碳酸盐岩生屑颗粒定量研究*——点计数法的理论分析与应用

碳酸盐岩中的生屑丰度数据为研究化石类群分异度、重建古生态环境提供了重要依据。点计数法易于定量统计各类生屑颗粒的丰度,比目估法、图像分析方法更适于碳酸盐岩组分的定量研究。在实际应用过程中,点计数法的最佳计点数常不易确定,往往会造成统计结果的精度不足,或统计工作耗时多、工作量大。应用点计数法和图像分析方法分别对视觉百分含量对比图和碳酸盐岩显微图像进行定量统计,分析沉积组分特征对点计数法测量误差的影响,以确定点计数法在碳酸盐岩生屑丰度统计时的最佳计点数。研究结果表明,点计数法适用于碳酸盐岩生屑颗粒丰度研究。对于大部分碳酸盐岩薄片定量分析工作,500点的计点数量基本可以将点计数法的测量误差控制在±2.5％以内。但是点计数法统计结果的精度受到薄片中生屑颗粒丰度、粒径大小、分选性甚至生屑分异度等沉积组分特征的影响。因此在实际工作中,应根据具体情况,适度调整计点数,从而在统计工作量和统计数据误差之间获得平衡。     

Calciturbidite composition related to exposure and flooding of a carbonate platform (Triassic, Eastern Alps)

The compositional variation of calciturbidites (Pedata/Pötschen Formation), deposited adjacent to the Dachstein Formation carbonate platform in the Triassic Hallstatt Basin, was analysed using detailed field measurements and point-counting of thin sections. The 35 m long section is located in the Northern Calcareous Alps of Austria. Six point-count groups were distinguished separating basinal from platform-derived input. Summary statistics, cluster and correspondence analysis of the point-count data reveals a close relationship between the biota present on the Dachstein carbonate platform and the calciturbidite composition. The variations in turbidite composition are attributed to fluctuations in sea level and resulting flooding and exposure of the platform, which alternately created and destroyed shallow-water habitats on the platform top.     

Extraction algorithm of mining subsidence information on water area based on support vector machine

Information on subsidence in a water area caused by mining has a great value on the research of the mining subsidence law of a mining area with a high groundwater level in Eastern China. Based on the measured data of the subsidence area without water, the data extraction of subsidence in a water area is studied in this paper, with a support vector machine, as subsidence in such an area is difficult to measure. Research shows that the training sample number and dimension should be strengthened by increasing the measuring times or using the interpolation method to obtain ideal prediction accuracy. The ε-Support Vector Regression model with three parameters optimized by the genetic algorithm or the particle swarm optimization algorithm is suitable to extract subsidence information in a water area caused by mining, and the algorithm is accomplished on Matlab. Data analysis showed that when the water is deeper than 1.8 m and the distance is over 60 m from the measured points, the prediction error of test samples will exceed 10 % out of all measured results, meaning that practicability is relatively poor; while water depth is <0.8 m or the distance is lower than 60 m from the measured points, the prediction error of test samples will be calculated to <5 % of the measured results, the prediction results can be used.     

砂样图像岩屑自动分割提取方法

通过将砂样图像进行单颗粒分割,识别砂样成分,可显著提高砂样岩性分析的准确性和效率。现有的砂样图像分割方法主要以传统分水岭算法和卷积神经网络为主,但由于对单颗粒岩屑轮廓细节提取不足,误分割率高。本文提出一种以图像融合算法为桥梁,将卷积神经网络和分水岭算法相结合的单颗粒图像分割提取方法。首先利用改进的Mask R-CNN网络快速分割砂样原图,获得其初分割图像;然后,将初分割图像与砂样原图进行融合,再使用改进的分水岭算法对融合结果进行分割;最后,利用砂样原图坐标点匹配方法,将分水岭分割得到的结果图像进行修正,完成单颗粒岩屑图像提取。实验结果表明,本文的单颗粒自动分割提取方法准确率高达96.77%,且模型更轻量和精准,为岩屑图像分割提供了一种可行且有效的方法,可满足有效测算油藏层构造变化、查找潜在沉积物源及储层动态变化的需求。     

火成岩结构的二维定量化分析方法

近些年,定量化火成岩结构研究表明,利用常规的岩矿鉴定设备,获取不同尺度的火成岩二维岩相学照片,通过肉眼识别矿物颗粒,并借助图像处理和结构分析软件,可以准确地量化火成岩的结构特征。本文结合近些年国内外同行的研究成果,对火成岩二维定量化结构分析方法中常用的多种观测方式优缺点进行了总结。粒度在毫米级以下的火成岩的定量化结构参数,可以用偏光显微镜下的透射光、反射光、阴极发光和电子探针背散射成像中的两种或两种以上观测方式进行分析,并具有较高的精度和准确度。粒度小于0.03 mm的各种镁铁质矿物可用反射光和背散射图进行分析,灰度近似的镁铁质矿物可以利用图像处理软件赋予不同的彩色,提高颗粒间的辨识度。常规偏光显微镜下不易区分的长英质矿物和多数副矿物可用偏光显微镜阴极发光进行分析。粒度在毫米级以上的造岩矿物可以用光片或野外测量的方式进行定量分析。为了方便相关领域学者使用火成岩二维定量化结构分析方法,本文详细列出了具体的分析步骤,并结合一个玄武岩样品中的橄榄石斑晶数据结果,重点分析以下4个方面的问题:(1)如何准确识别矿物颗粒边界;(2)矿物含量和形态的确定;(3)分析区域面积和颗粒数的确定;(4)不同晶体群的区分。分析结果表明,颗粒数100~500颗时,晶体粒度分布(CSD)的截距和斜率、矿物含量、定向程度和粒状矿物的三轴比在误差范围内没有显著区别,但颗粒最大长度和聚集程度会被低估。当颗粒数小于300颗时,晶体空间聚集程度的R值会被高估0.05~0.2,这一点在以往的研究中没有得到充分重视。当颗粒数大于500颗时,所有结构参数都趋于稳定,且精度和准确度都会显著提高。目前多数研究者提供的结构参数往往与观测和统计方式有关,缺乏对应的原始数据,不方便同行间的对比研究,建议学者今后发表相关成果时,提供详细的分析步骤和最原始的数据。分析步骤重点说明包括:(1)聚集矿物边界的识别和处理方式;(2)晶体三维形态的确定方法,样品间CSD参数的变化是否是由形态参数变化引起;(3)能够准确识别的矿物颗粒最小粒度;(4)利用颗粒数较多的样品选取较小的不同区域重复分析3到5个不同区域,评估样品的均一性,并据此估计样品的分析精度。原始数据方面包括:(1)提供同一个样品至少一个不同区域的分析结果,如果是多个作者的研究成果,建议提供至少两人独立分析的结果用来评估数据的精度和准确度;(2)文章正文或附件中应该提供每个样品不同粒度间隔的颗粒数,样品原始的高分辨率矿物轮廓描绘图或图片分析的相关原始参数。火成岩出现复杂晶体群时,定量化的结构参数往往体现的是多种晶体群的混合特征,并且与不同晶体群的比例有关。未来的研究需要结合多种观测方式和微区成分分析重点识别不同晶体群的结构参数,对粒度和成分近似的多种晶体群的识别,还需要开发更多有效的方法,这对准确认识火成岩结构多样性的成因和岩浆作用过程都有重要意义。     

Comparison of elemental composition of macerals determined by electron microprobe to whole-coal ultimate analysis data

The elemental composition of the individual macerals in a suite of Australian coals has been determined in polished sections using light-element electron microprobe techniques. The analyses of the individual macerals in each coal were combined with data on maceral abundance to produce an inferred chemical composition for the organic matter of the respective whole-coal samples, and this was compared, for each sample, to the respective whole-coal ultimate analysis data, corrected to a dry, ash-free (daf) basis. Except for slightly lower values in some lower-rank coals, the inferred percentages of whole-coal C estimated from the microprobe data were found to be very close to the respective whole-coal C percentages as determined by conventional ultimate analysis. The proportion of O in the coals indicated by the microprobe study, however, appears to be as much as 2% higher than that derived from the ultimate analysis data, especially in the lower-rank coal samples. The difference it may represent errors in calculating the O percentages in ultimate analysis, errors in the microprobe analysis due to difficulties in calibration or measurement, or increased proportions of O in the coals due to factors such as take-up with storage of the polished sections. The percentages of whole-coal N calculated from the microprobe data are up to 0.5% (absolute) below the proportion of N determined directly by whole-coal ultimate analysis. This may reflect the inherent difficulty of dealing with a light element at low concentrations by the microprobe technique, or it may indicate that some of the N occurs in the coals in mineral form. The percentages of whole-coal (organic) S calculated from the microprobe study are close to the percentages of organic S determined for each sample by more conventional techniques. With the exception of (organic) O, which may be affected by other factors, and also possibly of N, the electron microprobe technique appears from the study to provide results that are consistent with ultimate analysis over a wide rank range.     

中国陆相源岩显微组分的分类及其岩石学特征

本文通过对中国6个主要油田及15个煤田共三百多块陆相源岩所作的详细有机岩石学研究,提出了以全岩与干酪根为基础的分散有机质分类方案,系统总结了显微组分光性、成因及分布规律,鉴定出了我国陆相源岩中三种新显微组分。此分类不仅适用于低成熟源岩,而且还可用来划分过成熟干酪根的显微组分。     

Electron-probe microanalysis of light elements in coal and other kerogen

Recent advances in electron microprobe technology including development of layered synthetic microstructures, more stable electronics and better matrix-correction programs facilitated routine microanalysis of the light elements in coal. Utilizing an appropriately equipped electron micro-probe with suitable standards, it is now possible to analyze directly the light elements (C, O and N, if abundant) in coal macerals and other kerogen. The analytical results are both accurate compared to ASTM methods and highly precise, and provide an opportunity to access the variation in coal chemistry at the micrometre scale. Our experiments show that analyses using a 10 kV accelerating voltage and 10 nA beam current yield the most reliable data and result in minimum sample damage and contamination. High sample counts were obtained for C, O and N using a bi-elemental nickel-carbon pseudo-crystal (2d = 9.5 nm) as an analyzing crystal.Vitrinite isolated from anthracite rank coal proves the best carbon standard and is more desirable than graphite which has higher porosity, whereas lower rank vitrinite is too heterogeneous to use routinely as a standard. Other standards utilized were magnesite for oxygen and BN for nitrogen. No significant carbon, oxygen or nitrogen X-ray peak shifts or peak-shape changes occur between standards and the kerogen analyzed. Counting rates for carbon and oxygen were found to be constant over a range of beam sizes and currents for counting times up to 160 s. Probe-determined carbon and oxygen contents agree closely with those reported from ASTM analyses. Nitrogen analyses compare poorly to ASTM values which probably is in response to overlap between the nitrogen K α peak with the carbon K-adsorption edge and the overall low nitrogen content of most of our samples.Our results show that the electron microprobe technique provides accurate compositional data for both minor and major elements in coal without the necessity and inherent problems associated with mechanically isolating macerals. Studies to date have demonstrated the level of compositional variability within and between macerals in suites of Canadian coals.     

手持式X射线荧光光谱分析仪在斑岩铜矿快速勘查中的应用

现场X射线荧光光谱(XRF)测量因样品的不平度效应、不均匀效应和湿度效应等面临的技术难题,使得手持式XRF现场原位分析结果与实验室分析结果存在一定偏差.本文现场手持式X射线荧光光谱分析仪的测试时间、样品含量、测试距离、样品干湿度和样品粒度等测试条件对测试结果的影响进行了定量研究.结果表明:在最佳测试时间90s条件下,得...     

XRF半定量分析技术在矿石光片鉴定中的应用

偏光显微镜反光镜下鉴定金属矿物是最常用、最快捷有效的方法,然而鉴定结果容易受到鉴定者主观因素或磨片情况的影响。为了更快速、准确地在反光镜下鉴定矿物,利用XRF半定量分析技术快速、无损、前处理简单等特点,以及磨平抛光的矿石矿物在半定量分析过程中能较好地避免楔入效应和阴影效应的有利因素,采取了先用XRF半定量分析测得的结果去反推矿物,再在显微镜下鉴定矿物的方法。以多金属硫化物矿石、含铀多金属矿石及含微量铀的矿石样品为例进行鉴定,结果表明,在鉴定前知道光片上的元素及其质量分数,通过地球化学方法和经验法反推矿物,结合显微镜观察需要鉴定的矿物,可有效避免忽略掉透明/半透明矿物（锡石）、小粒径矿物（沥青铀矿）、易混淆矿物（铀黑）,提高光片鉴定工作的效率和准确性。     

Automated petrographic characterization of coal lithotypes

Although petrographic analysis of the lithotypes present in coal samples has been successfully used in the correlation of coal seams, the study of the environments of coal seam deposition, and the evaluation of the mining and cleaning properties of numerous coal seams, coal lithotype analysis is not routinely performed in North America at this time because it is very time consuming and requires the services of a highly skilled petrographer. The objective of this study was to evaluate the capability of one of the newly improved image analysis microscope systems to characterize coal lithotypes and perform automated lithotype analyses on polished block samples of coal.The results of this study show that each of the lithotypes examined, vitrain, clarain, fusain, and durain, yield a characteristic reflectance histogram and that analysis of reflectance histograms taken from a transverse, perpendicular to bedding, down a polished block sample yield results on the kinds and thicknesses of the lithotypes present that are in good agreement with the results obtained by manual methods.     

四川盆地五峰—龙马溪组黑色页岩有机岩石学特征研究

目前五峰—龙马溪组黑色页岩中显微组分缺乏统一的分类方案,命名也较为混乱,给页岩气勘探与评价造成了困难。为此,采用全岩光片和有机地球化学(TOC、δ¹³C_org)分析等方法,对四川盆地五峰—龙马溪组黑色页岩中显微组分进行有效识别与特征总结,探讨其可能成因,并判断其有机质类型。研究结果表明:五峰—龙马溪组页岩中显微组分主要由海相镜质组、腐泥组、动物有机碎屑组和次生组组成。其中,海相镜质组由无结构镜质体组成,呈浑圆状或长条状,具有强的光反射能力,但分布并不广泛;腐泥组主要由无结构腐泥体组成,为藻类遭受热降解过程而形成的无结构且无固定形态的显微组分,在富有机质页岩中广泛分布;动物有机碎屑组主要包括笔石表皮体、几丁虫和放射虫有机碎屑体;次生组由次生沥青体组成,广泛分布在页岩基质孔隙中,呈无固定形状。五峰—龙马溪组页岩中主要发育腐泥组和次生组,其次为动物有机碎屑组和海相镜质组,其有机质类型以Ⅰ-Ⅱ₁型干酪根为主,且腐泥组和次生组含量越高,有机质类型越好,其生烃潜力越大。     

A quantitative fluorescence technique for evaluating thermal maturity: Instrumentation and examples

Fluorescence microscopy is useful not only for identifying most of the oil-prone organic matter (macerals) in sedimentary rocks and coals but also for assessing their thermal maturities (ranks). This report introduces a violet-light excitation system which induces more than one order of magnitude stronger fluorescence intensity that the commonly used UV-light excitation system. The red/green quotient from violet-light excited fluorescence, Q_v, of sporinite can be easily measured using this system. Several examples using coal and cuttings samples are presented to demonstrate the use of this technique for evaluating the thermal maturities of coals and sedimentary rocks.From the results of our studies we conclude that:

• 1.(1) Violet-light excited fluorescence from sporinites can be routinely measured to assess thermal maturity.
• 2.(2) Spectral (Quantitative) fluorescence technique is useful for evaluating thermal maturity when samples are poorly polished or deficient in vitrinite.
• 3.(3) Visual (Strew-mounted) kerogen slides can not be used for fluorescence measurements unless a non-fluorescent mounting medium is used.

     

Digital gamma activation autoradiography: A method for the study of inclusions and mineralogical texture of large size geological polished thin sections

The nuclear analytical method of element mapping in large-sized (several dozen cm²) polished sections of geological samples was worked out. The method includes activation of the sample by bremstrahlung of an electron accelerator using a developed device for uniform sample irradiation. The next step is to obtain a series of digital autoradiograms, which is processed by the program for estimation of the decay dynamics of induced radioactivity for each pixel of the image. The data obtained are converted into a series of metaimages characterizing the distribution of induced radionuclides (measured elements) over the surface of polished thin sections. The results of mapping are in a good agreement with the data of scanning electron microscopy. The developed method is suggested for screening detection of element distribution including distinguishing of the sample zones containing PGE inclusions.     

基于数字图像处理技术的砂土颗粒级配分析研究

砂土颗粒级配是影响砂土工程性质的重要参数之一，传统的颗分试验方法由于试验原理不同而具有不同的适用范 围。为更加方便、准确地获取砂土颗粒级配，提出了一种基于数字图像处理技术来获取SEM照片中的砂颗粒粒径参数及级 配特征的新方法。将准备好的砂土样品打磨成薄片放在扫描电镜下拍照，然后利用Photoshop软件对照片进行拼接，并采用 自主研发的SMAS数字图像分析系统对拼接好的照片进行定量分析处理，获取样品的微观结构参数，将获得的“土颗粒等 效直径”和“土颗粒面积”分别等效为实际土颗粒粒径和土颗粒质量，进而换算得到砂土的颗粒级配曲线；然后将通过数 字图像技术获得的砂土颗粒级配曲线与通过传统筛分法和激光粒度分析法得到的颗粒级配曲线进行对比，验证了提出的数 字图像处理方法的有效性和可靠性，同时分析了两种方法之间存在的差异及其原因，并对数字图像处理方法和传统颗分方 法各自的优缺点进行了讨论。     

基于数字图像处理技术的砂土颗粒级配分析研究

砂土颗粒级配是影响砂土工程性质的重要参数之一,传统的颗分试验方法由于试验原理不同而具有不同的适用范 围。为更加方便、准确地获取砂土颗粒级配,提出了一种基于数字图像处理技术来获取SEM照片中的砂颗粒粒径参数及级 配特征的新方法。将准备好的砂土样品打磨成薄片放在扫描电镜下拍照,然后利用Photoshop软件对照片进行拼接,并采用 自主研发的SMAS数字图像分析系统对拼接好的照片进行定量分析处理,获取样品的微观结构参数,将获得的“土颗粒等 效直径”和“土颗粒面积”分别等效为实际土颗粒粒径和土颗粒质量,进而换算得到砂土的颗粒级配曲线;然后将通过数 字图像技术获得的砂土颗粒级配曲线与通过传统筛分法和激光粒度分析法得到的颗粒级配曲线进行对比,验证了提出的数 字图像处理方法的有效性和可靠性,同时分析了两种方法之间存在的差异及其原因,并对数字图像处理方法和传统颗分方 法各自的优缺点进行了讨论。     

An expert system based on hybrid ICA-ANN technique to estimate macerals contents of Indian coals

Coal, as an initial source of energy, requires a detailed investigation in terms of ultimate analysis, proximate analysis, and its biological constituents (macerals). The rank and calorific value of each type of coal are managed by the mentioned properties. In contrast to ultimate and proximate analyses, determining the macerals in coal requires sophisticated microscopic instrumentation and expertise. This study emphasizes the estimation of the concentration of macerals of Indian coals based on a hybrid imperialism competitive algorithm (ICA)–artificial neural network (ANN). Here, ICA is utilized to adjust the weight and bias of ANNs for enhancing their performance capacity. For comparison purposes, a pre-developed ANN model is also proposed. Checking the performance prediction of the developed models is performed through several performance indices, i.e., coefficient of determination (R ²), root mean square error and variance account for. The obtained results revealed higher accuracy of the proposed hybrid ICA-ANN model in estimating macerals contents of Indian coals compared to the pre-developed ANN technique. Results of the developed ANN model based on R ² values of training datasets were obtained as 0.961, 0.955, and 0.961 for predicting vitrinite, liptinite, and inertinite, respectively, whereas these values were achieved as 0.948, 0.947, and 0.957, respectively, for testing datasets. Similarly, R ² values of 0.988, 0.983, and 0.991 for training datasets and 0.989, 0.982, and 0.985 for testing datasets were obtained from developed ICA-ANN model.     

Variations in the type and distribution of organic matter in some Carboniferous sediments from northern England

The organic content of a number of sediments from the Carboniferous of northern England have been examined as a function of their depositional environment. Extraction of the sediments yielded the soluble organic matter whilst microscopic examination of polished blocks of shales enabled the detection of particles of organic detritus. A relationship between the amount of extract and the quantity of terrestrial plant material in the sediments has been established. However, the yield of extract (mg/g org. C) is higher in the more marine environment than the nonmarine environment. The proportion of saturated hydrocarbons in the extract appears to be related to the amount of identifiable organic matter (coal macerals) in the sediment. The n-alkane distribution patterns have been compared with these obtained from coal macerals. The suggestion that the pristane to phytane ratios may reflect the source material of the organic matter has been examined.     

X-ray fluorescence analysis of silicate rocks using fused glass discs and a side-window Rh source tube: accuracy, precision and reproducibility

In this paper, we provide a detailed account of our sample fusion, calibration and instrumentation methods for major-element whole-rock analysis by XRF, and we discuss several aspects of sample preparation and instrument performance that are important considerations for accurate analysis. The fusion procedure involves moderate capital costs and is easy to apply, yielding flat, polished, homogeneous glass discs as cast. The calibration method utilizes a least-squares procedure that rigorously fits data according to both compositional and counting statistical uncertainties. We use a side-window Rh tube for analyzing major elements (including Na) and employ real-time testing for constant count rate to reject spurious results.

The methods result in excellent analytical precision and reproducibility. The standards used for calibration lie within compositional and counting statistical uncertainties of best-fit straight lines. Analyses of replicate discs and repeated analyses of single discs show excellent long-term reproducibility over several months, approaching counting statistical uncertainties in several cases. Comparison with independent measurements made by other laboratories using instrumental neutron activation and X-ray fluorescence analyses shows excellent agreement with our results.

A side-window Rh tube gives increased detection limits for most major elements, but otherwise shows little difference in precision compared to a Cr tube. This means that major and trace elements can be analyzed without changing X-ray sources, which provides saving in terms of time and money, as well as being a convenience to the analyst.     

煤岩显微图像假边界对显微组分组自动识别的影响

在利用图像分析技术进行煤岩自动化检测过程中,发现煤岩显微图像中各种成分的边界表现为"镶边"状的灰度过渡区,过渡区像素点灰度不能反映其两侧显微成分的真实灰度。为了分析这种假边界对煤岩显微组分组识别检测的影响,通过对全国大量煤岩样品所采集显微图像分析的基础上,对各种相邻成分间假边界的特征、成因进行了分析。假边界一般多呈环状、条带状"镶边"形态,呈现出与相邻成分灰度相衔接的灰度斜坡特征,假边界灰度斜坡宽度与煤岩显微图像中各种成分的组合类型相关。假边界的形成是由于煤中各种成分的硬度及韧性差异引起突起高低不同,成像时在不同成分的边界呈现灰度斜坡。选取10个不同变质阶段代表性煤样,利用Prewitt算子对样本假边界进行边缘检测提取,提取的假边界过渡区像素占比整体煤颗粒图像的10%~27%;并将测定结果与国内资深煤岩专家人工鉴定的标准结果进行比对,结果表明,剔除假边界后测定的镜质组、惰质组、壳质组的极差远低于未剔除假边界的极差,更为接近人工鉴定结果。