石英的电子—空穴心在金矿评价中的意义

石英的电子-空穴心在金矿找矿勘探中具有重要意义。阳离子不等价类质同象造成的晶体缺陷,是使其具有电子-空穴心的内在因素。石英中常见的空穴心有Al-O~-、Ti-O~-、Fe-O~-,电子心有Al~(3+)+M、Fe~(3+)+M、Ti~(3+)+M等。电子顺磁共振波谱和热发光是检测石英中电子-空穴心的有效方法。在金矿床中,石英Al-O~-顺磁空穴心浓度较大者,其含金量也比较高。石英热发光曲线的发光峰的数量和强度与金成矿阶段有着明显的关系:早期成矿阶段结晶的基本不含金石英,热发光曲线常为近对称的单峰型,发光强度较大;主成矿阶段形成的含金石英,热发光曲线为多峰型,常具最大的发光强度;晚期成矿阶段生成的含金性较差的右英,热发光曲线呈单峰-双峰型,发光强度亦较大。石英热发光性与金矿体的空间展布表现出一定的联系;在矿体横向上,矿体中石英热发光曲线多为双峰-多峰型,围岩中石英热发光曲线多呈单峰型;在矿体垂向上,随矿体埋深的增加,石英热发光强度有逐渐增大的趋势。含金石英通常具有多个热发光温度,曲线形态为多峰型,且主热发光峰多位于相对较低的温度区间;不含金石英常仅有一个热发光温度,曲线形态为不对称的较平缓的单峰型,或为一平缓的曲线,发光强度较弱。     

Two modified smoky quartz centers in natural citrine

Electron paramagnetic resonance (EPR) measurements on natural citrine and greenish-yellow quartz revealed the presence of several localized hole centers adjacent to an aluminium impurity. The g tensors and their principal axes directions were determined for the two most prominent centers. The g-tensor variations and ²⁷Al hyperfine splittings are roughly half as large as for the well-known smoky quartz centers. Optical and infrared absorption, thermal stability and thermoluminescence were also studied. In these citrine centers an additional defect must be present in the immediate neighborhood of the hole, but the exact nature of this defect is still unknown.     

The investigation of defects in shock-metamorphosed quartz

The shock-metamorphosed quartz exhibits thermal luminescence (TL) with maxima at 365 nm, 470 nm and 610–680 nm. By electron paramagnetic resonance (EPR) analysis E₁ type electron centers and hole centers have been found which originate from vacancies including those from the substitution of Al³⁺ and/or Fe³⁺, for Si⁴⁺. The EPR and TL spectra may be interpreted mainly in terms of vacancy type defects associated with dislocations in the crystal structure of quartz.     

Conditions of localization of Mesozoic auriferous metasomatites in crystalline base of Central Aldan region

We investigated the distribution of electron hole centers produced by natural radioactivity in arkoses and their principal components (quartz-feldspar intergrowths, white and smoky quartz, and feldspars) using the electron paramagnetic resonance method. The relation between the concentrations of the Ecenters and uranium content in the rock provides information on the genetic characteristics of uranium mineralization. —Authors.     

Aluminum and germanium paramagnetic centers in vein quartz and rock crystals from the Subpolar Urals

The major economic types of vein quartz and rock crystals from the Subpolar Urals were studied using electron paramagnetic resonance. Quartz is characterized by widely variable concentrations of aluminum and germanium paramagnetic centers. The average values and ranges of these concentrations increase from older to younger generations of quartz. The lowest content of aluminum and germanium paramagnetic centers is typical of granulated and primary fine-grained quartz; in coarse-grained quartz and rock crystals, the content is much higher. According to the data obtained, granulated and primary fine-grained quartz should be regarded as a potentially high-quality raw material for glass melting, because these quartz varieties are distinguished by the lowest contents of alien structural centers. Once mineral impurities eliminated, high-quality quartz concentrate can be produced from this quartz.     

Al-related centers in relation to γ-irradiation

 The charge compensation problem for Si−Al substitution in Brazilian natural quartz is investigated in relation to γ-irradiation darkening response and impurity contents evaluated by atomic absorption spectrometry and infrared absorption spectroscopy. Al⁺³ in as-grown natural quartz is compensated by Li⁺ and H⁺ to form Al−Li and Al−OH centers. The content ratios (Al−Li)/(Al−OH) and Li/(broad OH band) depend on the environmental conditions of crystal growth and influence the formation of Al-hole centers due to γ-irradiation. Al−OH centers are the dominant Al-related centers in quartz from hydrothermal origin while Al−Li centers are dominant for that of pegmatitic origin. The formation of Al-hole centers is little in quartz with a high content of broad OH band which is from low temperature hydrothermal origin. Received May 23, 1995 / Revised, accepted May 8, 1996     

沉积物的ESR测年

对沉积物中石英ESR测年的特性进行了较为详细地研究，可用沉积物中石英的Ge心信号进行ESR测年；根据石英E心饱和功率较小这一特性，采用较大的微波功率可以测得较老海洋沉积物（大于0.5Ma）的ESR年龄；石英E心的异常较照剂量响应是判断海岸风成沙环境的一个标志。此外，还介绍了沉积物ESR测年在地质上的应用。     

Correlation of Fe4+ optical anisotropy,Brazil twinning and channels in the basal plane of amethyst quartz

The biaxial absorption bands in amethyst quartz, with peaks at 2.28 eV and 3.54 eV related to Fe⁴⁺ and a peak at 3.02 eV—which is the A₃ band related to the [AlO₄]° trapped hole center, have orientations of maximum light absorption in the basal plane of Brazil-twinnedr-growth sectors paralleling the planes of Brazil optical twinning. Absorption minima are at 90° to the maxima in all cases. The Brazil twinning planes always parallel thea-axes(1210,etc) of quartz and in many cases also parallel planes perpendicular to ther-faces(1011,etc.). These are directions of channels in the quartz structure. The anisotropy ratio,σ_max/σ_min, of the Fe⁴⁺ band is that of the A₂ absorption band in smoky quartz as would be expected if Fe³⁺ furnishes electrons to quench the trapped holes causing this absorption band. In the absence of the A₁ and A₂ absorption bands, the A₃ absorption band width at half-maximum decreases from 1.43 to 0.36 eV indicating decreased charge-transfer character of the [AlO₄]° center in the absence of the other types of Al trapped-hole centers in quartz. The key to the Brazil twinning in α-quartz are the channels which fill with large Fe³⁺ ions that force twinning to relieve strain in the structure. Amethyst color results only if aluminum is present substitutionally in the quartz as well as the interstitial iron plus ionizing radiation.     

Radiation-damage-induced defects in quartz. I. Single-crystal W-band EPR study of hole centers in an electron-irradiated quartz

Single-crystal W-band electron paramagnetic resonance (EPR) spectra of an electron-irradiated quartz, measured at room temperature, 110 and 77 K, disclose three previously reported hole centers (#1, G and an ozonide radical). The W-band EPR spectra of these three centers clearly resolve six magnetically nonequivalent sites each, whereas previous X- and Q-band EPR studies reported Centers #1 and the ozonide radical to consist of only three symmetry-related components and interpreted them to reside on twofold symmetry axes in the quartz structure. The calculated g matrices of Center #1 and the ozonide radical show that deviations from twofold symmetry axes are <10°, which are probably attributable to distortion related to neighboring charge compensating ions. The W-band EPR spectra of Center G not only result in improved g matrices but also allow quantitative determination of the nuclear hyperfine (A) and quadrupole (P) matrices of its ²⁷Al hyperfine structure that was incompletely resolved before. In particular, the g-maximum and g-minimum principal axes of Center G are approximately along two pairs of O–O edges of the SiO₄ tetrahedron, while the unique A principal axis is approximately along a Si–Si direction. These new spin-Hamiltonian parameters suggest that Center G most likely involves trapping of a hole between two oxygen atoms related to a silicon vacancy and stabilized by an Al³⁺ ion in the neighboring tetrahedron (hence an O₂ⁿ⁻–Al³⁺ defect, where n is either 1 or 3).     

相山铀矿床多期石英的天然热释光及EPR特征

本文对采自江西相山铀矿床不同成矿期的石英进行了天然热释光测定，并结合ＸＲＦＳ（Ｘ射线荧光光谱）、ＥＰＲ（电子顺磁共振）等分析数据对所取样品的天然热释光特征进行了研究。研究结果表明：不同成矿期石英的天然热释光在发光强度、发光谱线的峰形特征等方面存在明显差异；导致石英热发光的中心是ＳｉＯ３－３型电子心，电子心的多少与Ｕ、Ｔｈ总量有关；石英热释光强度与石英本身的颜色呈反消长关系；热释光发光谱线上的峰形特     

CCSD超高压变质岩绿辉石中的石英出溶体及其大陆动力学意义

单斜辉石中发育石英出溶体是UHP变质作用的典型矿物学标志之一,在世界上著名UHP变质地体中屡有发现。本文利用激光Raman光谱和电子探针分析在中国大陆科学钻探先导孔(CCSD-PP1)榴辉岩岩心的绿辉石中发现了大量石英(棒)出溶现象。通过与CCSD主孔榴辉岩各种赋存形式的绿辉石成分对比,发现含石英出溶体的绿辉石具有超硅特征,这是出溶现象发生的决定性因素之一。结合高压实验岩石学资料,提出在UHP变质的峰值期部分Si进入六次配位的Si-O八面体位置,压力降低这部分Si析出,形成石英出溶体的出溶机制。结合新的矿物学研究进展,认为绿辉石中出溶石英所标志的压力应远大于前人提出的2.5GPa,意味着苏鲁超高压变质带陆壳物质的俯冲深度要大于目前一般认为的80~120km范围。     

梯子崖-富子岭矿区复杂地层钻探技术问题与对策

陕西省凤县梯子崖-富子岭铅锌多金属矿区,其地层主要为产状较陡的千枚岩,局部含方解石或石英脉,断层破碎带发育,井壁稳定性差,施工中孔斜严重,许多钻孔因孔斜而达不到设计目的,防斜、治斜和泥浆护壁为该矿区施工方面的主要技术难题。文章从孔斜预防、定向造斜、护壁堵漏等方面介绍了所采取的工艺措施和取得的效果。     

粤北大东山地区地球化学特征与找矿前景

1:20万水系沉积物测量结果表明,粤北大东山地区富集Sn、W、Bi、Pb、Ag、F、B,且分布不均匀,叠加富集程度高,圈出的综合异常规模巨大,出现多个浓集中心。选择分析了潭岭、称架浓集中心的异常特征和所处的地质背景,认为成矿条件好,具较好的找矿潜力,以寻找云英岩型、蚀变构造带型、蚀变岩体型、石英脉型锡钨矿为主。     

Research Advances in ESR Provenance Tracing Methods of Quartz in Sediments

The ESR (Electron Spin Resonance) signals of quartz is a newly developed sediment provenance tracing method. In this paper, the various ESR signals in quartz, historical development of quartz ESR signals in sediment provenance tracing, thermal stability characteristics of heat treated E’ center, the potential use of quartz nature E’ center and the irradiated Al/Ti center, as well as successful applications in aeolian sediments, river sediments and marine sediments provenance tracing, were briefly reviewed. The most useful ESR centers of quartz include the heat treated E’ center, the nature E’ center, the Al center and the Ti center. According to recent application researches, the heat-treated E’ center is the most commonly practiced among them while the significance of provenance tracing by Al and Ti centers are still in experimental and theoretical stage. Moreover, nature signal intensities of quartz E’ center not only show a significant dependence on lithology both in bedrocks and deposits, but also can reflect the mixture ratio of deposits with different types of sourced bedrocks. As for the study objects, this method has been successfully used in the studies of provenance area of East Asian dust, the temporal and spatial changes of Loess Plateau provenance, the provenance change of aeolian sediment over time and space on Japanese Islands, as well as sediment provenance tracing of Japan Sea sediments. In addition, the ESR provenance tracing of quartz has promising application prospect in quantitative and semi-quantitative analysis of fluvial sediment provenance tracing. Along with the development of ESR dating, this method can significantly reflect and reconstruct the relationship among regional tectonic movements, geomorphic evolution, and climate evolution. In future work, the combination of trace elements provenance tracing and ESR signals provenance tracing in quartz will help improve and promote the development of sediments provenance tracing methods.     

Radiation-induced defects in euclase: formation of O<Superscript>−</Superscript> hole and Ti<Superscript>3+</Superscript> electron centers

Irradiation techniques are often applied to gem minerals for color enhancement purposes. Natural green, blue and colorless specimens of rare gemological quality euclase, BeAlSiO₄(OH), from Brazil were irradiated with gamma rays in the dose range from 10 to 500 kGy. Although the colors of the different specimens were not strongly influenced, two different irradiation-induced paramagnetic defect centers were found by electron paramagnetic resonance (EPR). The first one is an O⁻ hole center interacting with one Al neighbor and the second is a Ti³⁺ electron center. The EPR angular rotation patterns of both irradiation-induced defects were measured and analyzed. The results suggest that O⁻ hole centers are formed by dissociation of the hydroxyl ions, similar as in topaz crystals. In euclase the OH⁻ ions interconnect distorted Al octahedra and Be tetrahedra in O₅ positions. During irradiation, the electrons are captured by titanium ions (Ti⁴⁺ + e⁻), leading to the formation of paramagnetic Ti³⁺ ions. From the EPR rotation patterns it is clear that these ions substitute for Al ions. The spin Hamiltonian parameters of the irradiation-induced defects are analyzed and compared to similar defect centers in other mineral specimens. Thermal annealing experiments show that the O⁻ hole centers and Ti³⁺ electron centers are directly connected through the radiation process.     

Applications of Natural Radiation-Induced Paramagnetic Defects in Quartz to Exploration in Sedimentary Basins

INTRODUCTION Point defects in quartz have attracted intensiveand continuing research since the 1950s ( Weil ,2000 ,1984 ; Marfunin, 1979 ; Weeks , 1956 ; McClellandand Donoghue ,1953) because they are key factors inenhancing ( or reducing) device performance andquality of this i mportant piezoelectric and optical ma-terial (Beall ,1994) .Point defects in quartz are usu-ally dilute in concentration and,therefore ,are ame-nable to study by only a fewstructural techniques ,ofwhich electron…     

Simultaneous determination of alteration and eruption ages of volcanic rocks by electron spin resonance

The alteration and eruption ages of Japanese welded tuffs were estimated by the method of ESR using Ge, OHC and Al centers in quartz whose stabilities are different. The ages obtained from the Ge and OHC centers were 1–2 Ma, however the ages from the Al center varied from 0.059 to 1.36 Ma. The comparison of these ages with thermoluminescence (TL) and fission track (FT) ages proves that the ESR age of the Al center, which agrees with the TL age, shows the thermal history and, in an ideal case, gives the alteration age: those of the Ge and OHC centers, which agree with FT age, indicate the eruption age. Therefore, this method enables us to describe the thermal history of a rock.     

Radiation defects in feldspars

Various radiation defects were characterized and analyzed by electron paramagnetic resonance (EPR) in 15 feldspars of different compositions after X-ray irradiation. A hole center on oxygen adjacent to two aluminum ions is formed in most feldspars, except those with very high An content. Since the hole is not localized at room temperature, clusters of more than two Al must be present in all feldspars in amounts of at least 100 ppm. Less frequent radiation defects are trivalent titanium and holes on oxygen ions adjacent to a small divalent ion of a yet unidentified nature on a T site with Si and in some cases also Pb as further neighbors. The directions of the magnetic axes for these centers allowed their assignment to specific sites in the feldspar structure. Characteristic absorption and thermolu-minescence emission bands could also be assigned to these centers. Their properties are remarkably independent of composition and Al, Si disorder of the feldspars.     

辉绿岩侵位对半固结砂岩的改造作用--以松辽盆地东南部下白垩统为例

在偏光显微镜和扫描电镜下，发现辉绿岩．砂岩接触带附近半固结的长石砂岩中石英颗粒边部、颗粒间孔隙内及颗粒内裂隙中微晶石英发育．不论是纵向上还是横向上，距接触带较近的样品中，微晶石英多而细长．随着远离接触带，石英微晶逐渐减少，形状逐渐变的粗短．研究表明，这些微晶石英是辉绿岩侵位对围岩砂岩中碎屑石英的压溶或重结晶等作用形成的．     

Geochemistry and origin of Mn-deposits in the Waziristan ophiolite complex, north Waziristan, Pakistan

The Waziristan ophiolite complex is located along the western margin of the Indian plate in northwestern Pakistan. The Mn-deposits in the Saidgi and Shuidar areas are part of this ophiolite complex. These deposits, both banded and massive in nature, are hosted by metachert and are generally overlying metavolcanics. Braunite and cryptocrystalline quartz are the main constituents of the manganese ores in both areas. Hematite occurs in the Shuidar deposits as a minor phase. Metacherts are microcrystalline aggregates of microcrystalline quartz, chalcedony, and lesser hematite. Chemically, the studied Mn-deposits and associated metacherts are very similar to those formed by submarine hydrothermal effusive processes. The deposits originated along sea-floor spreading centers (mid-ocean ridges) within the Neo-Tethys Ocean and were later obducted as part of the Waziristan ophiolite complex. Received: 9 January 1998 / Accepted: 10 March 1999