投稿时间：2020-12-08
修订日期：2021-04-22
网络发布日期：2021-07-12
中文摘要:莫桑比克楠普拉省喀祖祖地区多条河流均有人工砂金开采活动。砂金分布在海拔300~450 m之间的石英砾石层，底部岩石主要为中元古代片麻状杂岩体。研究区为准平原-丘陵地貌，水动力条件受季节影响较大。砂金分布与河流不存在明显的耦合性，暗示了原生金矿化可能较分散。同时，研究区露头受第四纪覆盖严重，物化探效果不显著，砂金与重砂矿物组合因而成为重要的原生金找矿标志。结合双目镜观察及扫描电镜分析得出，与砂金密切相关的重砂矿物包括黄铁矿、钛铁矿、锆石等。砂金颗粒多呈棱角状，部分可观察到残留连生矿物，整体暗示了近源堆积的特征。根据电子探针分析结果，不同部位产出砂金成分相近，表现为较高的金成色（w（Au）均高于98%）及较低的微量元素（仅含少量Fe、Cu），暗示为同一构造背景下的产物。综上，莫桑比克楠普拉省喀祖祖地区原生金矿化可能是与黑云斜长片麻岩（及其长英质脉体）相关的低硫型热液金矿化，形成背景为泛非期造山运动。
Abstract:Artificial placer gold mining in rivers is reported in the Cazuzu region, Nampula Province, northern Mozambique. The placer gold is observed in the quartz gravel layer at an altitude of 300~450 m. The lithology at the bottom is composed of Mesoproterozoic gneiss complex. The study area is a landform between peneplain and hill, in which hydrodynamic condition is subjected by the season. The placer gold is widely distributed, without an obvious continuous law with the rivers, suggesting scattered primary gold mineralization. Meanwhile, the outcrops are mostly covered by the quaternary sediments, leading to the poor effects of the geophysical and geochemical prospecting. Thus, the characteristics of placer gold and heavy minerals have become an important primary gold prospecting mark. Combined with binocular microscope observation and scanning electron microscopy analysis, it is shown that heavy minerals are closely related to placer gold including pyrite, ilmenite, zircon and some other minerals. The angular morphology of gold particles and some residual contiguous minerals indicate near-source precipitation. Placer gold from different parts has similar composition, showing the characteristics of higher Au fineness (w(Au)≥98%) and lower trace elements (only a small amount of Fe, Cu), suggesting uniform mineralization type in the study area. To sum up, the primary gold mineralization has a genetic connection with low-sulfur hydrothermal gold mineralization associated with biotite plagiogneiss and its felsic veins closely related to the Pan-African orogeny.
keywords:geology placer gold genesis indicative significance Cazuzu region in Nampula Province Mozambique
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基金项目:本文得到江苏省财政厅、江苏省国土资源厅地勘专项资金项目（编号：苏财建〔2017〕160号）的资助
引用文本：
曾勇杰,王翠芝,宋英昕,刘峰,潘刚,许生武,康涛,李增胜.2021.莫桑比克楠普拉省喀祖祖地区砂金成因及其对岩金指示意义[J].矿床地质,40(3):574~586ZENG YongJie,WANG CuiZhi,SONG YingXin,LIU Feng,PAN Gang,XU ShengWu,KANG Tao,and LI ZengSheng.2021.Genesis of placer gold and its indicative significance for primary gold in Cazuzu Region, Nampula Province, Mozambique[J].Mineral Deposits40(3):574~586
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