共查询到17条相似文献,搜索用时 984 毫秒
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近年来,国内外有不少关于发现“狗头金”的报道。但在报道中通常对于这种块金是否伴生有脉石矿物及其所处的地质条件却很少叙述。通过报道资料的统计可以看出,这些“狗头金”绝大多数是在砂金矿中发现的,目前,世界上已知最大的是1873年在美国加利福尼亚州找到的,重达285千克。笔者将那些产于砂矿中的块金称为“狗头金”,产于原生矿中其重量大于1克的金块叫做自然金块,以示区别。现在已有不少金矿专家、学者,开展了对自然金块及“狗头金”形态和成因的研究,提 相似文献
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由地质矿产部成都地质矿产研究所负责,中国科学院成都生物研究所参加合作的国家自然科学基金和地质行业基金联合资助的中国西部“金三角”地区狗头金形成机理和生物—化学聚金工程”经过三年的努力,取得了显著成绩。 中国西部金三角地区(川西藏东及青—甘—陕南部)广泛分布的砂金及狗头金(块金),主要产于青藏高原及周缘切割带的新生代山间盆地边缘的河流支谷或阶地及坡积物中。如四川西部白玉山孔隆沟中下游一段长400m,宽50m的“弹丸之地”,近5年来挖掘出至少15块500g以上的狗头金(大块金)。松潘漳暗和盐源 相似文献
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王义文 《矿物岩石地球化学通报》1985,(2)
一般认为,沉积岩中的工业金矿床只有砂金和砾岩金矿,它们都是纯机械搬运作用的结果。但事实表明,除机械作用外,化学作用、生物作用和物理化学作用对金在沉积物中的聚集都是不可忽视的。 1.“狗头金”的形成与砂金矿的再生澳大利亚和苏联南乌拉尔是世界上发现“狗头金”最多的两个地区,南乌拉尔曾获得俄国最大的的“狗头金”(36公斤)。澳大利亚曾发现 相似文献
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利用化探方法寻找石英脉型金矿的成功实例,在近期报导中时有所見;然而多数是采用与金伴生的某些含量較高、易于分析的有色或特种金属元素作为找金的指标。与金伴生的元素,它們的原生分布特点与金可能一致,也可能不同;它們的分布范围較 相似文献
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C.O. Ingamells 《Geochimica et cosmochimica acta》1981,45(7):1209-1216
Histograms of mining exploration data are often skewed, with many low assays and fewer higher values. During evaluation, causes of the skew should be investigated. If it is due to large-scale gradation in the mineral content of the deposit, geostatistical evaluation is indicated. If. however, nugget effects or reduction and subsampling errors are large, geostatistical approaches are at a disadvantage.Nugget effects may arise from a practical impossibility of taking sufficiently large field samples: reduction and subsampling inadequacies may be difficult to detect and overcome during the urgencies of an exploration campaign. Means have been devised to measure variances due to nugget effect and subsampling error and remove them from the data. 相似文献
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Two different Markov models for cross-covariance and coregionalization modeling are proposed and compared in cokriging and stochastic simulation modes. The newly introduced Markov model 2 performs better in cases where the secondary data are defined on a larger support volume than the primary variable being estimated or simulated. Incorrect adoption of the more traditional Markov model 1 may result in cokriging estimated maps that are artificially too close to the secondary data map and in simulated realizations with too high nugget effect. 相似文献
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文中阐述并归纳了近年地质样品中铂族元素的分离、富集及测试方法方面的最新进展。铂族元素本身的超痕量性,要求实验过程中对空白值的控制,干扰元素的扣除和检测限的降低更为严格,同时要克服块金效应。文中对消解过程中常用的火试金法、酸溶、碱熔方法和卡洛斯管法(Carius tube),分离富集过程中的Te共沉淀和离子交换法,测试手段中的原子光谱法、中子活化法和等离子质谱法等方法的最新进展进行了总结。由于复杂的地质样品中PGE的浓度范围不一、赋存形式多样,要求在具体样品分析过程中灵活地搭配使用各种分离富集和检测方法,结合笔者所在实验室在实验过程中发现的问题,对各种不同类型地质样品中铂族元素的分离富集、样品处理及测定方法也进行了总结。 相似文献
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On the Existence of Mosaic and Indicator Random Fields with Spherical,Circular, and Triangular Variograms 总被引:1,自引:1,他引:0
Xavier Emery 《Mathematical Geosciences》2010,42(8):969-984
This paper focuses on two specific families of stationary random fields (namely, mosaic and indicator random fields) and examines
the question of whether the variogram of a member of these two families could be spherical, circular, or triangular. It is
shown that there are such examples in one-dimensional spaces, while there are counterexamples in higher-dimensional spaces
for mosaic random fields, indicators of Boolean random sets and indicators of excursion sets of Gaussian random fields. Further
results concerning the spherical plus nugget and circular plus nugget variograms are provided. 相似文献
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In order to elucidate the genesis of green and orange glasses in Apollo 15 and Apollo 17 samples of lunar rocks, two alternative hypotheses are analyzed, according to which the glasses are produced either (1) by a comet or meteorite impact (impact model) or (2) by volcanic activity (volcanic model). The green and orange glasses are clearly genetically and petrochemically autonomous, i.e., the composition of the glasses themselves differs from those of the major types of the primary rocks. The mechanisms responsible for the origin of the glasses are analyzed along with mathematical models of their genesis. The theoretically calculated size distribution of glass particles is in good agreement with those measured in Apollo 15 and Apollo 17 samples. Simulation results and the analysis of the composition and structure of the green and orange glasses lead to the conclusion that the impact hypothesis of their genesis is the most realistic. 相似文献
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根据岩石学特征,本文全岩样品被分为三组。各组岩石具有不同的微量元素含量和锶氧同位素组成,还呈现不同的变异特征。各类岩石的Rb,Ba,Nb,Sr等元素含量明显高于原始地幔值。这些特征与其他已发表的资料均反映出超镁铁岩和铬铁岩有地幔残余成因和岩浆结晶成因,以及上涌地幔经历过多期部分熔融和大陆岩石圈中壳幔物质混染作用。 相似文献