东天山双龙铜矿石英闪长岩锆石U-Pb定年、Hf同位素分析及对构造环境的制约     

郭远新  赵同阳  孙月园  李平  王芳 《新疆地质》2019,(2):146-155

通过对新疆东天山雅满苏岛弧带双龙铜矿成岩地质特征、岩石地球化学特征及Hf同位素分析,认为赋矿岩体为一套形成于后碰撞环境下的准铝质高钾钙碱性岩石系列的石英闪长岩,LA-ICP-MS锆石U-Pb同位素年龄为(300.9±1.2)Ma。岩石地球化学显示,赋矿岩石具富集大离子亲石元素(LILE)K,Rb等及高场强元素(HFSE)Th,U,Zr和Hf,贫Nb,Ta,Ti,Sr,P特征,可能形成于后碰撞构造环境。石英闪长岩锆石176Hf/177Hf变化范围0.282949~0.283002,平均值0.282979,εHf(t)值为12.32~14.40,平均13.40,tDM2(Hf)为375~482Ma,平均429Ma,表明岩浆物源可能来自志留纪新生地壳的部分熔融。  相似文献   

马庄山金矿床中石英特征与金矿化的关系     

唐俊红  郭清宏 《甘肃地质》1999,8(1):66-71

马庄山金矿床中自然金,除与多金属硫化物密切共生与伴生外,主要脉石矿物就是石英。历次的构造运动,多期的矿液活动及演化,无不在石英的宏观构造和微观构造上有直接或间接的反应。系统详细地研究这些构造,可以指示金矿的找矿方向及扩大金矿储量  相似文献   

四川瀑布沟地区断裂破碎带的物质成分与断裂活动年代          下载免费PDF全文

冯锦江  胡碧如  牛娈芳  张秉良 《地震地质》1988,10(1):87

本文主要研究断层泥中新生的粘土矿物特征,并研究断层泥中石英碎砾表面溶蚀的显微形貌结构特征。粘土矿物以X-射线衍射分析为主,石英碎砾则利用扫描电子显微镜对其显微形貌结构进行分析,并根据石英表面溶蚀的形貌特征来探讨断裂活动的相对年代  相似文献   

五台地震科技中心水平摆倾斜仪对应强远震前兆异常特征分析     

杨顺达  闫远芳 《山西地震》2019,(2):15-18

通过对数字石英水平摆倾斜仪最近几年积累数据的分析,发现在大多数中强远震发生前数小时,倾斜仪东西分量观测数据锯齿状异常、固体潮曲线出现畸变并伴有明显的抖动,这对异常识别和地震预测具有一定的参考价值。  相似文献   

Investigating the optically stimulated luminescence dose saturation behavior for quartz grains from dune sands in China     

《Quaternary Geochronology》2014

The optically stimulated luminescence (OSL) signals from quartz have been widely used to estimate the equivalent dose (D_e) of environment radiation after the deposition of mineral grains. However, the usage of quartz is often limited due to the lower saturation behavior compared with feldspar. Saturation limits among quartz (defining the upper dating range) vary significantly. It is important to better understand the reason for various dose saturation behaviors of the quartz OSL signals. In this study, coarse quartz grains were extracted from the Taklimakan Desert and the Hunshandake sandy land in north China and the dose saturation behavior of quartz OSL signals were studied. Our results suggest that the quartz grains produce very different aliquot-specific dose response curves, showing the significant variability in dose saturation characteristics for OSL signals. Laboratory dosing, optical bleaching and heating experiments were designed to simulate their effects on the dose saturation behavior for the quartz OSL. The results demonstrate that cycles of dosing and optical bleaching have insignificant impact on the OSL dose growth curves, while the heating to high temperature (above 400 °C) can significantly change the dose saturation characteristics for the quartz OSL. Such results suggest that the different heating history of quartz might be an important factor for the variability in dose saturation characteristics for OSL signals. Additionally, the quartz grains from the Hunshandake sandy land exhibit lower dose saturation level for OSL signals, compared with that from the Taklimakan Desert. This can be explained that the quartz grains from Hunshandake sandy land are mainly of igneous origin, while the quartz grains from Taklimakan Desert are mainly of metamorphic origin.  相似文献   

Interlaboratory comparison of cosmogenic 21Ne in quartz     

《Quaternary Geochronology》2015

We performed an interlaboratory comparison study with the aim to determine the accuracy of cosmogenic ²¹Ne measurements in quartz. CREU-1 is a natural quartz standard prepared from amalgamated vein clasts which were crushed, thoroughly mixed, and sieved into 125–250 μm and 250–500 μm size fractions. 50 aliquots of CREU-1 were analyzed by five laboratories employing six different noble gas mass spectrometers. The released gas contained a mixture of 16–30% atmospheric and 70–84% non-atmospheric (predominantly cosmogenic) ²¹Ne, defining a linear array on the ²²Ne/²⁰Ne-²¹Ne/²⁰Ne three isotope diagram with a slope of 1.108 ± 0.014. The internal reproducibility of the measurements is in good agreement with the formal analytical precision for all participating labs. The external reproducibility of the ²¹Ne concentrations between labs, however, is significantly overdispersed with respect to the reported analytical precision. We report an average reference concentration for CREU-1 of 348 ± 10 × 10⁶ at [²¹Ne]/g[SiO₂], and suggest that the 7.1% (2σ) overdispersion of our measurements may be representative of the current accuracy of cosmogenic ²¹Ne in quartz. CREU-1 was tied to CRONUS-A, which is a second reference material prepared from a sample of Antarctic sandstone. We propose a reference value of 320 ± 11 × 10⁶ at/g for CRONUS-A. The CREU-1 and CRONUS-A intercalibration materials may be used to improve the consistency of cosmogenic ²¹Ne to the level of the analytical precision.  相似文献   

OSL dating of fine-grained quartz from Holocene Yangtze delta sediments     

《Quaternary Geochronology》2015

Holocene flood events in the Yangtze River are associated with variations in East Asian Summer Monsoon (EASM) precipitation, and so Yangtze delta sediments may preserve information about the frequency and magnitude of EASM precipitation. These flood/drought cycles of the EASM directly affect the living standards of East Asian population. However, despite its importance, little chronological control is available for the Yangtze Delta sediments; because biogenic carbonate only occurs sporadically, it has proved the difficulty to discuss sedimentation mechanisms and rates in any detail.In 2013 two sediment cores (YD13-G3 and H1) were taken from the Yangtze subaqueous delta to investigate precipitation history. In this study, we investigate the potential of quartz OSL dating of the fine silt fraction (fine-grained quartz; 4–11 μm) from these cores to estimate the depositional age of the sediments. We test whether: (1) Yangtze subaqueous delta sediments contain quartz with suitable characteristics for dating, and (2) quartz grains are well-bleached during/before the transportation process, by examining a modern analogue of suspended particulate matter, and by cross-checking with the doses derived from infrared stimulated luminescence (IRSL) signals (both IR₅₀ and pIRIR₁₆₀) from feldspar in polymineral fine grains. We find that both the quartz and feldspar luminescence characteristics are satisfactory (quartz dose recovery ratio 1.067 ± 0.004; n = 250, pIRIR₁₆₀ dose recovery ratio 1.01 ± 0.02; n = 151). Modern suspended particulate matter has measured quartz equivalent doses between 0.1 and 0.2 Gy, suggesting that this material was sufficiently bleached during/before transportation to allow dating of Holocene sediments (mean dose rates of ∼3 Gy ka⁻¹). OSL ages of 44 samples from the 2 cores show apparently rapid accumulation at ∼6 ka between 9.65 and 5.50 m in core H1 and ∼2 ka throughout core G3 and between 5.0 and 0.0 m in core H1. The pIRIR₁₆₀ signals suggest less light exposure of the core top sediments and of those from the transition layer between ∼6 ka to ∼2 ka, although there is no evidence for incomplete bleaching of quartz. The question remains as to whether significant deposition took place only at these two times, or whether the record has been disturbed by erosion/reworking.  相似文献   

Radiofluorescence of quartz: A review     

《Quaternary Geochronology》2015

Radiofluorescence (RF) is the luminescence emitted during exposure to ionizing radiation. Charged particles or high-energy photons can be used as stimulation sources, and different designs for measurement equipment have been published. Only few studies have successfully used the quartz RF signal for dosimetry and dating. However, RF is a valuable tool in deciphering charge trafficking in quartz crystals, and also provides information for identifying types of defects causing specific luminescence emissions. Based on models for charge transfer in quartz, RF is seen as resulting from direct recombination of electrons with holes captured in recombination centers (or vice versa) during ionizing irradiation. Competition between reservoir and luminescent centers explains the initial decay of the modeled RF curve followed by a steady rise and also the observed ‘pre-dose’ effect. Emission spectra have been found to be similar to thermoluminescence (TL) spectra, with prevalent emissions in the UV and further emissions for some samples in the blue-green and red range. The high intensity levels and the possibility of choosing longer accumulation times compared to TL and OSL are advantages of RF for spectral measurements. Relative peak intensities in the emission spectra change with dose and absolute intensities with dose rate. Investigating the RF signal with changing measurement temperature allows calculating physical parameters of individual emissions that control thermal quenching. The degree of thermal quenching varies between the emissions, with most intense quenching in the UV. Sensitization of RF by several orders of magnitude has been observed after annealing at 500 °C.  相似文献   

Paramagnetic lattice defects in quartz for applications to ESR dating     

《Quaternary Geochronology》2015

Quartz is one of the minerals useful for ESR dating with many applications. Although the study has quite a long history since 1980's, ESR dating of quartz is still in a developing stage. After the basis in physics for the ESR signals in quartz is described, the current status of ESR dating of quartz is summarized for applications to fault gouge, tephra and sediment. Both basic studies for mechanisms and practical applications with independent age controls are still necessary to establish the protocols.  相似文献   

High resolution OSL and post-IR IRSL dating of the last interglacial–glacial cycle at the Sanbahuo loess site (northeastern China)     

《Quaternary Geochronology》2015

Northeastern China is located in the East Asian monsoon region; it is sensitive to both high and low latitude global climate systems. Loess deposits in the region have considerable potential as sensitive archives of past climate changes. However, research into loess deposition and climate change in this region is restricted by the lack of independent age control. In this study, coarse-grained quartz SAR OSL and K-feldspar post-IR infrared (IR) stimulated luminescence (post-IR IRSL; pIRIR₂₉₀) methods have been used to date the Sanbahuo loess site in northeastern China. The quartz OSL characteristics are satisfactory. The measured pIRIR₂₉₀ D_e's do not vary significantly with IR stimulation temperatures between 50 °C and 260 °C; a first IR stimulation temperature of 200 °C was adopted. Dose recovery tests were performed by adding different laboratory doses to both laboratory bleached (300 h SOL2) samples and natural samples; the results are satisfactory up to ∼800 Gy. Resulting quartz OSL and feldspar pIRIR₂₉₀ ages are in good agreement at least back to ∼44 ka; beyond this feldspar pIRIR₂₉₀ ages are older. The feldspar ages are consistent with the expected age of the S1 palaeosol (MIS 5). There appears to have been a period of fast loess deposition at ∼62 ka, perhaps indicative of winter monsoon intensification with a very cold and dry climate that lead to a serious desertification of dunefields in northeastern China.  相似文献