Caractérisation par résonance paramagnétique électronique (RPE) de quartz naturels issus de différentes sources

Natural quartz crystals coming from Madagascar, Angola, Brazil, and Spain were studied by EPR after β irradiation in order to characterise the paramagnetic centres due to impurities, and examine in which way their relative proportion could constitute a useful criterion for origin researches. In all our samples, EPR experiments revealed germanium centres [GeO₄/M⁺]° with M = Li or Na, aluminium ones [AlO₄/h]° and two titanium centres ([TiO₄/H⁺]° and [TiO₄/M⁺]°) also appeared, except for samples coming from Spain. The comparison of the relative concentrations of paramagnetic species led us on to draw diagrams that allowed distinguishing the origins of the studied samples using only EPR spectra. To cite this article: M. Duttine et al., C. R. Geoscience 334 (2002) 949–955.     

褶皱过程中含金石英脉形成的构造机制——以广西龙水金矿石英脉的成因研究为例

本文以广西龙水水政顶倾竖褶皱构造变形分析为基础,根据含金石英脉与非含金石英脉的变形差异,认为作用于岩层上的主剪切应力(σ_s)与主压缩应力(σ_p)随时间(t)的变化是导致岩层褶皱过程中石英脉多样性变形的主因;阐述了上述模型的动态应力场及其动力学过程;提出了构造变形的分解作用、水力压裂作用与裂开-愈合作用是石英脉形成的新构造机制。     

粉石英在微孔硅酸钙保温材料中的应用研究

本文介绍了一种新的优质硅质原料－－粉石英，着重探讨了它的矿物组成、粒度分布、物化性质及其合成硅酸钙的试验。试验结果表明，粉石英与石在高温、高压和搅拌的条件下，可以合成硅硅钙石型优质微孔硅酸钙制品。为微孔硅酸钙行业开发了一种新的质优、价廉的硅质原料。     

北亚热带江淮地区白浆化土壤的发生学特性

通过孢子花粉、石英砂颗粒和土壤微形态学分析,研究北亚热带江淮地区白浆化土壤的发生学特性。白浆化土壤下部土体经历了暖温带森林草原景观和亚热带草原景观,为高能化学环境。在母质沉积后,经历了褐土化过程或其他物质堆积,经过一定时期的沉积间断后,堆积新物质,随着气候的变化,成土环境演变为现代气候类型,属亚热带森林草原环境。淀积层也源于黄土状物质,风化程度更强,白浆层则为后期堆积物,不具备高能化学环境。淀积层在高能环境下,存在次生粘化和淀积粘化作用。     

Raman spectroscopy of natural silica in Chicxulub impactite,MexicoSpectroscopie Raman de silices naturelles dans l'impactite de Chicxulub,Mexique

A series of natural silica impactite samples from Chicxulub (Mexico) was investigated by Raman microprobe (RMP) analysis. The data yield evidence for high-pressure shock metamorphism in the rock. The impactite contains three polymorphs of silica: the original α-quartz, and two high-pressure varieties – coesite and disordered quartz representing various degrees of crystallinity. We found systematic changes in frequencies and half-widths of the Raman bands, caused by increasing irregularities of bond-lengths and bond-angles and a general breaking-up of the structure as a result of impact events. Therefore, RMP is an adequate tool for measuring the crystallinity of disordered quartz. The half-width Γ and the frequency ω of the symmetric SiOSi stretching vibrational band (A₁ mode) of the SiO₄ tetrahedra are the most amenable parameters for estimating the degree of crystallinity. In well-crystallized quartz, Γ=5 cm^?1 and ω=464 cm^?1, while in highly disordered quartz this line shifts up to ω=455 cm^?1 and broadens up to Γ=30 cm^?1. The Raman lineshapes appear to depend strongly on the degree of lattice disorder subsequent to impact events. To cite this article: M. Ostroumov et al., C. R. Geoscience 334 (2002) 21–26     

受冲击石英砂岩碎屑分析

利用二级轻气炮将６ｍｍ直径的钢球加速到５～７ｋｍ／ｓ后撞击石英砂岩靶，利用磁性分选，扫描电镜和Ｘ射线衍射等方法对嵌靶受击后形成碎屑进行了矿物分类和鉴别，碎屑主要由石英，高硅玻璃，微量柯石英以及铁碎屑，微细钢球等组成，７０％的碎屑分布在０．０９７～０．９０ｍｍ范围内，无一弱磁性碎屑约占总重量的９２％，其它为强磁性碎屑。     

The Thermal History of the Huangmeijian Granite Intrusion in Anhui and Its Relation to Mineralization: Isotopic Evidence

Whole-rock Rb-Sr, zircon U-Pb and hornblende, biotite and K-feldspar K-Ar ages areused to reconstruct the cooling history of the Huangmeijian intrusion in the Anqing-Lujiangquartz-syenite belt in Anhui. Oxygen isotope geothermometry of mineral pairs demonstrates thatdiffusion is a dominant factor controlling the closure of isotopic systems. Assuming the coolingof the intrusion is synchronous with a dicrease in local geothermal gradients, an emplacementdepth of about 8 km and the magma crystallization temperature of 800±50℃ are estimated. TheHuangmeijian intrusion experienced a rapid cooling process and uplifted after its emplacementand crystallization at 133 Ma B.P. with a cooling rate of 34.5℃/Ma and an uplifting rate of 0.35mm/a. The intrusion was rising until it rested at a depth of 3km at a temperature of 300±50℃about 14 Ma later. Then the intrusion was in slow cooling and uplifting with a cooling rate of4.4℃/Ma and an uplifting rate of 0.04 mm/a. U-Pb dating of pitchblende is done for the hydrothermal uranium deposit formed in thecontact zone of the Huangmeijian intrusion. The result shows that the mineralization age is closeto the closing time of the K-Ar system in biotite. The fluid inclusion thermometry indicates thatthe mineralization temperature is in agreement with the closure temperature of the biotite K-Arsystem. This suggests a close relationship between the slow cooling of the intrusion and thehydrothermal uranium mineralization process.     

金矿石英脉K-Ar年龄测定

本文从不同地质时代含金石英脉中选取石英进行了K-Ar年龄实验研究，认为石英是含微量钾的矿物。Ar的析出曲线呈“马鞍型”，显示含过剩40Ar。几个石英K-Ar年龄实测结果均含过剩40Ar，其表面年龄无地质年代学意义。     

珠江口SX97孔7000aB.P.以来石英矿物含量反映的气候变化

珠江口北岸SX97孔的石英矿物含量变化与该孔孢粉数据及华南沿海其它地质地貌资料所揭示的古气候古环境演化能很好对应。古气候古环境通过控制物源区的植被发育、风化强度和侵蚀能力及河口沉积区的进退，对河口沉积物中石英矿物含量有很好的调控作用。在华南沿海地区，河口沉积物中的石英矿物含量可能是指示气候环境演化的一个方便和实用的指标。     

南极无冰区古海蚀龛石英颗粒表面结构特征及其环境意义

石英砂表面结构特征组合能指示沉积物的搬运历史和沉积环境。利用电镜扫描方法分析了南极法尔兹半岛上海蚀成因的古海蚀龛沉积物中的石英砂表面结构特征组合。结果表明，在所有的石英砂表面上均表现出冰川和水流共同作用的结构特征组合，龛中沉积物是冰水沉积环境下的产物，在沉积过程中，沉积物先经过较薄的冰川搬运，后经历了不同能量的流水改造作用，但冰川和流水的搬运距离有限。上述研究结果表明，南极法尔兹半岛上的冰盖解体并退出长城站区的时间应早于4600aBP。