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251.
东昆仑成矿带是我国西部重大成(找)矿潜力的贵金属-有色金属成矿带。野外调查期间,对东昆仑东段都兰县诺木洪南下石炭统哈拉郭勒组(C1h)杏树沟金矿(化)点进行了年代学及围岩地球化学研究。通过高精度LA-ICP-MS锆石微区原位U-Pb同位素测年,获得金矿(化)点的石英钠长斑岩 206Pb/238U 年龄加权平均值为243.4±1.9 Ma,确定金矿(化)发生在早三叠世。地球化学分析表明,杏树沟金矿(化)点围岩(安山玄武岩)具有高Al2O3、Na2O,低TiO2、K2O的特征。在Zr/TiO2-Nb/Y图解中全部样品均落入安山玄武岩区,TFeO/Mg-SiO2图解中全部样品均落入拉斑系列区域中,属于拉斑系列玄武岩。稀土和微量元素显示其富集LREE、LILE和部分HFSE,Nb、Ta、Nd、Zr、Hf相对亏损,REE表现为LREE/HREE明显分离的分配模式,从多种判别图解综合分析,认为该套火山岩形成于大陆裂谷环境中。 相似文献
252.
Approx. 120 resonant column (RC) tests with additional P-wave velocity measurements using piezoelectric elements have been performed on 19 clean quartz sands with piecewise linear, gap-graded, S-shaped or other smoothly shaped grain size distribution curves. For each material different pressures and densities were tested. It is demonstrated that the extended empirical equations for the small-strain constrained elastic modulus proposed by the authors in an earlier paper work well also for most of the more complex grain size distribution curves tested in the present study. These equations considering the influence of the uniformity coefficient of the grain size distribution curve were developed based on the data from tests on linear gradations. A further improvement of the prediction for the more complex grain size distributions can be achieved if the correlation equations are applied with a specially defined average inclination of the grain size distribution curve. Such an improvement is demonstrated not only for the small-strain constrained elastic modulus, but also for small-strain shear modulus, modulus degradation and Poisson's ratio. 相似文献
253.
254.
Quartz optically stimulated luminescence (OSL) dating is widely used to determine the time of deposition and burial of Late Quaternary sediments. Application of the method is usually limited to the past 150,000 years due to early saturation of the OSL signal. Here we explore the potential to date Quaternary sediments using the violet (402 nm) stimulated luminescence (VSL) signal of quartz. We develop and test a new post-blue VSL single aliquot regenerative dose dating protocol, and demonstrate that the VSL signal originates from a deep trap at about 1.9 eV with a thermal lifetime of 1011 years at 10 °C, and that this trap is bleachable by sunlight. The VSL signal grows with dose to ∼6400 Gy, a factor ∼20 higher than the conventional quartz OSL signal, and with the proposed protocol we recover a known dose of 1000 Gy in three out of four samples. The potential of the VSL protocol for dating Quaternary sediments is highlighted by its successful application to a suite of geological samples ranging in age between 13 and 330 ka. Based on our investigations, we propose that the VSL protocol has the potential to extend the quartz dating range to cover the full Quaternary. 相似文献
255.
Imaging the heterogeneity of mineral surface reactivity using Ag(I) and synchrotron X-ray microscopy
J. E.?AmonetteEmail author S. M.?Heald C. K.?Russell 《Physics and Chemistry of Minerals》2003,30(9):559-569
Microscopic-scale imaging of reduced zones on the surfaces of minerals can be achieved by reaction with dilute Ag(I) solutions and subsequent analysis using synchrotron X-ray microscopy (XRM) above the Ag K-edge (25.5 keV). The principal reductant is Fe(II), but other reductants such as sulfide may contribute. Reduced zones may exist instrinsically, as in the structure of biotite and augite, or may be generated by reaction with chemical agents such as dithionite or treatment with sulfate-reducing bacteria (SRB). We demonstrate the method on flakes of specular hematite and biotite, as well as on thin sections of different rocks (arfvedsonitic granite, oolitic hematite, diabase, and quartz conglomerate) treated with SRB, and discuss possible artifacts that can occur. To our knowledge, this is the only microscopic technique that can image Fe(II) zones on the surface of an Fe-bearing mineral with monolayer sensitivity. 相似文献
256.
西爪哇金矿位于印度尼西亚西角湾火山岩金、铅锌铜多金属成矿带,该区有众多金矿床(点)。出露的三叠系火山岩地层,以火山喷发沉积为主,岩性组合为安山岩、英安岩、流纹岩及火山角砾岩,具爆发-喷溢沉积的特点,总体表现为火山弧特征。断裂构造破碎带是该地区主要控矿、容矿构造。岩石蚀变强烈,硅化与金矿化关系密切。 相似文献
257.
258.
与冬瓜山叠生式层状铜矿有关岩体地质地球化学特征 总被引:4,自引:0,他引:4
主量元素全碱-硅投影显示青山脚岩体岩性为闪长岩、石英闪长岩;里特曼指数计算结果表明岩性呈钙碱性;岩体中Cu呈明显的正异常,说明含铜岩浆热液一方面叠加改造原始矿胚层,使层状铜矿进一步富集;另一方面含铜的岩浆热液在岩体边缘或接触带形成浸染状、网脉状矿床(既斑岩型矿床)。钾化与Cu富集呈正相关,钾化越强,Cu富集程度越高。稀土元素球粒陨石标准化曲线显示轻稀土富集重稀土亏损;δEu接近1.0,说明岩体分异演化程度不高。该岩体是重要的成矿物质和成矿流体来源,岩浆侵入与岩浆热液的叠加改造促使矿床规模扩大、品位提高。 相似文献
259.
Fluid inclusion petrography 总被引:32,自引:0,他引:32
260.
K. Kihara 《Physics and Chemistry of Minerals》2001,28(6):365-376
Constant temperature and constant pressure molecular dynamics (MD) simulations were applied to quartz to calculate the structural
details which are indeterminable in usual X-ray structure studies. The dynamics of the structural changes was analyzed by
means of time-dependent atomic displacement parameters. The Si-O bonds expand with increasing temperatures through the α-
and β-phases, and atoms vibrate around the α1- (or α2-) sites at lower temperatures in the α-phase, and over the energy barriers between the α1- and the α2-sites at higher temperatures in the α- and the β-phases. The ratios of time lengths spent by atoms in the α1- and α2-sites determine the apparent atomic positions as obtained in usual structure studies of α-quartz. More frequent transfer
of atoms over the α1- and the α2-sites contributes positively to the thermal expansions, whereas larger amplitudes of vibrations, which carry atoms more distantly
and more frequently from the β-sites, contribute negatively. The well-known steep thermal expansion in the α-phase is attributed
to the additive contribution from the expansions of the Si-O bond lengths, the widening of Si-O-Si angles, and the increase
of the atomic transfer-frequency between the α1- and the α2-sites. The nearly zero or negative expansion in the β-phase is caused by balancing the negative to the positive effects.
The MD crystal transforms to the β-phase via a transitional state, where the α- and β-structures appear alternately with time,
or coexist. The slight and continuous expansions observed right after the steep rise(s) of the volume or cell dimensions up
to the nearly horizontal curve(s) are attributed to the continuous changes within the transitional state.
Received: 17 July 2000 / Accepted: 13 January 2001 相似文献