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近二十年来 ,热带地区普遍存在的红土型风化作用及其对矿床与矿化带的影响引起了普遍的关注。红土型风化壳的主要矿物成分是以铁铝的氧化物及氢氧化物和粘土矿物为主 ,如针铁矿、赤铁矿、铝土矿、高岭石及石英等 ,与其未风化的母岩相比 ,含有相当高的铁和铝。红土型风化过程中 ,易溶元素均不同程度地被淋滤 ,而难溶元素则相对富集。红土型金矿床就是在这样强烈的风化作用中由原生的金矿化带进一步富集而成 ,并可形成极富的矿体。金矿体常常赋存于风化壳的上部 ,易于露天开采。目前 ,在澳大利亚、巴西、巴布亚新几内亚、印度以及非洲的一些国家均发现了红土型金矿床。红土型风化剖面一般可分为 5个特征带 ,由上而下为 :表土带、铁质带、斑点带、浅色带、腐岩带 ,下面即为未风化的母岩 ,金矿体主要赋存于铁质带和斑点带中。红土型风化壳厚度变化很大 ,薄则几米 ,厚可达数百米。金在风化过程中往往向矿化带两侧运移 ,矿体常呈上宽下窄状。次生金常呈自形晶、树枝晶、浑圆状及不规则状产出 ,并常常与铁质结核共生。一般地说 ,次生金的成色很高 ,因为红土型风化作用常常是在氧化并且酸性的地球化学环境中进行 ,金和银主要以氯化物的形式运移 ,局部地球化学环境的变化可导致金的沉淀 ,而银的氯化物则较稳定 ,?
In the past 20 years, the prevalence of lateritic weathering in the tropics and its influence on mineralization and mineralization have caused widespread concern. The main mineral components of lateritic weathering crusts are mainly iron and aluminum oxides and hydroxides and clay minerals, such as goethite, hematite, bauxite, kaolinite and quartz, etc., and their non-weathering mother Compared to rock, it contains relatively high levels of iron and aluminum. In the laterite-type weathering process, the soluble elements are leached to different degrees, while the insoluble elements are relatively enriched. Lateritic gold deposits are further enriched by the native gold mineralization during such strong weathering and can form extremely rich ore bodies. Gold ore bodies are often found in the upper part of weathering crust, easy to open-air mining. Later, laterite-type gold deposits were found in some countries in Australia, Brazil, Papua New Guinea, India and Africa. The laterite weathering profile can be generally divided into five characteristic bands, from top to bottom: topsoil, iron belt, spot belt, light ribbon, sag rock belt, the following is the non-weathered rock, gold ore body Occurred in the iron zone and the spot zone. Laterite weathering crust thickness varies widely, while a few meters thin, up to several hundred meters thick. Gold in the weathering process tend to migrate to both sides of the mineralization, the ore body is often wide and narrow narrow shape. Secondary gold often showed self crystal, dendrite, rounded and irregular shaped output, and often coexist with iron tuberculosis. In general, secondary gold is of high quality because lateritic weathering is often performed in an oxidative and acidic geochemical environment, gold and silver migrate mainly as chlorides, and changes in the local geochemical environment can lead to Gold precipitation, while the silver chloride is more stable ,?