坦桑尼亚环维多利亚湖地区航磁异常特征及金矿床类型勘查地域划分

Aeromagnetic anomaly characteristics and survey region division of gold deposit types in Lake Victoria area of Tanzania

坦桑尼亚环维多利亚湖地区绿岩带为太古宙绿岩带,是坦桑尼亚的主要金矿来源,被称为坦桑尼亚金矿带;铁建造(BIF)型金矿、构造蚀变岩型金矿(或石英脉型)是坦桑尼亚太古宙绿岩带中的主要金矿床类型,这两种类型金矿床赋矿地质体的物理性质不同,成矿环境差异,其与两种类型金矿有关的条带状含铁建造和剪切构造蚀变带所引起的磁场特征有着明显的差别;依据坦桑尼亚环维多利亚湖地区岩石磁性特征、航磁异常特征、绿岩带地质特征以及该地区不同类型的中-大型金矿床的分布规律,同时结合近几年来我国在环维多利亚湖地区绿岩带上所发现的典型隐伏金矿床地面磁测异常特征,对坦桑尼亚环维多利亚湖地区8个次级绿岩区带内寻找何种类型金矿进行了研究划定;提出盖塔(Geita)、东卡哈马(East-Kahama)等绿岩带以寻找受"岩性、构造"双重控制的铁建造(BIF)型金矿为主,穆索马—马拉(Musoma-Mara)、西卡哈马(West-Kahama)等绿岩带以寻找受剪切断裂带控制的构造蚀变岩型或石英脉型金矿为主,同时针对这两种类型金矿床所赋存地质体的物理特征,提出了寻找这两种金矿床的物探找矿方法组合.

The greenstone belt around Lake Victoria in Tanzania is an archean greenstone belt and is the main source of gold in Tanzania,it is called the Tanzania gold belt.Iron formation(BIF)type gold deposit and tectonic rock type gold deposit(or quartz vein type)are the main gold deposit types in the archean greenstone belt in Tanzania.The physical properties of the ore bearing geological bodies of these two types of gold deposits are different,and the metallogenic environment is different.There is a significant difference in the magnetic field characteristics caused by the banded iron formation and shear structural alteration belts related to the two types of gold mines.Based on the magnetic characteristics of rocks,aeromagnetic anomalies,the geological characteristics of the greenstone belt and the distribution of different types of medium to large gold deposits in the Lake Victoria region of Tanzania,meanwhile,based on the characteristics of geomagnetic anomaly of the typical hidden gold deposit found on the greenstone belt of Lake Victoria in China in recent years,this paper has studied and demarcated the types of gold deposits in the eight sub-greenstone belts of Lake Victoria in Tanzania.It is proposed that greenstone belts such as Geita and East-Kahama be used to find iron formation(BIF)type gold deposit under the dual control of"lithology and structure".The Greenstone belts such as Musoma-Mara and West-Kahama are mainly used to search for tectonic altered rock or quartz vein gold deposits controlled by shear fracture zones,and at the same time for these two types of gold deposits.The physical characteristics of the geological bodies that exist in the deposits,A combination of geophysical prospecting methods for these two gold deposits is proposed.