用自然伽玛曲线与岩石粒序关系解释沉积相

分析了三角洲相的自然伽测井曲线与岩石粒度的相关关系，并应用数学处理方法，对自然伽至测井曲线形态特征进行了量化，建立起与各种沉积相相对应的测井曲线形态标准特征模式，利用计算机自动解释沉积相类型。     

A multivariate sedimentary environmental analysis of Great South Bay and South Oyster Bay, New York

A multivariate statistical strategy for classifying paleoenvironments is effective for studying modern sedimentary processes in western Great South Bay and South Oyster Bay, New York. The 13 whole phi weight percent variables were tested for redundancy with R-mode cluster analysis. The samples were partitioned statistically into five environmentally significant facies using Q-mode cluster analysis: (A)sandy gravel, (B)sandy silt, (C)silty sand, (D)slightly gravelly sand, and (E)fine sand. An ordination depicted gradational relationships among the samples and the facies. It was used to evaluate the environmental and textural parameter gradients within the sample space. Interpretations obtained in this manner and by examination of the grain-size curves suggest that these sediments were deposited by waves and currents on beaches and in wave zones (facies C and E),shoal areas (facies B),and tidal channels (facies A and D).Tidal currents, wave action, and eelgrass control the distribution of sediments within the two bays.     

基于地面光谱的海涂土壤开发程度评价研究——以浙江省上虞市海涂围垦区为例

过去 30年间 ,浙江沿海滩涂地不断地被围垦成农用地。为了科学地掌握海涂土壤的变化规律 ,讨论了地面光谱评价海涂土壤开发程度的可行性。以浙江省上虞市北部海涂围垦区作为研究区域 ,根据围垦历史时间的不同 ,将研究区划分成 4个子区域。借助GPS定位 ,样区内大致间隔 1km进行混合采样。分别在实验室内测定土壤理化性质和土壤光谱反射率。理化性质分析结果表明海涂土壤有机质含量低 ,电导率和含砂量高 ,并且随着围垦时间的增长呈现出规律性的变化。 9个吸收波段与土壤电导率、阳离子交换量和机械组成的Person相关分析表明 ,海涂土壤砂粒、粉粒含量与各波段相关性显著。依据不同围垦历史 ,对所有土样进行分组 ,并进行逐步判别分析。判别结果表明 ,处于不同围垦区并具有不同改良程度的土样 ,其光谱数据具有很好的类可分性。对原始样点数据回代到Fisher辨别函数可以获得 86 8%的判别精度 ,而对 2 8个待判土样代入判别函数可获 89 3%的判别精度。从地面光谱研究结果可见 ,相比于常规的野外耗时调查 ,星载或机载遥感探测器有可能作为大范围快速评价盐碱土开发程度的有效潜在工具     

甘肃寨上金矿床构造地球化学特征

寨上金矿位于西秦岭中部岷-礼成矿带西部,所发现的三十余条金矿化脉体的空间分布及其产出特征严格受断裂和褶皱的双重控制,以扎麻树背斜为界分为南北2个成矿带,产出的已知矿脉均严格受控于NWW向断裂.通过对寨上金矿50件构造地球化学样品16种微量元素数据的聚类分析、因子分析,以及对样品元素的组合特征研究,北矿带含矿断裂的元素组合为Au,Bi,Pb,Zn;南矿带的为Au,Sb,Hg,Cu,Zn,Pb,Co,Bi,As.以已知的矿与非矿构造样品为母体,利用多元统计判别分析,建立了断裂含矿性的判别函数,并对未知的17个样品进行判别分析,其判别结果与野外验证一致.     

Statistical Evaluation of Compositional Differences Between Upper Eocene Impact Ejecta Layers

Melt droplets formed by the impact of a large meteorite impact event(s) have been found in upper Eocene marine sediments from the Atlantic, Pacific, and Indian oceans. The number of discreet impacts that occurred to form these melt droplets can be gleaned by compositionally analysing the droplets and establishing the number of distinct groups. Previous studies have inferred two, three, or more source impact events, although we believe the statistical techniques used to distinguish the groupings are open to criticism. Multivariate and univariate analysis (including discriminant analysis) of the major-element composition of an increased data set of impact melt ejecta droplets have been performed. The results demonstrate that the uppermost ejecta layer is geochemically distinct from other late Eocene melt ejecta. Our statistical analysis suggests two underlying, purportedly stratigraphically separate ejecta layers, possess minimal differences that cannot be distinguished clearly from one another by discriminant analysis, which adds to the plausibility that they have a common source. Finally, our results reveal apparent disparities between the new major-element data from this study and data compiled from existing sources.     

Apatite as an indicator mineral for mineral exploration: trace-element compositions and their relationship to host rock type

Over 700 apatite grains from a range of rock types have been analysed by laser-ablation microprobe ICPMS for 28 trace elements, to investigate the potential usefulness of apatite as an indicator mineral in mineral exploration. Apatites derived from different rock types have distinctive absolute and relative abundances of many trace elements (including rare-earth elements (REE), Sr, Y, Mn, Th), and chondrite-normalised trace-element patterns. The slope of chondrite-normalised REE patterns varies systematically from ultramafic through mafic/intermediate to highly fractionated granitoid rock types. (Ce/Yb)_cn is very high in apatites from carbonatites and mantle-derived lherzolites (over 100 and over 200, respectively), while (Ce/Yb)_cn values in apatites from granitic pegmatites are generally less than 1, reflecting both HREE enrichment and LREE depletion. Within a large suite of apatites from granitoid rocks, chemical composition is closely related to both the degree of fractionation and the oxidation state of the magma, two important parameters in determining the mineral potential of the magmatic system. Apatite can accept high levels of transition and chalcophile elements and As, making it feasible to recognise apatite associated with specific types of mineralisation. Multivariate statistical analysis has provided a user-friendly scheme to distinguish apatites from different rock types, based on contents of Sr, Y, Mn and total REE, the degree of LREE enrichment and the size of the Eu anomaly. The scheme can be used for the recognition of apatites from specific rock types or styles of mineralisation, so that the provenance of apatite grains in heavy mineral concentrates can be determined and used in geochemical exploration.     

李坝金矿田构造地球化学特征及其找矿意义

本文从野外地质实际出发 ,系统研究了区内广泛发育的断裂构造特征及其与金矿化的关系 ,将断裂分为三级 , 、 级断裂主要为导矿和配矿构造 ,NW、NWW向的 级断裂为最有利的赋矿构造。据此 ,以构造地球化学的观点为指导 ,借助计算机化探数据处理系统 ,对系统采集的构造地球化学样品的 17个元素分析成果进行系统研究和 R型聚类分析等处理 ,将构造与金矿化的关系转化为构造地球化学特征 ,进而转化为找矿指标。研究表明 :含矿 (赋矿 +矿化 )断裂的特征元素组合为 :Au、Ag、As、Sb、Pb;非矿断裂的特征元素组合为 :Cr、Mn、Ti、V。将已知的赋矿、矿化和非矿断裂作为母体 ,利用多类判别分析建立了非矿、矿化和赋矿断裂判别函数 ,对已知的 2 3条断裂进行判别分类 ,错判 3条 ,准确率为 87%。该成果已应用于实际找矿工作中 ,通过对 11处未知区构造的含矿性研究 ,系统采取构造地球化学样品和进行相应的多元素分析 ,经判别后指导找矿 ,共发现金矿体三条 ,矿化体五条 ,取得了良好的找矿效果     

苏皖北部上元古界地球化学特征及其波浪式演化

本文应用多种数学地质方法研究苏皖北部上元古界的地球化学特征,并探讨了地球化学演化的波浪式特征及其与构造运动波动性的关系。作者认为,化学波浪是普遍存在的客观事实,其时空演化特征可以在一定范围内用来进行地层的划分和对比。     

Classification problems of samples of finite mixtures of compositions

A discriminant technique based on mixture models is presented to be applied when observations are a sample of a mixture of compositions with each component following an additive logistic normal distribution on the d-dimensional simplex. The efficiency of this discriminant technique is compared empirically with the efficiency of the standard discriminant technique based on logcontrast. Simulated compositional data and a real dataset are used to carry out these comparisons.     

Application of discriminant analysis to evaluate compositional controls of stratiform massive sulfide deposits in Canada

Multiple discriminant analysis is used to identify systematic variations of Cu, Pb, Zn, Ag, and Au grade values in the Canadian massive sulfide deposits with the three geological parameters of age, environment, and composition of volcanic lithology. The deposits have been separated into three groups on each of the three parameter scales and discriminant functions that separated the three groups on the basis of metal grades were then obtained. The results of the analysis indicated that Pb and Cu are the most significant in indicating specific trends along the three geological parameter scales. Pb grade increases in younger deposits with an increase in the sedimentary character of their environments, or with a more felsic nature to their volcanic rocks. On the other hand, Cu grade increases in deposits that occur in volcanic environments and with a more mafic nature to the volcanic host rocks. The results could have useful applications in mineral exploration.