due to variations in elemental concentrations during transport from the rutile along the titanite grain boundaries. The transport pathway is complex because grain boundary migration is important during titanite growth. Such irregular element distribution is also found in a natural sample of titanite overgrowth on rutile from an eclogite with retrograde overprint in the amphibolite facies. Transport of Ti and trace elements was focused on grain boundaries and shielded from the rutile as a source of these elements. We conclude that this type of zoning is not related to changes in P–T or composition in an open system, but solely controlled by transport in and through the titanite rim.     

湖南杏枫山钨矿床热液榍石的地球化学特征、U-Pb定年及其地质意义

杏枫山钨矿床是湘中地区近年新发现的、产出于浅变质岩系中的矽卡岩型钨矿。本文通过电子探针与LA-ICP-MS等技术手段,对杏枫山矿区矽卡岩中的热液榍石进行了主、微量元素组成以及U-Pb年代学研究。研究表明,榍石具有以下特征:(1)较低的∑REE、Ti O2含量,极低的Th/U,以及较高的Al_2O_3和F含量,这些均为典型热液榍石的地球化学特征;(2)富W而亏损Mo,表明其形成的热液流体具有富W贫Mo的特征;(3)稀土配分模式为左倾的、轻稀土显著亏损的重稀土富集型,正Ce、Eu异常表明其形成环境较为还原。此外,榍石原位U-Pb定年结果显示该矿形成于215.2±2.7Ma,与邻近白马山钛铁矿花岗岩形成的时间一致,基于地质及年代学证据,我们认为该矿的形成与白马山印支期的岩浆热液活动有关。结合前人的研究结果,我们发现湘中地区钨成矿与印支期还原性花岗质岩浆岩密切相关,为湘中印支晚期区域性成矿作用的产物。