The structural history and mineralization controls of the world-class Geita Hill gold deposit, Geita Greenstone Belt, Tanzania

详细信息    查看全文

• 作者：I. V. Sanislav ; M. Brayshaw ; S. L. Kolling ; P. H. G. M. Dirks…
• 关键词：Archean ; Geita Hill ; Gold deposits ; Structural controls ; Tanzania
• 刊名：Mineralium Deposita
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：52
• 期：2
• 页码：257-279
• 全文大小：
• 刊物类别：Earth and Environmental Science
• 刊物主题：Geology; Mineral Resources; Mineralogy;
• 出版者：Springer Berlin Heidelberg
• ISSN：1432-1866
• 卷排序：52

文摘

The Geita Hill gold deposit is located in the Archean Geita Greenstone Belt and is one of the largest gold deposits in East Africa. The Geita Greenstone Belt experienced a complex deformation and intrusive history that is well illustrated and preserved in and around the Geita Hill gold deposit. Deformation involved early stages of ductile shearing and folding (D₁ to D₅), during which episodic emplacement of large diorite intrusive complexes, sills, and dykes occurred. These ductile deformation phases were followed by the development of brittle-ductile shear zones and faults (D₆ to D₈). The last stages of deformation were accompanied by voluminous felsic magmatism involving the intrusion of felsic porphyry dykes, within the greenstone belt, and the emplacement of large granitic bodies now forming the margins of the greenstone belt. Early, folded lamprophyre dykes, and later lamprophyre dykes, crosscutting the folded sequence are common, although volumetrically insignificant. The gold deposit formed late during the tectonic history of the greenstone belt, post-dating ductile deformation and synchronous with the development of brittle-ductile shear zones that overprinted earlier structural elements. The main mineralizing process involved sulfide replacement of magnetite-rich layers in ironstone and locally the replacement of ferromagnesian phases and magnetite in the diorite intrusions. The intersection between the brittle-ductile (D₆) Geita Hill Shear Zone and different structural elements of ductile origin (e.g., fold hinges), and the contact between banded ironstone and folded diorite dykes and sills provided the optimal sites for gold mineralization.