层序地层地球化学及其在油气勘探中的作用

层序地层地球化学主要研究基于层序地层格架下的烃源层空间分布特征和源岩有机质的地球化学性质随层序、体系域的变化规律。以大民屯凹陷为实例的研究结果表明,层序地层地球化学研究在油气勘探中具有4个方面的主要作用:(1)预测未钻井或未取心地区烃源层空间分布特征和源岩有机质地球化学性质;(2)通过细化烃源岩评价单元,提高资源量计算中烃源岩体积估算和有机质性质评价的精度;(3)为基于层序地层格架的油气成藏系统研究提供“油气源”和“资源量”的要素;(4)可以作为盆地沉积充填分析的线索,并对已建立的层序地层格架进行检验和校正。层序地层地球化学研究不仅对中国东部老油田隐蔽油气藏的勘探工作具有重要的意义,对勘探程度低、钻井少、源岩取心少的西部含油气盆地中的烃源岩评价工作更为有效。     

An application of cluster analysis in mineral exploration

This paper presents a technique for evaluating the similarity of ore deposits utilizing several geological variables. Information on tungsten mines in North America, taken from published literature, was used for a cluster analysis to group samples according to their similarity based on a simple matching coefficient. It was possible to interpret and evaluate different ore environments that clustered according to age, mineralogy, and other variables. Cluster analysis may be important in mineral exploration where considerable amounts of data are available for analysis. Subtle relationships that might be overlooked because the data are too voluminous can be isolated using this technique. It also can be used to establish exploration priority in unknown areas on the basis of similarity to known metallogenetic provinces.     

Fuzzy cluster analysis in geochemical exploration

As a classification method, cluster analysis has been widely used in geology and geochemical exploration, but sometimes the results of clustering were difficult to interpret, or missclassification of geochemically similar members into entirely different clusters might occur. The reason for this is suggested and discussed. A new technique, fuzzy clustering is introduced. Comparision of the results of fuzzy clustering with conventional clustering using a set of hypothetical data is made. An example of a practical application indicating the apparent merits of fuzzy clustering is given. This technique might show great promise when applicated to geochemical exploration problems.     

石榴石微量元素地球化学及其在沉积物源分析中的应用

石榴石是沉积物中常见的重矿物,其可来源于多种岩石,而且不同类型母岩中石榴石具有多样的地球化学组成,因此碎屑石榴石的地球化学分析在沉积物源研究中应用广泛。通过电子探针分析可以容易地获得单颗粒碎屑石榴石的主量元素地球化学组成,可借此探讨其母岩类型,但也存在一定的局限性,比如中酸性火成岩和部分变沉积岩来源的石榴石通常都具有高Fe、Mn的特征,不易于区分。本文系统地收集了不同岩石类型的石榴石微量元素数据,尝试利用微量元素地球化学的差异性对碎屑石榴石物源分析进行补充。最终得出以下结论:(1)石榴石的稀土元素(REE)组成与钇(Y)元素指标可区分中酸性火成岩和变沉积岩来源的碎屑石榴石;(2)基性岩(橄榄岩、辉石岩)及所对应的变基性岩石(榴辉岩)中石榴石的微量元素地球化学组成相近,但部分橄榄岩来源的石榴石在镨/钬(Pr_N/Ho_N)值和重稀土总量(ΣHREE含量)上与辉石岩和榴辉岩的有显著差别,这一特点可运用于以基性岩母岩为主的碎屑沉积物源研究中;(3)夕卡岩中的石榴石在主量元素地球化学组成上表现为高度一致的高Ca特征,而稀土元素组成具有两种典型的分配模式,岩浆型(指示富铁、氧化环境)与热液型(指示富铝、还原环境)。综上所述,石榴石微量元素地球化学可以有效地运用于沉积物源分析研究中,是其主量元素物源分析方法的重要补充。     

地球化学勘查新技术应用研究

地球化学勘查是资源和环境领域一种十分重要的勘查评价方法技术.最近十年来地球化学勘查新方法新技术研究的重要进展主要表现在以下几个方面:①基本解决了森林沼泽区、干旱半干旱高寒山区、高寒湖沼丘陵区中普遍存在的有机质和/或风成沙对水系沉积物测量的严重干扰问题,确定采样粒级为:森林沼泽区和高寒湖沼丘陵区-10～+60目,干旱半干...     

对应聚类分析与盲矿体的地球化学预测

为利用矿区地球化学数据进行找矿靶区预测,采用了对应聚类分析方法。以山东省平度地区旧店金矿3号脉的实例,说明该方法的实施过程和应用效果。结果表明,该方法以简单步骤和单一图件揭示了在多元地球化学数据中隐藏的核心信息,正确识别了元素含量较低地段的隐伏矿体,为隐伏矿靶区预测探索了一种新的途径。     

定向岩芯构造分析及在金矿勘查中的运用

系统测量定向岩芯中构造面的α角和β角,结合钻孔的方位角和钻孔倾角,通过赤平投影可以还原真实的构造面产状.通过穿过金矿体的定向岩芯的构造编录和系统分析,计算矿体中的主要含矿节理、含矿蚀变带等构造面的产状,并进行统计分析,可以了解矿化与各类构造之间的关系,计算矿体的空间产状,并推断主矿体的延伸等,为矿区的深部勘查设计提供依据.     

The application of different analytical extractions and soil profile sampling in exploration geochemistry

This paper deals briefly with the principles of geochemical migration in the secondary (soil, sediment) environment, a knowledge of which is essential to a correct interpretation of exploration geochemical data. Examples are given which illustrate that the principles which apply in the more easily interpreted tropical areas, also apply in the more complicated glaciated regions. Any person employing exploration geochemistry in geomorphologically complicated areas, is well advised to study data from strictly residual soil areas where the fundamentals of geochemical migration are more easily observed. From this base it is easier to understand the additional complications of geochemistry in mountainous and glaciated terrain. Of the variety of exploration geochemical techniques which can be used, this paper deals specifically with two: soil profile sampling, and different strengths of acid extraction of metal from samples. Examples from the different environments are compared and contrasted.     

Determination of background and threshold in exploration geochemistry

The graphical methods of analysing bi-modal frequency distributions are reviewed. The effects of inflection point position, curvature of the sigmoid, polymodality, and graphical and analytical precision are found to be important and are discussed in detail. The optimum method is a cumulative plot on log-probability paper with the two component distributions (linear) being asymptotic to the sigmoid tails and having a symmetry with each other about the inflection point. The method is illustrated with five natural examples to emphasise its advantages and limitations.     

Google Earth高程数据精度分析及在地震勘探中的应用

地震勘探勘查区往往位于偏远地区,已知地形资料较少。 Google Earth（简称GE）采用的数字高程模型数据为SRTM,精度较高。笔者在批量提取GE高程数据的基础上,分别对山区和平原地区的GE高程数据的精度进行了分析。结果表明,无论是在山区还是平原地区,GE高程数据均与地表实际高程基本一致;在平原地区的精度高于山区;GE高程数据可以满足等高线生成和观测系统参数分析的需要。     

云南金宝山铂钯矿床铂族元素地球化学及找矿意义

金宝山是中国目前发现的最大的独立铂钯矿床,该岩体基性程度高,主要由橄榄石、单斜辉石组成,含大量铬铁矿〔w(Cr)约为0.5%〕。铂钯矿石呈稀疏浸染状,硫化物含量少,高铂族元素、低铜镍含量。矿体与超基性围岩界线不明显,且二者具有相似的微量、稀土元素参数和微量、稀土、铂族元素标准化配分模式,表明两者的原始岩浆具有相似的性质。超基性围岩具有高的Pd/Ir、Ni/Cu比值和Pb负异常,相反,铂钯矿石显示为低的Pd/Ir、Ni/Cu比值和Pb正异常,两者具有相似的Cu/Pd、Cu/Pt比值(≤原始地幔值),表明铂钯矿石形成于地幔柱S低度饱和环境,超基性围岩可能形成于S饱和/不饱和的地球化学界面。铂族元素地球化学的差异表明含少量富铂族元素的硫化物的含矿岩浆可能注入于稍前侵入的、且未完全固结的超基性围岩中,形成似层状矿体。峨眉地幔柱早期硫低度饱和、融离出少量硫化物以及铂族元素在硫化物/硅酸盐相中极高的分配系数是导致金宝山矿石富铂钯、贫铜镍的根本原因。金宝山是极少有的全岩体Cu/Pd、Cu/Pt值均小于原始地幔值的矿床,表明该岩体的岩浆经历了硫化物富集铂族元素的过程,推测靠近峨眉地幔柱喷发中心的基性-超基性岩体是寻找铂族元素矿床最佳远景区之一。     

Supergene geochemistry and crystal morphology of gold in a semiarid weathering environment: application to gold exploration

Oxidation of sulfide- and carbonate-rich vein gold deposits under semiarid conditions can be represented as a three-stage process, each creating supergene environments conducive to dissolution and reprecipitation of gold-silver alloys. The three-stage weathering process of sulfide-carbonate gold veins is depth-dependent, and develops from the relatively young, lowermost weathering horizon just below the water table, through an intermediate weathering horizon in the oxidation zone above the water table, and culminating in the oxide-rich upper saprolite and oxisol.Neoformed gold crystals in the weathering profile have distinct composition and morphologic characteristics from the hypogene gold crystals associated with the sulfide- and carbonate-rich ores. Two distinct types of secondary gold are present in the weathering profile: (1) gold crystals associated with sulfates and arsenates; and (2) gold crystals associated with iron and aluminum oxides/hydroxides, or with kaolinite. The distinct crystal morphologies and mineralogical associations of primary and secondary gold are useful in prospecting for gold deposits in weathered terrains.     

The application of cluster analysis in geophysical data interpretation

A clustering algorithm that is based on density and is adaptive density-reachable is developed and presented for arbitrary data point distributions in some real-world applications, especially in geophysical data interpretation. Through comparisons of the new algorithm and other algorithms, it is shown that the new algorithm can reduce the dependency of domain knowledge and the sensitivity of abnormal data points, that it can improve the effectiveness of clustering results in which data are distributed in different shapes and different densities, and that it can get a better clustering efficiency. The application of the new clustering algorithm demonstrates that data mining techniques can be used in geophysical data interpretation and can get meaningful and useful results, and that the new clustering algorithm can be used in other real-world applications.     

Conceptual models in exploration geochemistry: Norden 1975

This compilation and summary of geochemical exploration conditions in Norden is the second in a series of special issues on exploration geochemistry. The first issue dealt with the Canadian Cordillera and Canadian Shield. The conceptual models from the Canadian Shield form an integral part of the present volume. These studies are an attempt to pull together very extensive exploration geochemical information and define it in terms of a limited number of conceptual models.A total of 45 case histories are presented in this volume which cover various aspects of collection, analysis and interpretation of data from glacial till, stratified drift, organic deposits, stream sediments and water. These data are described in a relationship to the conceptual models outlined by Bradshaw (1975). An overall summary is given with respect to these models and also a summary is given of the relative importance of frost heave, transport by glaciation, transport by water and wind, multiple glacial transport, ion and molecular dispersion, groundwater transport, transport by capillary water, electrochemical transport and mixed dispersion.The final section contains 13 short articles dealing with methods of geochemical exploration which are presently used in the different countries of Norden.