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摘要:
东北非地区主要包括埃及、苏丹、厄立特里亚和埃塞俄比亚。该地区金、银、铜、锌等矿产资源丰富, 主要矿床类型为VMS(火山成因块状硫化物)矿床。自发现Ariab、Bisha等大型VMS矿床以来, 各国矿业公司在东北非地区开展勘探和开发, 并新发现大量矿床, 铜、金等矿产资源量不断增加。通过对区域内各国VMS矿床的勘查、研究进展进行梳理和总结, 以期为本地区开展矿产勘查和投资开发的企业提供参考。区内VMS矿床围岩多为双峰式偏长英质火山岩, 与火山弧岩石组合有一定相关性, 主要控矿因素为剪切带、褶皱和具有一定特征的变质火山沉积岩系, 矿床形成集中于3个阶段, 时间跨度为890 ~ 695 Ma, 矿床形成于两类古构造环境, 即洋内汇聚板块边缘的岛弧环境和弧后盆地环境。许多矿床都经历了近地表氧化和表生富集作用, 金和铜在浅层相对富集。已发现的矿床主要位于东北非努比亚地盾偏中北部地区, 集中于Barka、Gabgaba、Eastern Desert地体, 找矿有利区位于Barka、Nakasib、Keraf、Nugrus缝合带附近。
Abstract:The Northeast Africa mainly includes Egypt, Sudan, Eritrea and Ethiopia, hosting rich mineral resources such as gold, silver, copper and zinc, and the main types of mineral deposits are VMS.Since the discovery of large VMS deposits such as Ariab and Bisha, mining companies from various countries have been conducting exploration and mining in this region, and the discovery of a large number of new deposits elevate the mineral resources of copper and gold.The summary of exploration and research progress of VMS deposits in those countries can provide references for enterprises that carry out mineral exploration and investment in this region.The host rocks of VMS deposits in this region are mainly bimodal felsic volcanic rocks, which indicate a certain correlation with the volcanic arc rock combination, and the main controlling factors for the deposits are shear zones, folds and characteristic metamorphosed volcanic-sedimentary series.The ages of these deposits are mainly concentrated in three stages ranging from 890 Ma to 695 Ma, and were formed in two types of paleotectonic environments, island arc on the margins of convergent plates and back-arc basin in the oceans.Most deposits experienced near-surface oxidation and supergene enrichment, with gold and copper relatively enriched near surface.The discovered VMS deposits are mainly distributed in the north-central part of the Arabian Nubian Shield, including Barka, Gabgaba, Eastern Desert terranes, and the prospects are near the Barka, Nakasib, Keraf, and Nugrus suture zones.
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Key words:
- VMS deposits /
- Northeast Africa /
- Nubian shield /
- metallogeny /
- mineral exploration engineering
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表 1 东北非主要VMS型矿床产量及金属资源量
Table 1. Metal output and mineral resources of major VMS deposits in Northeast Africa
矿床 控股方 矿石产量/(104t·a-1) 金属资源量 国家 金/ t 铜/ 104 t 锌/ 104 t Bisha 紫金矿业 240 38.06 66.00 317.00 厄立特里亚 Asmara 四川路桥 645 42.90 69.15 112.06 Harvest 紫金矿业 26 7.84 7.52 9.27 埃塞俄比亚 Adyabo 西藏华钰 71 8.49 2.98 - Ariab Ariab Mining 198 31.00 135.35 - 苏丹 Galat Sufar Orca Gold 570 126.04 - - Hamama Aton Resources 83 14.86 - - 埃及 Abu Marawat Aton Resources - 5.08 2.23 3.34 注：除Bisha、Ariab外，其他矿床为可研设计产量; 资源量数据据各公司官网及标普数据库 
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表 2 Bisha矿床典型矿石类型矿化特征[33]
Table 2. Mineralization characteristics of the typical ores in the Bisha mine
矿石类型 岩性 平均品位 厚度及矿化特征 氧化带 铁帽 6 g/t Au 0~10 m厚，深棕色，Fe、Au含量高的表层 半风化层 5~30 m厚，棕色，Fe、Au含量高的氧化物，无硫化物 酸性淋滤带 白色硅质粘土层 6 g/t Au 0~15 m厚，白色，不规则状，硅质淋滤带 黑色硅质含铅层 25 g/t Au 0.5~1.5 m厚，黑色，粉末状，富Au-Ag-Pb，少量黄铁矿 次生富集带 黄铁矿砂层 10 g/t Au 0.5~5 m厚，黄色，细粒黄铁矿砂(未固结)，贫Cu富Ag 次生富集硫化物层 4.09% Cu 0.5~15 m厚，富Cu贫Au块状硫化物(黄铁矿为主)Cu含量随深度增加 原生锌矿带 原生硫化物 5%~7% Zn 富Zn硫化物
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