小秦岭地区脉金矿床找矿评价的石英矿物学标志及模型

通过区内505和530等主要矿脉石英红外吸收光谱、热爆裂及热发咣特征的系统研究，总结了该区无矿、贫矿及矿体石英脉评价的石英矿物学标志，表现为：①无矿石英起爆温度为210－330℃，热爆裂曲线无明显峰型；石英热发光总强度大于20000cps，峰值强度大于500cps;②贫金石英脉其石英红外吸收相对光密度DCO2／DH2O值大于1．1；起爆温度为210－280℃，石英热爆裂曲线为明显单峰形态，主爆峰对应温度值为420－440℃；石英热发光总强度介于10000－20000cps之间，峰值强度介于150－300cps之间；③矿体石英脉其石英红外吸收相对光密度DCO2／DH2O值小于1．0；起爆温度100－160℃，热爆曲线为单峰型，主爆峰对应温度为140－180℃；石英热发光总强度值小于10000cps，峰值强度小于150cps。根据本区含金矿脉矿化分带模式及石英红外吸收光谱、热及热发光参数系统变化规律，建立了该区石英脉型金矿床找矿评价的石英矿物学标志模型。     

石湖金矿区中石英的找矿信息研究

石英与金矿床关系十分密切,石英中含有众多的信息.通过对它的研究,可提取出许多找金矿的信息或标志.石英热发光曲线反映金的矿化强度,矿体中的石英热发光曲线呈双蜂或多峰;而矿化带中则呈包含多种隐伏峰的单蜂曲线.与成矿有关的石英红外吸光度D_2、D_2/D_1可定性地评价其含金性.含金石英中的Al_2O_3、K_2O、Na_2O、H_3O~(+)的含量随着矿体埋藏深度的增大而增加,可用其判别矿体的埋藏深度.     

Radiation-induced defects in quartz. IV. Thermal properties and implications

The thermal stabilities and decay kinetics of three peroxy radicals (Centers #1, B and B′) and three other radiation-induced defects (#3, C′ and E₁′) in natural quartz from the high-grade McArthur River uranium deposit (Athabasca basin, Canada) have been investigated by isochronal and isothermal annealing experiments and electron paramagnetic resonance (EPR) spectroscopy. Single-crystal EPR spectra of isochronally (2 h) annealed quartz show that these centers all grow in intensity to 280°C and then decay with further increase in temperature, but their disappearance temperatures differ markedly and depend on the initial concentrations (e.g., Center #1 in a dark smoky quartz is annealed out at 380°C, B and B′ at 420°C and #3 and C′ at 580°C). The isothermal decay processes of these centers are all of the second order type. The calculated activation energies for the peroxy radicals [#1 and B + B′ at 0.36 (9) and 0.83 (8) eV, respectively] are smaller than those of Centers #3, C′ and E₁′ [1.09 (8), 1.24 (8) and 1.45 (7) eV, respectively]. Gamma-ray irradiations of thermally bleached quartz restore a fraction of the peroxy radicals, suggesting that their diamagnetic precursors are stable up to at least 800°C. The unusual decay characteristics of “peroxy radicals” in quartz reported in the literature are shown to most likely arise from multiple radiation-induced defects. These results have implications for not only applications of peroxy radicals in quartz for EPR dating but also better understanding of thermoluminescence and cathodoluminescence spectra of this mineral.     

石英E'心的热力学特征及其指示意义

石英EPR是一种利用矿物吸收的累积辐射能进行测年的技术方法,尽管多用于第四纪,但石英E'心在热活化后极大增强的EPR信号为拓展EPR的测年范围提供了契机.然而石英E'心的热活化条件及形成转化机理存在诸多争议.通过对花岗岩和断层带样品施加人工γ辐照,并通过步进式的阶梯退火实验,运用电子顺磁共振技术测定了不同辐射条件及温度条件下的石英E'心信号强度,探讨了石英E'心的增长和成因机理.结果表明,石英E'心可在常温常规γ辐照和高温加热2种条件下增长,并分别探讨了常温和高温E'心的测年方法及其地质意义.常温E'心的信号强度在150℃以下相对稳定,可用常规附加剂量法标定EPR信号强度以求取累积辐射能,常用于测定第四纪范围内断层的形成年龄;石英E'心在热活化后信号得到极大增强,可测定第四纪前的地质年龄,但需采用已知年龄的石英E'心热力学峰值强度作标杆或通过高剂量的γ辐照或中子辐照使氧空位再生,建立石英氧空位的剂量响应曲线以标定高温E'心代表的累积辐射能.E'心的热力学峰值通过步进式的阶梯退火实验确定,其在高温和常温时的信号强度比(I₂/I₁)具有记录辐射能和地质计时的意义.      

Behaviour of biotites,amphiboles, plagioclases and K-feldspars in response to tectonic events with the 40Ar-39Ar radiometric method. Example of Corsican granite

Alpine deformation of Variscan granites in Corsica has resulted in fundamentally disturbing effects in minerals with regard to ³⁹Ar-⁴⁰Ar systematics. These deformational effects, as studied in quartz, biotite, feldspar, show an evolution in their development which is related to the intensity of deformation.Amphibole yields very disturbed age spectra, with loss of radiogenic Ar in low temperature steps, excess radiogenic Ar in intermediate temperature steps and undisturbed ages in high temperature steps. These effects similarly increase with the intensity of deformation.Biotite also shows disturbed spectra; we suggest that deformation induces equal loss of radiogenic Ar from all domains in this mineral and that this loss increases with the intensity of deformation. Only less-deformed biotite gives geologically significant age spectra.Spectra of deformed K-feldspar give results similar to those disturbed by thermal events. The most deformed K-feldspar gives high temperature spectra of Alpine age. High temperature steps however do not give the true age of the granite regardless of deformational intensity. Age spectra of plagioclase are quite disturbed and give geologically meaningless results. These results thus demonstrate the influence of deformation on the relative retentivities of terrestrial minerals.     

An X-ray excited optical luminescence study of a zoned quartz crystal from an emerald-bearing quartz vein,Hiddenite, North Carolina,USA

The optical luminescence excited with synchrotron radiation along a preferential orientation of a quartz crystal has been investigated. It is found that the crystal is composed of two distinct regions, only one of which luminesces upon X-ray excitation. This luminescence is generally uniform and exhibits emission bands in the blue (470 nm with a shoulder at 522 nm) and in the UV (340 nm) regions of the spectrum. The branching ratio for the intensity of these bands is sensitive to the excitation energy across the Si K-edge. XANES spectra collected by partial luminescence yield (PLY) suggest that both emission bands originate from the de-excitation of Si atoms in the quartz. The possible defect sites within the crystal structure that could account for the observed luminescence are investigated and discussed. Additional experiments are proposed to verify this assignment of the optical emission bands.     

浙江治岭头金矿石英热释光研究

分析测试了治岭头金矿床各种成因石英的热释光,对比研究各种成因石英的热释光特征差 别。揭示金矿化与变质热液成矿作用的关系,燕山期火山热液对金矿化的叠加作用。各期各阶段石英热 释光研究也为评价石英脉体的含金性,工业价值提供了依据,为矿区深入勘察评价提供辅助手段。发现 石英热释光强度与石英结晶粒度有负相关关系。     

Thermoluminescence spectra of igneous quartz and hydrothermal vein quartz

Variations in thermoluminescence spectra are reported for four types of geological quartz examined with a new spectrometer featuring dual imaging photon detectors that separately and simultaneously detect (1) uv-blue (200–450 nm) and (2) blue to near infrared (400–800 nm) emission. Samples show striking differences which appear to be characteristic of their geological origin. Volcanic quartz phenocrysts from acid volcanics show red thermoluminescence (TL) emission bands centered at 620–630 nm that are 100 times more intense than similar bands in other quartz, while a violet emission at 420–435 nm was observed exclusively in igneous quartz (volcanic and granitic). A broad emission band centered at 560–580 nm was observed only in quartz formed hydrothermally. Massive quartz from Li-rich pegmatite bodies shows narrow, intense 470 nm emission bands at 230° C apparently related to Al and to Ge defects detected with electron paramagnetic resonance (EPR), and emission bands at 330 and 280 nm, possibly related to recombination at oxygen vacancies. The common 380 nm emission band of quartz was observed in both volcanic and granitic quartz, but was not detected in either the pegmatitic or the hydrothermal vein quartz. Observed spectral variation is identified as a potential source of error in luminescence dating.     

Paleoclimatic significance of quartz/illite variations in cores from the eastern equatorial north Atlantic

Detailed X-ray diffraction analysis of cores taken in the eastern equatorial Atlantic suggest that during approximately the last 600,000 yr a relatively constant background of clay mineral deposition has existed on which are superimposed large oscillations in quartz input (relative to illite). The quartz is transported from the Sahara Desert by the northeast trade winds and the quartz/illite oscillations appear to reflect past changes in the transporting effectiveness (intensity) of the trade winds. Comparison of the quartz/illite variations with paleotemperature variations for the northeast Atlantic suggests that major inputs of quartz correlate with cold periods and that warm periods correlate with low quartz input. The parallelism between the curves indicates a fundamental link between trade wind intensity and past climatic fluctuations, and further suggests that the changes of intensity are closely atuned to temperature fluctuations in the northern latitudes. The relationship between the quartz/illite variations and wind intensity is complicated by the fact that other climatically controlled factors may also affect quartz deposition in the equatorial Atlantic.     

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     

Origin of the color in cobalt-doped quartz

Synthetic Co-doped quartz was grown hydrothermally in steel autoclaves at the Technological Center of Minas Gerais (CETEC), Brazil. The quartz samples, originally yellow in the as-grown state acquired blue coloration after prolonged heat treatment times at 500°C near the alpha–beta transition temperature. UV–VIS–NIR absorption spectroscopy shows the characteristic spectra of Co³⁺ before heat treatment. After heat treatment, the optical absorption spectrum is dominated by two split-triplet bands the first in the near infrared region centered at about 6,700 cm⁻¹ (1,490 nm) and the second in the visible spectral range at about 16,900 cm⁻¹ (590 nm). Both split-triplet bands are typical for Co²⁺ ions in tetrahedral coordination environments. From the absence of electron paramagnetic resonance (EPR) spectra, we conclude that the Co²⁺ found in the optical absorption spectra of the blue quartz is not due to an isolated structural site in the quartz lattice. Instead, the blue color is associated with electronic transitions of Co²⁺ in small inclusions in which the Co site has tetrahedral symmetry. The non-observation of polarization-depend optical absorption spectra is also in agreement with this model. The results for Co²⁺ in quartz are different from Co-bearing spinel and staurolite and other silicates like orthopyroxene, olivine, and beryls. The formation process of the color center is discussed.     

广东河台云西金矿床石英的拉曼光谱特征及其对含金性的评价

本文对广东河台云西金矿的石英进行了拉曼光谱研究。结果表明,含金石英与不含金石英的拉曼光谱有着本质的差异。作者通过量子理论的研究,对其差异进行了剖析,发现这种差异与它们之间成分、组构、形成温度的差异紧密联系。因此,作者得出结论:石英的拉曼光谱可以用于评价其含金性。     

塔里木盆地柯坪隆起典型沉积岩类的热红外光谱特征研究

塔里木盆地西北缘柯坪隆起一些典型碎屑岩、碳酸盐岩及蒸发岩的热红外发射光谱曲线的分析表明:利用残余辐射谱带（又叫低发射率带）的中心波长位置可以确定沉积岩中的主要矿物成份，并可利用残余辐射谱带的强度判断矿物成份含量的多少。这对于利用热红外多光谱遥感技术直接找矿具有重要意义。     

广东海南岛石碌铁矿石英的研究及其意义

本文在显微镜研究基础上,综合运用扫描电镜、光谱分析、X射线分析、差热分析和红外光谱等手段,对铁矿中石英进行矿物标型特征的研究。论证了这种石英的绝大多数有蛋白石→玉髓→石英的形成过程。同时,成矿时也很可能有一些火山成因石英斑晶或晶屑掺杂其中,而陆源碎屑石英少见。还发现了铁矿中玉髓的似生物结构。因而为石碌铁矿海相火山(胶体)沉积变质成因说提供了新的科学依据。     

吉林海沟金矿床石英的研究

海沟金矿床是产于绿岩带中的层控矿床。石英是金矿床主要的脉石矿物。本文研究了石英的颜色、化学成分、晶胞参数、红外吸收光谱及热发光性等特征。初步研究表明,该区含金石英脉中的石英与不含金石英脉中的石英,其特征是不相同的。     

文峪金矿床石英热发光特征及其在预测找矿中的意义

文峪金矿床石英热发光研究表明,含矿与无矿石英由于其构成不同,其热发光特征明显差异,含矿石英热发光曲线呈平缓开阔的弱单峰形态,峰强值低于150cps;总发光强度低于10000cps;而无矿石英热发光曲线呈中等-尖锐的单峰形态,峰强值大于150cps,总发光强度大于10000cps。上述标志对指导该区矿脉含金性评价及找矿工作均有重要指导意义。     

Cathodoluminescence petrography of syntectonic quartz fibres

The cathodoluminescence of low grade metamorphic quartz is reported in the literature to be uniformly brown. This study describes an investigation of syntectonic quartz fibres from veins and pressure shadows contained in different carbonate units of the Helvetic Alps, Switzerland, and of Anglesey, U.K., with the Scanning Electron Microscope in the cathodoluminescence mode. The cathodoluminescence spectra measured show systematic variations between older and younger parts of the same fibre, and between fibres from different tectonic units. These variations can be related first to variations in the temperature of formation of the quartz fibres, and second to deformation-induced differences in the microstructure of the earlier formed parts of fibres during later imposed strains.     

29Si MAS NMR relaxation study of shocked Coconino Sandstone from Meteor Crater, Arizona

 ²⁹Si nuclear magnetic resonance (NMR) spectroscopy was used to characterize the silica phases in a moderately-shocked Coconino sandstone from Meteor Crater, Arizona. The spectra were recorded using direct polarization, magic-angle spinning, and variable delay times in a saturation recovery pulse sequence. Resonances observed at -97.3, -107.1, -113.9 and -191.2 ppm were assigned to a densified hydrous form of amorphous silica (D phase), quartz, coesite and stishovite phases, respectively. The relative percentages were estimated as 1.7, 80.6, 16.4 and 1.3% for the D, quartz, coesite, and stishovite phases. The power-law recoveries of the magnetization for the quartz and coesite phases can be interpreted in terms of their phase geometries. Received: January 3 1997 / Revised, accepted: August 4 1997     

Thermoluminescence of quartz from Shihu gold deposit, western Hebei province, China: some implications for gold exploration

Thermoluminescence (TL) of monomineralic separates have been widely used in various geosciences fields in order to trace the thermal history and aid in prospecting for gold deposits. Quartz is a ubiquitous mineral in the Shihu gold deposit, which is situated in the northern part of the Taihang orogenic belt in the North China craton (NCC). The deposit is hosted by ductile-brittle faults within an Archean metamorphic core complex of the Fuping Group. This deposit is characterized by gold-bearing quartz-polymetallic sulfides and quartz veins. New TL results have been obtained for quartz, in which four type-TL glow curves were identified. The gold-bearing quartz present type III glow curves that consist of two peak glow curves at the middle and high peak temperatures with the similar TL intensity. In addition, the cross-sections of peak temperatures and TL intensity highlight the valuable area where the Au-bearing quartz present weak TL intensity and low-middle peak temperatures. Our results significantly enhance the usefulness of quartz in metallogenic studies of the North China craton and as an indicator mineral in mineral exploration of the Taihang Mountain region.