3-D Mohr circle analysis of vein opening, Indarama lode-gold deposit, Zimbabwe: implications for exploration
The Indarama lode gold deposit is hosted by vertically-dipping basalt in the Late Archaean Midlands Greenstone Belt of Zimbabwe. Major deformation events at 2.68 and 2.58 Ga established a complex array of fractures. A limited range of orientations of this fracture network opened towards the end of t...
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Published in | Journal of structural geology Vol. 26; no. 6; pp. 1275 - 1291 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Elsevier Ltd
01.06.2004
|
Subjects | |
Online Access | Get full text |
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Summary: | The Indarama lode gold deposit is hosted by vertically-dipping basalt in the Late Archaean Midlands Greenstone Belt of Zimbabwe. Major deformation events at 2.68 and 2.58
Ga established a complex array of fractures. A limited range of orientations of this fracture network opened towards the end of the younger deformation event, creating a lode pattern where 92% of mineralised veins dip at less than 50°, mainly to the E and W, and most strike directions are represented. A clustered distribution of poles to the quartz–carbonate veins indicates a constrictional stress field at the time of vein opening where
σ
1 and
σ
2 were near horizontal, (directed NNW–SSE and ENE–WSW, respectively), and
σ
3 was near vertical. 3-D Mohr circle analysis demonstrates that
σ
2 was approximately 67% of
σ
1 (the stress ratio) and that the driving pressure ratio (
R′) was approximately 0.4, reflecting the role of fluid pressure, mean stress, and the maximum shear stress in controlling conditions of fracture opening. |
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ISSN: | 0191-8141 1873-1201 |
DOI: | 10.1016/j.jsg.2003.11.001 |