An overview of gold systems in Uganda

Abstract

Detailed analyses of historic and recent information on active and abandoned gold mines and alluvial workings in combination with new regional geochronology, documentation and interpretation of the lithostratigraphy, structural setting, hydrothermal alteration and mineralisation, and geochemistry of mineralised rocks have formed the basis for the definition of four major gold districts in Uganda: (1) the Busia gold district hosted in the Neoarchean Busia-Kakamega granite–greenstone belt in the SE of Uganda, which contains the structurally controlled mesozonal Tira gold mine; (2) the Mubende gold district in the Paleoproterozoic Rwenzori fold belt in central Uganda, which hosts the structurally controlled metasediment-hosted mesozonal Kamalenge and Kisita gold mines; (3) the Buhweju-Mashonga gold district in SW Uganda, which contains the vein hosted Pb–Zn–Au Kitaka mine, the structurally controlled intrusion-hosted mesozonal Mashonga gold mine and the structurally controlled sandstone-hosted mesozonal Muti and Kanywambogo mines; and (4) the Karamoja gold district, which is hosted in reworked Archean basement rocks and/or in the upper amphibolite–lower granulite facies rocks of the Neoproterozoic Mozambique fold belt in NE and W Uganda and in the northern part of the Karamoja gold district containing numerous hypozonal shear zone-controlled gold workings. Other areas in Uganda where alluvial gold mineralisation and/or shallow gold workings are reported comprise the Kitgum area within the Aswa shear zone in northern Uganda, the Western Nile area, which represents the western extremity of the Bomu-Kibalian shield of NE Congo, and the Kabale-Kisoro area hosted in the Mesoproterozoic North Kibaran fold belt in SW Uganda. The results of this work are an early attempt to portray the gold metallogeny of Uganda. Future studies, including geological mapping at all scales, geochronology, whole-rock geochemistry and chemical and mineralogical studies of mineralised samples, will help clarify the distribution and origin of diverse gold systems in this poorly understood part of Africa.

对开采中和被遗弃的金矿及冲积作用的历史和最新资料的详细分析，与新的区域地质年代学、岩石地层学、构造背景、热液蚀变和矿化、地球化学、矿化岩石资料和解释相结合，形成了乌干达四大黄金区的定义的基础：（1）乌干达东南部新太古代Busia-Kakamega绿岩带中的 Busia金矿区，包括构造控制的中带Tira金矿; （ 2）在乌干达中部的古元古代Rwenori褶皱带中的Mubende黄金区带有构造控制的变质沉积岩內中带Kamalenge金矿和Kisita金矿; （ 3） 乌干达西南部的Buhweju - Mashonga金区，包括含有铅 - 锌 - 金的Kitaka矿的矿脉,构造控制的侵入岩内的中带Mashonga金矿和构造控制的砂岩内中带Muti矿和Kanywambogo矿;（ 4 ）Karamoja金矿区，存在于经改造的太古代基底岩石和/或乌干达东北和西部的新元古代莫桑比克褶皱带的上部为高角闪岩、下部为麻粒岩相的岩石中，Karamoja金矿区北部含大量深变质带的剪切带控制的金矿。在乌干达其它地区，冲积金矿化和/或浅水金沉积区据报告组成了乌干达Aswa剪切带内的Kitgum区、代表刚果东北的Bomu - Kibalian地盾的西端的西尼罗河区、以及乌干达西南部中元古代北Kibaran褶皱带之内的Kabake-Kisoro区。这项工作的结果是描绘乌干达的金成矿作用的一个早期尝试。未来的研究，包括所有尺度地质填图、年代学、全岩地球化学和矿化样本的化学和矿物学研究，将有助于澄清这片了解比较粗浅的非洲大陆的不同的黄金体系。

KEYWORDS:

• Uganda
• gold
• orogenic gold
• mining
• exploration
• structural controls
• hydrothermal alteration

ACKNOWLEDGEMENTS

We acknowledge the support and help of the Centre for Exploration Targeting (CET) research team especially my colleagues Dr Thomas Angerer, Dr Paul Duuring, Christian Schindler and Ana-Sophie Hensler for their friendly and professional support towards the success of this study. This project was initiated by the Geological Survey of Uganda and the Centre for Exploration Targeting, and was sponsored by Nero Resources Australia Pty and the Society for Economic Geology student chapter.