Refold structures of the Archaean Nyanzaga gold Project, Sukumaland Greenstone Belt, Tanzania: Precursors to the gold-bearing fault system

IF 2.6 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Journal of Structural Geology Pub Date : 2024-08-14 DOI:10.1016/j.jsg.2024.105233
Célestine Berthier , Alain Chauvet , Julien Feneyrol , Anne-Sylvie André-Mayer , Aurélien Eglinger , John McIntyre , Rémi Bosc
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Abstract

This study presents a complete investigation into the structural-hydrothermal evolution of the Nyanzaga and Kilimani gold deposits within the Neoarchean Sukumaland Greenstone Belt, Tanzania Craton. The first compressional stage, D1a, creates upright E-W folds in response to N-S-oriented shortening. The second stage, D1b, refolds the previously formed structures during ongoing compression/transpression under N-S-oriented shortening. Due to the brittle nature of late deformation, during D1c, a set of faults emerges, with the NW-SE ones exhibit dextral shearing and control the formation of normal N-S vertical faults.

A protracted hydrothermal history is recorded, beginning with a disseminated silicate minerals- and pyrite-rich, gold-barren stage associated with the D1a and D1b deformations, followed by the development of a gold-endowed vein system during progressive D1b and D1c stages. Gold was mainly concentrated within vertical NW-SE (Kilimani) and N-S (Nyanzaga) faults. Our findings challenge traditional polyphase deformation models presented in the other gold deposits of the area, by proposing a progressive and continuous deformation-hydrothermal history. In addition, we highlight the influence of refold structures on fault geometry, which is crucial in concentrating gold mineralization under continuous N-S compression and transpression.

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坦桑尼亚苏库马兰绿岩带太古宙尼扬扎加金项目的折叠结构:含金断层系统的前身
本研究对坦桑尼亚克拉通新元古代苏库马兰绿岩带内的尼扬扎加和基里马尼金矿床的构造-热液演化进行了全面调查。第一个压缩阶段(D1a)形成了直立的东西向褶皱,以应对南北向的缩短。第二阶段(D1b)在 N-S 向缩短作用下的持续压缩/挤压过程中重新折叠了之前形成的结构。在 D1c 阶段,由于后期变形的脆性,出现了一系列断层,其中 NW-SE 断层表现为向斜剪切,并控制了正常 N-S 垂直断层的形成。记录了一段漫长的热液历史,首先是与 D1a 和 D1b 变形相关的富含硅酸盐矿物和黄铁矿的散布型贫金阶段,随后在渐进的 D1b 和 D1c 阶段形成了含金矿脉系统。金主要集中在NW-SE(基里马尼)和N-S(尼扬扎加)垂直断层内。我们的发现对该地区其他金矿床的传统多相变形模型提出了挑战,提出了一个渐进和连续的变形-热液历史。此外,我们还强调了折返结构对断层几何形状的影响,这对于在持续的 N-S 压缩和转位作用下集中金矿化至关重要。
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来源期刊
Journal of Structural Geology
Journal of Structural Geology 地学-地球科学综合
CiteScore
6.00
自引率
19.40%
发文量
192
审稿时长
15.7 weeks
期刊介绍: The Journal of Structural Geology publishes process-oriented investigations about structural geology using appropriate combinations of analog and digital field data, seismic reflection data, satellite-derived data, geometric analysis, kinematic analysis, laboratory experiments, computer visualizations, and analogue or numerical modelling on all scales. Contributions are encouraged to draw perspectives from rheology, rock mechanics, geophysics,metamorphism, sedimentology, petroleum geology, economic geology, geodynamics, planetary geology, tectonics and neotectonics to provide a more powerful understanding of deformation processes and systems. Given the visual nature of the discipline, supplementary materials that portray the data and analysis in 3-D or quasi 3-D manners, including the use of videos, and/or graphical abstracts can significantly strengthen the impact of contributions.
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