共查询到18条相似文献，搜索用时 343 毫秒
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中国大部分狗头金分布在湖南、四川、黑龙江、青海与山东五省。狗头金分布与水系有密切关系。狗头金可划分为两大类成因类型:表生成矿型(物理风化、化学溶解、再生-齐汞化)与原生成矿型(原生金块与原生改造)。含金地貌与新构造运动在成矿作用中占有重要地位。 相似文献
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中外“块金”集锦及其成因分析 总被引：2，自引：1，他引：2
本文叙述了中外“块金”(狗头金)的产地、块数和成因分析.世界上已发现的块金愈万块,最大者重235.87kg,产于澳大利亚.多数研究者认为块金是化学成因.在表生条件下,金可呈溶液迁移,金络合物的稳定性与氧化还原条件有关.这种条件的变化,使金溶解-沉淀反复交替进行.在适当条件下,金粒再生、长大,形成块金. 相似文献
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微生物参与下的自然界金的循环 总被引：5，自引：1，他引：5
引用比较丰富的资料论述了微生物参与下自然界金的循环，强调了微生物对砂金和“狗头金”形成的特殊作用，对了解金矿成因、金矿寻找和微生物浸金有参考价值。 相似文献
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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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本文从水文地球化学角度研究了金的表生地球化学作用，并应用热力学方法计算了茅排地区水中金的存在形式，研究了水溶金的迁移和沉淀条件，得出了一个重要结论：是该区水中金的主要存在形式。在此基础上初步探讨了砂金矿的形成条件。 相似文献
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室温条件下微生物环境中块金生长机理的实验研究 总被引：6，自引：1，他引：5
室温条件下,用真菌、硅藻、固氮菌及芽孢杆菌等不同微生物,经３个月至１８个月的时间,可将砖红色的海绵金培育成片状、丝状及粒状的Ａｕ颗粒,这表明在表生条件及微生物环境中,Ａｕ可以被活化、迁移、再生长、测定结果表明,培养液中的Ａｕ质量浓度与其中的Ｈ２Ｏ２质量浓度有正相关关系;而且,Ａｕ和Ｈ２Ｏ２质量浓度高的样品,其中的金粒生长速率也快,说明表生条件下块金的生长与溶液中的Ｈ２Ｏ２质量浓度密切相关。 相似文献
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A. R. Cabral G. Beaudoin M. Choquette B. Lehmann J. C. Polônia 《Mineralogy and Petrology》2007,90(1-2):141-150
Summary The Córrego Bom Sucesso alluvial deposit near Serro, Minas Gerais, probably provided the specimens from which the element
palladium was first discovered. Its Pt–Pd nuggets are characteristically botryoidal, arborescent and coralloidal, and exhibit
an external halo with the composition of palladiferous platinum to virtually pure platinum. X-ray mapping of an arborescent
Pt–Pd nugget from the historical occurrence documents selective palladium depletion, similar to the high-fineness gold haloes
developed on detrital Au–Ag grains under supergene conditions. The Pd-depleted alteration zone truncates inclusions of crystals
stoichiometrically close to PdPt within the Pt–Pd aggregate. Selective metal leaching in the weathering environment can account
for the frequently observed Pt-enriched rims on alluvial platiniferous alloys which may lead to the formation of platinum
nuggets at an advanced degree of weathering.
Present address: Department of Geology: Exploration Geology Rhodes University PO Box 94, Grahamstown, 6140 South Africa 相似文献
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A rare collection of centimetre-scale proximal gold nuggets has been examined in the context of the Late Pleistocene to Holocene eluvial and colluvial sediments in which they occur, in a range of environments from arid temperate to periglacial. Liberation of supergene nuggets from their basement source in fault zones occurred progressively by physical erosion as the host basement rocks were uplifted between middle Miocene and Holocene. The host sediments are made up of poorly sorted angular greenschist facies schist debris. Some nuggets were recycled through several generations of these colluvial deposits, and additional nuggets were liberated to younger sediments during this time. The nuggets did not migrate laterally more than a few tens of metres during this repeated recycling, and were passively elevated vertically with the rising basement on to the crest and slopes of a 1600 m high mountain range. The most recently liberated nuggets retain almost all the morphological features of their supergene origin, including coarse (cm scale) crystal shapes, delicate crystalline internal structure, and imprints of oxidised pyrite crystals. Minor transport in colluvium has caused some abrasion and rounding of gold crystals. Repeated recycling progressively obscured the crystal shapes, although relict crystals are still recognisable on parts of most nuggets. Differential timing of liberation from basement has resulted in a wide range of rounding effects in groups of closely-coexisting nuggets. Variably crystalline gold overgrowths (micron scale) coat abraded surfaces of all or part of most nuggets, commonly intergrown with authigenic smectite clay minerals. These overgrowths developed from alkaline groundwater (pH 7–9) that had undergone extensive chemical interaction with labile minerals in the host colluvium. Abrasion during recycling removed some of the overgrowths, but this was replaced in the new sedimentary hosts. Physical and chemical processes affecting nuggets in these sediments have similarly affected eluvial and colluvial nuggets in a wide range of settings around the world, including Yukon (Canada), California (USA) and arid parts of Australia. 相似文献
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Gold nuggets (centimetre scale) have formed in a supergene alteration zone on hydrothermal gold deposits, and occur intergrown with quartz and iron oxyhydroxide pseudomorphs after sulphide minerals, and along fractures in quartz and host rocks. The supergene alteration was driven by groundwater-driven water-rock interaction near to a regional unconformity beneath fluvial sediments, and involved clay alteration and oxidation that extended up to 50 m below the unconformity. Oxidation of pyrite and arsenopyrite produced temporary thiosulphate ligands that mobilised microparticulate gold encapsulated in the sulphide minerals. The nuggets have some crystalline form, and internally they consist of anhedral grains, elongated gold plates, and intimate intergrowths of gold and iron oxyhydroxide. Nugget surfaces have further micron scale overgrowths of microparticulate gold, gold plates, and gold crystals. Nuggets were eroded and recycled into nearby proximal Miocene quartz pebble conglomerates, where they concentrated in placers near the basal unconformity. Later recycling transferred gold into Pleistocene fluvial channels. Gold dissolution and redeposition as plates and crystals occurred on the exterior surfaces of placer gold particles, with little change in mass. All groundwater maintained high pH throughout the geological history because there was sufficient calcite in the basement rocks to neutralise any acid generated by pyrite oxidation. Hence, gold mobility in sediments was driven by thiosulphate complexes as for the in situ nuggets, albeit with lower dissolved sulphur concentrations. Despite aridification of the climate in the late Cenozoic, with resulting localised high dissolved chloride concentrations, chloride complexation did not contribute to gold mobility. 相似文献
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