埃塞俄比亚北部阿迪布拉达VMS型铜多金属矿成矿特征与找矿标志
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摘要
埃塞俄比亚北部施瑞地区处于非洲东部阿斯玛拉VMS型铜锌多金属成矿带的西南段,该区先后发现有大型VMS型铜锌多金属矿床2处,小型VMS型铜锌多金属矿床3处,北东向成群成带分布,构成了埃塞俄比亚北部大型有色金属资源基地。阿迪布拉达VMS型铜多金属矿床产于新元古界Nebrid岩群变质中基性—酸性火山岩岩组中,是该区域VMS型块状硫化物矿床的赋矿岩系,属活动大陆边缘(岛弧)中浅海海底环境。矿体受火山机构和岩性界面双重因素控制,成矿期为火山活动晚期或间歇期,矿体呈透镜状、似层状北东向展布,矿石类型以块状、条带状含铜黄铁矿型矿石为主,中基性与酸性火山岩岩性界面转换处发育的铁帽是直接找矿标志,正负磁异常转换处并叠加低阻—高极化—剩余重力异常区及Au-Ag-Cu-Pb-Zn-As-Sb-Bi-Hg-Ba-Mn化探组合异常区是间接找矿标志。
Shirearea located in northern Ethiopia,occurs at southwestern part of Asmara VMS type Cu-Zn polytimetallogenic belt,East Africa. In recent years two large-sized VMS type copper-zinc polymetallic deposits,and three small sized VMS copper zinc deposits had been found. Those deposits as a group are distributed along northeast trending,which constitute the large sized non-ferrous metal resources in northern Ethiopia. The Adi Bladie VMS copper-zinc polymetal deposit occurs within metamorphic basic to acid volcanic rock named Neoproterozoic Nebrid group. Tectonically,The deposit was formed in the active continental margin arc in shallow sea floor environment. The ore body was controlled by volcanic mechanism and lithologic interface combination,and the deposit was formed in the late volcanic activity or intermittent period. Orebodies occur in forms of lenticular and layered and main ore type is massive ore and banded ore. Well developed gossan occuring between interface between the basic and intermediate and acid volcanic rock can be taken as direct prospecting indicator. The transtion area between positive and negative magnetic anomaly,which overlapped with low resistance and high polarization and residual gravity anomaly area,also consistent with geochemical anomalies of Au-Ag-Cu-PbZn-As-Sb-Bi-Hg-Ba-Mn elements,is indirectly prospecting marks.
Shirearea located in northern Ethiopia,occurs at southwestern part of Asmara VMS type Cu-Zn polytimetallogenic belt,East Africa. In recent years two large-sized VMS type copper-zinc polymetallic deposits,and three small sized VMS copper zinc deposits had been found. Those deposits as a group are distributed along northeast trending,which constitute the large sized non-ferrous metal resources in northern Ethiopia. The Adi Bladie VMS copper-zinc polymetal deposit occurs within metamorphic basic to acid volcanic rock named Neoproterozoic Nebrid group. Tectonically,The deposit was formed in the active continental margin arc in shallow sea floor environment. The ore body was controlled by volcanic mechanism and lithologic interface combination,and the deposit was formed in the late volcanic activity or intermittent period. Orebodies occur in forms of lenticular and layered and main ore type is massive ore and banded ore. Well developed gossan occuring between interface between the basic and intermediate and acid volcanic rock can be taken as direct prospecting indicator. The transtion area between positive and negative magnetic anomaly,which overlapped with low resistance and high polarization and residual gravity anomaly area,also consistent with geochemical anomalies of Au-Ag-Cu-PbZn-As-Sb-Bi-Hg-Ba-Mn elements,is indirectly prospecting marks.
引文
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[3]王京彬,朱思才,甘凤伟,等.埃塞俄比亚北部施瑞地区VMS型铜锌金矿床地质特征、成矿规律和找矿预测研究[R].中色地科矿产勘查股份有限公司.2015.
[4]Large R R.Australian volcanic-hosted massive sulphide deposits:Features,styles and genetic models[J].Economic Geology,1992,(87):471-510.
[5]顾连兴.块状硫化物矿床研究进展评述[J].地质评论,1999,45(3):265-276.
[6]李文渊.块状硫化物矿床的类型、分布和形成环境[J].地球科学与环境学报,2007,29(4):331-344.
[7]Tadesse T,Hoshino M,Suzuki K,et al.Sm-Nd,Rb-Sr and ThU-Pb zircon ages of syn-and post-tectonic granitoids from the Axum area of northern Ethiopia[J].Journal of African Earth Scineces,2000,30(2):313-327.
[8]Ghebreab W,Greiling R O,Solomon S.Structural setting of Neoproterozoic mineralization,Asmara district,Eritrea[J]Journal of African Earth Sciences,2009,(55):219-235.
[9]Tadesse T,Hoshino M,Sawada Y.Geochemistry of low-grade metavolcanic rocks from the Pan-African of the Axum area,northern Ethiopia[J].Precambrian Research,1999,96(1/2):101-124.
[10]Alene M,Jenkin G R T,Leng M J,et al.Ethiopia:an early Cryogenian(ca.800-735 Ma)neoproterozoic sequence in the Arabian Nubian shield[J].Precambrian Research,2006,(149):79-89.
[11]Large R R.Australian volcanic-hosted massive sulphide deposits:Features,styles and genetic models[J].Economic Geology,1992,87:471-510.
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