Identification and valuation of paramagnetic radicals in natural dolomites as an indicator of geological events     

R. W. A. Franco  F. Pelegrini  A. M. Rossi 《Physics and Chemistry of Minerals》2003,30(1):39-43

 Geological sedimentary dolomite samples from the Superior Proterozoic are studied using electron paramagnetic resonance (EPR) spectroscopy. The complex spectra in the g=2.0 region is composed of Mn²⁺ lines and signals due to crystallization and radiation-induced defects. Measurements in microwave frequencies of 9.5 GHz (X-band) and 35 GHz (Q-band), and thermal and/or radiation treatments allowed identification of seven paramagnetic radicals in the g=2.0 region: (1) isotropic organic radical; (2) axial SO₂ ⁻; (3) axial PO₂ ⁰ or PO₂ ²⁻; (4) isotropic CO₂ ⁻; (5) axial CO₂ ⁻; (6) axial CO₃ ³⁻; (7) isotropic unknown line. The use of these paramagnetic centres as indicators of geological events is discussed. Received: 18 March 2002 / Accepted: 3 October 2002  相似文献   

含金黄铁矿中存在晶格金的佐证——以河北省灵寿县土岭—石湖金矿床为例     

高学军  李高山  许虹 《吉林大学学报(地球科学版)》1992,(3)

通过化学物相分析和EPR波谱分析两种方法,对土蛉—石湖金矿床中含金黄铁矿中的金赋存状态进行了研究.含金黄铁矿中存在着主要类型为Au~(+)的晶格金,它的EPR波谱分析的超精细结构谱线g因子=2.001士0.001.分析讨论了HNO_3溶解黄铁矿的氧化还原反应的复杂性以及黄铁矿中含金量与FS谱线强度之间的关系.  相似文献   

Growth history of hydrothermal chimneys at EPR 9―10°N: A structural and mineralogical study     

PENG Xiaotong  ZHOU Huaiyang 《中国科学D辑(英文版)》2005,48(11)

Based on structural and mineralogical characteristics of four hydrothermal chimney samples collected by submersible Alvin, growth history and formation environment of hydrothermal chimney at EPR 9―10°N are established. It is shown that there occur two types of hydrothermal chimney with different deposition environments at EPR 9―10°N according to differences in their shape, structure and mineral assemblage: type I chimney forms in an environment with high temperature, low pH and strong reducing hydrothermal focus flow and type II chimney forms in a relatively low temperature, high pH and rich Zn hydrothermal environment. Growth of type I chimney begins with the formation of anhydrite. Subsequently deposition of Cu-Fe-Zn sulphide in various directions of chimneys decides the final structure of this type of chimney. According to observation and analysis of mineral assemblages, the formation process of type I chimney could be divided into three stages from early, middle to late. Changes of temperature and major chemical reaction type in the process of hydrothermal chimney formation are also deduced. Different from type I chimney, quenching crystalline of pyrite and/or crystalline of sphalerite provide the growth foundation of type II chimney in the early stage of chimney formation.  相似文献   

云龙锡矿锡石的振动光谱和电子顺磁共振谱研究          下载免费PDF全文

邹正光 《岩石矿物学杂志》1988,7(3):252-258

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。  相似文献   

热处理低温钠长石的EPR和X射线衍射研究     

富毓德 《矿物学报》1989,9(4):296-303

利用电子顺磁共振(EPR)和X射线衍射方法研究了天然和热处理钠长石单晶。热处理在500—850℃水热条件下完成。在外加磁场B平行于晶体c~*轴的方向上,测量了加热前后Fe~(3+)的EPR谱和线宽△B随温度和加热时间的变化。结果显示,线宽随Al、Si无序的增大而增加。由此得出结论,在低温钠长石中,Fe~(3+)位于Al~(3+)占据的T_1(o)位置,在被研究的温度范围内,Fe~(3+)未参与四面体位置T间Al、Si交换。谱线的加宽主要是由在Fe~(3+)邻近位置上Al、Si无序的增大引起的,同时与观测到的晶胞参数变化有关。在Al、Si无序更强的晶体中,Fe~(3+)谱变得极宽。  相似文献   

9 and 34 GHz EPR study of the free radicals in various asphaltenes: Statistical correlation of the g-values with heteroatom content     

V.M. Malhotra  H.A. Buckmaster 《Organic Geochemistry》1985,8(4):235-239

The 9 and 34 GHz EPR spectra of eight asphaltenes from different locations have been studied at 294 K in an attempt to correlate the observed g-values with the heteroatom content. It is found that the EPR linewidths are larger and the g-values are smaller at 34 GHz than at 9 GHz. Quantitative statistical analysis of the g-values observed in those asphaltenes derived from tar sand bitumens and crude oils shows that they are uncorrelated with the heteroatom content, unlike those from coal. It is concluded that g-values may not be a good analytical tool for elucidating the structure of those asphaltenes not derived from coal.  相似文献   

河北张家口金矿床石英的电子顺磁共振谱（EPR）研究   总被引：1，自引：0，他引：1  

银剑钊  史红云 《矿物岩石》1994,14(1):11-17

本文对采自河北张家口金矿床中不同种类、不同金含量的石英在不同的温度条件（Ｔ＝３００Ｋ，常温；Ｔ＝７２Ｋ，低温、液氮）下进行电子顺磁共振谱（ＥＰＲ）研究表明：①石英中顺磁中心的浓度随温度变化而变化，即随温度的降低，石英中顺磁中心的浓度将增大；②不同温度条件下，石英ＥＰＲ谱国中吸收峰的差异仅体现在吸收强度上，形态上的差异不很明显；③石英中金含量与其ＥＰＲ谱图中吸收峰的强度之间存在着统计性的正相关关系；④石英中含有部分离子态的金──晶格金。  相似文献   

我国北方两种高岭石的电子顺磁共振研究   总被引：4，自引：2，他引：4  

何宏平  郭九皋 《矿物学报》1994,14(3):265-269

笔者对我国北方两种不同类型的高岭石进行了化学分析、差热和热重分析、X射线衍射、红外吸收光谱及电子顺磁共振等研究。结果表明，在酸性还原条件下形成的高岭石中，铁主要以Fe2＋的形式置换结构中的Al3＋，同时也有部分铁以亚铁化合物形式存在；在氧化条件下形成的高岭石中，铁主要以Fe3＋形式存在于晶体结构和杂质铁氧化合物中，也有部分以Fe2＋置换Al3＋形式存在。  相似文献   

Iron speciation in interaction with organic matter: Modelling and experimental approach   总被引：1，自引：0，他引：1  

T. Weber  T. Allard  M.F. Benedetti 《Journal of Geochemical Exploration》2006,88(1-3):166

The present study aims to model iron speciation when interacting with natural organic matter. Experimental data for iron speciation were achieved with insolubilized humic acid as an organic matter analogue for 1.8 × 10^− 3 M and 1.8 × 10^− 4 M iron concentrations and 2–5 pH range. Combining EPR spectroscopy and chemical analysis allowed us to fit NICA-Donnan model parameters for both organic complexation of iron and oxides precipitation.  相似文献   

Color centers in topaz: comparison between neutron and gamma irradiation     

K. Krambrock  L. G. M. Ribeiro  M. V. B. Pinheiro  A. S. Leal  M. Â. de B. C. Menezes  J. -M. Spaeth 《Physics and Chemistry of Minerals》2007,34(7):437-444

Neutron- and gamma irradiation-induced paramagnetic centers in natural colorless topaz from four different Brazilian localities were studied by electron paramagnetic resonance (EPR) and optical absorption as a function of irradiation dose and thermal treatment. Gamma irradiation doses were applied up to 1,000 kGy with a dose rate of 15 kGy h⁻¹. For the neutron irradiation experiments, a neutron flux of 4 × 10¹² cm⁻² s⁻¹ was used with an integrated flux of up to 1 × 10¹⁸ cm⁻². From the experiments, it is concluded that brownish colors are induced by gamma-rays and may be associated with a single broad isotropic EPR line with g = 2.015(2). Both the EPR line and the related optical absorption band at 460 nm (2.7 eV) are lost during thermal treatments between 150 and 200°C. Fast neutrons create the paramagnetic peroxyl radicals O₂ ⁻ and the paramagnetic O⁻ hole centers. The O⁻ centers have the same thermal stability as the optical absorption band at 620 nm (2.0 eV). It is confirmed that the absorption due to the O⁻ center is responsible for the blue color in topaz. Both color centers and their absorption bands are discussed in the context of O⁻ bound small polarons.  相似文献