X-ray diffraction investigation of native Si-Fe alloy minerals from Luobusha, Tibet

The origin of native Si-Fe alloy mineral is thought to be related with mantle and aerolite. The native Si-Fe alloy minerals from podiform chromites of the Luobusha ophiolite in the Yarlong Zangbo suture zone were examined by a new method for powder-like diffractograms of small single crystals, using an SMART APEX-CCD area-detector X-ray diffractometer. The powder diffraction pattern shows that the minerals are composed of FeSi, FeSi₂, β-FeSi₂ and native silicon. The association of these minerals suggests that the crystallization order of the mineral may be from early to late FeSi→FeSi₂→native silicon, accompanied by gradually increasing deoxidization. Translated from Acta Petrologica et Mineralogica, 2005, 24(5): 453–456 [译自: 岩石矿物学杂志]     

应用矿物磁测技术和X射线衍射研究氧化土中的磁性矿物

应用矿物磁测、Ｘ射线衍射和化学分析对氧化土的磁性矿物进行了研究。结果表明矿物磁测及磁分离技术与Ｘ射线衍射结合是鉴别土壤中磁性矿物的类型及其晶粒特征的有效方法,证明氧化土中的主要氧化铁矿物是赤铁矿和磁赤铁矿,针铁矿次之,磁铁矿偶见,其磁赤铁矿的含量可达１．６２％￣１．９２％。土壤中磁性矿物的晶粒特征多以超顺磁性和稳定单畴态存在,认为磁性矿物的成因是通过缓慢的成土化学作用产生的。     

热液矿床中不透明矿物的流体包裹体研究进展

脉石矿物中流体包裹体所提供的有关流体与成矿的物理化学条件不一定代表成矿时的实际流体和成矿条件,最好的办法是直接测定矿石矿物捕获的包裹体。红外显微镜的运用开拓了不透明矿物中流体包裹体研究的新领域。文章对红外显微镜工作的基本原理及设备做了简要的综述,重点介绍了不透明矿物中流体包裹体岩相学、显微测温以及成分分析研究,并举例说明了不透明矿物流体包裹体在W-Sn矿床以及其他矿床研究中的应用,最后指出了不透明矿物中流体包裹体研究尚且存在的问题、部分解决方法,并简单展望了其在中国的发展前景。     

Interactions between organic matter and minerals in two bituminous coals of different rank

The association between specific mineral and organic constituents in two Asturian bituminous coals of different rank was studied. For this, raw coals were fractionated by density and the variation of a number of parameters was followed in parallel. Results of coal chemical analyses, including analyses for 22 elements, were used to establish the elemental association with coal organic matter. Petrographic analyses determined the distribution of macerals among densimetric fractions, vitrinite reflectance being at a minimum in the intermediate density fractions. Mineral species were identified by X-ray diffraction, FT-IR spectroscopy and Mössbauer spectroscopy. Comparison of trends for different parameters determined using this set of techniques allowed classification of the various minerals according to their association with organic matter. Carbonates seem to be specifically associated with the organic matter of the low-volatile bituminous coal whereas sulfides concentrate in the organic matter of the high-volatile bituminous coal. Vitrinite is the maceral exhibiting the most probable association with inorganic matter. The possibility of a merely physical association of fine-grained detrital minerals with organic matter cannot be excluded; nevertheless, one must bear in mind that even this type of interaction is important due to its effect on various coal preparation and utilization processes.     

名义上无水矿物中"水"的原位变温红外光谱研究

名义上无水矿物(nominally anhydrous minerals, 简称NAMs, 如橄榄石、辉石、石榴石、长石等)中以缺陷形式存在的结构水的重要性已经被地球科学界广泛认同,并得到了越来越多的关注。由于对OH振动的高度敏感性,红外光谱方法被广泛用来测量NAMs中"水"的赋存状态、含量以及在晶体结构中的位置。随着傅立叶变换红外光谱仪的不断发展及分析技术的提高,以及红外附件的更新换代,出现了一些新的分析方法。原位变温红外光谱实验就是利用变温红外附件测量样品在不同温度下的红外光谱,通过研究不同温度下红外光谱图的峰形、峰位、峰数等参数的变化,了解温度改变过程中样品所发生的物理、化学变化,且具有实时监测的优点,因此广泛用于含水矿物和玻璃中OH和H₂O的研究。主要包括含水矿物和玻璃的脱水机理及脱水动力学研究,OH和H₂O的红外吸收系数的温度依赖性及不同温度下红外吸收系数的校正等方面。虽然原位变温红外光谱广泛应用于含水矿物和玻璃中水的研究,但是应用于名义上无水矿物还是刚刚起步。NAMs中的H是活动的,高温下H的赋存状态及其在晶体中的位置可能会不同于室温,而地质过程往往都在高温下进行,研究高温下NAMs中的水具有重要的地质学意义。因此,有必要利用原位变温红外光谱实时监测不同温度下NAMs中水的变化。有关NAMs中水的原位变温红外光谱实验早期工作只是观察不同温度下谱图参数的变化并给予一定的解释,以及用此法来确定NAMs中水的赋存状态。受含水矿物和玻璃的研究结果的启发,原位变温红外光谱实验目前也开始用来研究NAMs中水的脱水机理和扩散动力学。此外,利用原位变温红外光谱技术,通过研究不同温度下OH的积分吸收面积可探索NAMs中OH红外吸收系数温度依赖性;通过研究OH峰位随温度移动的幅度与某些化学成分的关系,可给出NAMs中OH的结合机理方面的有用信息。虽然近些年来已经开展了一些工作,取得了一些新的成果,但是总的说来还处在起步阶段,今后针对NAMs的研究重点应该集中在以下三个方面:(1)吸收系数温度依赖性的定量化,(2)脱水机理和动力学的扩展,(3) OH结合机理研究的深入。     

滑带土粘土矿物定向性的x射线衍射及其对滑坡的作用

本文首先论述了粘土矿物颗粒定向排列测定的基本原理并提出粘土矿物定向性定量评价方法,然后根据实例—庙上北滑坡的滑带土粘土矿物的X射线衍射结果,进行定向性定量分析计算,得出滑带土粘土矿物颗粒的定向度为弱到中等定向,并以中等定向为主。因而在水的往返作用下,滑带土具一定的胀缩性及胀缩的不均匀性,再加上粘土矿物本身亦具有的胀缩性及胀缩的可逆性和循环性,故导致滑带土抗剪强度和结构强度不断降低,大大影响斜坡的稳定性。     

In situ time resolved synchrotron powder diffraction study of thaumasite

Structural changes during dehydration and subsequent decomposition in thaumasite Ca₃Si(SO₄)(CO₃)(OH)₆·12 H₂O were studied by in situ synchrotron powder diffraction between 303 and 1,098 K. Evolution of the crystal structure was observed through 28 structure refinements, by full profile Rietveld analysis performed in the P6₃ space group, between 300 and 417 K, whereupon the thaumasite structure was observed to breakdown. Within this temperature range, the cell parameters of thaumasite increased as a function of temperature in a nearly linear fashion up to about 393 K, at which temperature, a slight slope change was observed. Above 400 K, the thermogravimetric analysis revealed that the dehydration process proceeded very rapidly while the refined occupancy of water molecules dropped below a critical level, leading to instability in the thaumasite structure. At a same time, a remarkable change in the unit cell parameters occurring at about 417 K indicated that the crystal structure of thaumasite collapsed on losing the crystallization water and it turned amorphous. This result indicated that the dehydration/decomposition of thaumasite was induced by the departure of the crystallization water. At about 950 K, anhydrite and cristobalite crystallized from the thaumasite glass.     

天然硫化物矿物对地球深部热能的热电转化效应研究

金属硫化物半导体矿物在地壳中分布广泛,其中一些禁带宽度较窄的硫化物矿物,如黄铁矿、黄铜矿和斑铜矿等,在地热梯度下产生的天然热电势可将地球内部热能转化为电能。本文选取黄铁矿、磁黄铁矿、方铅矿、黄铜矿、斑铜矿以及斑铜矿-赤铁矿-辉铜矿集合体等天然硫化物矿物样品,研究了其热电特性。研究结果表明,300～700K下,除磁黄铁矿具有低塞贝克系数和超高电导率而表现出金属导体的电输运行为外,黄铁矿和黄铜矿为n型半导体,斑铜矿和斑铜矿-赤铁矿-辉铜矿集合体为p型半导体,具有150～500μV/K的显著塞贝克系数和5～95 S/cm的电导率,说明样品在地热梯度下具有产生显著热电效应的能力。根据激光闪射法测得的热扩散率以及样品的理论比热、密度计算热导率,斑铜矿及硫化物矿物集合体样品表现出小于1 W/(m·K)的低热导率,说明样品在局部热源影响下可形成较大温差。根据热电基本理论和地热梯度构建天然热电效应模型,对硫化物半导体矿物集合体产生的天然热电势、额外地表电流密度及热电转换效率进行了模拟计算得出经验公式,发现硫化物半导体矿物在300～650 K条件下能产生100 m V左右的天然热电势,产生的最大热电转化率可达4‰,且可以通过偶极电流源模型计算矿物体产生的额外地表电流密度。研究认为硫化物半导体矿物可能作为天然热电转换介质深刻影响地球内部能量的转化与传递过程。     

In situ X-ray diffraction study of an aluminous phase in MORB under lower mantle conditions

In situ X-ray diffraction study was conducted to identify the crystal structure of the “Al-phase”, which was previously reported to form in basaltic compositions at pressures and temperatures of the uppermost part of the lower mantle. Le Bail whole-pattern fitting method was adopted to investigate the structure of the Al-phase under high pressure and temperature as well as ambient conditions. Observed patterns were satisfactorily fitted using the “hexagonal phase” with space group P6₃/m (plus minor amount of garnet) under both of these conditions. On the other hand, the calcium ferrite structure model proposed in some earlier studies based on quench experiments yielded profile-fitting results at significantly lower confidence levels, particularly at simultaneous high pressure and high temperature conditions, suggesting that this phase may not form in oceanic crust materials subducted in the uppermost lower mantle. The difference in densities of hexagonal and calcium ferrite phases, however, is only ~1% under pressures and temperatures of the uppermost part of the lower mantle conditions, which yields a negligible effect on the bulk density of the subducted oceanic crust.     

天然矿物低温催化脂肪酸酯生烃反应动力学研究

选择十八烷酸甲酯为模型化合物,以 10种天然矿物为载体,通过动力学方法考察了天然矿物对脂肪酸酯生烃反应的催化作用.结果表明,地质低温条件下天然矿物对脂肪酸酯生烃反应具有催化作用.矿物的催化作用主要体现在对反应活化能和指前因子的影响上.粘土、碳酸盐和金属元素对于脂肪酸酯生烃反应具有不同的催化作用,碳酸盐矿物相对于粘土矿物使生烃反应的活化能降低,过渡金属化合物矿物存在时,催化反应活化能介于碳酸盐和粘土矿物之间.天然矿物的存在能够升高或降低反应指前因子.     

九种现代双壳类壳体物相组成的对比研究

利用X射线衍射分析技术,对黄东海常见的9种现代双壳类壳体进行了物相分析,结果表明这些双壳类壳体分别属于三种类型,即文石质壳、方解石质壳、文石+方解石混合质壳。其中,菲律宾蛤仔(Ruditapesphilippinarum)、中国蛤蜊(Mactrachinensis)、四角蛤蜊(Mactraveneriformis)、薄片镜蛤(Dosinialaminata)、毛蚶(Scapharcasubcrenata)属于文石质壳,长牡蛎(Crassostreagigas)、中国不等蛤(Anomiachinensis)、海湾扇贝(Argopectenirradieus)属于方解石质壳,紫贻贝(Mytilusedulis)属于文石+方解石质的混合质壳;双壳类壳体物相组成与其生活方式有着一定的联系,营底栖埋入式生活者趋于形成文石质壳,底栖固着生活方式者趋于形成方解石质壳或混合质壳;不同大小的菲律宾蛤仔(Ruditapesphilippinarum)的物相组成上几乎没有差别,表明其壳体物相组成不受生命效应的影响。     

Weathering effects on the strength and deformational behaviour of crystalline rocks under uniaxial compression state

Uniaxial compression tests were performed on different categories of weathering of three lithological units: Malanjkhand granite; Nagpur basalt; and Delhi quartzite, occurring in central and northern parts of India. The deformational behaviour is studied in terms of variation in tangent modulus (E_t50) and initial modulus (E_i) due to weathering. The power relationship between uniaxial compressive strength (σ_c) and E_t50 shows strong correspondence for weathering sequence of common rock types. This relationship has been established by regression analysis and significant correlation parameter (coefficient of determination, r²=0.87) for crystalline rocks. It is shown that there is a systematic decrease in stiffness ratio, that is, ratio of tangent modulus and uniaxial compressive strength with increased weathering state. Comparison of E_t50 and E_i values has shown that E_t50 decreases more gradually than E_i, and reduction is more drastic for E_i values with an increased degree of weathering in all the three rock types. The mode of failure has been found to be influenced by weathering extent in rocks. A brief account is given of the intrinsic characteristics of fresh and weathered rocks and mineralogical changes produced by weathering investigated quantitatively. Correlation drawn between the petrographical and mechanical indices has shown that mechanical properties are apparently dependent on the intrinsic characteristics of weathered rocks.     

藏南沙拉岗锑矿流体包裹体红外显微测温研究

沙拉岗锑矿是藏南金锑成矿带内最具有代表性的锑矿床。为了更直接地了解该矿床的流体物理化学特征,本文利用红外显微镜对辉锑矿及紧密共生石英中的流体包裹体进行了显微测温研究。红外显微测温分析结果表明,辉锑矿中包裹体均一温度在134.9～221.9℃,峰值在160～190℃之间,盐度在1.7%～7.3%NaCleqv,峰值在5.0%～6.0%NaCleqv之间,密度在0.879～0.958g/cm3之间,平均值为0.934g/cm3;共生石英中包裹体均一温度在142.5～205.6℃,峰值在160～190℃之间,盐度在2.3%～7.0%NaCleqv,峰值在4.0%～6.0%NaCleqv之间,密度在0.910～0.947g/cm3之间,平均值为0.929g/cm3。通过对比研究认为沙拉岗辉锑矿及共生石英形成于同一物理化学条件,捕获同一成矿流体。结合石英中单个流体包裹体激光拉曼成分分析认为成矿流体为含微量CO2、N2、CH4气体的低温、低盐度和低密度的NaCl-H2O热液体系。成矿流体的沸腾作用是辉锑矿大量沉淀主要原因。     

内蒙古乌兰拜其铅锌矿床成因探讨:流体包裹体及矿石矿物S-Pb同位素、微量元素证据

乌兰拜其铅锌矿床是近年来在大兴安岭中南段地区新发现的一处中型铅锌多金属矿床,目前已探明铅锌储量约27万吨,其中Ⅰ号矿段为主要的组成矿段。本文以乌兰拜其矿床Ⅰ号矿段作为研究对象,试图讨论乌兰拜其铅锌矿床成矿流体性质、成矿物质来源、成矿地质背景及成因类型。乌兰拜其矿床Ⅰ号矿段矿体主要呈似层状赋存于白音高老组地层中酸性火山碎屑岩中。根据矿物的组构和穿插关系,初步将I号矿段成矿作用划分为：毒砂-黄铁矿阶段、多金属硫化物阶段和绢云母-绿泥石阶段等三个主要成矿阶段。其中矿床中主成矿阶段的石英、闪锌矿中的流体包裹体可分为气液两相包裹体(Ⅰ型)和含子晶多相包裹体(Ⅱ型)两类。石英中气液两相包裹体的均一温度范围为125~481℃,盐度为2.74%~7.02% NaCleqv;闪锌矿中的流体包裹体均一温度范围为110~327℃,盐度为2.90%~7.02% NaCleqv。分析计算得出的包裹体形成时的成矿压力为8.27~37.43MPa,平均压力为21.26MPa;成矿深度为0.28~1.25km,平均深度为0.71km。这表明乌兰拜其铅锌矿床的成矿流体具有中低温、低密度、低盐度的特征,其形成于压力较低,深度较浅的环境下。矿床主成矿阶段的多金属硫化物具有较小的δ³⁴S值变化范围(-6.73‰~0.17‰,均值为-4.10‰),指示硫来源于深源岩浆。闪锌矿、黄铜矿Pb同位素(²⁰⁶Pb/²⁰⁴Pb为18.130~18.267,²⁰⁷Pb/²⁰⁴Pb为15.488~15.545,²⁰⁸Pb/²⁰⁴Pb为37.920~38.104)组成较为稳定。其μ值为9.27~9.28,ω值为33.46~34.02,暗示乌兰拜其矿床铅具有壳幔混合来源特征。乌兰拜其硫铅同位素组成与大兴安岭地区成矿物质为岩浆来源的金属矿床特征相似,与早白垩世火山岩浆活动关系密切,是深部岩浆热液逐步演化的产物。结合矿区与成矿关系密切的燕山晚期花岗岩,本次研究初步认为乌兰拜其铅锌多金属矿床是受燕山晚期中酸性火山岩-次火山岩和断裂控制的,与岩浆活动有关的中低温热液铅锌多金属矿床。

     

黄土高原马兰黄土粘土矿物的定量研究

本文在回顾和总结中国西北黄土粘土矿物研究进展的基础上,提供了采用现代X-射线衍射(XRD)定量测试技术(包括粘土矿物样品处理和全自动数据处理技术)对陕北晋西12个县市马兰黄土粘土矿物定量研究的最新结果。测试结果表明,马兰黄土的主要粘土矿物为伊利石／蒙脱石混层矿物(相对含量为60％～70％),而不是以往所认为的伊利石。伊利石在黄土中主要呈两种形式存在,即单矿物伊利石和伊／蒙混层矿物中的伊利石。研究还发现,各地马兰黄土粘土矿物组成变化不大,但在神木、河曲、偏关一带伊／蒙混层比有局部增高的现象。根据扫描电子显微镜观察,黄土中粘土矿物不是以单粒形式存在,而主要是以集粒粘附物的形式包裹在碎屑颗粒表面。黄土中粘土矿物组成及其存在形式一方面可以充分揭示黄土物源区的表生化学环境特征;另一方面,伊／蒙混层矿物作为一种广泛分布的膨胀性粘土矿物和它在黄土粘土矿物中所占地位,对于认识马兰黄土在水作用下的湿陷变形和强度衰减的本质具有重要意义。     

In situ X-ray observations of the decomposition of brucite and the graphite–diamond conversion in aqueous fluid at high pressure and temperature

 An experimental technique to make real-time observations at high pressure and temperature of the diamond-forming process in candidate material of mantle fluids as a catalyst has been established for the first time. In situ X-ray diffraction experiments using synchrotron radiation have been performed upon a mixture of brucite [Mg(OH)₂] and graphite as starting material. Brucite decomposes into periclase (MgO) and H₂O at 3.6 GPa and 1050 °C while no periclase is formed after the decomposition of brucite at 6.2 GPa and 1150 °C, indicating that the solubility of the MgO component in H₂O greatly increases with increasing pressure. The conversion of graphite to diamond in aqueous fluid has been observed at 7.7 GPa and 1835 °C. Time-dependent X-ray diffraction profiles for this transformation have been successfully obtained. Received: 17 July 2001 / Accepted: 18 February 2002     

西南喀斯特地区不同石漠化阶段土壤黏土矿物组成及其含量变异研究

为了探索西南喀斯特地区土壤中黏土矿物组成及其含量的变异规律,以贵州省普定县和荔波县不同石漠化阶段典型土壤的黏土矿物为例,采用x-射线衍射仪图谱分析方法,计算得到黏土矿物组成及其含量,探讨不同石漠化阶段黏土矿物组成变化规律及其含量之间的线性关系。结果表明：不同石漠化阶段黏土矿物的组成是相同的,均为高岭石、蒙脱石和伊利石;在未石漠化、轻度石漠化、中度石漠化阶段,蒙脱石在剖面表层的质量分数分别为27．82％、29．34％、58．32％,高岭石分别为21．39％、31．81％、36．93％,伊利石分别为50．79％、38．85％、4．75％;在西南喀斯特地区,各石漠化阶段伊利石与蒙脱石的含量之间以及伊利石和高岭石的含量之间都呈显著的线性相关,相关系数分别为-0．9703、-0．9456;西南喀斯特地区土壤相似的成土作用和成土环境造成了黏土矿物相同的组成,而黏土矿物含量的差异说明各成土作用的程度或阶段是不同的;粉粒中的黏土矿物主要为石英和白云母,而砂砾中的黏土矿物主要为石英。     

In situ study of the $$ R\overline{3} c \to R\overline{3} m $$ orientational disorder in calcite

The temperature dependences of the crystal structure and intensities of the (113) and (211) reflections in calcite, CaCO₃, were studied using Rietveld structure refinements based on synchrotron powder X-ray diffraction data. Calcite transforms from to at about T _c = 1,240 K. A CO₃ group occupies, statistically, two positions with equal frequency in the disordered phase, but with unequal frequency in the partially ordered phase. One position for the CO₃ group is rotated by 180° with respect to the other. The unequal occupancy of the two orientations in the partially ordered phase is obtained directly from the occupancy factor, x, for the O1 site and gives rise to the order parameter, S = 2x − 1. The a cell parameter shows a negative thermal expansion at low T, followed by a plateau region at higher T, then a steeper contraction towards T _c, where the CO₃ groups disorder in a rapid process. Using a modified Bragg–Williams model, fits were obtained for the order parameter S, and for the intensities of the (113) and (211) reflections. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

In situ X-ray observations of phase transitions in MgAl<Subscript>2</Subscript>O<Subscript>4</Subscript> spinel to 40 GPa using multianvil apparatus with sintered diamond anvils

 Phase transitions in MgAl₂O₄ spinel have been studied at pressures 22–38 GPa, and at temperatures up to 1600 °C, using a combination of synchrotron radiation and a multianvil apparatus with sintered diamond anvils. Spinel dissociated into a mixture of MgO plus Al₂O₃ at pressures to 25 GPa, while it transformed to the CaFe₂O₄ (calcium ferrite) structure at higher pressures via the metastably formed oxide mixture upon increasing temperature. Neither the e-phase nor the CaTi₂O₄-type MgAl₂O₄, which were reported in earlier studies using the diamond-anvil cell, were observed in the present pressure and temperature range. The zero-pressure bulk modulus of the calcium-ferrite-type MgAl₂O₄ was calculated as K=213 (3) GPa, which is significantly lower than that reported by Yutani et al. (1997), but is consistent with a more recent result by Funamori et al. (1998) and that estimated by an ab initio calculation by Catti (2001). Received: 2 April 2002 / Accepted: 29 July 2002 Acknowledgements The authors thank Y. Higo, Y. Sueda, T.␣Ueda, Y. Tanimoto, A. Fukuyama, K. Ochi, F. Kurio and T. Kawahara for help in the in situ X-ray observations at SPring-8 (No: 2000A0061-CD-np and 2000B0093-ND-np). We also thank W.␣Utsumi, J. Ando and O. Shimomura for advice and encouragement during this study, and N. Funamori and an anonymous reviwer for comments on the article. The present study is partly supported by the grant-in-aid for Scientific Research (A) of the Ministry of Education, Science, Sport and Culture of the Japanese government (no: 11694088).     

桂北向阳坪铀矿床矿石矿物LA-ICP-MS原位稀土元素地球化学特征及其对成矿流体的制约

向阳坪铀矿床是桂北苗儿山地区最具代表性的花岗岩型铀矿床,对该矿床矿石矿物REE开展了微区原位研究并结合前人研究成果进行了综合分析,表明铀黑∑REE介于689.12×10^-6～869.31×10^-6之间,LREE相对富集,HREE相对亏损具强Eu负异常及Ce正异常,TE_1,3值介于1.26～1.33之间,具典型M型四分组效应;沥青铀矿∑REE介于569.73×10^-6～3 373.83×10^-6之间表现出两种特征:①LREE富集,HREE亏损,轻重稀土元素分馏程度较大具强Eu负异常和弱Ce正异常,配分曲线呈右倾型;②轻重稀土元素分馏程度较小,Eu负异常明显弱Ce负异常,配分曲线呈海鸥型。围岩稀土元素配分模式相似,Y/Ho值范围狭窄,指示具有相同物源;矿石矿物稀土元素与围岩存在较大差异,亲缘性不明显。成矿作用伴随围岩发生蚀变及围岩高铀背景;成矿流体具多阶段、富U-Y-REE特征,铀主要来自深部热液,围岩贡献不显著;矿床定位受构造-岩体联合控制,矿体规模、形态受构造规模、产状控制。